ICN2 Publications


  • 2 × 2 charge density wave in single-layer TiTe2

    Guster B., Robles R., Pruneda M., Canadell E., Ordejón P. 2D Materials; 6 (1, 015027) 2019. 10.1088/2053-1583/aaf20b. IF: 7.343

    Theory and Simulation

    A density functional theory study concerning the origin of the recently reported 2 × 2 charge density wave (CDW) instability in single-layer TiTe2 is reported. It is shown that, whereas calculations employing the semi-local functional PBE favor the undistorted structure, the hybrid functional HSE06 correctly predicts a 2 × 2 distortion. The study suggests that the magnitude of the semimetallic overlap between the valence band top at - and the conduction band bottom at M is a key factor controlling the tendency towards the distortion. It is also shown that tensile strain stabilizes a 2 × 2 CDW, and we suggest that this fact could be further used to induce the instability in doublelayers of TiTe2, which in the absence of strain remain undistorted in the experiment. The driving force for the CDW instability seems to be the same phonon mediated mechanism acting for singlelayer TiSe2, although in single-layer TiTe2 the driving force is smaller, and the semimetallic character is kept below the transition temperature. © 2018 IOP Publishing Ltd.

  • A Coordinative Solubilizer Method to Fabricate Soft Porous Materials from Insoluble Metal–Organic Polyhedra

    Carné-Sánchez A., Craig G.A., Larpent P., Guillerm V., Urayama K., Maspoch D., Furukawa S. Angewandte Chemie - International Edition; 58 (19): 6347 - 6350. 2019. 10.1002/anie.201901668. IF: 12.257

    Supramolecular NanoChemistry and Materials

    Porous molecular cages have a characteristic processability arising from their solubility, which allows their incorporation into porous materials. Attaining solubility often requires covalently bound functional groups that are unnecessary for porosity and which ultimately occupy free volume in the materials, decreasing their surface areas. Here, a method is described that takes advantage of the coordination bonds in metal–organic polyhedra (MOPs) to render insoluble MOPs soluble by reversibly attaching an alkyl-functionalized ligand. We then use the newly soluble MOPs as monomers for supramolecular polymerization reactions, obtaining permanently porous, amorphous polymers with the shape of colloids and gels, which display increased gas uptake in comparison with materials made with covalently functionalized MOPs. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • A MOF@COF Composite with Enhanced Uptake through Interfacial Pore Generation

    Garzón-Tovar L., Pérez-Carvajal J., Yazdi A., Hernández-Muñoz J., Tarazona P., Imaz I., Zamora F., Maspoch D. Angewandte Chemie - International Edition; 58 (28): 9512 - 9516. 2019. 10.1002/anie.201904766. IF: 12.257

    Supramolecular NanoChemistry and Materials

    Herein, we describe a new class of porous composites comprising metal–organic framework (MOF) crystals confined in single spherical matrices made of packed covalent-organic framework (COF) nanocrystals. These MOF@COF composites are synthesized through a two-step method of spray-drying and subsequent amorphous (imine-based polymer)-to-crystalline (imine-based COF) transformation. This transformation around the MOF crystals generates micro- and mesopores at the MOF/COF interface that provide far superior porosity compared to that of the constituent MOF and COF components added together. We report that water sorption in these new pores occurs within the same pressure window as in the COF pores. Our new MOF@COF composites, with their additional pores at the MOF/COF interface, should have implications for the development of new composites. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • A nitrocellulose paper strip for fluorometric determination of bisphenol A using molecularly imprinted nanoparticles

    Üzek R., Sari E., Şenel S., Denizli A., Merkoçi A. Microchimica Acta; 186 (4, 218) 2019. 10.1007/s00604-019-3323-y. IF: 5.479

    Nanobioelectronics and Biosensors

    The authors describe a test stripe for fluorometric determination of the endocrine disruptor bisphenol A (BPA). Graphene quantum dots (GQDs) were immobilized on molecularly imprinted nanoparticles which then were placed on nitrocellulose paper. The GQDs display blue fluorescence (with excitation/emission peaks at 350/440 nm) which is reduced in the presence of BPA. The test stripe has a 43.9 ± 0.8 μg·L −1 limit of detection in case of water samples. The stripe was applied to the determination of BPA in (spiked) tap water and sea water, and the LODs were found to be 1.8 ± 0.2 μg·L −1 and 4.2 ± 0.5 μg·L −1 , respectively. Structural analogs of BPA, such as aminophenol, phenol, hydroquinone and naphthol were found not to interfere. [Figure not available: see fulltext.]. © 2019, Springer-Verlag GmbH Austria, part of Springer Nature.

  • Anderson Photon-Phonon Colocalization in Certain Random Superlattices

    Arregui G., Lanzillotti-Kimura N.D., Sotomayor-Torres C.M., García P.D. Physical Review Letters; 122 (4, 043903) 2019. 10.1103/PhysRevLett.122.043903. IF: 9.227

    Phononic and Photonic Nanostructures

    Fundamental observations in physics ranging from gravitational wave detection to laser cooling of a nanomechanical oscillator into its quantum ground state rely on the interaction between the optical and the mechanical degrees of freedom. A key parameter to engineer this interaction is the spatial overlap between the two fields, optimized in carefully designed resonators on a case-by-case basis. Disorder is an alternative strategy to confine light and sound at the nanoscale. However, it lacks an a priori mechanism guaranteeing a high degree of colocalization due to the inherently complex nature of the underlying interference processes. Here, we propose a way to address this challenge by using GaAs/AlAs vertical distributed Bragg reflectors with embedded geometrical disorder. Because of a remarkable coincidence in the physical parameters governing light and motion propagation in these two materials, the equations for both longitudinal acoustic waves and normal-incidence light become practically equivalent for excitations of the same wavelength. This guarantees spatial overlap between the electromagnetic and displacement fields of specific photon-phonon pairs, leading to strong light-matter interaction. In particular, a statistical enhancement in the vacuum optomechanical coupling rate, go, is found, making this system a promising candidate to explore Anderson localization of high frequency (∼20 GHz) phonons enabled by cavity optomechanics. The colocalization effect shown here unlocks the access to unexplored localization phenomena and the engineering of light-matter interactions mediated by Anderson-localized states. © 2019 American Physical Society.

  • Aptamer-peptide conjugates as a new strategy to modulate human α-thrombin binding affinity

    Aviñó A., Jorge A.F., Huertas C.S., Cova T.F.G.G., Pais A., Lechuga L.M., Eritja R., Fabrega C. Biochimica et Biophysica Acta - General Subjects; 1863 (10): 1619 - 1630. 2019. 10.1016/j.bbagen.2019.06.014. IF: 3.681

    NanoBiosensors and Bioanalytical Applications

    Aptamers are single-stranded RNA or DNA molecules that specifically recognize their targets and have proven valuable for functionalizing sensitive biosensors. α-thrombin is a trypsin-like serine proteinase which plays a crucial role in haemostasis and thrombosis. An abnormal activity or overexpression of this protein is associated with a variety of diseases. A great deal of attention was devoted to the construction of high-throughput biosensors for accurately detect thrombin for the early diagnosis and treatment of related diseases. Herein, we propose a new approach to modulate the interaction between α-thrombin and the aptamer TBA15. To this end, TBA15 was chemically conjugated to two peptide sequences (TBA-G3FIE-Ac and TBA-G3EIF-Ac) corresponding to a short fragment of the acidic region of the human factor V, which is known to interact directly with exosite I. Surface Plasmon Resonance (SPR) results showed enhanced analytical performances of thrombin with TBA-G3EIF-Ac than with TBA wild-type, reaching a limit of detection as low as 44.9 pM. Electrophoresis mobility shift assay (EMSA) corroborated the SPR results. Molecular dynamics (MD) simulations support experimental evidences and provided further insight into thrombin/TBA-peptide interaction. Our findings demonstrate that the combination of TBA15 with key interacting peptides offers good opportunities to produce sensitive devices for thrombin detection and potential candidates to block thrombin activity. © 2019 Elsevier B.V.

  • Beyond the Scavenging of Reactive Oxygen Species (ROS): Direct Effect of Cerium Oxide Nanoparticles in Reducing Fatty Acids Content in an In Vitro Model of Hepatocellular Steatosis

    Parra-Robert M., Casals E., Massana N., Zeng M., Perramón M., Fernández-Varo G., Morales-Ruiz M., Puntes V., Jiménez W., Casals G. Biomolecules; 9 (9) 2019. 10.3390/biom9090425. IF: 4.694

    Inorganic Nanoparticles

    Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic accumulation of lipids. Antisteatotic effects of cerium oxide nanoparticles (CeO2NPs) have recently been shown in animal models of liver disease. However, it is unclear whether the activity of CeO2NPs is related solely to the decrease in oxidative stress or, in addition, they directly decrease liver fatty acid accumulation. To address this question, in this work, we used an in vitro model of hepatocellular steatosis, exposing HepG2 cells to oleic and palmitic acid. Cell uptake of CeO2NPs and their effect on oxidative stress and viability of hepatic cells cultured with H2O2 were also evaluated. Results show that CeO2NPs were uptaken by HepG2 cells and reduced oxidative stress and improved cell viability. Treatment with oleic and palmitic acid increased lipogenesis and the content of different fatty acids. CeO2NPs reduced palmitic and stearic acid and most fatty acids consisting of more than 18 carbon atoms. These effects were associated with significant changes in elongase and desaturase activity. In conclusion, CeO2NPs directly protected HepG2 cells from cell injury in oxidative stress conditions and reduced fatty acid content in steatotic conditions by inducing specific changes in fatty acid metabolism, thus showing potential in the treatment of NAFLD.

  • Biodistribution of liposome-encapsulated bacteriophages and their transcytosis during oral phage therapy

    Otero J., García-Rodríguez A., Cano-Sarabia M., Maspoch D., Marcos R., Cortés P., Llagostera M. Frontiers in Microbiology; 10 (APR, 689) 2019. 10.3389/fmicb.2019.00689. IF: 4.259

    Supramolecular NanoChemistry and Materials

    This study sheds light on the biodistribution of orally administered, liposome-encapsulated bacteriophages, and their transcytosis through intestinal cell layers. Fluorochrome-labeled bacteriophages were used together with a non-invasive imaging methodology in the in vivo visualization of bacteriophages in the stomach and intestinal tract of mice. In those studies, phage encapsulation resulted in a significant increase of the labeled phages in the mouse stomach, even 6 h after their oral administration, and without a decrease in their concentration. By contrast, the visualization of encapsulated and non-encapsulated phages in the intestine were similar. Our in vivo observations were corroborated by culture methods and ex vivo experiments, which also showed that the percentage of encapsulated phages in the stomach remained constant (50%) compared to the amount of initially administered product. However, the use of conventional microbiological methods, which employ bile salts to break down liposomes, prevented the detection of encapsulated phages in the intestine. The ex vivo data showed a higher concentration of non-encapsulated than encapsulated phages in liver, kidney, and even muscle up to 6 h post-administration. Encapsulated bacteriophages were able to reach the liver, spleen, and muscle, with values of 38% ± 6.3%, 68% ± 8.6%, and 47% ± 7.4%, respectively, which persisted over the course of the experiment. Confocal laser scanning microscopy of an in vitro co-culture of human Caco-2/HT29/Raji-B cells revealed that Vybrant-Dil-stained liposomes containing labeled bacteriophages were preferably embedded in cell membranes. No transcytosis of encapsulated phages was detected in this in vitro model, whereas SYBR-gold-labeled non-encapsulated bacteriophages were able to cross the membrane. Our work demonstrates the prolonged persistence of liposome-encapsulated phages in the stomach and their adherence to the intestinal membrane. These observations could explain the greater long-term efficacy of phage therapy using liposome-encapsulated phages. Copyright © 2019 Otero, García-Rodríguez, Cano-Sarabia, Maspoch, Marcos, Cortés and Llagostera. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

  • Bioinspired Functional Catechol Derivatives through Simple Thiol Conjugate Addition

    Mancebo-Aracil J., Casagualda C., Moreno-Villaécija M.Á., Nador F., García-Pardo J., Franconetti-García A., Busqué F., Alibés R., Esplandiu M.J., Ruiz-Molina D., Sedó-Vegara J. Chemistry - A European Journal; 2019. 10.1002/chem.201901914. IF: 5.160

    Nanostructured Functional Materials | Magnetic Nanostructures

    The combination of the surface-adhesive properties of catechol rings and functional moieties conveying specific properties is very appealing to materials chemistry, but the preparation of catechol derivatives often requires elaborate synthetic routes to circumvent the intrinsic reactivity of the catechol ring. In this work, functional catechols are synthesized straightforwardly by using the bioinspired reaction of several functional thiols with o-benzoquinone. With one exception, the conjugated addition of the thiol takes place regioselectively at the 3-position of the quinone, and is rationalized by DFT calculations. Overall, this synthetic methodology provides a general and straightforward access to functional and chain-extended catechol derivatives, which are later tested with regard to their hydro-/oleophobicity, colloidal stability, fluorescence, and metal-coordinating capabilities in proof-of-concept applications. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Bipolar “table with legs” resistive switching in epitaxial perovskite heterostructures

    Bagdzevicius S., Boudard M., Caicedo J.M., Mescot X., Rodríguez-Lamas R., Santiso J., Burriel M. Solid State Ionics; 334: 29 - 35. 2019. 10.1016/j.ssi.2019.01.027. IF: 2.886

    Nanomaterials Growth Unit

    We report the experimental investigation of bipolar resistive switching with “table with legs” shaped hysteresis switching loops in epitaxial perovskite GdBaCo 2 O 5+δ /LaNiO 3 bilayers deposited by pulsed laser deposition. The possibility of varying the resistivity of GdBaCo 2 O 5+δ by changing its oxygen content allowed engineering this perovskite heterostructure with controlled interfaces creating two symmetric junctions. It has been proved that the resistance state of the device can be reproducibly varied by both continuous voltage sweeps and by electrical pulses. The symmetric devices show slightly non-symmetric resistance profiles, which can be explained by a valence change resistive switching model, and presented promising multilevel properties required for novel memories and neuromorphic computing. © 2019

  • Boosting Photoelectrochemical Water Oxidation of Hematite in Acidic Electrolytes by Surface State Modification

    Tang P.-Y., Han L.-J., Hegner F.S., Paciok P., Biset-Peiró M., Du H.-C., Wei X.-K., Jin L., Xie H.-B., Shi Q., Andreu T., Lira-Cantú M., Heggen M., Dunin-Borkowski R.E., López N., Galán-Mascarós J.R., Morante J.R., Arbiol J. Advanced Energy Materials; (1901836) 2019. 10.1002/aenm.201901836. IF: 24.884

    Nanostructured Materials for Photovoltaic Energy | Advanced Electron Nanoscopy

    State-of-the-art water-oxidation catalysts (WOCs) in acidic electrolytes usually contain expensive noble metals such as ruthenium and iridium. However, they too expensive to be implemented broadly in semiconductor photoanodes for photoelectrochemical (PEC) water splitting devices. Here, an Earth-abundant CoFe Prussian blue analogue (CoFe-PBA) is incorporated with core–shell Fe2O3/Fe2TiO5 type II heterojunction nanowires as composite photoanodes for PEC water splitting. Those deliver a high photocurrent of 1.25 mA cm−2 at 1.23 V versus reversible reference electrode in acidic electrolytes (pH = 1). The enhancement arises from the synergic behavior between the successive decoration of the hematite surface with nanolayers of Fe2TiO5 and then, CoFe-PBA. The underlying physical mechanism of performance enhancement through formation of the Fe2O3/Fe2TiO5/CoFe-PBA heterostructure reveals that the surface states’ electronic levels of hematite are modified such that an interfacial charge transfer becomes kinetically favorable. These findings open new pathways for the future design of cheap and efficient hematite-based photoanodes in acidic electrolytes. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Building of a flexible microfluidic plasmo-nanomechanical biosensor for live cell analysis

    Solis-Tinoco V., Marquez S., Quesada-Lopez T., Villarroya F., Homs-Corbera A., Lechuga L.M. Sensors and Actuators, B: Chemical; 291: 48 - 57. 2019. 10.1016/j.snb.2019.04.038. IF: 6.393

    NanoBiosensors and Bioanalytical Applications

    Biosensor devices can constitute an advanced tool for monitoring and study complex dynamic biological processes, as for example cellular adhesion. Cellular adhesion is a multipart process with crucial implications in physiology (i.e. immune response, tissue nature, architecture maintenance, or behaviour and expansion of tumor cells). This work focuses on offering a controlled methodology in order to fabricate a flexible plasmo-nanomechanical biosensor placed within a microfluidic channel as a new tool for future cell adhesion studies. We designed, fabricated, and optically and mechanically characterized this novel optical biosensor. As a proof-of-concept of its functionality, the biosensor was employed to observe fibroblasts adhesion in a cell culture. The device is configured by an hexagonal array of flexible rigid/soft polymeric nanopillars capped with plasmonic gold nanodisks integrated inside a microfluidic channel. The fabrication employs low-cost and large-scale replica molding techniques using two different polymers materials (EPOTECK OG142 and 310 M). By using those materials the spring constant of the polymer nanopillars (k) can be fabricated from 1.19E-02 [N/m] to 5.35E+00 [N/m] indicating different mechanical sensitivities to shear stress. Therefore, the biosensor has the feasibility to mimic soft and rigid tissues important for the description of cellular nanoscale behaviours. The biosensor exhibits a suitable bulk sensitivity of 164 nm or 206 nm/refractive index unit respectively, depending on the base material. The range of calculated forces goes from ≈1.98 nN to ≈.942 μN. This supports that the plasmo-nanomechanical biosensors could be employed as novel tool to study living cells behavior. © 2019

  • Cerium oxide nanoparticles display antilipogenic effect in rats with non-alcoholic fatty liver disease

    Carvajal S., Perramón M., Oró D., Casals E., Fernández-Varo G., Casals G., Parra M., González de la Presa B., Ribera J., Pastor Ó., Morales-Ruíz M., Puntes V., Jiménez W. Scientific Reports; 9 (1, 12848) 2019. 10.1038/s41598-019-49262-2. IF: 4.011

    Inorganic Nanoparticles

    Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide, ranging from steatosis to non-alcoholic steatohepatitis (NASH). Recently, cerium oxide nanoparticles (CeO2NPs) have emerged as a new antioxidant agent with hepatoprotective properties in experimental liver disease. The aim of the current investigation was to elucidate whether CeO2NPs display beneficial effects in an experimental model of NAFLD.Therefore, fifteen Wistar rats were subjected to a methionine and choline deficient diet (MCDD) for 6 weeks and intravenously treated with CeO2NP or vehicle during the weeks three and four of the diet. The effect of CeO2NPs on serum biochemistry, hepatic steatosis, inflammation, fatty acid content and expression of reactive oxygen species (ROS) and lipid metabolism related genes was assessed. MCDD fed rats showed increased inflammation, enhanced hepatic lipid accumulation of both saturated and unsaturated fatty acids (FAs) and overexpression of genes related to fatty liver and ROS metabolism. Treatment with CeO2NPs was able to reduce the size and content of hepatocyte lipid droplets, the hepatic concentration of triglyceride- and cholesterol ester-derived FAs and the expression of several genes involved in cytokine, adipokine and chemokine signaling pathways. These findings suggest that CeO2NPs could be of beneficial value in NAFLD. © 2019, The Author(s).

  • Chromium phosphide CrP as highly active and stable electrocatalysts for oxygen electroreduction in alkaline media

    Liu J., Yu X., Du R., Zhang C., Zhang T., Llorca J., Arbiol J., Wang Y., Meyns M., Cabot A. Applied Catalysis B: Environmental; 256 (117846) 2019. 10.1016/j.apcatb.2019.117846. IF: 14.229

    Advanced Electron Nanoscopy

    Catalysts for oxygen reduction reaction (ORR) are key components in emerging energy technologies such as fuel cells and metal-air batteries. Developing low-cost, high performance and stable electrocatalysts is critical for the extensive implementation of these technologies. Herein, we present a procedure to prepare colloidal chromium phosphide CrP nanocrystals and we test their performance as ORR electrocatalyst. CrP-based catalysts exhibited remarkable activities with a limiting current density of 4.94 mA cm−2 at 0.2 V, a half-potential of 0.65 V and an onset potential of 0.8 V at 1600 rpm, which are comparable to commercial Pt/C. Advantageously, CrP-based catalysts displayed much higher stabilities and higher tolerances to methanol in alkaline solution. Using density functional theory calculations, we demonstrate CrP to provide a very strong chemisorption of O2 that facilitates its reduction and explains the excellent ORR performance experimentally demonstrated. © 2019

  • Coating aerosolized nanoparticles with low-volatile organic compound (LVOC) vapors modifies surface functionality and oxidative reactivity

    Zhao J., Suárez G., Tran N., Puntes V., Riediker M. NanoImpact; 14 (100150) 2019. 10.1016/j.impact.2019.100150. IF: 0.000

    Inorganic Nanoparticles

    Engineered nanoparticles (ENPs) released into the environment have a high probability of interacting with other pollutants before human exposure. These interactions can modify the physicochemical characteristics of ENPs’ surface functionality. The toxicity of ENPs can thus largely depend on the coatings picked up in the environment rather than particle core alone. We built a dynamic system to simulate this barely-studied scenario and open up a novel and convenient way to form hydrophobic coatings directly on airborne ENPs. We coated airborne ENPs with low-volatile organic compounds (LVOCs)—common pollutants that exhibit a high affinity for surfaces. Measurement of airborne particle size distribution showed an increase in particle size after coating. The coating thickness was adjustable by controlling the parameters of LVOC generator, namely the reaction temperature and the flow rate through LVOC reservoir, to create 5–90 nm coatings. Transmission electron microscopy images and nanotracking analyses of ENPs suspended in liquid were used to further characterize the coating thickness. Both methods suggested that the system yielded stable, replicable, and well controlled surface coatings. ROS generation of the coated ENPs significantly depended on the type and thickness of LVOC coating. Chemically non-reactive coatings led to significantly reduced ROS generation of silver-ENPs with a 20 nm inert coating quenching close to 100% of ROS generation; this was attributed to the blocked reactive zones on the ENP surfaces. Chemically reactive anthracene coatings, in contrast, first passivated the surface but then contributed to the redox cycle, leading to an increased generation of ROS, which was at a 90 nm coating thickness comparable to that of bare ENPs. Our results add to the understanding of ENP surface functionality—an important aspect of nanotoxicity. Furthermore, the high controllability of our ENP coating system makes it useful for other applications in inducing hydrophobic coating on airborne ENPs. © 2019 Elsevier B.V.

  • Coexistence of Elastic Modulations in the Charge Density Wave State of 2 H-NbSe 2

    Guster B., Rubio-Verdú C., Robles R., Zaldívar J., Dreher P., Pruneda M., Silva-Guillén J.Á., Choi D.-J., Pascual J.I., Ugeda M.M., Ordejón P., Canadell E. Nano Letters; 19 (5): 3027 - 3032. 2019. 10.1021/acs.nanolett.9b00268. IF: 12.279

    Theory and Simulation

    Bulk and single-layer 2H-NbSe 2 exhibit identical charge density wave order (CDW) with a quasi-commensurate 3 × 3 superlattice periodicity. Here we combine scanning tunnelling microscopy (STM) imaging at T = 1 K of 2H-NbSe 2 with first-principles density functional theory (DFT) calculations to investigate the structural atomic rearrangement of this CDW phase. Our calculations for single-layers reveal that six different atomic structures are compatible with the 3 × 3 CDW distortion, although all of them lie on a very narrow energy range of at most 3 meV per formula unit, suggesting the coexistence of such structures. Our atomically resolved STM images of bulk 2H-NbSe 2 unambiguously confirm this by identifying two of these structures. Remarkably, these structures differ from the X-ray crystal structure reported for the bulk 3 × 3 CDW which in fact is also one of the six DFT structures located for the single-layer. Our calculations also show that due to the minute energy difference between the different phases, the ground state of the 3 × 3 CDW could be extremely sensitive to doping, external strain or internal pressure within the crystal. The presence of multiphase CDW order in 2H-NbSe 2 may provide further understanding of its low temperature state and the competition between different instabilities. © 2019 American Chemical Society.

  • Coherent generation and detection of acoustic phonons in topological nanocavities

    Arregui G., Ortíz O., Esmann M., Sotomayor-Torres C.M., Gomez-Carbonell C., Mauguin O., Perrin B., Lemaître A., García P.D., Lanzillotti-Kimura N.D. APL Photonics; 4 (3, 030805) 2019. 10.1063/1.5082728. IF: 4.383

    Phononic and Photonic Nanostructures

    Inspired by concepts developed for fermionic systems in the framework of condensed matter physics, topology and topological states are recently being explored also in bosonic systems. Recently, some of these concepts have been successfully applied to acoustic phonons in nanoscale multilayered systems. The reported demonstration of confined topological phononic modes was based on Raman scattering spectroscopy [M. Esmann et al., Phys. Rev. B 97, 155422 (2018)], yet the resolution did not suffice to determine lifetimes and to identify other acoustic modes in the system. Here, we use time-resolved pump-probe measurements using an asynchronous optical sampling (ASOPS) technique to overcome these resolution limitations. By means of one-dimensional GaAs/AlAs distributed Bragg reflectors (DBRs) used as building blocks, we engineer high frequency (∼200 GHz) topological acoustic interface states. We are able to clearly distinguish confined topological states from stationary band edge modes. The generation/detection scheme reflects the symmetry of the modes directly through the selection rules, evidencing the topological nature of the measured confined state. These experiments enable a new tool in the study of the more complex topology-driven phonon dynamics such as phonon nonlinearities and optomechanical systems with simultaneous confinement of light and sound. © 2019 Author(s).

  • Color-Tunable White-Light-Emitting Materials Based on Liquid-Filled Capsules and Thermally Responsive Dyes

    Vázquez-Mera N.A., Otaegui J.R., Sánchez R.S., Prats G., Guirado G., Ruiz-Molina D., Roscini C., Hernando J. ACS Applied Materials and Interfaces; 11 (19): 17751 - 17758. 2019. 10.1021/acsami.9b02169. IF: 8.456

    Nanostructured Functional Materials

    Color-tunable white-light-emitting materials are currently attracting much attention because of their potential applications in artificial lighting, sensing, and imaging. However, preparation of these systems from organic emitters is often cumbersome due to the interchromophoric interactions occurring upon solvent drying in the final solid materials, which can be hardly predicted and may lead to detrimental effects. To circumvent these obstacles, we have developed a new fabrication methodology that relies on dye encapsulation within liquid-filled capsules, thus enabling direct transfer of the luminescent properties from solution to the solid state and as such, rational design of miniaturized white-light-emitting materials. By introducing a thermally responsive chromophore into the capsules, these materials are further endowed with color tunability, which does not only allow ample modulation of the emitted color but also facilitate external fine control of the system so as to ensure precise realization of white light at the desired temperature and excitation wavelength. © 2019 American Chemical Society.

  • Combined High Catalytic Activity and Efficient Polar Tubular Nanostructure in Urchin-Like Metallic NiCo2Se4 for High-Performance Lithium–Sulfur Batteries

    Zhang C., Biendicho J.J., Zhang T., Du R., Li J., Yang X., Arbiol J., Zhou Y., Morante J.R., Cabot A. Advanced Functional Materials; 29 (34, 1903842) 2019. 10.1002/adfm.201903842. IF: 15.621

    Advanced Electron Nanoscopy

    Urchin-shaped NiCo2Se4 (u-NCSe) nanostructures as efficient sulfur hosts are synthesized to overcome the limitations of lithium–sulfur batteries (LSBs). u-NCSe provides a beneficial hollow structure to relieve volumetric expansion, a superior electrical conductivity to improve electron transfer, a high polarity to promote absorption of lithium polysulfides (LiPS), and outstanding electrocatalytic activity to accelerate LiPS conversion kinetics. Owing to these excellent qualities as cathode for LSBs, S@u-NCSe delivers outstanding initial capacities up to 1403 mAh g−1 at 0.1 C and retains 626 mAh g−1 at 5 C with exceptional rate performance. More significantly, a very low capacity decay rate of only 0.016% per cycle is obtained after 2000 cycles at 3 C. Even at high sulfur loading (3.2 mg cm−2), a reversible capacity of 557 mAh g−1 is delivered after 600 cycles at 1 C. Density functional theory calculations further confirm the strong interaction between NCSe and LiPS, and cytotoxicity measurements prove the biocompatibility of NCSe. This work not only demonstrates that transition metal selenides can be promising candidates as sulfur host materials, but also provides a strategy for the rational design and the development of LSBs with long-life and high-rate electrochemical performance. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Comparative study of electrical and rheological properties of different solutions used in endoscopic mucosal resection

    Bon I., Bartolí R., Cano-Sarabia M., de la Ossa N., de Vega V.M., Marín I., Boix J., Lorenzo-Zúñiga V. Digestive Endoscopy; 31 (3): 276 - 282. 2019. 10.1111/den.13297. IF: 3.640

    Supramolecular NanoChemistry and Materials

    Background and Aim: The study of electrical and rheological properties of solutions to carry out endoscopic resection procedures could determinate the best candidate. An ex vivo study with porcine stomachs was conducted to analyze electrical resistivity (R) and rheological properties (temperature, viscosity, height and lasting of the cushion) of different substances used in these techniques. Methods: Tested solutions were: 0.9% saline (S), platelet-rich plasma (PRP), Gliceol (GC), hyaluronic acid 2% (HA), Pluronic-F127 20% (PL), saline with 10% glucose (GS), Gelaspan (GP), Covergel-BiBio (TB) and PRP with TB (PRP+TB). Measurements of electrical and rheological properties were done at 0, 15, 30, 45 and 60 min after submucosal injection. Results: Solutions showed a wide variability of transepithelial R after submucosal injection. Substances able to maintain the highest R 60 min postinjection were TB (7 × 104 Ω), HA (7 × 104 Ω) and PL (7 × 104 Ω). Protective solutions against deep thermal injury (Tª lower than 60°C) were PL (47.6°C), TB (55°C) and HA (56.63°C). Shortest time to carry out resections were observed with GC (17.66″), PRP (20.3″) and GS (23.45″). Solutions with less cushion decrease (<25%) after 60 min were TB (11.74%), PL (18.63%) and PRP (22.12%). Conclusions: Covergel-BiBio, PL and HA were the best solutions with long-term protective effects (transepithelial R, lower thermal injury and less cushion decrease). Solutions with quicker resection time were GC, PRP and GS. © 2018 Japan Gastroenterological Endoscopy Society

  • Comparison of Insulin Determination on NiNPs/chitosan- MWCNTs and NiONPs/chitosan-MWCNTs Modified Pencil Graphite Electrode

    Šišoláková I., Hovancová J., Oriňaková R., Oriňak A., Rueda Garcia D., Shylenko O., Radoňák J. Electroanalysis; 31 (1): 103 - 112. 2019. 10.1002/elan.201800483. IF: 2.691

    Novel Energy-Oriented Materials

    The rising amount of patients suffering for diabetes mellitus increases the requirements for effective insulin sensors. Carbon materials are a suitable choice for the development of insulin sensors due to their electrochemical characteristics. Pencil graphite electrodes (PGE) represent the trade-off between price and excellent conductive properties. The modification of PGE by NiO and Ni nanoparticles fixed by chitosan results in surface area enlargement and improved electrocatalytic properties. This paper is focused on the comparison of different properties of Ni and NiO nanoparticles and their effect on redox reaction mechanism of insulin and detection characteristics. The electrode modified by Ni nanoparticles displays linear range of 1 μM–5 μM (R2 0.80), limit of detection (LOD) of 4.34 μM and sensitivity of 0.12 μA/μM. On the other hand, the electrode modified by NiO nanoparticles displays enhanced electrochemical characteristics such as linear range of 0.05 μM–5 μM (R2 0.99), limit of detection of 260 nM and sensitivity of 0.64 μA/μM. These properties make the NiO nanoparticles modified PGE the appropriate candidate for insulin determination. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Compositionally tuned Ni x Sn alloys as anode materials for lithium-ion and sodium-ion batteries with a high pseudocapacitive contribution

    Li J., Xu X., Luo Z., Zhang C., Yu X., Zuo Y., Zhang T., Tang P., Arbiol J., Llorca J., Liu J., Cabot A. Electrochimica Acta; 304: 246 - 254. 2019. 10.1016/j.electacta.2019.02.098. IF: 5.383

    Advanced Electron Nanoscopy

    Nickel tin alloy nanoparticles (NPs) with tuned composition Ni x Sn (0.6 ≤ x ≤ 1.9) were synthesized by a solution-based procedure and used as anode materials for Li-ion batteries (LIBs) and Na-ion batteries (SIBs). Among the compositions tested, Ni 0.9 Sn-based electrodes exhibited the best performance in both LIBs and SIBs. As LIB anodes, Ni 0.9 Sn-based electrodes delivered charge-discharge capacities of 980 mAh g −1 after 340 cycles at 0.2 A g −1 rate, which surpassed their maximum theoretical capacity considering that only Sn is lithiated. A kinetic characterization of the charge-discharge process demonstrated the electrode performance to be aided by a significant pseudocapacitive contribution that compensated for the loss of energy storage capacity associated to the solid-electrolyte interphase formation. This significant pseudocapacitive contribution, which not only translated into higher capacities but also longer durability, was associated to the small size of the crystal domains and the proper electrode composition. The performance of Ni x Sn-based electrodes toward Na-ion storage was also characterized, reaching significant capacities above 200 mAh g −1 at 0.1 A g −1 but with a relatively fast fade over 120 continuous cycles. A relatively larger pseudocapacitive contribution was obtained in Ni x Sn-based electrodes for SIBs when compared with LIBs, consistently with the lower contribution of the Na ion diffusion associated to its larger size. © 2019 Elsevier Ltd

  • Converse flexoelectricity yields large piezoresponse force microscopy signals in non-piezoelectric materials

    Abdollahi A., Domingo N., Arias I., Catalan G. Nature Communications; 10 (1, 1266) 2019. 10.1038/s41467-019-09266-y. IF: 11.878

    Oxide Nanophysics

    Converse flexoelectricity is a mechanical stress induced by an electric polarization gradient. It can appear in any material, irrespective of symmetry, whenever there is an inhomogeneous electric field distribution. This situation invariably happens in piezoresponse force microscopy (PFM), which is a technique whereby a voltage is delivered to the tip of an atomic force microscope in order to stimulate and probe piezoelectricity at the nanoscale. While PFM is the premier technique for studying ferroelectricity and piezoelectricity at the nanoscale, here we show, theoretically and experimentally, that large effective piezoelectric coefficients can be measured in non-piezoelectric dielectrics due to converse flexoelectricity. © 2019, The Author(s).

  • Co–Sn Nanocrystalline Solid Solutions as Anode Materials in Lithium-Ion Batteries with High Pseudocapacitive Contribution

    Li J., Xu X., Luo Z., Zhang C., Zuo Y., Zhang T., Tang P., Infante-Carrió M.F., Arbiol J., Llorca J., Liu J., Cabot A. ChemSusChem; 12 (7): 1451 - 1458. 2019. 10.1002/cssc.201802662. IF: 7.804

    Advanced Electron Nanoscopy

    Co–Sn solid-solution nanoparticles with Sn crystal structure and tuned metal ratios were synthesized by a facile one pot solution-based procedure involving the initial reduction of a Sn precursor followed by incorporation of Co within the Sn lattice. These nanoparticles were used as anode materials for Li-ion batteries. Among the different compositions tested, Co 0.7 Sn and Co 0.9 Sn electrodes provided the highest capacities with values above 1500 mAh g −1 at a current density of 0.2 A g −1 after 220 cycles, and up to 800 mAh g −1 at 1.0 A g −1 after 400 cycles. Up to 81 % pseudocapacitance contribution was measured for these electrodes at a sweep rate of 1.0 mV s −1 , thereby indicating fast kinetics and long durability. The excellent performance of Co–Sn nanoparticle alloy-based electrodes was attributed to both the small size of the crystal domains and their suitable composition, which buffered volume changes of Sn and contributed to a suitable electrode restructuration. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Cr2Te3 Thin Films for Integration in Magnetic Topological Insulator Heterostructures

    Burn D.M., Duffy L.B., Fujita R., Zhang S.L., Figueroa A.I., Herrero-Martin J., van der Laan G., Hesjedal T. Scientific Reports; 9 (1, 10793) 2019. 10.1038/s41598-019-47265-7. IF: 4.011

    Physics and Engineering of Nanodevices

    Chromium telluride compounds are promising ferromagnets for proximity coupling to magnetic topological insulators (MTIs) of the Cr-doped (Bi,Sb)2(Se,Te)3 class of materials as they share the same elements, thus simplifying thin film growth, as well as due to their compatible crystal structure. Recently, it has been demonstrated that high quality (001)-oriented Cr2Te3 thin films with perpendicular magnetic anisotropy can be grown on c-plane sapphire substrate. Here, we present a magnetic and soft x-ray absorption spectroscopy study of the chemical and magnetic properties of Cr2Te3 thin films. X-ray magnetic circular dichroism (XMCD) measured at the Cr L2,3 edges gives information about the local electronic and magnetic structure of the Cr ions. We further demonstrate the overgrowth of Cr2Te3 (001) thin films by high-quality Cr-doped Sb2Te3 films. The magnetic properties of the layers have been characterized and our results provide a starting point for refining the physical models of the complex magnetic ordering in Cr2Te3 thin films, and their integration into advanced MTI heterostructures for quantum device applications. © 2019, The Author(s).

  • Critical Role of Phenyl Substitution and Catalytic Substrate in the Surface-Assisted Polymerization of Dibromobianthracene Derivatives

    Moreno C., Panighel M., Vilas-Varela M., Sauthier G., Tenorio M., Ceballos G., Peña D., Mugarza A. Chemistry of Materials; 31 (2): 331 - 341. 2019. 10.1021/acs.chemmater.8b03094. IF: 10.159

    Research Support Division | Atomic Manipulation and Spectroscopy

    Understanding the nature and hierarchy of on-surface reactions is a major challenge for designing coordination and covalent nanostructures by means of multistep synthetic routes. In particular, intermediates and final products are hard to predict since the reaction paths and their activation windows depend on the choice of both the molecular precursor design and the substrate. Here, we report a systematic study of the effect of the catalytic metal surface to reveal how a single precursor can give rise to very distinct polymers that range from coordination and covalent nonplanar polymer chains of distinct chirality to atomically precise graphene nanoribbons and nanoporous graphene. Our precursor consists on adding two phenyl substituents to 10,10′-dibromo-9,9′-bianthracene, a well-studied precursor in the on-surface synthesis of graphene nanoribbons. The critical role of the monomer design in the reaction paths is inferred from the fact that the phenyl substitution leads to very distinct products in each one of the studied metallic substrates. © 2018 American Chemical Society.

  • Crossover from ballistic to diffusive thermal transport in suspended graphene membranes

    El Sachat A., Köenemann F., Menges F., Del Corro E., Garrido J.A., Sotomayor Torres C.M., Alzina F., Gotsmann B. 2D Materials; 6 (2, 025034) 2019. 10.1088/2053-1583/ab097d. IF: 7.343

    Phononic and Photonic Nanostructures | Advanced Electronic Materials and Devices

    We report heat transport measurements on suspended single-layer graphene disks with radius of 150-1600 nm using a high-vacuum scanning thermal microscope. The results of this study revealed a radius-dependent thermal contact resistance between tip and graphene, with values between 1.15 and 1.52 × 108 KW-1. The observed scaling of thermal resistance with radius is interpreted in terms of ballistic phonon transport in suspended graphene discs with radius smaller than 775 nm. In larger suspended graphene discs (radius >775 nm), the thermal resistance increases with radius, which is attributed to in-plane heat transport being limited by phonon-phonon resistive scattering processes, which resulted in a transition from ballistic to diffusive thermal transport. In addition, by simultaneously mapping topography and steady-state heat flux signals between a self-heated scanning probe sensor and graphene with 17 nm thermal spatial resolution, we demonstrated that the surface quality of the suspended graphene and its connectivity with the Si/SiO2 substrate play a determining role in thermal transport. Our approach allows the investigation of heat transport in suspended graphene at sub-micrometre length scales and overcomes major limitations of conventional experimental methods usually caused by extrinsic thermal contact resistances, assumptions on the value of the graphene's optical absorbance and limited thermal spatial resolution. © 2019 IOP Publishing Ltd.

  • Delamination of 2D coordination polymers: The role of solvent and ultrasound

    Contreras-Pereda N., Hayati P., Suárez-García S., Esrafili L., Retailleau P., Benmansour S., Novio F., Morsali A., Ruiz-Molina D. Ultrasonics Sonochemistry; 55: 186 - 195. 2019. 10.1016/j.ultsonch.2019.02.014. IF: 7.279

    Nanostructured Functional Materials

    Two novel cadmium-based 2D coordination polymers have been synthesized and characterized. Experimental results evidence that the best delamination processes occurs when weak interactions dominate the cohesion between layers and solvent molecules are occluded within the crystalline network. In this case, the delamination of the crystals occurs spontaneously in water. On top of that, and thanks to the high stability of the resulting (flake) colloidal dispersions, we have completed a detailed study of the sonication assisted delamination impact by: I) comparison of two different sonication approaches (bath vs. tip sonication) and II) optimization of final flake morphology and yield by controlling solvent and sonication time. Our results definitely pave the way for the fabrication and implementation of 2D coordination polymers using ultrasound. © 2019 Elsevier B.V.

  • Design strategies for shape-controlled magnetic iron oxide nanoparticles

    Roca A.G., Gutiérrez L., Gavilán H., Fortes Brollo M.E., Veintemillas-Verdaguer S., Morales M.D.P. Advanced Drug Delivery Reviews; 138: 68 - 104. 2019. 10.1016/j.addr.2018.12.008. IF: 15.519

    Magnetic Nanostructures

    Ferrimagnetic iron oxide nanoparticles (magnetite or maghemite) have been the subject of an intense research, not only for fundamental research but also for their potentiality in a widespread number of practical applications. Most of these studies were focused on nanoparticles with spherical morphology but recently there is an emerging interest on anisometric nanoparticles. This review is focused on the synthesis routes for the production of uniform anisometric magnetite/maghemite nanoparticles with different morphologies like cubes, rods, disks, flowers and many others, such as hollow spheres, worms, stars or tetrapods. We critically analyzed those procedures, detected the key parameters governing the production of these nanoparticles with particular emphasis in the role of the ligands in the final nanoparticle morphology. The main structural and magnetic features as well as the nanotoxicity as a function of the nanoparticle morphology are also described. Finally, the impact of each morphology on the different biomedical applications (hyperthermia, magnetic resonance imaging and drug delivery) are analysed in detail. We would like to dedicate this work to Professor Carlos J. Serna, Instituto de Ciencia de Materiales de Madrid, ICMM/CSIC, for his outstanding contribution in the field of monodispersed colloids and iron oxide nanoparticles. We would like to express our gratitude for all these years of support and inspiration on the occasion of his retirement. © 2018 Elsevier B.V.

  • Detection of resistance protein A (MxA) in paper-based immunoassays with surface enhanced Raman spectroscopy with AuAg nanoshells

    Russo L., Sánchez-Purrà M., Rodriguez-Quijada C., Leonardo B.M., Puntes V., Hamad-Schifferli K. Nanoscale; 11 (22): 10819 - 10827. 2019. 10.1039/c9nr02397f. IF: 6.970

    Inorganic Nanoparticles

    Myxovirus protein A (MxA) is a biomarker that can be used to distinguish between viral and bacterial infections. While MxA lateral flow assays (LFAs) have been successfully used for viral vs. bacterial differential diagnosis for children, the clinically relevant level of MxA for adults has been reported to be 100 times lower, which is too low for traditional LFAs. We present results applying the use of surface enhanced Raman spectroscopy (SERS) to detect MxA. AuAg nanoshells (AuAg NSs) were used to enhance the Raman signal of mercaptobenzoic acid (4-MBA), enabling readout by SERS. The AuAg NSs were conjugated to antibodies for the biomarker of interest, resulting in a "nanotag", that could be used in a dipstick immunoassay for detection. We first optimized the nanotag parameters using anti-human IgG/human IgG as a model antibody/antigen system, and then demonstrated detection of MxA using anti-MxA antibodies. We show that SERS readout of immunoassays for MxA can quantify MxA levels at clinically relevant levels for adult viral infection. © 2019 The Royal Society of Chemistry.

  • Development of low-melting point molten salts and detection of solid-to-liquid transitions by alternative techniques to DSC

    Rodríguez-Laguna M.D.R., Gómez-Romero P., Sotomayor Torres C.M., Lu M.-C., Chávez-Ángel E. Solar Energy Materials and Solar Cells; 202 (110107) 2019. 10.1016/j.solmat.2019.110107. IF: 6.019

    Phononic and Photonic Nanostructures | Novel Energy-Oriented Materials

    The ‘Solar salt’ (60% NaNO3-40% KNO3, wt. %) is the most used heat transfer and storage material in high temperature CSP systems. The main drawback is its high melting temperature of 228 °C, which requires extra-energy to keep it in the liquid state and avoid damage to pipes at low temperatures. Multi-component salts are combinations of different cations and anions. The difference in size of the ions hinders the crystallization of the material and provides lower melting temperatures. Multi-component salts are considered in this study to replace simpler combinations, such as binary and ternary eutectic mixtures. Herein, we report on two novel six-component nitrates with a melting temperature of 60–75 °C and a thermal stability up to ~500 °C under a linear heating program in N2 atmosphere. Properties such as the thermal conductivity in solid and molten state, heat capacity and vibrational spectra were evaluated. The study of the thermal behaviour of these materials using differential scanning calorimetry was insufficient, hence alternative and complementary techniques were used, such as: the three-omega technique, optical transmission and Raman spectroscopy. Multi-component salts were found to solidify as amorphous solids even at slow cooling rates and water was found to behave as a catalyst of crystallization. © 2019 Elsevier B.V.

  • Disposable Sensors in Diagnostics, Food, and Environmental Monitoring

    Dincer C., Bruch R., Costa-Rama E., Fernández-Abedul M.T., Merkoçi A., Manz A., Urban G.A., Güder F. Advanced Materials; 31 (30, 1806739) 2019. 10.1002/adma.201806739. IF: 25.809

    Nanobioelectronics and Biosensors

    Disposable sensors are low-cost and easy-to-use sensing devices intended for short-term or rapid single-point measurements. The growing demand for fast, accessible, and reliable information in a vastly connected world makes disposable sensors increasingly important. The areas of application for such devices are numerous, ranging from pharmaceutical, agricultural, environmental, forensic, and food sciences to wearables and clinical diagnostics, especially in resource-limited settings. The capabilities of disposable sensors can extend beyond measuring traditional physical quantities (for example, temperature or pressure); they can provide critical chemical and biological information (chemo- and biosensors) that can be digitized and made available to users and centralized/decentralized facilities for data storage, remotely. These features could pave the way for new classes of low-cost systems for health, food, and environmental monitoring that can democratize sensing across the globe. Here, a brief insight into the materials and basics of sensors (methods of transduction, molecular recognition, and amplification) is provided followed by a comprehensive and critical overview of the disposable sensors currently used for medical diagnostics, food, and environmental analysis. Finally, views on how the field of disposable sensing devices will continue its evolution are discussed, including the future trends, challenges, and opportunities. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Diverse structural assemblies and influence in morphology of different parameters in a series of 0D and 1D mercury(II) metal–organic coordination complexes by sonochemical process

    Mohammadi M.K., Gutiérrez A., Hayati P., Mohammadi K., Rezaei R. Polyhedron; 160: 20 - 34. 2019. 10.1016/j.poly.2018.12.016. IF: 2.284

    Four new mercury coordination supramolecular complexes (1D and 0D), [Hg(L)(Br)2]n (1), [Hg(L)(Cl)2]n (2), [Hg(L)(SCN)2]n (3) and [Hg2(L)2(I)4] (4) where L = C6H8N2 (3-picolylamine), have been synthesized under different experimental conditions. Micrometric crystals (bulk) or nano-sized materials have been obtained depending on using the branch tube method or sonochemical irradiation. All materials have been characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD) and FT-IR spectroscopy. Single crystal X-ray analyses on complexes 1–4 show that Hg2+ ions are 4, 5, 4 and 4-coordinated, respectively. Topological analysis shows that the complexes 1–4 are 2C1, 2,2,4C1, 2C1 and 1,2,4M16-1 net, respectively. Also, by changing counter ions, various structures were obtained: 1–4 (0D and 1D) which are helical chain, linear chain and rectangular molecule. The role of different parameters like temperature, reaction time, power of ultrasound irradiation and concentration of initial reactants on the growth and morphology of the micro-nano structures are studied. © 2018 Elsevier Ltd

  • Early sepsis diagnosis via protein and miRNA biomarkers using a novel point-of-care photonic biosensor

    Fabri-Faja N., Calvo-Lozano O., Dey P., Terborg R.A., Estevez M.-C., Belushkin A., Yesilköy F., Duempelmann L., Altug H., Pruneri V., Lechuga L.M. Analytica Chimica Acta; 1077: 232 - 242. 2019. 10.1016/j.aca.2019.05.038. IF: 5.256

    NanoBiosensors and Bioanalytical Applications

    Sepsis is a condition characterized by a severe stage of blood-infection often leading to tissue damage, organ failure and finally death. Fast diagnosis and identification of the sepsis stage (sepsis, severe sepsis or septic shock) is critical for the patient's evolution and could help in defining the most adequate treatment in order to reduce its mortality. The combined detection of several biomarkers in a timely, specific and simultaneous way could ensure a more accurate diagnosis. We have designed a new optical point-of-care (POC) device based on a phase-sensitive interferometric biosensor with a label-free microarray configuration for potential high-throughput evaluation of specific sepsis biomarkers. The sensor chip, which relies on the use of metallic nanostructures, provides versatility in terms of biofunctionalization, allowing the efficient immobilization of different kind of receptors such as antibodies or oligonucleotides. We have focused on two structurally different types of biomarkers: proteins, including C-reactive protein (CRP) and Interleukin 6 (IL6), and miRNAs, using miRNA-16 as an example. Limits of Detection (LoD) of 18 μg mL−1, 88 μg mL−1 and 1 μM (6 μg mL−1) have been respectively obtained for CRP, IL6 and miRNA-16 in individual assays, with high accuracy and reproducibility. The multiplexing capabilities have also been assessed with the simultaneous analysis of both protein biomarkers. © 2019 Elsevier B.V.

  • Effect of the Molecular Polarizability of SAMs on the Work Function Modification of Gold: Closed- versus Open-Shell Donor–Acceptor SAMs

    Diez-Cabanes V., Morales D.C., Souto M., Paradinas M., Delchiaro F., Painelli A., Ocal C., Cornil D., Cornil J., Veciana J., Ratera I. Advanced Materials Technologies; 4 (5, 1800152) 2019. 10.1002/admt.201800152. IF: 5.395

    Atomic Manipulation and Spectroscopy

    Charge injection barriers at metal/organic interfaces can be tuned by modifying the work function of metallic electrodes using self-assembled monolayers (SAMs) of polar molecules. An interesting example of polar molecules is offered by donor–acceptor (D–A) dyads based on ferrocene (Fc) as electron-donor unit and either a polychlorotriphenylmethyl radical or a polychlorotriphenylmethane as electron-acceptor units, connected by a π-conjugated vinylene bridge. The D–A radical exhibits high chemical and thermal stability and presents different electronic, optical, and magnetic properties with respect to the closed-shell form. The magnitude of the shift in the charge injection barriers for these two D–A systems is estimated by means of surface potential measurements performed by Kelvin probe force microscopy. The experimental data are compared with density functional theory calculations, which evidence the importance of the molecular dipole moments and polarizabilities to understand the experimental values. In order to achieve high work function shifts of metals upon SAM formation, the molecules forming the SAM have to exhibit both a high permanent dipole moment and a low polarizability along the direction normal to the substrate. In presence of polarizable molecules, the work function shifts can be enhanced by reducing the intermolecular interactions; by using mixed SAMs with active molecules embedded into a passive matrix. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Electrochemical detection of plant virus using gold nanoparticle-modified electrodes

    Khater M., de la Escosura-Muñiz A., Quesada-González D., Merkoçi A. Analytica Chimica Acta; 1046: 123 - 131. 2019. 10.1016/j.aca.2018.09.031. IF: 5.256

    Nanobioelectronics and Biosensors

    Tristeza is one of the destructive diseases of citrus causing by citrus tristeza virus (CTV). Historically, CTV has been associated with serious outbreaks of quick decline of citrus, therefore CTV monitoring is important aspect for avoiding such re-emerging epidemics, which would threat citrus production through the world. In this context, we have designed for the first time a label-free impedimetric biosensor for the detection of nucleic acid of CTV. The sensing platform based on a screen-printed carbon electrode (SPCE) was modified by electrodeposited gold nanoparticles (AuNPs), which allowed to efficiently immobilizing thiolated ssDNA probes as well to enhance the electrode conductivity. The growth of AuNPs was optimized and characterized using scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). We investigated the behavior of thiolated ssDNA probe layer and its hybridization with target DNA onto AuNP surfaces by EIS measurements in Fe(CN 6 ) 4- /Fe(CN 6 ) 3- red-ox system. The main sensor design aspects such as AuNPs size, probe DNA concentration and immobilization time together with DNA hybridization time were optimized so as to achieve the best performance. Impedance values of DNA hybridization increased with Citrus tristeza-related synthetic DNA concentration, showing a logarithmic relation in the range of 0.1–10 μM. The results also indicate that the biosensor was able to selectively detect CTV nucleic acids in the presence of other non-specific DNAs. Moreover, we have demonstrated the good performance of the system in a real plant sample matrix. In addition, the sensor reproducibility enhanced after the hybridization onto MCH/poly (AT) thiolated DNA probes which was confirmed by intra- and inter-day variability assays. © 2018 Elsevier B.V.

  • Enhanced thermoelectric properties of lightly Nb doped SrTiO3 thin films

    Bhansali S., Khunsin W., Chatterjee A., Santiso J., Abad B., Martin-Gonzalez M., Jakob G., Sotomayor Torres C.M., Chávez-Angel E. Nanoscale Advances; 1 (9): 3647 - 3653. 2019. 10.1039/c9na00361d.

    Phononic and Photonic Nanostructures | Nanomaterials Growth Unit

    Novel thermoelectric materials developed for operation at room temperature must have similar or better performance along with being as ecofriendly as those commercially used, e.g., Bi2Te3, in terms of their toxicity and cost. In this work, we present an in-depth study of the thermoelectric properties of epitaxial Nb-doped strontium titanate (SrTi1-xNbxO3) thin films as a function of (i) doping concentration, (ii) film thickness and (iii) substrate type. The excellent crystal quality was confirmed by high resolution transmission electron microscopy and X-ray diffraction analysis. The thermoelectric properties were measured by the three-omega method (thermal conductivity) and van der Pauw method (electrical resistivity), complemented by Seebeck coefficient measurements. A maximum power factor of 8.9 × 10-3 W m-1 K-2 and a thermoelectric figure of merit of 0.49 were measured at room temperature in 50 nm-thick films grown on lanthanum strontium aluminate. The mechanisms behind this high figure of merit are discussed in terms of a possible two-dimensional electron gas, increase of the effective mass of the electrons, electron filtering and change in strain due to different substrates. The overall enhancement of the thermoelectric properties suggests that SrTi1-xNbxO3 is a very promising n-type candidate for room- to high-temperature applications. © 2019 The Royal Society of Chemistry.

  • Enhancing the intrinsic p-type conductivity of the ultra-wide bandgap Ga2O3 semiconductor

    Chikoidze E., Sartel C., Mohamed H., Madaci I., Tchelidze T., Modreanu M., Vales-Castro P., Rubio C., Arnold C., Sallet V., Dumont Y., Perez-Tomas A. Journal of Materials Chemistry C; 7 (33): 10231 - 10239. 2019. 10.1039/c9tc02910a. IF: 6.641

    Oxide Nanophysics

    While there are several n-type transparent semiconductor oxides (TSO) for optoelectronic applications (e.g. LEDs, solar cells or display TFTs), their required p-type counterpart oxides are known to be more challenging. At this time, the n-type TSO with the largest bandgap (∼5 eV) is Ga2O3 that holds the promise of extending the light transparency further into the deep ultraviolet. In this work, it is demonstrated that strongly compensated Ga2O3 is also an intrinsic (or native) p-type TSO with the largest bandgap for any reported p-type TSO (e.g. NiO, SnO, delafossites, oxychalcogenides). The achievement of hole mobility in excess of 10 cm2 V-1 s-1 and (high temperature) free hole concentrations in the ∼1017 cm-3 range challenges the current thinking about achieving p-type conductivity in Ga2O3 being "out of the question". The results presented in this paper therefore further clarify that p-type Ga2O3 is possible, although more research must be conducted to determine what are the real prospects for Ga2O3 solar blind bipolar optoelectronics and ultra-high power electronics based on p-n homojunctions. © The Royal Society of Chemistry 2019.

  • Epitaxial graphene/silicon carbide intercalation: A minireview on graphene modulation and unique 2D materials

    Briggs N., Gebeyehu Z.M., Vera A., Zhao T., Wang K., De La Fuente Duran A., Bersch B., Bowen T., Knappenberger K.L., Robinson J.A. Nanoscale; 11 (33): 15440 - 15447. 2019. 10.1039/c9nr03721g. IF: 6.970

    Physics and Engineering of Nanodevices

    Intercalation of atomic species through epitaxial graphene on silicon carbide began only a few years following its initial report in 2004. The impact of intercalation on the electronic properties of the graphene is well known; however, the intercalant itself can also exhibit intriguing properties not found in nature. This realization has inspired new interest in epitaxial graphene/silicon carbide (EG/SiC) intercalation, where the scope of the technique extends beyond modulation of graphene properties to the creation of new 2D forms of 3D materials. The mission of this minireview is to provide a concise introduction to EG/SiC intercalation and to demonstrate a simplified approach to EG/SiC intercalation. We summarize the primary techniques used to achieve and characterize EG/SiC intercalation, and show that thermal evaporation-based methods can effectively substitute for more complex synthesis techniques, enabling large-scale intercalation of non-refractory metals and compounds including two-dimensional silver (2D-Ag) and gallium nitride (2D-GaNx). © The Royal Society of Chemistry.

  • Evidence for the weak coupling scenario of the Peierls transition in the blue bronze

    Guster B., Pruneda M., Ordejón P., Canadell E., Pouget J.-P. Physical Review Materials; 3 (5, 055001) 2019. 10.1103/PhysRevMaterials.3.055001. IF: 2.926

    Theory and Simulation

    On the basis of first-principles DFT calculations the wave-vector and temperature dependencies of the Lindhard response function of the blue bronze K0.3MoO3 have been calculated. The kFI+kFII interband component of the response, which is responsible for the Peierls instability, has been quantitatively analyzed. It is found that (i) the electron-hole coherence length of this response determines the length scale of the experimental intrachain CDW correlations, and (ii) the intrachain q⥠dependence of such a response also determines the shape of the Kohn anomaly experimentally measured. These findings provide compelling evidence that the Peierls transition of the blue bronze K0.3MoO3 follows the weak electron-phonon coupling scenario in the adiabatic approximation, something that had not yet been proved on the basis of first-principles calculations for a real material. It is proposed that the CDW interchain coupling occurs through a Coulomb coupling between dipolar CDWs. The nature of the phonon mode leading to the dipolar nature of the CDWs is also discussed, and the relevance of these results to rationalize the CDW instabilities in other oxides and bronzes is pointed out. These findings are also contrasted with recent results for other CDW materials like chalcogenides and tellurides. © 2019 American Physical Society.

  • Exploring the impact of core expansion on the vortex distribution in superconducting-normal-metal hybrid nanostructures

    Panghotra R., Timmermans M., Xue C., Raes B., Moshchalkov V., Van De Vondel J. Physical Review B; 100 (5, 054519) 2019. 10.1103/PhysRevB.100.054519. IF: 3.736

    The superconducting condensate in a bilayer normal-metal-superconducting film has a nonuniform dependence throughout the layer. For sufficiently thin normal metallic films, the superconducting correlations induced by the contacting superconducting layer result in the formation of a minigap and the characteristic length scales governing the response of the condensate will be different. In this work we use scanning tunneling spectroscopy to visualize the vortex states as a function of the applied magnetic field in a Au-MoGe nanostructure. By comparing the obtained zero-bias conductance maps with time-dependent Ginzburg-Landau simulations, we directly confirm that the observed vortex distributions can only be explained by taking into account the impact of the normal metallic layer. We illustrate this impact on the vortex state for two lithographically fabricated mesoscopic bilayer structures containing an identical antidot array but having different lateral sizes. © 2019 American Physical Society.

  • Fast and Sensitive Terahertz Detection Using an Antenna-Integrated Graphene pn Junction

    Castilla S., Terrés B., Autore M., Viti L., Li J., Nikitin A.Y., Vangelidis I., Watanabe K., Taniguchi T., Lidorikis E., Vitiello M.S., Hillenbrand R., Tielrooij K.-J., Koppens F.H.L. Nano Letters; 19 (5): 2765 - 2773. 2019. 10.1021/acs.nanolett.8b04171. IF: 12.279

    Ultrafast Dynamics in Nanoscale Systems

    Although the detection of light at terahertz (THz) frequencies is important for a large range of applications, current detectors typically have several disadvantages in terms of sensitivity, speed, operating temperature, and spectral range. Here, we use graphene as a photoactive material to overcome all of these limitations in one device. We introduce a novel detector for terahertz radiation that exploits the photothermoelectric (PTE) effect, based on a design that employs a dual-gated, dipolar antenna with a gap of ?100 nm. This narrow-gap antenna simultaneously creates a pn junction in a graphene channel located above the antenna and strongly concentrates the incoming radiation at this pn junction, where the photoresponse is created. We demonstrate that this novel detector has an excellent sensitivity, with a noise-equivalent power of 80 pW/Hz at room temperature, a response time below 30 ns (setup-limited), a high dynamic range (linear power dependence over more than 3 orders of magnitude) and broadband operation (measured range 1.8-4.2 THz, antenna-limited), which fulfills a combination that is currently missing in the state-of-the-art detectors. Importantly, on the basis of the agreement we obtained between experiment, analytical model, and numerical simulations, we have reached a solid understanding of how the PTE effect gives rise to a THz-induced photoresponse, which is very valuable for further detector optimization. © 2019 American Chemical Society.

  • Flexoelectric Fracture-Ratchet Effect in Ferroelectrics

    Cordero-Edwards K., Kianirad H., Canalias C., Sort J., Catalan G. Physical Review Letters; 122 (13, 135502) 2019. 10.1103/PhysRevLett.122.135502. IF: 9.227

    Oxide Nanophysics

    The propagation front of a crack generates large strain gradients and it is therefore a strong source of gradient-induced polarization (flexoelectricity). Herein, we demonstrate that, in piezoelectric materials, a consequence of flexoelectricity is that crack propagation is helped or hindered depending on whether it is parallel or antiparallel to the piezoelectric polar axis. The discovery of crack propagation asymmetry proves that fracture physics cannot be assumed to be symmetric in polar materials, and indicates that flexoelectricity should be incorporated in any realistic model. © 2019 American Physical Society.

  • From rational design of a new bimetallic MOF family with tunable linkers to OER catalysts

    Zhang X., Luo J., Wan K., Plessers D., Sels B., Song J., Chen L., Zhang T., Tang P., Morante J.R., Arbiol J., Fransaer J. Journal of Materials Chemistry A; 7 (4): 1616 - 1628. 2019. 10.1039/c8ta08508k. IF: 10.733

    Advanced Electron Nanoscopy

    Innovative bimetallic MOFs offer more possibilities to further tailor the properties of MOFs, which have attracted great attention for wide applications. However, it is still a great challenge to rationally design bimetallic MOFs due to the lack of a tunable and reasonable hybrid structure architecture. Herein, a new series of bimetallic metal-organic frameworks (MOFs) with tunable pillar linkers were prepared by a one-step synthesis method. These bimetallic MOFs retain the same crystal structure when the mole fraction (based on metal) of the two metals changes from 0 to 1 and both metal ions occupy random nodal positions. The incorporation of a second metal cation has a large influence on the intrinsic properties (e.g. thermal stabilities and band gaps) of the MOFs. Furthermore, these bimetallic MOFs were used as self-sacrificial templates to prepare bimetal oxide catalysts for the oxygen evolution reaction (OER). After pyrolysis, a porous and hierarchical honeycomb-like structure with carbon network covered (bi)metal oxides is formed. Among all the bimetallic MOF-derived catalysts, CoNi1@C showed the best performance for the OER with the lowest Tafel slopes (55.6 mV dec -1 ) and overpotentials (335 mV on a glassy carbon electrode and 276 mV on Ni foam) at a current density of 10 mA cm -2 , which is higher than those of state-of-the-art Co-Ni mixed oxide catalysts derived from MOFs for the OER. Our results indicate that the incorporation of a second metal ion is a promising strategy to tailor the properties of MOFs. More importantly, this new bimetallic MOF family with tunable linkers is expected to serve as a flexible assembly platform to offer broad possibilities for practical applications of MOFs. © 2019 The Royal Society of Chemistry.

  • Full integration of photonic nanoimmunosensors in portable platforms for on-line monitoring of ocean pollutants

    Fernández-Gavela A., Herranz S., Chocarro B., Falke F., Schreuder E., Leeuwis H., Heideman R.G., Lechuga L.M. Sensors and Actuators, B: Chemical; 297 (126758) 2019. 10.1016/j.snb.2019.126758. IF: 6.393

    NanoBiosensors and Bioanalytical Applications

    We have developed a photonic nano-immunosensor platform for the on-site analysis of harmful organic ocean pollutants, intended to be allocated in stand-alone buoys. The main aim is bringing the monitoring tools directly to the contaminated place, resulting in cost and time savings as compared to the standard analytical techniques. As sensor we have employed an integrated asymmetric Mach-Zehnder interferometer (aMZI) of micro/nano dimensions, based on silicon photonic technology. In order to obtain a multiplexed system, a four-channel microfluidic cell has been designed, manufactured and incorporated in the miniaturized sensor. Additionally, a microfluidic delivery module enabling automatic sample analysis has been designed, evaluated and assembled. Moreover, we have implemented the optical interconnections of the sensor chip by fiber optics, as well the electronics and the required software and data processing. Pollutant detection is based on a competitive immunoassay using bioreceptors previously biofunctionalized on the aMZI sensor arms and incubation with a specific antibody. As proof of concept, two types of pollutants have been analysed: the biocide Irgarol 1051, and the antibiotic Tetracycline. Results show limits of detection in the range of few ng/mL, accomplished the European legislation. © 2019 Elsevier B.V.

  • Fully printed one-step biosensing device using graphene/AuNPs composite

    Nagar B., Balsells M., de la Escosura-Muñiz A., Gomez-Romero P., Merkoçi A. Biosensors and Bioelectronics; 129: 238 - 244. 2019. 10.1016/j.bios.2018.09.073. IF: 9.518

    Novel Energy-Oriented Materials | Nanobioelectronics and Biosensors

    Driven by the growing need of simple, cost efficient and flexible sensing systems, we have designed here a fully printed Reduced Graphene Oxide (rGO) based impedimetric sensor for one step sensing of DNA. The DNA sensor was fabricated by stamping of layered rGO and rGO/gold nanoparticles/single stranded DNA (rGO/AuNPs/ssDNA) composites over PET substrates using wax-printing technique. rGO works as an excellent working electrode, while the AuNPs create a suitable environment for ssDNA immobilization. Counter and reference electrodes were previously screen-printed on the plastic substrate, making thus a compact and highly integrated sensing platform. The change in electron transfer resistance after hybridization with a target ssDNA specific of Coxsackie B3 virus was monitored using electrochemical impedance spectroscopy (EIS), finding a linear response in the range of concentrations 0.01–20 µM. The novel, simple and straightforward one-step printing process for fabrication of a biosensing device developed keeps in mind the growing need of large scale device manufacturing. The successful proof-of-concept for the detection of DNA hybridization can be extended to other affinity biosensors, taking advantage of the integration of the bioreceptor on the sensor surface. Such ready-to-use biosensor would lead to a one-step electrochemical detection. © 2018 Elsevier B.V.

  • Functional Oxides for Photoneuromorphic Engineering: Toward a Solar Brain

    Pérez-Tomás A. Advanced Materials Interfaces; 6 (15, 1900471) 2019. 10.1002/admi.201900471. IF: 4.713

    Oxide Nanophysics

    New device concepts and new computing principles are needed to balance our ever-growing appetite for data and information with the realization of the goals of increased energy efficiency, reduction in CO2 emissions, and the circular economy. Neuromorphic or synaptic electronics is an emerging field of research aiming to overcome the current computer's Von-Neumann bottleneck by building artificial neuronal systems to mimic the extremely energy efficient biological synapses. The introduction of photovoltaic and/or photonic aspects into these neuromorphic architectures will produce self-powered adaptive electronics but may also open new possibilities in artificial neuroscience, artificial neural communications, sensing, and machine learning which would enable, in turn, a new era for computational systems owing to the possibility of attaining high bandwidths with much reduced power consumption. This perspective is focused on recent progress in the implementation of functional oxide thin-films into photovoltaic and neuromorphic applications toward the envisioned goal of self-powered photovoltaic neuromorphic systems or a solar brain. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Functionalized cerium oxide nanoparticles mitigate the oxidative stress and proinflammatory activity associated to the portal vein endothelium of cirrhotic rats

    Ribera J., Rodríguez-Vita J., Cordoba B., Portolés I., Casals G., Casals E., Jiménez W., Puntes V., Ruiz M.M. PLoS ONE; 14 (6, e0218716) 2019. 10.1371/journal.pone.0218716. IF: 2.776

    Inorganic Nanoparticles

    Background and aims The occurrence of endothelial alterations in the liver and in the splanchnic vasculature of cirrhotic patients and experimental models of liver diseases has been demonstrated. However, the pathological role of the portal vein endothelium in this clinical context is scarcely studied and, therefore, deserves attention. In this context, we aimed to investigate whether pathological endothelial activation occurs in the portal vein of cirrhotic rats. Methods Cirrhosis was induced in wistar rats by CCl4 inhalation. We generated immortalized endothelial cells from the portal vein of control (CT-iPVEC) and cirrhotic rats (CH-iPVEC) by retroviral transduction of the SV40 T antigen. We assessed differential gene expression and intracellular reactive oxygen species (ROS) levels in iPVECs and in portal veins of control and cirrhotic rats. Finally, we assessed the therapeutic effectiveness of cerium oxide nanoparticles (CeO2NP) on reversing PVEC activation and macrophage polarization. Results CH-iPVECs overexpressed collagen-I, endothelin-1, TIMP-1, TIMP-2, IL-6 and PlGF genes. These results were consistent with the differential expression showed by whole portal veins from cirrhotic rats. In addition, CH-iPVECs showed a significant increase in intracellular ROS and the capacity of potentiating M1 polarization in macrophages. The treatment of CH-iPVECs with CeO2NPs blocked intracellular ROS formation and IL-6 and TIMP-2 gene overexpression. In agreement with the in vitro results, the chronic treatment of cirrhotic rats with CeO2NPs also resulted in the blockade of both ROS formation and IL-6 gene overexpression in whole portal veins. Conclusions Endothelial cells from portal vein of cirrhotic rats depicted an abnormal phenotype characterized by a differential gene expression and the induction of M1 polarization in macrophages. We identified the excess of intracellular reactive oxygen species (ROS) as a major contributor to this altered phenotype. In addition, we demonstrated the utility of the nanomaterial cerium oxide as an effective antioxidant capable of reverse some of these pathological features associated with the portal vein in the cirrhosis condition. © 2019 Ribera et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

  • Gate electrostatics and quantum capacitance in ballistic graphene devices

    Caridad J.M., Power S.R., Shylau A.A., Gammelgaard L., Jauho A.-P., Bøggild P. Physical Review B; 99 (19, 195408) 2019. 10.1103/PhysRevB.99.195408. IF: 3.736

    Theoretical and Computational Nanoscience

    We experimentally investigate the charge induction mechanism across gated, narrow, ballistic graphene devices with different degrees of edge disorder. By using magnetoconductance measurements as the probing technique, we demonstrate that devices with large edge disorder exhibit a nearly homogeneous capacitance profile across the device channel, close to the case of an infinitely large graphene sheet. In contrast, devices with lower edge disorder (<1nm roughness) are strongly influenced by the fringing electrostatic field at graphene boundaries, in quantitative agreement with theoretical calculations for pristine systems. Specifically, devices with low edge disorder present a large effective capacitance variation across the device channel with a nontrivial, inhomogeneous profile due not only to classical electrostatics but also to quantum mechanical effects. We show that such quantum capacitance contribution, occurring due to the low density of states across the device in the presence of an external magnetic field, is considerably altered as a result of the gate electrostatics in the ballistic graphene device. Our conclusions can be extended to any two-dimensional (2D) electronic system confined by a hard-wall potential and are important for understanding the electronic structure and device applications of conducting 2D materials. © 2019 American Physical Society.

  • Ge-Doped ZnSb/β-Zn4Sb3 Nanocomposites with High Thermoelectric Performance

    Ostovari Moghaddam A., Shokuhfar A., Zhang Y., Zhang T., Cadavid D., Arbiol J., Cabot A. Advanced Materials Interfaces; (1900467) 2019. 10.1002/admi.201900467. IF: 4.713

    Advanced Electron Nanoscopy

    ZnSb/β-Zn4Sb3 nanocomposites are produced from Zn1.1−xGexSb mixtures using a two-step process. First, proper amounts of the three elements are mixed, melted, and reacted at 800 K. During this process, the nonstoichiometric mixture is crystallized in a combination of ZnSb and β-Zn4Sb3 phases. Then, the material is ball milled and subsequently hot pressed. Through this process, a dense ZnSb/β-Zn4Sb3 composite, consisting of β-Zn4Sb3 nanoinclusions embedded within a ZnSb matrix, is formed. The particular phase distribution of the final ZnSb/β-Zn4Sb3 composites is a consequence of the harder and more brittle nature of ZnSb than Zn4Sb3, which translates into a stronger reduction of the size of the ZnSb crystal domains during ball milling. This small particle size and the high temperature generated during ball milling result in the melting of the ZnSb phase and the posterior crystallization of the two phases in a ZnSb/β-Zn4Sb3 matrix/nanoinclusion-type phase distribution. This particular phase distribution and the presence of Ge result in excellent thermoelectric performances, with power factors up to 1.5 mW m−1 K−2, lattice thermal conductivities down to 0.74 W m−1 K−1, and a thermoelectric figures of merit, ZT, up to 1.2 at 650 K, which is among the highest ZT values reported for ZnSb. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Giant bulk photovoltaic effect in solar cell architectures with ultra-wide bandgap Ga2O3 transparent conducting electrodes

    Pérez-Tomás A., Chikoidze E., Dumont Y., Jennings M.R., Russell S.O., Vales-Castro P., Catalan G., Lira-Cantú M., Ton –That C., Teherani F.H., Sandana V.E., Bove P., Rogers D.J. Materials Today Energy; 14 (100350) 2019. 10.1016/j.mtener.2019.100350.

    Oxide Nanophysics | Nanostructured Materials for Photovoltaic Energy

    The use of ultra-wide bandgap transparent conducting beta gallium oxide (β-Ga2O3) thin films as electrodes in ferroelectric solar cells is reported. In a new material structure for energy applications, we report a solar cell structure (a light absorber sandwiched in between two electrodes - one of them - transparent) which is not constrained by the Shockley–Queisser limit for open-circuit voltage (Voc) under typical indoor light. The solar blindness of the electrode enables a record-breaking bulk photovoltaic effect (BPE) with white light illumination (general use indoor light). This work opens up the perspective of ferroelectric photovoltaics which are not subject to the Shockley-Queisser limit by bringing into scene solar-blind conducting oxides. © 2019 Elsevier Ltd

  • Graphene Oxide as an Optical Biosensing Platform: A Progress Report

    Morales-Narváez E., Merkoçi A. Advanced Materials; 31 (6, 1805043) 2019. 10.1002/adma.201805043. IF: 25.809

    Nanobioelectronics and Biosensors

    A few years ago, crucial graphene oxide (GO) features such as the carbon/oxygen ratio, number of layers, and lateral size were scarcely investigated and, thus, their impact on the overall optical biosensing performance was almost unknown. Nowadays valuable insights about these features are well documented in the literature, whereas others remain controversial. Moreover, most of the biosensing systems based on GO were amenable to operating as colloidal suspensions. Currently, the literature reports conceptually new approaches obviating the need of GO colloidal suspensions, enabling the integration of GO onto a solid phase and leading to their application in new biosensing devices. Furthermore, most GO-based biosensing devices exploit photoluminescent signals. However, further progress is also achieved in powerful label-free optical techniques exploiting GO in biosensing, particularly using optical fibers, surface plasmon resonance, and surface enhanced Raman scattering. Herein, a critical overview on these topics is offered, highlighting the key role of the physicochemical properties of GO. New challenges and opportunities in this exciting field are also highlighted. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Graphene-supported palladium phosphide PdP 2 nanocrystals for ethanol electrooxidation

    Liu J., Luo Z., Li J., Yu X., Llorca J., Nasiou D., Arbiol J., Meyns M., Cabot A. Applied Catalysis B: Environmental; 242: 258 - 266. 2019. 10.1016/j.apcatb.2018.09.105. IF: 14.229

    Advanced Electron Nanoscopy

    We present a procedure to produce single-phase PdP 2 nanocrystals (NCs). The approach involves the reaction of palladium(II) acetylacetonate and hexamethylphosphoroustriamide to nucleate defective Pd 5 P 2 nanoparticles that subsequently, with further phosphorous incorporation, crystallize into PdP 2 . The synthesized PdP 2 NCs were supported on reduced graphene oxide (rGO) and applied as electrocatalysts for ethanol oxidation. The activity of PdP 2 toward the ethanol oxidation reaction (EOR) was over a threefold higher than that of Pd NCs prepared under similar conditions. Even better performance was obtained from PdP 2 NCs supported on rGO, which showed current densities up to 51.4 mA cm −2 and mass activities of 1.60 A mg -1 Pd , that is 4.8 and 15 times higher than Pd NCs. Besides, PdP 2 NCs and PdP 2 /rGO catalysts showed improved stability during EOR than Pd NCs and Pd/rGO. © 2018 Elsevier B.V.

  • Green function, quasi-classical Langevin and Kubo-Greenwood methods in quantum thermal transport

    Sevinçli H., Roche S., Cuniberti G., Brandbyge M., Gutierrez R., Sandonas L.M. Journal of Physics Condensed Matter; 31 (27, 273003) 2019. 10.1088/1361-648X/ab119a. IF: 2.711

    Theoretical and Computational Nanoscience

    With the advances in fabrication of materials with feature sizes at the order of nanometers, it has been possible to alter their thermal transport properties dramatically. Miniaturization of device size increases the power density in general, hence faster electronics require better thermal transport, whereas better thermoelectric applications require the opposite. Such diverse needs bring new challenges for material design. Shrinkage of length scales has also changed the experimental and theoretical methods to study thermal transport. Unsurprisingly, novel approaches have emerged to control phonon flow. Besides, ever increasing computational power is another driving force for developing new computational methods. In this review, we discuss three methods developed for computing vibrational thermal transport properties of nano-structured systems, namely Green function, quasi-classical Langevin, and Kubo-Green methods. The Green function methods are explained using both nonequilibrium expressions and the Landauer-type formula. The partitioning scheme, decimation techniques and surface Green functions are reviewed, and a simple model for reservoir Green functions is shown. The expressions for the Kubo-Greenwood method are derived, and Lanczos tridiagonalization, continued fraction and Chebyshev polynomial expansion methods are discussed. Additionally, the quasi-classical Langevin approach, which is useful for incorporating phonon-phonon and other scatterings is summarized. © 2019 IOP Publishing Ltd.

  • Heterostructured 2D ZnO hybrid nanocomposites sensitized with cubic Cu2O nanoparticles for sunlight photocatalysis

    Segovia M., Alegría M., Aliaga J., Celedon S., Ballesteros L., Sotomayor-Torres C., González G., Benavente E. Journal of Materials Science; 54 (21): 13523 - 13536. 2019. 10.1007/s10853-019-03878-x. IF: 3.442

    Phononic and Photonic Nanostructures

    In this research, we report a series of new heterostructured hybrid 2D ZnO nanocomposites sensitized with Cu2O nanoparticles for sunlight photocatalysis. The Cu2O nanoparticles were synthesized by a surfactant-free method and size reduced by a solvothermal method. 2D ZnO/Cu2O composites were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, reflectance diffuse spectroscopy and Fourier transform infrared. The results showed that the product is a material comprised of layered hybrid 2D ZnO with cubic Cu2O nanoparticles. The photocatalytic activities of the composites were investigated for photodegradation of methylene blue solution as models’ pollutant under sunlight irradiation. The photocatalytic efficiency of a 0.1:1 mixture of Cu2O nanoparticles with 2D ZnO showed that the degradation rate was faster than those of individual ZnO nanocomposites and bulk nanoparticles, respectively. The photocatalytic degradation mechanism studied using specific radical scavengers corroborates the synergy between both semiconductors in the composite and evidences a Z-scheme mechanism to explain the electron transfer. The catalytic reuse tests show that the presence of the ZnO nanocomposite avoids the typical corrosion of Cu2O. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

  • Hierarchical Porous Ni 3 S 4 with Enriched High-Valence Ni Sites as a Robust Electrocatalyst for Efficient Oxygen Evolution Reaction

    Wan K., Luo J., Zhou C., Zhang T., Arbiol J., Lu X., Mao B.-W., Zhang X., Fransaer J. Advanced Functional Materials; 29 (18, 1900315) 2019. 10.1002/adfm.201900315. IF: 15.621

    Advanced Electron Nanoscopy

    Electrochemical water splitting is a common way to produce hydrogen gas, but the sluggish kinetics of the oxygen evolution reaction (OER) significantly limits the overall energy conversion efficiency of water splitting. In this work, a highly active and stable, meso–macro hierarchical porous Ni 3 S 4 architecture, enriched in Ni 3+ is designed as an advanced electrocatalyst for OER. The obtained Ni 3 S 4 architectures exhibit a relatively low overpotential of 257 mV at 10 mA cm −2 and 300 mV at 50 mA cm −2 . Additionally, this Ni 3 S 4 catalyst has excellent long-term stability (no degradation after 300 h at 50 mA cm −2 ). The outstanding OER performance is due to the high concentration of Ni 3+ and the meso–macro hierarchical porous structure. The presence of Ni 3+ enhances the chemisorption of OH − , which facilitates electron transfer to the surface during OER. The hierarchical porosity increases the number of exposed active sites, and facilitates mass transport. A water-splitting electrolyzer using the prepared Ni 3 S 4 as the anode catalyst and Pt/C as the cathode catalyst achieves a low cell voltage of 1.51 V at 10 mA cm −2 . Therefore, this work provides a new strategy for the rational design of highly active OER electrocatalysts with high valence Ni 3+ and hierarchical porous architectures. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • High-resolution mapping of infraslow cortical brain activity enabled by graphene microtransistors

    Masvidal-Codina E., Illa X., Dasilva M., Calia A.B., Dragojević T., Vidal-Rosas E.E., Prats-Alfonso E., Martínez-Aguilar J., De la Cruz J.M., Garcia-Cortadella R., Godignon P., Rius G., Camassa A., Del Corro E., Bousquet J., Hébert C., Durduran T., Villa R., Sanchez-Vives M.V., Garrido J.A., Guimerà-Brunet A. Nature Materials; 18 (3): 280 - 288. 2019. 10.1038/s41563-018-0249-4. IF: 38.887

    Advanced Electronic Materials and Devices

    Recording infraslow brain signals (<0.1 Hz) with microelectrodes is severely hampered by current microelectrode materials, primarily due to limitations resulting from voltage drift and high electrode impedance. Hence, most recording systems include high-pass filters that solve saturation issues but come hand in hand with loss of physiological and pathological information. In this work, we use flexible epicortical and intracortical arrays of graphene solution-gated field-effect transistors (gSGFETs) to map cortical spreading depression in rats and demonstrate that gSGFETs are able to record, with high fidelity, infraslow signals together with signals in the typical local field potential bandwidth. The wide recording bandwidth results from the direct field-effect coupling of the active transistor, in contrast to standard passive electrodes, as well as from the electrochemical inertness of graphene. Taking advantage of such functionality, we envision broad applications of gSGFET technology for monitoring infraslow brain activity both in research and in the clinic. © 2018, The Author(s), under exclusive licence to Springer Nature Limited.

  • Highly active ZnO-based biomimetic fern-like microleaves for photocatalytic water decontamination using sunlight

    Serrà A., Zhang Y., Sepúlveda B., Gómez E., Nogués J., Michler J., Philippe L. Applied Catalysis B: Environmental; 248: 129 - 146. 2019. 10.1016/j.apcatb.2019.02.017. IF: 14.229

    Magnetic Nanostructures

    Here we present the highly enhanced sunlight photocatalytic efficiency and photocorrosion resistance of biomimetic ZnO-modified micro/nanofern fractal architectures, which are synthesized by using a novel, simple, inexpensive and green electrochemical deposition approach in high stirring conditions. Such fern-like hierarchical structures simultaneously combine enhanced angle independent light trapping and surface/bulk modifications of the ZnO morphology to drastically increase: i) the light trapping and absorption in the visible near-infrared range, and ii) the surface to volume ratio of the architecture. This combination is crucial for boosting the sunlight photocatalytic efficiency. To modulate the electronic properties for extending the operation of the ZnO photocatalysts into the visible domain we have used three different modification approaches: sulfidation (leading to a ZnS shell), Ag decoration, and Ni-doping. The different ZnO-modified bioinspired fern-like fractal structures have been used to demonstrate their efficiency in the photodegradation and photoremediation of three different persistent organic pollutants –methylene blue, 4-nitrophenol, and Rhodamine B – under UV light, simulated and natural UV-filtered sunlight. Remarkably, the ZnO@ZnS core@shell structures exhibited an outstanding photocatalytic activity compared to the pristine ZnO catalyst, with over 6-fold increase in the pollutant degradation rate when using solar light. In fact, the catalytic performance of the ZnO@ZnS micro/nanoferns for the photoremediation of persistent organic pollutants is comparable to or better than the most competitive state-of-the-art ZnO photocatalysts, but showing a negligible photocorrosion. Ag-decorated ZnO, and Ni-doped ZnO exhibited similar excellent visible-sunlight photodegradation efficiency. Although the Ni-doped photocatalysts showed a relatively poor photocorrosion resistance, it was acceptable for Ag-decorated ZnO. Therefore, the easy fabrication and the capacity to drastically enhance the sunlight photocatalytic efficiency of the ZnO@ZnS bioinspired micro/nanoferns, together with their practically negligible photocorrosion and simple recyclability in terms of non-catalyst poisoning, makes them very promising photocatalysts for water remediation. © 2019 Elsevier B.V.

  • III-V Integration on Si(100): Vertical Nanospades

    Güniat L., Martí-Sánchez S., Garcia O., Boscardin M., Vindice D., Tappy N., Friedl M., Kim W., Zamani M., Francaviglia L., Balgarkashi A., Leran J.-B., Arbiol J., Fontcuberta I Morral A. ACS Nano; 13 (5): 5833 - 5840. 2019. 10.1021/acsnano.9b01546. IF: 13.903

    Advanced Electron Nanoscopy

    III-V integration on Si(100) is a challenge: controlled vertical vapor liquid solid nanowire growth on this platform has not been reported so far. Here we demonstrate an atypical GaAs vertical nanostructure on Si(100), coined nanospade, obtained by a nonconventional droplet catalyst pinning. The Ga droplet is positioned at the tip of an ultrathin Si pillar with a radial oxide envelope. The pinning at the Si/oxide interface allows the engineering of the contact angle beyond the Young-Dupré equation and the growth of vertical nanospades. Nanospades exhibit a virtually defect-free bicrystalline nature. Our growth model explains how a pentagonal twinning event at the initial stages of growth provokes the formation of the nanospade. The optical properties of the nanospades are consistent with the high crystal purity, making these structures viable for use in integration of optoelectronics on the Si(100) platform. © 2019 American Chemical Society.

  • Impact of P3HT materials properties and layer architecture on OPV device stability

    Meitzner R., Faber T., Alam S., Amand A., Roesch R., Büttner M., Herrmann-Westendorf F., Presselt M., Ciammaruchi L., Visoly-Fisher I., Veenstra S., Diaz de Zerio A., Xu X., Wang E., Müller C., Troshin P., Hager M.D., Köhn S., Dusza M., Krassas M., Züfle S., Kymakis E., Katz E.A., Berson S., Granek F., Manceau M., Brunetti F., Polino G., Schubert U.S., Lira-Cantu M., Hoppe H. Solar Energy Materials and Solar Cells; 202 (110151) 2019. 10.1016/j.solmat.2019.110151. IF: 6.019

    Nanostructured Materials for Photovoltaic Energy

    We report a cooperative study conducted between different laboratories to investigate organic solar cell degradation with respect to P3HT material properties and different solar cell architectures. Various batches of P3HT were collected from different suppliers reflecting commercial availability as well as properties variability. Among the materials properties explicitly considered were the molar mass, dispersity, regio-regularity, impurities by trace metals and intrinsic doping evaluated from radical concentrations. Each of the participating laboratories contributing test devices applied their own layer stack, i.e. their own device architecture and layout. This variation was appreciated as another parameter for evaluation. Even though a large amount of devices failed due to extrinsic degradation effects, indeed, some materials properties were found to be more important than others for obtaining long lifetimes and high stability of P3HT-based polymer solar cells. © 2019

  • Impact of the regularization parameter in the mean free path reconstruction method: Nanoscale heat transport and beyond

    Sanchez-Martinez M.-Á., Alzina F., Oyarzo J., Torres C.M.S., Chavez-Angel E. Nanomaterials; 9 (3, 414) 2019. 10.3390/nano9030414. IF: 4.034

    Phononic and Photonic Nanostructures

    The understanding of the mean free path (MFP) distribution of the energy carriers in materials (e.g., electrons, phonons, magnons, etc.) provides a key physical insight into their transport properties. In this context, MFP spectroscopy has become an important tool to describe the contribution of carriers with different MFP to the total transport phenomenon. In this work, we revise the MFP reconstruction technique and present a study on the impact of the regularization parameter on the MFP distribution of the energy carriers. By using the L-curve criterion, we calculate the optimal mathematical value of the regularization parameter. The effect of the change from the optimal value in the MFP distribution is analyzed in three case studies of heat transport by phonons. These results demonstrate that the choice of the regularization parameter has a large impact on the physical information obtained from the reconstructed accumulation function, and thus cannot be chosen arbitrarily. The approach can be applied to various transport phenomena at the nanoscale involving carriers of different physical nature and behavior. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

  • In Situ Electrochemical Oxidation of Cu2S into CuO Nanowires as a Durable and Efficient Electrocatalyst for Oxygen Evolution Reaction

    Zuo Y., Liu Y., Li J., Du R., Han X., Zhang T., Arbiol J., Divins N.J., Llorca J., Guijarro N., Sivula K., Cabot A. Chemistry of Materials; 2019. 10.1021/acs.chemmater.9b02790. IF: 10.159

    Supramolecular NanoChemistry and Materials | Oxide Nanophysics | Advanced Electron Nanoscopy

    Development of cost-effective oxygen evolution catalysts is of capital importance for the deployment of large-scale energy-storage systems based on metal-air batteries and reversible fuel cells. In this direction, a wide range of materials have been explored, especially under more favorable alkaline conditions, and several metal chalcogenides have particularly demonstrated excellent performances. However, chalcogenides are thermodynamically less stable than the corresponding oxides and hydroxides under oxidizing potentials in alkaline media. Although this instability in some cases has prevented the application of chalcogenides as oxygen evolution catalysts and it has been disregarded in some others, we propose to use it in our favor to produce high-performance oxygen evolution catalysts. We characterize here the in situ chemical, structural, and morphological transformation during the oxygen evolution reaction (OER) in alkaline media of Cu2S into CuO nanowires, mediating the intermediate formation of Cu(OH)2. We also test their OER activity and stability under OER operation in alkaline media and compare them with the OER performance of Cu(OH)2 and CuO nanostructures directly grown on the surface of a copper mesh. We demonstrate here that CuO produced from in situ electrochemical oxidation of Cu2S displays an extraordinary electrocatalytic performance toward OER, well above that of CuO and Cu(OH)2 synthesized without this transformation. © 2019 American Chemical Society.

  • In Situ Plant Virus Nucleic Acid Isothermal Amplification Detection on Gold Nanoparticle-Modified Electrodes

    Khater M., Escosura-Muñiz A.D.L., Altet L., Merkoçi A. Analytical Chemistry; 91 (7): 4790 - 4796. 2019. 10.1021/acs.analchem.9b00340. IF: 6.350

    Nanobioelectronics and Biosensors

    Solid-phase isothermal recombinase polymerase amplification (RPA) offers many benefits over the standard RPA in homogeneous phase in terms of sensitivity, portability, and versatility. However, RPA devices reported to date are limited by the need for heating sources to reach sensitive detection. With the aim of overcoming such limitation, we propose here a label-free highly integrated in situ RPA amplification/detection approach at room temperature that takes advantage of the high sensitivity offered by gold nanoparticle (AuNP)-modified sensing substrates and electrochemical impedance spectroscopic (EIS) detection. Plant disease (Citrus tristeza virus (CTV)) diagnostics was selected as a relevant target for demonstration of the proof-of-concept. RPA assay for amplification of the P20 gene (387-bp) characteristic of CTV was first designed/optimized and tested by standard gel electrophoresis analysis. The optimized RPA conditions were then transferred to the AuNP-modified electrode surface, previously modified with a thiolated forward primer. The in situ-amplified CTV target was investigated by EIS in a Fe(CN 6 ) 4- /Fe(CN 6 ) 3- red-ox system, being able to quantitatively detect 1000 fg μL -1 of nucleic acid. High selectivity against nonspecific gene sequences characteristic of potential interfering species such as Citrus psorosis virus (CPsV) and Citrus caxicia viroid (CCaV) was demonstrated. Good reproducibility (RSD of 8%) and long-term stability (up to 3 weeks) of the system were also obtained. Overall, with regard to sensitivity, cost, and portability, our approach exhibits better performance than RPA in homogeneous phase, also without the need of heating sources required in other solid-phase approaches. © 2019 American Chemical Society.

  • In vivo behaviour of glyco-NaI@SWCNT ‘nanobottles’

    De Munari S., Sandoval S., Pach E., Ballesteros B., Tobias G., Anthony D.C., Davis B.G. Inorganica Chimica Acta; 495 (118933) 2019. 10.1016/j.ica.2019.05.032. IF: 2.433

    Electron Microscopy Unit

    Carbon nanotubes are appealing imaging and therapeutic systems. Their structure allows not only a useful display of molecules on their outer surface but at the same time the protection of encapsulated cargoes. Despite the interest they have provoked in the scientific community, their applications have not yet been fully realised due to the limited knowledge we possess concerning their physiological behaviour. Previously, we have shown that the encapsulation of radionuclide in the inner space of glycan-functionalized single-walled carbon nanotubes (glyco-X@SWCNT) redirected in vivo distribution of radioactivity from the thyroid to the lungs. Here we test the roles played by such glycans attached to carbon nanotubes in controlling sites of accumulation using nanotubes carrying both ‘cold’ and ‘hot’ salt cargoes decorated with two different mammalian carbohydrates, N-acetyl-D-glucosamine (GlcNAc) or galactose (Gal)-capped disaccharide lactose (Gal–Glc). This distinct variation of the terminal glycan displayed between two types of glycan ligands with very different in vivo receptors, coupled with altered sites of administration, suggest that distribution in mammals is likely controlled by physiological mechanisms that may include accumulation in the first capillary bed they encounter and not by glycan-receptor interaction and that the primary role of glycan is in aiding the dispersibility of the CNTs. © 2019

  • Independent Tuning of Optical Transparency Window and Electrical Properties of Epitaxial SrVO3 Thin Films by Substrate Mismatch

    Mirjolet M., Vasili H.B., López-Conesa L., Estradé S., Peiró F., Santiso J., Sánchez F., Machado P., Gargiani P., Valvidares M., Fontcuberta J. Advanced Functional Materials; (1904238) 2019. 10.1002/adfm.201904238. IF: 15.621

    Nanomaterials Growth Unit

    Transparent metallic oxides are pivotal materials in information technology, photovoltaics, or even in architecture. They display the rare combination of metallicity and transparency in the visible range because of weak interband photon absorption and weak screening of free carriers to impinging light. However, the workhorse of current technology, indium tin oxide (ITO), is facing severe limitations and alternative approaches are needed. AMO3 perovskites, M being a nd1 transition metal, and A an alkaline earth, have a genuine metallic character and, in contrast to conventional metals, the electron–electron correlations within the nd1 band enhance the carriers effective mass (m*) and bring the transparency window limit (marked by the plasma frequency, ωp*) down to the infrared. Here, it is shown that epitaxial strain and carrier concentration allow fine tuning of optical properties (ωp*) of SrVO3 films by modulating m* due to strain-induced selective symmetry breaking of 3d-t2g(xy, yz, xz) orbitals. Interestingly, the DC electrical properties can be varied by a large extent depending on growth conditions whereas the optical transparency window in the visible is basically preserved. These observations suggest that the harsh conditions required to grow optimal SrVO3 films may not be a bottleneck for their future application. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Insight into the Degradation Mechanisms of Atomic Layer Deposited TiO2 as Photoanode Protective Layer

    Ros C., Carretero N.M., David J., Arbiol J., Andreu T., Morante J.R. ACS Applied Materials and Interfaces; 11 (33): 29725 - 29735. 2019. 10.1021/acsami.9b05724. IF: 8.456

    Advanced Electron Nanoscopy

    Around 100 nm thick TiO2 layers deposited by atomic layer deposition (ALD) have been investigated as anticorrosion protective films for silicon-based photoanodes decorated with 5 nm NiFe catalyst in highly alkaline electrolyte. Completely amorphous layers presented high resistivity; meanwhile, the ones synthesized at 300 °C, having a fully anatase crystalline TiO2 structure, introduced insignificant resistance, showing direct correlation between crystallization degree and electrical conductivity. The conductivity through crystalline TiO2 layers has been found not to be homogeneous, presenting preferential conduction paths attributed to grain boundaries and defects within the crystalline structure. A correlation between the conductivity atomic force microscopy measurements and grain interstitials can be seen, supported by high-resolution transmission electron microscopy cross-sectional images presenting defective regions in crystalline TiO2 grains. It was found that the conduction mechanism goes through the injection of electrons coming from water oxidation from the electrocatalyst into the TiO2 conduction band. Then, electrons are transported to the Si/SiOx/TiO2 interface where electrons recombine with holes given by the p+n-Si junction. No evidences of intra-band-gap states in TiO2 responsible of conductivity have been detected. Stability measurements of fully crystalline samples over 480 h in anodic polarization show a continuous current decay. Electrochemical impedance spectroscopy allows to identify that the main cause of deactivation is associated with the loss of TiO2 electrical conductivity, corresponding to a self-passivation mechanism. This is proposed to reflect the effect of OH- ions diffusing in the TiO2 structure in anodic conditions by the electric field. This fact proves that a modification takes place in the defective zone of the layer, blocking the ability to transfer electrical charge through the layer. According to this mechanism, a regeneration of the degradation process is demonstrated possible based on ultraviolet illumination, which contributes to change the occupancy of TiO2 electronic states and to recover the defective zone's conductivity. These findings confirm the connection between the structural properties of the ALD-deposited polycrystalline layer and the degradation mechanisms and thus highlight main concerns toward fabricating long-lasting metal-oxide protective layers for frontal illuminated photoelectrodes. Copyright © 2019 American Chemical Society.

  • Internalization and toxicological mechanisms of uncoated and PVP-coated cerium oxide nanoparticles in the freshwater alga: Chlamydomonas reinhardtii

    Pulido-Reyes G., Briffa S.M., Hurtado-Gallego J., Yudina T., Leganés F., Puntes V., Valsami-Jones E., Rosal R., Fernández-Piñas F. Environmental Science: Nano; 6 (6): 1959 - 1972. 2019. 10.1039/c9en00363k. IF: 7.704

    Inorganic Nanoparticles

    Due to the wide range of applications of cerium oxide nanoparticles (CeO2NPs), a risk assessment of their biological effects using environmentally relevant species becomes highly important. There are contradictory reports on the effects of CeO2NPs, which may be related to the use of different types of nanoparticles (NPs) and coatings. CeO2NPs may act as an oxidant causing toxicity or as an antioxidant able to scavenge free radicals. As a consequence of such complexity, the toxicological behaviour of these NPs is still poorly understood. Moreover, little is known about the internalization process of CeO2NPs in algae. There is evidence of CeO2NP-internalization by the green alga Chlamydomonas reinhardtii, but the mechanism and route of uptake are still unknown. In this study, we used uncoated and different polyvinylpyrrolidone (PVP)-coated CeO2NPs with the aim of identifying their toxicological mechanisms to C. reinhardtii and exploring their possible internalization. Our results showed that PVP coated-CeO2NPs significantly increased the formation of reactive oxygen species in exposed cells, indicating that oxidative stress is an important toxicity mechanism for these particles. Direct contact and damage of the cellular membrane was identified as the mechanism causing the toxicity of uncoated NPs. From experiments with endocytosis inhibitors, clathrin-dependent endocytosis was revealed as the main internalization route for all NPs. However, as uncoated CeO2NPs led to severe cellular membrane damage, direct passage of NPs through membrane holes could not be discarded. To our knowledge, this is the first report with evidence of direct linking between NP internalization and a specific endocytic pathway. The results presented here will help to unravel the toxicological mechanism and behaviour of CeO2NPs and provide input information for the environmental health and safety assessment of CeO2NPs. © 2019 The Royal Society of Chemistry.

  • Iridium oxide (IV) nanoparticle-based electrocatalytic detection of PBDE

    Quesada-González D., Baiocco A., Martos A.A., de la Escosura-Muñiz A., Palleschi G., Merkoçi A. Biosensors and Bioelectronics; 127: 150 - 154. 2019. 10.1016/j.bios.2018.11.050. IF: 9.518

    Nanobioelectronics and Biosensors

    Polybrominated diphenyl ethers (PBDEs) are a type of flame retardants which are currently banned in EU and USA due their hazardousness for humans and mammals. However, these compounds were highly used during more than 30 years and still persist in the environment since they are resistant to degradation. Herein we present a biosensor for the detection of PBDEs using screen printed carbon electrodes (SPCEs) based on the electrochemical monitoring of water oxidation reaction (WOR) catalyzed by iridium oxide (IV) nanoparticles (IrO 2 NPs). Our assay shows a limit of detection of 21.5 ppb of PBDE in distilled water. We believe that such an IrO 2 NPs-based electrocatalytic sensing system can lead to a rapid, sensitive, low cost and miniaturizable device for the detection of PBDEs. © 2018 Elsevier B.V.

  • Iridium oxide (IV) nanoparticle-based lateral flow immunoassay

    Quesada-González D., Sena-Torralba A., Wicaksono W.P., de la Escosura-Muñiz A., Ivandini T.A., Merkoçi A. Biosensors and Bioelectronics; 132: 132 - 135. 2019. 10.1016/j.bios.2019.02.049. IF: 9.518

    Nanobioelectronics and Biosensors

    Lateral flow biosensors are paper-based devices that allow the detection of different types of analytes with quickness, robustness and selectivity, without leaving behind paper sensors benefits as low-cost, recyclability and sustainability. Nanomaterials have been widely reported in lateral flow biosensors, offering new sensing strategies based on optical or electrical detection techniques. Looking for other advantageous nanomaterials, we propose for the first time the use of iridium oxide (IV) nanoparticles in lateral flow assays for the detection of human immunoglobulin as a model protein. These nanoparticles can be easily prepared and conjugated with biomarkers. Their dark blue color gives a high contrast against the white background of the strips being in this way excellent labels. © 2019 Elsevier B.V.

  • Kidney nanotoxicity studied in human renal proximal tubule epithelial cell line TH1

    Sramkova M., Kozics K., Masanova V., Uhnakova I., Razga F., Nemethova V., Mazancova P., Kapka-Skrzypczak L., Kruszewski M., Novotova M., Puntes V.F., Gabelova A. Mutation Research - Genetic Toxicology and Environmental Mutagenesis; 845 (403017) 2019. 10.1016/j.mrgentox.2019.01.012. IF: 2.256

    Inorganic Nanoparticles

    Progressive expansion of nanomaterials in our everyday life raises concerns about their safety for human health. Although kidneys are the primary organs of xenobiotic elimination, little attention has been paid to the kidneys in terms of nanotoxicological studies up to now. Here we investigate the cytotoxic and genotoxic potential of four solid-core uncoated inorganic nanoparticles (TiO2NPs, SiO2NPs, Fe3O4NPs and AuNPs) using the human renal proximal tubule epithelial TH1 cells. To mimic the in vivo conditions more realistic, TH1 cells were exposed in vitro to inorganic NPs under static as well as dynamic conditions for 3 h and 24 h. The medium throughput alkaline comet assay (12 minigels per slide) was employed to evaluate the impact of these NPs on genome integrity and their capacity to produce oxidative lesions to DNA. The accumulation and localization of studied inorganic NPs inside the cells was monitored by transmission electron microscopy (TEM) and the efficacy of internalization of particular NPs was determined by atomic absorption spectroscopy (AAS) and inductively coupled plasma mass spectrometry (ICP-MS). From all the tested NPs, only Fe3O4NPs induced a slight cytotoxicity in TH1 cells exposed to high concentrations (>700 μg/ml) for 24 h. On the other hand, the inorganic NPs did not increase significantly the level of DNA strand breaks or oxidative DNA damage regardless of the treatment mode (static vs. dynamic conditions). Interestingly, substantial differences were observed in the internalized amount of inorganic NPs in TH1 cells exposed to equivalent (2.2 μg/ml) concentration. Fe3O4NPs were most efficiently taken up while the lowest quantity of particles was determined in TiO2NPs-treated cells. As the particle size and shape of individual inorganic NPs in culture medium was nearly identical, it is reasonable to suppose that the chemical composition may contribute to the differences in the efficacy of NPs uptake. © 2019 The Authors

  • Label-free Bacteria Quantification in Blood Plasma by a Bioprinted Microarray Based Interferometric Point-of-Care Device

    Dey P., Fabri-Faja N., Calvo-Lozano O., Terborg R.A., Belushkin A., Yesilkoy F., Fàbrega A., Ruiz-Rodriguez J.C., Ferrer R., González-López J.J., Estévez M.C., Altug H., Pruneri V., Lechuga L.M. ACS Sensors; 4 (1): 52 - 60. 2019. 10.1021/acssensors.8b00789. IF: 6.944

    NanoBiosensors and Bioanalytical Applications

    Existing clinical methods for bacteria detection lack speed, sensitivity, and, importantly, point-of-care (PoC) applicability. Thus, finding ways to push the sensitivity of clinical PoC biosensing technologies is crucial. Here we report a portable PoC device based on lens-free interferometric microscopy (LIM). The device employs high performance nanoplasmonics and custom bioprinted microarrays and is capable of direct label-free bacteria (E. coli) quantification. With only one-step sample handling we offer a sample-to-data turnaround time of 40 min. Our technology features detection sensitivity of a single bacterial cell both in buffer and in diluted blood plasma and is intrinsically limited by the number of cells present in the detection volume. When employed in a hospital setting, the device has enabled accurate categorization of sepsis patients (infectious SIRS) from control groups (healthy individuals and noninfectious SIRS patients) without false positives/negatives. User-friendly on-site bacterial clinical diagnosis can thus become a reality. © 2018 American Chemical Society.

  • Label-free plasmonic biosensors for point-of-care diagnostics: a review

    Soler M., Huertas C.S., Lechuga L.M. Expert Review of Molecular Diagnostics; 19 (1): 71 - 81. 2019. 10.1080/14737159.2019.1554435. IF: 3.099

    NanoBiosensors and Bioanalytical Applications

    Introduction: Optical biosensors, particularly those based on nanoplasmonics technology, have emerged in recent decades as a potential solution for disease diagnostics and therapy follow-up at the point-of-care (POC). These biosensor platforms could overcome some of the challenges faced in conventional diagnosis techniques offering label-free assays with immediate results and employing small and user-friendly devices. Areas covered: In this review, we will provide a critical overview of the recent advances in the development of nanoplasmonic biosensors for the POC diagnostics. We focus on those systems with demonstrated capabilities for integration in portable platforms, highlighting some of the most relevant diagnostics applications targeting proteins, nucleic acids, and cells as disease biomarkers. Expert commentary: Despite the attractive features of label-free nanoplasmonic sensors in terms of miniaturization and analytical robustness, the route toward an effective clinical implementation involves the integration of fully automated microfluidic systems for sample processing and analysis, and the optimization of surface biofunctionalization procedures. Additionally, the development of multiplexed sensors for high-throughput analysis and including specific neoantigens and novel biomarkers in detection panels will provide the means for delivering a powerful analytical technology for an accurate and improved medical diagnosis. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

  • Ligand-mediated band engineering in bottom-up assembled SnTe nanocomposites for thermoelectric energy conversion

    Ibañ ez M., Hasler R., Genc A., Liu Y., Kuster B., Schuster M., Dobrozhan O., Cadavid D., Arbiol J., Cabot A., Kovalenko M.V. Journal of the American Chemical Society; 141 (20): 8025 - 8029. 2019. 10.1021/jacs.9b01394. IF: 14.695

    Supramolecular NanoChemistry and Materials | Advanced Electron Nanoscopy

    The bottom-up assembly of colloidal nanocrystals is a versatile methodology to produce composite nanomaterials with precisely tuned electronic properties. Beyond the synthetic control over crystal domain size, shape, crystal phase, and composition, solution-processed nanocrystals allow exquisite surface engineering. This provides additional means to modulate the nanomaterial characteristics and particularly its electronic transport properties. For instance, inorganic surface ligands can be used to tune the type and concentration of majority carriers or to modify the electronic band structure. Herein, we report the thermoelectric properties of SnTe nanocomposites obtained from the consolidation of surface-engineered SnTe nanocrystals into macroscopic pellets. A CdSe-based ligand is selected to (i) converge the light and heavy bands through partial Cd alloying and (ii) generate CdSe nanoinclusions as a secondary phase within the SnTe matrix, thereby reducing the thermal conductivity. These SnTe-CdSe nanocomposites possess thermoelectric figures of merit of up to 1.3 at 850 K, which is, to the best of our knowledge, the highest thermoelectric figure of merit reported for solution-processed SnTe. © 2019 American Chemical Society

  • Long-Term Functionality of Transversal Intraneural Electrodes is Improved by Dexamethasone Treatment

    De La Oliva N., Del Valle J., Delgado-Martinez I., Mueller M., Stieglitz T., Navarro X. IEEE Transactions on Neural Systems and Rehabilitation Engineering; 27 (3, 8633873): 457 - 464. 2019. 10.1109/TNSRE.2019.2897256. IF: 3.478

    Advanced Electronic Materials and Devices

    Neuroprostheses aimed to restore lost functions after a limb amputation are based on the interaction with the nervous system by means of neural interfaces. Among the different designs, intraneural electrodes implanted in peripheral nerves represent a good strategy to stimulate nerve fibers to send sensory feedback and to record nerve signals to control the prosthetic limb. However, intraneural electrodes, as any device implanted in the body, induce a foreign body reaction (FBR) that results in the tissue encapsulation of the device. The FBR causes a progressive decline of the electrode functionality over time due to the physical separation between the electrode active sites and the axons to the interface. Modulation of the inflammatory response has arisen as a good strategy to reduce the FBR and maintain electrode functionality. In this paper, transversal intraneural multi-channel electrodes (TIMEs) were implanted in the rat sciatic nerve and tested for three months to evaluate stimulation and recording capabilities under chronic administration of dexamethasone. Dexamethasone treatment significantly reduced the threshold for evoking muscle responses during the follow-up compared to saline-treated animals, without affecting the selectivity of stimulation. However, dexamethasone treatment did not improve the signal-to-noise ratio of the recorded neural signals. Dexamethasone treatment allowed to maintain more working active sites along time than saline treatment. Thus, systemic administration of dexamethasone appears as a useful treatment in chronically implanted animals with neural electrodes as it increases the number of functioning contacts of the implanted TIME and reduces the intensity needed to stimulate the nerve. © 2001-2011 IEEE.

  • Low-cost and portable UV holographic microscope for high-contrast protein crystal imaging

    Daloglu M.U., Ray A., Collazo M.J., Brown C., Tseng D., Chocarro-Ruiz B., Lechuga L.M., Cascio D., Ozcan A. APL Photonics; 4 (3, 030804) 2019. 10.1063/1.5080158. IF: 4.383

    NanoBiosensors and Bioanalytical Applications

    Imaging protein crystals and distinguishing them from salt crystals is an important task for protein crystallographers. The conventional tool used for this purpose is a dual-mode microscope composed of bright-field and ultraviolet (UV) induced fluorescence modes. The distinction between a protein and a salt crystal is made based upon the fluorescence response to the UV excitation, where most protein crystals absorb the UV excitation and emit fluorescence, unlike salt crystals. These dual-mode optical microscopes are sensitive; however, they are relatively bulky and expensive as they require UV-grade optics. As an alternative, here we demonstrate that on-chip UV holographic imaging offers a low-cost, portable, and robust technique to image and distinguish protein crystals from salt crystals, without the need for any expensive and bulky optical components. Only composed of a UV light-emitting-diode at 280 nm and a consumer-grade complementary metal-oxide-semiconductor image sensor de-capped and interfaced to a Raspberry Pi single-board computer, the necessary information from the crystal samples (placed very close to the sensor active area) is captured in the form of in-line holograms and extracted through digital back-propagation. In these holographic amplitude reconstructions, protein crystals appear significantly darker compared to the background due to the strong UV absorption, unlike salt crystals which do not show any contrast, enabling us to clearly distinguish between them. We believe that the on-chip UV holographic microscope could serve as a low-cost, sensitive, and robust alternative to conventional lens-based UV-microscopes used in protein crystallography. © 2019 Author(s).

  • Low-cost vertical taper for highly efficient light in-coupling in bimodal nanointerferometric waveguide biosensors

    Daniel Grajales, Adrián Fernández Gavela, Carlos Domínguez, Jose Ramón Sendra, Laura M Lechuga Journal of Physics: Photonics; 1 (2): 25002. 2019. 10.1088/2515-7647/aafebb. IF: 0.000

    NanoBiosensors and Bioanalytical Applications

    There is still the need for a compact and cost-effective solution for efficient light in-coupling in integrated waveguides employed in photonic biosensors, especially when these waveguides are of submicron dimensions and operate at visible wavelengths. The employment of a vertically stacked taper with a larger input area is proposed to meet this need. The design of the taper is divided into two stages: in the first stage, light is guided downwards by two vertically stacked tapers; in the second stage, an inverted taper directly confines the light inside the waveguide. The design parameters are optimized using commercial software, obtaining a total theoretical light coupling efficiency of 72.25%. The taper is manufactured using SU-8 polymer as the main material, employing standard photolithography techniques at wafer level. After characterization, the results show the practicality of the taper when coupling light from macrometric sources to nanometric waveguides, obtaining an experimental coupling efficiency of 55%. With this vertical taper, a compact, easy-to-couple and cost-effective solution is achieved for waveguide-based biosensors operating at visible wavelengths, opening the way for a truly portable point-of-care biosensor for low-cost and label-free diagnostics.

  • Metal–Organic Framework (MOF) Derived Electrodes with Robust and Fast Lithium Storage for Li-Ion Hybrid Capacitors

    Dubal D.P., Jayaramulu K., Sunil J., Kment Š., Gomez-Romero P., Narayana C., Zbořil R., Fischer R.A. Advanced Functional Materials; 29 (19, 1900532) 2019. 10.1002/adfm.201900532. IF: 15.621

    Hybrid metal–organic frameworks (MOFs) demonstrate great promise as ideal electrode materials for energy-related applications. Herein, a well-organized interleaved composite of graphene-like nanosheets embedded with MnO 2 nanoparticles (MnO 2 @C-NS) using a manganese-based MOF and employed as a promising anode material for Li-ion hybrid capacitor (LIHC) is engineered. This unique hybrid architecture shows intriguing electrochemical properties including high reversible specific capacity 1054 mAh g −1 (close to the theoretical capacity of MnO 2 , 1232 mAh g −1 ) at 0.1 A g −1 with remarkable rate capability and cyclic stability (90% over 1000 cycles). Such a remarkable performance may be assigned to the hierarchical porous ultrathin carbon nanosheets and tightly attached MnO 2 nanoparticles, which provide structural stability and low contact resistance during repetitive lithiation/delithiation processes. Moreover, a novel LIHC is assembled using a MnO 2 @C-NS anode and MOF derived ultrathin nanoporous carbon nanosheets (derived from other potassium-based MOFs) cathode materials. The LIHC full-cell delivers an ultrahigh specific energy of 166 Wh kg −1 at 550 W kg −1 and maintained to 49.2 Wh kg −1 even at high specific power of 3.5 kW kg −1 as well as long cycling stability (91% over 5000 cycles). This work opens new opportunities for designing advanced MOF derived electrodes for next-generation energy storage devices. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Modification of the raman spectra in graphene-based nanofluids and its correlation with thermal properties

    Rodríguez-Laguna M.D.R., Romero P.G., Torres C.M.S., Chavez-Angel E. Nanomaterials; 9 (5, 804) 2019. 10.3390/nano9050804. IF: 4.034

    Phononic and Photonic Nanostructures

    It is well known that by dispersing nanoparticles in a fluid, the thermal conductivity of the resulting nanofluid tends to increase with the concentration of nanoparticles. However, it is not clear what the mechanism behind this phenomenon is. Raman spectroscopy is a characterization technique connecting the molecular and macroscopic world, and therefore, it can unravel the puzzling effect exerted by the nanomaterial on the fluid. In this work, we report on a comparative study on the thermal conductivity, vibrational spectra and viscosity of graphene nanofluids based on three different amides: N, N-dimethylacetamide (DMAc); N, N-dimethylformamide (DMF); and N-methyl-2-pyrrolidinone (NMP). A set of concentrations of highly stable surfactant-free graphene nanofluids developed in-house was prepared and characterized. A correlation between the modification of the vibrational spectra of the fluids and an increase in their thermal conductivity in the presence of graphene was confirmed. Furthermore, an explanation of the non-modification of the thermal conductivity in graphene-NMP nanofluids is given based on its structure and a peculiar arrangement of the fluid. © 2019, MDPI AG. All rights reserved.

  • MoS x @NiO Composite Nanostructures: An Advanced Nonprecious Catalyst for Hydrogen Evolution Reaction in Alkaline Media

    Ibupoto Z.H., Tahira A., Tang P., Liu X., Morante J.R., Fahlman M., Arbiol J., Vagin M., Vomiero A. Advanced Functional Materials; 29 (7, 1807562) 2019. 10.1002/adfm.201807562. IF: 15.621

    Advanced Electron Nanoscopy

    The design of the earth-abundant, nonprecious, efficient, and stable electrocatalysts for efficient hydrogen evolution reaction (HER) in alkaline media is a hot research topic in the field of renewable energies. A heterostructured system composed of MoS x deposited on NiO nanostructures (MoS x @NiO) as a robust catalyst for water splitting is proposed here. NiO nanosponges are applied as cocatalyst for MoS 2 in alkaline media. Both NiO and MoS 2 @NiO composites are prepared by a hydrothermal method. The NiO nanostructures exhibit sponge-like morphology and are completely covered by the sheet-like MoS 2 . The NiO and MoS 2 exhibit cubic and hexagonal phases, respectively. In the MoS x @NiO composite, the HER experiment in 1 m KOH electrolyte results in a low overpotential (406 mV) to produce 10 mA cm −2 current density. The Tafel slope for that case is 43 mV per decade, which is the lowest ever achieved for MoS 2 -based electrocatalyst in alkaline media. The catalyst is highly stable for at least 13 h, with no decrease in the current density. This simple, cost-effective, and environmentally friendly methodology can pave the way for exploitation of MoS x @NiO composite catalysts not only for water splitting, but also for other applications such as lithium ion batteries, and fuel cells. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Multilayered Hematite Nanowires with Thin-Film Silicon Photovoltaics in an All-Earth-Abundant Hybrid Tandem Device for Solar Water Splitting

    Urbain F., Tang P., Smirnov V., Welter K., Andreu T., Finger F., Arbiol J., Morante J.R. ChemSusChem; 12 (7): 1428 - 1436. 2019. 10.1002/cssc.201802845. IF: 7.804

    Advanced Electron Nanoscopy

    The concept of hybrid tandem device structures that combine metal oxides with thin-film semiconducting photoabsorbers holds great promise for large-scale, robust, and cost-effective bias-free photoelectrochemical water splitting (PEC-WS). This work highlights important steps toward the efficient coupling of high-performance hematite photoanodes with multijunction thin-film silicon photocathodes providing high bias-free photocurrent density. The hybrid PEC-WS device is optimized by testing three types of multijunction silicon photocathodes with the hematite photoanode: amorphous silicon (a-Si:H) tandem: a-Si:H/a-Si:H and triple junction with microcrystalline silicon (μc-Si:H): a-Si:H/a-Si:H/μc-Si:H and a-Si:H/μc-Si:H/μc-Si:H. The results provide evidence that the multijunction structures offer high flexibility for hybrid tandem devices with regard to tunable photovoltages and spectral matching. Furthermore, both photoanode and photocathode are tested under various electrolyte and light concentration conditions, respectively, with respect to their photoelectrochemical performance and stability. A 27 % enhancement in the solar-to-hydrogen conversion efficiency is observed upon concentrating light from 100 to 300 mW cm −2 . Ultimately, bias-free water splitting is demonstrated, with a photocurrent density of 4.6 mA cm −2 (under concentrated illumination) paired with excellent operation stability for more than 24 h of the all-earth-abundant and low-cost hematite/silicon tandem PEC-WS device. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • NanoElectronics roadmap for Europe: From nanodevices and innovative materials to system integration

    Ahopelto J., Ardila G., Baldi L., Balestra F., Belot D., Fagas G., De Gendt S., Demarchi D., Fernandez-Bolaños M., Holden D., Ionescu A.M., Meneghesso G., Mocuta A., Pfeffer M., Popp R.M., Sangiorgi E., Sotomayor Torres C.M. Solid-State Electronics; 155: 7 - 19. 2019. 10.1016/j.sse.2019.03.014. IF: 1.492

    Phononic and Photonic Nanostructures

    The NEREID project (“NanoElectronics Roadmap for Europe: Identification and Dissemination”) is dedicated to mapping the future of European Nanoelectronics. NEREID's objective is to develop a medium and long term roadmap for the European nanoelectronics industry, starting from the needs of applications to address societal challenges and leveraging the strengths of the European eco-system. The roadmap will also identify promising novel nanoelectronic technologies, based on the advanced concepts developed by Research Centres and Universities, as well as identification of potential bottlenecks along the innovation (value) chain. Industry applications include Energy, Automotive, Medical/Life Science, Security, loT, Mobile Convergence and Digital Manufacturing. The NEREID roadmap covers Advanced Logic and Connectivity, Functional Diversification (Smart Sensors, Smart Energy and Energy for Autonomous Systems), Beyond-CMOS, Heterogeneous Integration and System Design as well as Equipment, Materials and Manufacturing Science. This article gives an overview of the roadmap's structure and content. © 2019 Elsevier Ltd

  • Nanomaterial-based Sensors for the Study of DNA Interaction with drugs

    De la Cruz Morales K., Alarcón-Angeles G., Merkoçi A. Electroanalysis; 2019. 10.1002/elan.201900286. IF: 2.691

    Nanobioelectronics and Biosensors

    The interaction of drugs with DNA has been searched thoroughly giving rise to an endless number of findings of undoubted importance, such as a prompt alert to harmful substances, ability to explain most of the biological mechanisms, or provision of important clues in targeted development of novel chemotherapeutics. The existence of some drugs that induce oxidative damage is an increasing point of concern as they can cause cellular death, aging, and are closely related to the development of many diseases. Because of a direct correlation between the response, strength/ nature of the interaction and the pharmaceutical action of DNA-targeted drugs, the electrochemical analysis is based on the signals of DNA before and after the interaction with the DNA-targeted drug. Nowadays, nanoscale materials are used extensively for offering fascinating characteristics that can be used in designing new strategies for drug-DNA interaction detection. This work presents a review of nanomaterials (NMs) for the study of drug-nucleic acid interaction. We summarize types of drug-DNA interactions, electroanalytical techniques for evidencing these interactions and quantification of drug and/or DNA monitoring. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Nanostructural changes upon substitutional Al doping in ZnO sputtered films

    Landa-Cánovas A.R., Santiso J., Agulló-Rueda F., Herrero P., Navarrete-Astorga E., Ochoa-Martínez E., Ramos-Barrado J.R., Gabás M. Ceramics International; 45 (5): 6319 - 6327. 2019. 10.1016/j.ceramint.2018.12.116. IF: 3.450

    Nanomaterials Growth Unit

    Al:ZnO layers, with low and high Al content, 0.2% and 2.1% cat. respectively, have been prepared using the RF magnetron sputtering technique. Noticeable differences in the optical and electrical properties have been detected in these films. With doping, the resistivity decreases and the band-gap increases. The alterations in the films crystalline structure are explained in terms of the nanostructural changes induced by Al substitutional doping, such as a higher concentration of edge dislocation defects and a higher rotation of crystalline nanodomains in the plane of the films (normal to the preferential orientation c-axis) for the high content Al:ZnO layer. A complete description of such effects has been accomplished using several characterization techniques, such as X-ray diffraction, Raman spectroscopy and transmission electron microscopy. The combination of these techniques provides an exhaustive understanding of the films nanostructure. © 2018 Elsevier Ltd and Techna Group S.r.l.

  • Nanowire forest of pnictogen-chalcogenide alloys for thermoelectricity

    Singhal D., Paterson J., Ben-Khedim M., Tainoff D., Cagnon L., Richard J., Chavez-Angel E., Fernandez J.J., Sotomayor-Torres C.M., Lacroix D., Bourgault D., Buttard D., Bourgeois O. Nanoscale; 11 (28): 13423 - 13430. 2019. 10.1039/c9nr01566c. IF: 6.970

    Phononic and Photonic Nanostructures

    Pnictogen and chalcogenide compounds have been seen as high-potential materials for efficient thermoelectric conversion over the past few decades. It is also known that with nanostructuration, the physical properties of these pnictogen-chalcogenide compounds can be further enhanced towards a more efficient heat conversion. Here, we report the reduced thermal conductivity of a large ensemble of Bi2Te3 alloy nanowires (70 nm in diameter) with selenium for n-type and antimony for p-type (Bi2Te3-ySey and Bi2-xSbxTe3 respectively). The nanowire growth was carried out through electrodeposition in nanoporous aluminium oxide templates with high aspect ratios leading to a forest (109 per centimetre square) of nearly identical nanowires. The temperature dependence of thermal conductivity for the nanowire ensembles was acquired through a highly sensitive 3ω measurement technique. The change in the thermal conductivity of nanowires is largely affected by the roughness in addition to the size effect due to enhanced boundary scattering. The major factor that influences the thermal conductivity was found to be the ratio of the rms roughness to the correlation length of the nanowire. With a high Seebeck coefficient and electrical conductivity at room temperature, the overall thermoelectric figure of merit ZT allows the consideration of such forests of nanowires as efficient potential building blocks of future TE devices. © 2019 The Royal Society of Chemistry.

  • Non-cytotoxic carbon nanocapsules synthesized via one-pot filling and end-closing of multi-walled carbon nanotubes

    Martincic M., Vranic S., Pach E., Sandoval S., Ballesteros B., Kostarelos K., Tobias G. Carbon; 141: 782 - 793. 2019. 10.1016/j.carbon.2018.10.006. IF: 7.466

    Electron Microscopy Unit

    Filled carbon nanotubes (CNTs) find application in a variety of fields that expand from sensors to supercapacitors going through targeted therapies. Bulk filling of CNTs in general results in samples that contain a large amount of non-encapsulated material external to the CNTs. The presence of external material can dominate the properties of the resulting hybrids and can also induce side effects when employed in the biomedical field. Unless the encapsulated payloads have a strong interaction with the inner CNT walls, an additional step is required to block the ends of the CNTs thus allowing the selective removal of the non-encapsulated compounds while preserving the inner cargo. Herein we present a fast, easy and versatile approach that allows both filling (NaI, KI, BaI2, GdCl3 and SmCl3) and end-closing of multi-walled CNTs in a single-step, forming “carbon nanocapsules”. Remarkably the encapsulation of GdCl3 and SmCl3 leads to the formation of tubular van der Waals heterostructures. The prepared nanocapsules are efficiently internalized by cells without inducing cytotoxicity, thus presenting a safe tool for the delivery of therapeutic and dianostic agents to cells. The synergies of novel carbon and inorganic hybrid materials can be explored using the present approach. © 2018 Elsevier Ltd

  • Nonvolatile Memories Based on Graphene and Related 2D Materials

    Bertolazzi S., Bondavalli P., Roche S., San T., Choi S.-Y., Colombo L., Bonaccorso F., Samorì P. Advanced Materials; 31 (10, 1806663) 2019. 10.1002/adma.201806663. IF: 25.809

    Theoretical and Computational Nanoscience

    The pervasiveness of information technologies is generating an impressive amount of data, which need to be accessed very quickly. Nonvolatile memories (NVMs) are making inroads into high-capacity storage to replace hard disk drives, fuelling the expansion of the global storage memory market. As silicon-based flash memories are approaching their fundamental limit, vertical stacking of multiple memory cell layers, innovative device concepts, and novel materials are being investigated. In this context, emerging 2D materials, such as graphene, transition metal dichalcogenides, and black phosphorous, offer a host of physical and chemical properties, which could both improve existing memory technologies and enable the next generation of low-cost, flexible, and wearable storage devices. Herein, an overview of graphene and related 2D materials (GRMs) in different types of NVM cells is provided, including resistive random-access, flash, magnetic and phase-change memories. The physical and chemical mechanisms underlying the switching of GRM-based memory devices studied in the last decade are discussed. Although at this stage most of the proof-of-concept devices investigated do not compete with state-of-the-art devices, a number of promising technological advancements have emerged. Here, the most relevant material properties and device structures are analyzed, emphasizing opportunities and challenges toward the realization of practical NVM devices. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Numerical study of a high sensitive polymer biosensor using a trimodal waveguide interferometer

    Ramirez J.C., Lechuga L.M., Gabrielli L.H., Hernandez-Figueroa H.E. Proceedings 2015 European Conference on Lasers and Electro-Optics - European Quantum Electronics Conf; 2019. . IF: 0.000

    NanoBiosensors and Bioanalytical Applications

    [No abstract available]

  • On the Enhancement of the Thermal Conductivity of Graphene-Based Nanofluids

    Rodriguez-Laguna M.R., Torres C.M.S., Gomez-Romero P., Chavez-Angel E. Proceedings of the IEEE Conference on Nanotechnology; 2018-July (8626244) 2019. 10.1109/NANO.2018.8626244. IF: 0.000

    Phononic and Photonic Nanostructures | Novel Energy-Oriented Materials

    Heat transfer fluids have been extensively used in both low-temperature and high temperature applications (e.g. microelectronics cooling and concentrated solar power). However, their low thermal conductivity is still a limit on performance. One way to enhance thermal properties is to disperse nanomaterials, such as graphene flakes in the base fluid. In this work, we have developed highly stable DMAc-graphene nanofluids with enhanced thermal properties. Furthermore, the displacement of several Raman bands as a function of graphene concentration in DMAc suggests that the solvent molecules are able to interact with graphene surfaces strongly. © 2018 IEEE.

  • On the role of ceria in Ni-Al2O3 catalyst for CO2 plasma methanation

    Biset-Peiró M., Guilera J., Zhang T., Arbiol J., Andreu T. Applied Catalysis A: General; 575: 223 - 229. 2019. 10.1016/j.apcata.2019.02.028. IF: 4.630

    Advanced Electron Nanoscopy

    The effect of Ce loading content on Ni-CeO2/Al2O3 catalysts for CO2 plasma methanation was evaluated. Catalysts were prepared by one-pot evaporation-induced self-assembly, Ni content was fixed at 15 wt. %, while CeO2 ranged 0–50 wt. %. The catalysts performances were tested under atmospheric pressure in two operation modes, thermal- and plasma-catalysis. As for conventional thermal catalysis, the catalyst was thermally activated between 200 and 400 °C; while in plasma-catalysis, the catalyst was activated by plasma generated by a dielectric barrier discharges (DBD) reactor. By the application of plasma in the catalyst bed, the reaction temperature was reduced from 350 °C to 150 °C to obtain the same level of conversion than thermal-catalysis. In addition, the incorporation of Ce in Ni-CeO2/Al2O3 led to an improvement of the catalytic performance in both thermal- and plasma-catalysis. Nevertheless, divergences on the optimum Ce content were found. On plasma experiments, the catalyst was more active at a lower amount of CeO2 (˜10 wt.%) with respect to thermal catalysis (˜40 wt.%), reducing the catalyst fabrication cost. Those differences highlights that the CO generated by plasma CO2 dissociation has a significant role for methane production, and thus the need to consider the by-products as reactant for the optimization of catalysts composition for DBD plasma-catalysis. © 2019 Elsevier B.V.

  • Optical Fiber Humidity Sensor Based on Polyvinylidene Fluoride Fabry-Perot

    Vaz A., Barroca N., Ribeiro M., Pereira A., Frazao O. IEEE Photonics Technology Letters; 31 (7, 8653388): 549 - 552. 2019. 10.1109/LPT.2019.2901571. IF: 2.553

    Oxide Nanophysics

    An optical fiber Fabry-Perot (FP) for relative humidity (RH) sensing is proposed. The FP cavity is fabricated by splicing a short length of hollow silica tube in a single mode fiber. The fiber is then coated with a polyvinylidene fluoride (PVDF) thin film to work as a mirror. The fabrication process of the FP interferometer with a dip coating process in a PVDF/dimethyl formamide solution is presented. The pattern fringes of the FP suffer a wavelength shift due to the change in the PVDF's refractive index with the ambient RH variation. A short overview of the cavity's formation and stability is presented. The RH response of the FPI cavity is tested. The sensor presented a sensitivity of 32.54 pm/%RH at constant temperature and -15.2 pm/°C for temperature variation. © 1989-2012 IEEE.

  • Optimization study of bimodal waveguide interferometric biosensors

    Grajales D., Lechuga L.M. Proceedings 2015 European Conference on Lasers and Electro-Optics - European Quantum Electronics Conf; 2019. . IF: 0.000

    NanoBiosensors and Bioanalytical Applications

    [No abstract available]

  • Optimizing the Limit of Detection of Waveguide-Based Interferometric Biosensor Devices

    Leuermann J., Fernández-Gavela A., Torres-Cubillo A., Postigo S., Sánchez-Postigo A., Lechuga L.M., Halir R., Molina-Fernández Í. Sensors (Basel, Switzerland); 19 (17) 2019. 10.3390/s19173671. IF: 3.031

    NanoBiosensors and Bioanalytical Applications

    Waveguide-based photonic sensors provide a unique combination of high sensitivity, compact size and label-free, multiplexed operation. Interferometric configurations furthermore enable a simple, fixed-wavelength read-out making them particularly suitable for low-cost diagnostic and monitoring devices. Their limit of detection, i.e., the lowest analyte concentration that can be reliably observed, mainly depends on the sensors response to small refractive index changes, and the noise in the read-out system. While enhancements in the sensors response have been extensively studied, noise optimization has received much less attention. Here we show that order-of-magnitude enhancements in the limit of detection can be achieved through systematic noise reduction, and demonstrate a limit of detection of ∼ 10 - 8 RIU with a silicon nitride sensor operating at telecom wavelengths.

  • Paper Based Photoluminescent Sensing Platform with Recognition Sites for Tributyltin

    Sari E., Üzek R., Merkoçi A. ACS Sensors; 4 (3): 645 - 653. 2019. 10.1021/acssensors.8b01396. IF: 6.944

    Nanobioelectronics and Biosensors

    In this study, a novel photoluminescence material for the detection of tributyltin (TBT) was developed by using a paper-based nanocomposite system. For this purpose, molecularly imprinted polymeric nanoparticles (MIN) were synthesized with mini-emulsion polymerization technique. Graphene quantum dots obtained by the hydrothermal pyrolysis were immobilized to the nanoparticle surface via EDC-NHS coupling. The fabrication of sensing platform for TBT can be divided into two steps that are the preparation of nanocomposite and the applying the nanocomposite onto nitrocellulose membrane. The selectivity constant and association kinetics were calculated to analyze the interaction of TBT with immobilized MINs. The results proved that the developed nanosensor is promising for the determination of TBT with high selectivity and sensitivity reaching a detection limit of 0.23 ppt in seawater. This novel photoluminescent nanosensor has the potential to pave the way for further studies and applications. © 2019 American Chemical Society.

  • PbZrTiO 3 ferroelectric oxide as an electron extraction material for stable halide perovskite solar cells

    Pérez-Tomas A., Xie H., Wang Z., Kim H.-S., Shirley I., Turren-Cruz S.-H., Morales-Melgares A., Saliba B., Tanenbaum D., Saliba M., Zakeeruddin S.M., Gratzel M., Hagfeldt A., Lira-Cantu M. Sustainable Energy and Fuels; 3 (2): 382 - 389. 2019. 10.1039/c8se00451j. IF: 4.912

    Oxide Nanophysics | Nanostructured Materials for Photovoltaic Energy

    State-of-the-art halide perovskite solar cells employ semiconductor oxides as electron transport materials. Defects in these oxides, such as oxygen vacancies (O vac ), act as recombination centres and, in air and UV light, reduce the stability of the solar cell. Under the same conditions, the PbZrTiO 3 ferroelectric oxide employs O vac for the creation of defect-dipoles responsible for photo-carrier separation and current transport, evading device degradation. We report the application of PbZrTiO 3 as the electron extraction material in triple cation halide perovskite solar cells. The application of a bias voltage (poling) up to 2 V, under UV light, is a critical step to induce charge transport in the ferroelectric oxide. Champion cells result in power conversion efficiencies of ∼11% after poling. Stability analysis, carried out at 1-sun AM 1.5 G, including UV light in air for unencapsulated devices, shows negligible degradation for hours. Our experiments indicate the effect of ferroelectricity, however alternative conducting mechanisms affected by the accumulation of charges or the migration of ions (or the combination of them) cannot be ruled out. Our results demonstrate, for the first time, the application of a ferroelectric oxide as an electron extraction material in efficient and stable PSCs. These findings are also a step forward in the development of next generation ferroelectric oxide-based electronic and optoelectronic devices. © 2019 The Royal Society of Chemistry.

  • Periodicity-Doubling Cascades: Direct Observation in Ferroelastic Materials

    Everhardt A.S., Damerio S., Zorn J.A., Zhou S., Domingo N., Catalan G., Salje E.K.H., Chen L.-Q., Noheda B. Physical Review Letters; 123 (8, 087603) 2019. 10.1103/PhysRevLett.123.087603. IF: 9.227

    Oxide Nanophysics

    Very sensitive responses to external forces are found near phase transitions. However, transition dynamics and preequilibrium phenomena are difficult to detect and control. We have observed that the equilibrium domain structure following a phase transition in ferroelectric and ferroelastic BaTiO3 is attained by halving of the domain periodicity multiple times. The process is reversible, with periodicity doubling as temperature is increased. This observation is reminiscent of the period-doubling cascades generally observed during bifurcation phenomena, and, thus, it conforms to the "spatial chaos" regime earlier proposed by Jensen and Bak [Phys. Scr. T 9, 64 (1985)PHSTER0281-184710.1088/0031-8949/1985/T9/009] for systems with competing spatial modulations. © 2019 American Physical Society.

  • Peripheral administration of human recombinant ApoJ/clusterin modulates brain beta-amyloid levels in APP23 mice

    De Retana S.F., Marazuela P., Solé M., Colell G., Bonaterra A., Sánchez-Quesada J.L., Montaner J., Maspoch D., Cano-Sarabia M., Hernández-Guillamon M. Alzheimer's Research and Therapy; 11 (1, 42) 2019. 10.1186/s13195-019-0498-8. IF: 6.142

    Supramolecular NanoChemistry and Materials

    Background: ApoJ/clusterin is a multifunctional protein highly expressed in the brain. The implication of ApoJ in β-amyloid (Aβ) fibrillization and clearance in the context of Alzheimer's disease has been widely studied, although the source and concentration of ApoJ that promotes or inhibits Aβ cerebral accumulation is not clear yet. ApoJ is abundant in plasma and approximately 20% can appear bound to HDL-particles. In this regard, the impact of plasmatic ApoJ and its lipidation status on cerebral β-amyloidosis is still not known. Hence, our main objective was to study the effect of a peripheral increase of free ApoJ or reconstituted HDL particles containing ApoJ in an experimental model of cerebral β-amyloidosis. Methods: Fourteen-month-old APP23 transgenic mice were subjected to subchronic intravenous treatment with rHDL-rApoJ nanodiscs or free rApoJ for 1 month. Aβ concentration and distribution in the brain, as well as Aβ levels in plasma and CSF, were determined after treatments. Other features associated to AD pathology, such as neuronal loss and neuroinflammation, were also evaluated. Results: Both ApoJ-based treatments prevented the Aβ accumulation in cerebral arteries and induced a decrease in total brain insoluble Aβ 42 levels. The peripheral treatment with rApoJ also induced an increase in the Aβ 40 levels in CSF, whereas the concentration remained unaltered in plasma. At all the endpoints studied, the lipidation of rApoJ did not enhance the protective properties of free rApoJ. The effects obtained after subchronic treatment with free rApoJ were accompanied by a reduction in hippocampal neuronal loss and an enhancement of the expression of a phagocytic marker in microglial cells surrounding Aβ deposits. Finally, despite the activation of this phagocytic phenotype, treatments did not induce a global neuroinflammatory status. In fact, free rApoJ treatment was able to reduce the levels of interleukin-17 (IL17) and keratinocyte chemoattractant (KC) chemokine in the brain. Conclusions: Our results demonstrate that an increase in circulating human rApoJ induces a reduction of insoluble Aβ and CAA load in the brain of APP23 mice. Thus, our study suggests that peripheral interventions, based on treatments with multifunctional physiological chaperones, offer therapeutic opportunities to regulate the cerebral Aβ load. © 2019 The Author(s).

  • Persistent M2 phase in strongly strained (011)-oriented grains in VO2 films grown on sapphire (001) in reactive sputtering

    Matsuoka K., Okimura K., Azhan N.H., Zaghrioui M., Sakai J. Journal of Applied Physics; 125 (16, 165304) 2019. 10.1063/1.5068700. IF: 2.328

    Oxide Nanophysics

    We report on the first observation of the persistent M2 phase in strongly strained (011)-oriented grains in VO2 films grown on Al2O3 (001) substrates by means of conventional rf reactive sputtering under adequate deposition conditions. Spatially resolved micro-Raman spectra clearly showed that (011)-oriented large crystalline grains with the cR-axis parallel to the substrate resulted in the appearance of the M2 phase over a wide temperature range of 30 °C. A close correlation of the appearance range of the M2 phase with the in-plane tensile stress of (011)-oriented grains was revealed by X-ray diffraction. We present a phase diagram for the M1, M2, and R phases in relation to the stress of (011)-oriented grains and temperature. It was shown that (011)-oriented micrometer-sized long grains play a crucial role in the emerging structural phase transition (SPT) via an M2 phase even in a film grown on Al2O3 (001), which is ordinarily reserved for the (020)-oriented VO2 growth. The results shown here will contribute to make clear the conditions for obtaining VO2 films with the appearance of the M2 phase in their SPT process. © 2019 Author(s).

  • Polarization dependence of angle-resolved photoemission with submicron spatial resolution reveals emerging one-dimensionality of electrons in NbSe3

    Valbuena M.A., Chudzinski P., Pons S., Conejeros S., Alemany P., Canadell E., Berger H., Frantzeskakis E., Avila J., Asensio M.C., Giamarchi T., Grioni M. Physical Review B; 99 (7, 075118) 2019. 10.1103/PhysRevB.99.075118. IF: 3.736

    Atomic Manipulation and Spectroscopy

    In materials with nearly commensurate band filling the electron liquid may spontaneously separate into components with distinct properties, yielding complex intra-and interunit cell ordering patterns and a reduced dimensionality. Polarization-dependent angle-resolved photoemission data with submicron spatial resolution demonstrate such an electronic self-organization in NbSe3, a compound considered to be a paradigm of charge order. The new data indicate the emergence of a novel order, and reveal the one-dimensional (1D) physics hidden in a material which naively could be considered the most three dimensional of all columnar chalcogenides. The 1D physics is evidenced by a new selection rule-in two polarizations we observe two strikingly different dispersions each closely resembling apparently contradicting results of previous studies of this material. © 2019 American Physical Society.

  • Polypyrrole Nanopipes as a Promising Cathode Material for Li-ion Batteries and Li-ion Capacitors: Two-in-One Approach

    Dubal D., Jagadale A., Chodankar N.R., Kim D.-H., Gomez-Romero P., Holze R. Energy Technology; 7 (2): 193 - 200. 2019. 10.1002/ente.201800551. IF: 3.163

    Novel Energy-Oriented Materials

    Lithium ion capacitor (LIC) is a promising energy storage system that can simultaneously provide high energy with high rate (high power). Generally, LIC is fabricated using capacitive cathode (activated carbon, AC) and insertion-type anode (graphite) with Li-ion based organic electrolyte. However, the limited specific capacities of both anode and cathode materials limit the performance of LIC, in particular energy density. In this context, we have developed “two in one” synthetic approach to engineer both cathode and anode from single precursor for high performance LIC. Firstly, we have engineered a low cost 1D polypyrrole nanopipes (PPy-NPipes), which was utilized as cathode material and delivered a maximum specific capacity of 126 mAh/g, far higher than that of conventional AC cathodes (35 mAh/g). Later, N doped carbon nanopipes (N-CNPipes) was derived from direct carbonization of PPy-NPipes and successfully applied as anode material in LIC. Thus, a full LIC was fabricated using both pseudo-capacitive cathode (PPy-NPipes) and anode (N-CNPipes) materials, respectively. The cell delivered a remarkable specific energy of 107 Wh/kg with maximum specific power of 10 kW/kg and good capacity retention of 93 % over 2000 cycles. Thus, this work provide a new approach of utilization of nanostructured conducting polymers as a promising pseudocapacitive cathode for high performance energy storage systems. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Porous NiTiO3/TiO2 nanostructures for photocatatalytic hydrogen evolution

    Xing C., Liu Y., Zhang Y., Liu J., Zhang T., Tang P., Arbiol J., Soler L., Sivula K., Guijarro N., Wang X., Li J., Du R., Zuo Y., Cabot A., Llorca J. Journal of Materials Chemistry A; 7 (28): 17053 - 17059. 2019. 10.1039/c9ta04763h. IF: 10.733

    Advanced Electron Nanoscopy

    We present a strategy to produce porous NiTiO3/TiO2 nanostructures with excellent photocatalytic activity toward hydrogen generation. In a first step, nickel-doped TiO2 needle bundles were synthesized by a hydrothermal procedure. Through the sintering in air of these nanostructures, porous NiTiO3/TiO2 heterostructured rods were obtained. Alternatively, the annealing in argon of the nickel-doped TiO2 needle bundles resulted in NiOx/TiO2 elongated nanostructures. Porous NiTiO3/TiO2 structures were tested for hydrogen evolution in the presence of ethanol. Such porous heterostructures exhibited superior photocatalytic activity toward hydrogen generation, with hydrogen production rates up to 11.5 mmol h-1 g-1 at room temperature. This excellent performance is related here to the optoelectronic properties and geometric parameters of the material. © 2019 The Royal Society of Chemistry.

  • Postsynthetic Covalent and Coordination Functionalization of Rhodium(II)-Based Metal-Organic Polyhedra

    Carné-Sánchez A., Albalad J., Grancha T., Imaz I., Juanhuix J., Larpent P., Furukawa S., Maspoch D. Journal of the American Chemical Society; 141 (9): 4094 - 4102. 2019. 10.1021/jacs.8b13593. IF: 14.695

    Supramolecular NanoChemistry and Materials

    Metal-organic polyhedra (MOP) are ultrasmall (typically 1-4 nm) porous coordination cages made from the self-assembly of metal ions and organic linkers and are amenable to the chemical functionalization of its periphery; however, it has been challenging to implement postsynthetic functionalization due to their chemical instability. Herein, we report the use of coordination chemistries and covalent chemistries to postsynthetically functionalize the external surface of â‰2.5 nm stable Rh(II)-based cuboctahedra through their Rh-Rh paddlewheel units or organic linkers, respectively. We demonstrate that 12 N-donor ligands, including amino acids, can be coordinated on the periphery of Rh-MOPs. We used this reactivity to introduce new functionalities (e.g., chirality) to the MOPs and to tune their hydrophilic/hydrophobic characteristics, which allowed us to modulate their solubility in diverse solvents such as dichloromethane and water. We also demonstrate that all 24 organic linkers can be postsynthetically functionalized with esters via covalent chemistry. In addition, we anticipate that these two types of postsynthetic reactions can be combined to yield doubly functionalized Rh-MOPs, in which a total of 36 new functional molecules can be incorporated on their surfaces. Likewise, these chemistries could be synergistically combined to enable covalent functionalization of MOPs through new linkages such as ethers. We believe that both reported postsynthetic pathways can potentially be used to engineer Rh-MOPs as scaffolds for applications in delivery, sorption, and catalysis. © Copyright 2019 American Chemical Society.

  • Precise Size Control of the Growth of Fe3O4 Nanocubes over a Wide Size Range Using a Rationally Designed One-Pot Synthesis

    Muro-Cruces J., Roca A.G., López-Ortega A., Fantechi E., Del-Pozo-Bueno D., Estradé S., Peiró F., Sepúlveda B., Pineider F., Sangregorio C., Nogues J. ACS Nano; 2019. 10.1021/acsnano.9b01281. IF: 13.903

    Magnetic Nanostructures

    The physicochemical properties of spinel oxide magnetic nanoparticles depend critically on both their size and shape. In particular, spinel oxide nanocrystals with cubic morphology have shown superior properties in comparison to their spherical counterparts in a variety of fields, like, for example, biomedicine. Therefore, having an accurate control over the nanoparticle shape and size, while preserving the crystallinity, becomes crucial for many applications. However, despite the increasing interest in spinel oxide nanocubes there are relatively few studies on this morphology due to the difficulty to synthesize perfectly defined cubic nanostructures, especially below 20 nm. Here we present a rationally designed synthesis pathway based on the thermal decomposition of iron(III) acetylacetonate to obtain high quality nanocubes over a wide range of sizes. This pathway enables the synthesis of monodisperse Fe3O4 nanocubes with edge length in the 9-80 nm range, with excellent cubic morphology and high crystallinity by only minor adjustments in the synthesis parameters. The accurate size control provides evidence that even 1-2 nm size variations can be critical in determining the functional properties, for example, for improved nuclear magnetic resonance T2 contrast or enhanced magnetic hyperthermia. The rationale behind the changes introduced in the synthesis procedure (e.g., the use of three solvents or adding Na-oleate) is carefully discussed. The versatility of this synthesis route is demonstrated by expanding its capability to grow other spinel oxides such as Co-ferrites, Mn-ferrites, and Mn3O4 of different sizes. The simplicity and adaptability of this synthesis scheme may ease the development of complex oxide nanocubes for a wide variety of applications. © 2019 American Chemical Society.

  • Preface

    Lechuga L., Raptis I., Jorge P., Cusano A. Optics and Laser Technology; 113: 35 - 36. 2019. 10.1016/j.optlastec.2018.12.006. IF: 3.319

    NanoBiosensors and Bioanalytical Applications

    [No abstract available]

  • Probing the nanoscale origin of strain and doping in graphene-hBN heterostructures

    Vincent T., Panchal V., Booth T., Power S.R., Jauho A.-P., Antonov V., Kazakova O. 2D Materials; 6 (1, 015022) 2019. 10.1088/2053-1583/aaf1dc. IF: 7.343

    Theoretical and Computational Nanoscience

    We use confocal Raman microscopy and a recently proposed vector analysis scheme to investigate the nanoscale origin of strain and carrier concentration in exfoliated graphene-hexagonal boron nitride (hBN) heterostructures on silicon dioxide (SiO2). Two types of heterostructures are studied: graphene on SiO2 partially covered by hBN, and graphene fully encapsulated between two hBN flakes. We extend the vector analysis method to produce separated spatial maps of the strain and doping variation across the heterostructures. This allows us to visualise and directly quantify the much-speculated effect of the environment on carrier concentration in graphene. Moreover, we demonstrate that variations in strain and carrier concentration in graphene arise from nanoscale features of the heterostructures such as fractures, folds and bubbles trapped between layers. For bubbles in hBN-encapsulated graphene, hydrostatic strain is shown to be greatest at bubble centres, whereas the maximum carrier concentration is localised at bubble edges. Raman spectroscopy is shown to be a non-invasive tool for probing strain and doping in graphene, which could prove useful for engineering of two-dimensional devices. © 2018 IOP Publishing Ltd.

  • Production and printing of graphene oxide foam ink for electrocatalytic applications

    Baptista-Pires L., de la Escosura-Muñiz A., Balsells M., Zuaznabar-Gardona J.C., Merkoçi A. Electrochemistry Communications; 98: 6 - 9. 2019. 10.1016/j.elecom.2018.11.001. IF: 4.197

    Nanobioelectronics and Biosensors

    A graphene-based ink printed as a foam-like structure with open pores is reported. The production of the ink is easier and faster than using existing methods and the obtained product is stable in water suspension. Electrocatalytic applications of 3D structured electrodes printed onto plastic substrates were explored. © 2018 Elsevier B.V.

  • Programmable Self-Assembling 3D Architectures Generated by Patterning of Swellable MOF-Based Composite Films

    Troyano J., Carné-Sánchez A., Maspoch D. Advanced Materials; 31 (21, 1808235) 2019. 10.1002/adma.201808235. IF: 25.809

    Supramolecular NanoChemistry and Materials

    The integration of swellable metal–organic frameworks (MOFs) into polymeric composite films is a straightforward strategy to develop soft materials that undergo reversible shape transformations derived from the intrinsic flexibility of MOF crystals. However, a crucial step toward their practical application relies on the ability to attain specific and programmable actuation, which enables the design of self-shaping objects on demand. Herein, a chemical etching method is demonstrated for the fabrication of patterned composite films showing tunable self-folding response, predictable and reversible 2D-to-3D shape transformations triggered by water adsorption/desorption. These films are fabricated by selective removal of swellable MOF crystals allowing control over their spatial distribution within the polymeric film. Upon exposure to moisture, various programmable 3D architectures, which include a mechanical gripper, a lift, and a unidirectional walking device, are generated. Remarkably, these 2D-to-3D shape transformations can be reversed by light-induced desorption. The reported strategy offers a platform for fabricating flexible MOF-based autonomous soft mechanical devices with functionalities for micromanipulation, automation, and robotics. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Puzzling robust 2D metallic conductivity in undoped β-Ga 2 O 3 thin films

    Chikoidze E., Rogers D.J., Teherani F.H., Rubio C., Sauthier G., Von Bardeleben H.J., Tchelidze T., Ton-That C., Fellous A., Bove P., Sandana E.V., Dumont Y., Perez-Tomas A. Materials Today Physics; 8: 10 - 17. 2019. 10.1016/j.mtphys.2018.11.006. IF: 0.000

    Oxide Nanophysics | Nanomaterials Growth Unit

    Here, we report the analogy of an extremely stable topological-like ultra-wide bandgap insulator, a solid that is a pure insulator in its bulk but has a metallic conductive surface, presenting a two-dimensional conductive channel at its surface that challenges our current thinking about semiconductor conductivity engineering. Nominally undoped epitaxial β-Ga 2 O 3 thin films without any detectable defect (after a range of state-of-the-art techniques) showed the unexpectedly low resistivity of 3 × 10 −2 Ωcm which was found to be also resistant to high dose proton irradiation (2 MeV, 5 × 10 15 cm −2 dose) and was largely invariant (metallic) over the phenomenal temperature range of 2 K up to 850 K. The unique resilience and stability of the electrical properties under thermal and highly ionizing radiation stressing, combined with the extended transparency range (thanks to the ultra-wide bandgap) and the already known toughness under high electrical field could open up new perspectives for use as expanded spectral range transparent electrodes (e.g., for UV harvesting solar cells or UV LEDs/lasers) and robust Ohmic contacts for use in extreme environments/applications and for novel optoelectronic and power device concepts. © 2018 Elsevier Ltd

  • Real space manifestations of coherent screening in atomic scale Kondo lattices

    Moro-Lagares M., Korytár R., Piantek M., Robles R., Lorente N., Pascual J.I., Ibarra M.R., Serrate D. Nature Communications; 10 (1, 2211) 2019. 10.1038/s41467-019-10103-5. IF: 11.878

    Theory and Simulation

    The interaction among magnetic moments screened by conduction electrons drives quantum phase transitions between magnetically ordered and heavy-fermion ground states. Here, starting from isolated magnetic impurities in the Kondo regime, we investigate the formation of the finite size analogue of a heavy Fermi liquid. We build regularly-spaced chains of Co adatoms on a metallic surface by atomic manipulation. Scanning tunneling spectroscopy is used to obtain maps of the Kondo resonance intensity with sub-atomic resolution. For sufficiently small interatomic separation, the spatial distribution of Kondo screening does not coincide with the position of the adatoms. It also develops enhancements at both edges of the chains. Since we can rule out any other interaction between Kondo impurities, this is explained in terms of the indirect hybridization of the Kondo orbitals mediated by a coherent electron gas, the mechanism that causes the emergence of heavy quasiparticles in the thermodynamic limit. © 2019, The Author(s).

  • Replication of nanoscale surface gratings via injection molding

    Muntada-López O., Pina-Estany J., Colominas C., Fraxedas J., Pérez-Murano F., García-Granada A. Micro and Nano Engineering; 3: 37 - 43. 2019. 10.1016/j.mne.2019.03.003. IF: 0.000

    Force Probe Microscopy and Surface Nanoengineering

    Nanostructured gratings fabricated on silicon chips have been successfully transferred to polypropylene plastic parts by means of injection molding. Different sets of experiments were carried out along with a repeatability analysis in order to study the effect in the replication of process parameters such as maximum injection pressure, injection time, charge and polymer temperature, geometric factors such as width and separation between lines of the gratings and flow direction as well as demolding conditions. Among all factors, the one with a larger effect is the separation between consecutive trenches, which was studied in detail through Computational Fluid Dynamics simulations. In addition, a previously not reported sinking effect in the nanostructured area and a shrinking of the pattern period were characterized and simulated. © 2019 The Authors

  • Robust one-pot synthesis of citrate-stabilized Au@CeO 2 hybrid nanocrystals with different thickness and dimensionality

    Bastús N.G., Piella J., Perez S., Patarroyo J., Genç A., Arbiol J., Puntes V. Applied Materials Today; 15: 445 - 452. 2019. 10.1016/j.apmt.2019.03.003. IF: 8.013

    Inorganic Nanoparticles | Advanced Electron Nanoscopy

    Well-defined colloidal Au@CeO 2 hybrid nanocrystals (NCs) comprising different core/shell morphologies have been synthesized via a novel and simple one-pot aqueous approach. The method allows producing hybrid morphologies composed by an active and accessible Au core coated by a porous CeO 2 shell with varying shell thickness and dimensionality by simply adjusting the Au 3+ /Ce 3+ precursor ratio. These hybrid NCs are highly monodisperse and well-dispersed in water, showing intense surface plasmon resonance bands that offer unique opportunities for advanced material applications, such as plasmonics and catalysis. © 2019 Elsevier Ltd

  • Role of Boron and Phosphorus in Enhanced Electrocatalytic Oxygen Evolution by Nickel Borides and Nickel Phosphides

    Masa J., Andronescu C., Antoni H., Sinev I., Seisel S., Elumeeva K., Barwe S., Marti-Sanchez S., Arbiol J., Roldan Cuenya B., Muhler M., Schuhmann W. ChemElectroChem; 6 (1): 235 - 240. 2019. 10.1002/celc.201800669. IF: 3.975

    Advanced Electron Nanoscopy

    The modification of nickel with boron or phosphorus leads to significant enhancement of its electrocatalytic activity for the oxygen evolution reaction (OER). However, the precise role of the guest elements, B and P, in enhancing the OER of the host element (Ni) remains unclear. Herein, we present insight into the role of B and P in enhancing electrocatalysis of oxygen evolution by nickel borides and nickel phosphides. The apparent activation energy, Ea*, of electrocatalytic oxygen evolution on Ni2P was 78.4 kJ/mol, on Ni2B 65.4 kJ/mol, and on Ni nanoparticles 94.0 kJ/mol, thus revealing that both B and P affect the intrinsic activity of nickel. XPS data revealed shifts of −0.30 and 0.40 eV in the binding energy of the Ni 2p3/2 peak of Ni2B and Ni2P, respectively, with respect to that of pure Ni at 852.60 eV, thus indicating that B and P induce opposite electronic effects on the surface electronic structure of Ni. The origin of enhanced activity for oxygen evolution cannot, therefore, be attributed to such electronic modification or ligand effect. Severe changes induced on the nickel lattice, specifically, the Ni-Ni atomic order and interatomic distances (strain effect), by the presence of the guest atoms seem to be the dominant factors responsible for enhanced activity of oxygen evolution in nickel borides and nickel phosphides. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Role of Penetrability into a Brush-Coated Surface in Directed Self-Assembly of Block Copolymers

    Evangelio L., Fernández-Regúlez M., Fraxedas J., Müller M., Pérez-Murano F. ACS Applied Materials and Interfaces; 11 (3): 3571 - 3581. 2019. 10.1021/acsami.8b19062. IF: 8.456

    Force Probe Microscopy and Surface Nanoengineering

    High-density and high-resolution line and space patterns on surfaces are obtained by directed self-assembly of lamella-forming block copolymers (BCPs) using wide-stripe chemical guiding patterns. When the width of the chemical pattern is larger than the half-pitch of the BCP, the interaction energy between each BCP domain and the surface is crucial to obtain the desired segregated film morphology. We investigate how the intermixing between BCPs and polymer brush molecules on the surface influences the optimal surface and interface free energies to obtain a proper BCP alignment. We have found that computational models successfully predict the experimentally obtained guided patterns if the penetrability of the brush layer is taken into account instead of a hard, impenetrable surface. Experiments on directed self-assembly of lamella-forming poly(styrene-block-methyl methacrylate) using chemical guiding patterns corroborate the models used in the simulations, where the values of the surface free energy between the BCP and the guiding and background stripes are accurately determined using an experimental method based on the characterization of contact angles in droplets formed after dewetting of homopolymer blends. © 2018 American Chemical Society.

  • Room-Temperature Spin Hall Effect in Graphene/MoS 2 van der Waals Heterostructures

    Safeer C.K., Ingla-Aynés J., Herling F., Garcia J.H., Vila M., Ontoso N., Calvo M.R., Roche S., Hueso L.E., Casanova F. Nano Letters; 2019. 10.1021/acs.nanolett.8b04368. IF: 12.279

    Theoretical and Computational Nanoscience

    Graphene is an excellent material for long-distance spin transport but allows little spin manipulation. Transition-metal dichalcogenides imprint their strong spin-orbit coupling into graphene via the proximity effect, and it has been predicted that efficient spin-to-charge conversion due to spin Hall and Rashba-Edelstein effects could be achieved. Here, by combining Hall probes with ferromagnetic electrodes, we unambiguously demonstrate experimentally the spin Hall effect in graphene induced by MoS 2 proximity and for varying temperatures up to room temperature. The fact that spin transport and the spin Hall effect occur in different parts of the same material gives rise to a hitherto unreported efficiency for the spin-to-charge voltage output. Additionally, for a single graphene/MoS 2 heterostructure-based device, we evidence a superimposed spin-to-charge current conversion that can be indistinguishably associated with either the proximity-induced Rashba-Edelstein effect in graphene or the spin Hall effect in MoS 2 . By a comparison of our results to theoretical calculations, the latter scenario is found to be the most plausible one. Our findings pave the way toward the combination of spin information transport and spin-to-charge conversion in two-dimensional materials, opening exciting opportunities in a variety of future spintronic applications. © 2019 American Chemical Society.

  • S53P4 Bioactive Glass Inorganic Ions for Vascularized Bone Tissue Engineering by Dental Pulp Pluripotent-Like Stem Cell Cocultures

    Núñez-Toldrà R., Montori S., Bosch B., Hupa L., Atari M., Miettinen S. Tissue Engineering - Part A; 25 (17-18): 1213 - 1224. 2019. 10.1089/ten.tea.2018.0256. IF: 3.616

    Vascularization of large bone grafts is one of the main challenges that limit the clinical application of bone tissue engineering (BTE). In this way, cell cocultures, which involve the cross-talk between endothelial and osteogenic cells, have shown to be an effective strategy for in vitro prevascularization. Dental pulp represents an easily accessible autologous source of adult stem cells. A subset of these cells, named dental pulp pluripotent-like stem cells (DPPSCs), shows high plasticity and great capacity to differentiate into different tissues. Here, we suggested a combination of bone-like DPPSC and endothelial-like DPPSC to induce vascularized bone formation from a unique stem cell population. In addition, we evaluated the use of inorganic ions dissolved from S53P4 bioactive glass (BaG) in different medium compositions. Results show that endothelial medium with BaG extracts provides an effective way to enhance both endothelial and osteogenic processes, supporting the formation of vascular-like structures and mineralization simultaneously. Furthermore, 3D DPPSC cocultures in the same medium conditions demonstrated the formation of vessel-like structures that appear to be functional as indicated by the presence of an internal lumen. Overall, these results would provide a new promising system for the prevascularization of BTE constructs. In this study, we proposed for the first time the use of inorganic ions dissolved from BaG in a cell coculture system to induce vascularized bone formation in vitro. For that, we used dental pulp pluripotent-like stem cells from a single individual source obtained in a minimally invasive extraction manner. Moreover, we carried out all the experiments under xeno-free conditions, allowing the extrapolation of the results to the development of clinically orientated applications. Overall, these results would provide a new promising system to promote the success and survival of bone tissue engineering constructs after implantation. © 2019, Mary Ann Liebert, Inc., publishers 2019.

  • Segregation scheme of indium in AlGaInAs nanowire shells

    Francaviglia L., Tütüncüoglu G., Martí-Sánchez S., Di Russo E., Escobar Steinvall S., Segura Ruiz J., Potts H., Friedl M., Rigutti L., Arbiol J., Fontcuberta I Morral A. Physical Review Materials; 3 (2, 023001) 2019. 10.1103/PhysRevMaterials.3.023001. IF: 2.926

    Advanced Electron Nanoscopy

    Quaternary alloys enable the independent optimization of different semiconductor properties, such as the separate tuning of the band gap and the lattice constant. Nanowire core-shell structures should allow a larger range of compositional tuning as strain can be accommodated in a more effective manner than in thin films. Still, the faceted structure of the nanowire may lead to local segregation effects. Here, we explore the incorporation of indium in AlGaAs shells up to 25%. In particular, we show the effect of In incorporation on the energy shift of the AlGaInAs single-photon emitters present in the shell. We observe a redshift up to 300 meV as a function of the group-III site fraction of In. We correlate the shift with segregation at the nanoscale. We find evidence of the segregation of the group-III elements at different positions in the nanowire, not observed before. We propose a model that takes into account the strain distribution in the nanowire shell and the adatom diffusion on the nanowire facets to explain the observations. This work provides novel insights on the segregation phenomena necessary to engineer the composition of multidinary alloys. © 2019 American Physical Society.

  • Selectivity Map for Molecular Beam Epitaxy of Advanced III-V Quantum Nanowire Networks

    Aseev P., Fursina A., Boekhout F., Krizek F., Sestoft J.E., Borsoi F., Heedt S., Wang G., Binci L., Martí-Sánchez S., Swoboda T., Koops R., Uccelli E., Arbiol J., Krogstrup P., Kouwenhoven L.P., Caroff P. Nano Letters; 19 (1): 218 - 227. 2019. 10.1021/acs.nanolett.8b03733. IF: 12.279

    Advanced Electron Nanoscopy

    Selective-area growth is a promising technique for enabling of the fabrication of the scalable III-V nanowire networks required to test proposals for Majorana-based quantum computing devices. However, the contours of the growth parameter window resulting in selective growth remain undefined. Herein, we present a set of experimental techniques that unambiguously establish the parameter space window resulting in selective III-V nanowire networks growth by molecular beam epitaxy. Selectivity maps are constructed for both GaAs and InAs compounds based on in situ characterization of growth kinetics on GaAs(001) substrates, where the difference in group III adatom desorption rates between the III-V surface and the amorphous mask area is identified as the primary mechanism governing selectivity. The broad applicability of this method is demonstrated by the successful realization of high-quality InAs and GaAs nanowire networks on GaAs, InP, and InAs substrates of both (001) and (111)B orientations as well as homoepitaxial InSb nanowire networks. Finally, phase coherence in Aharonov-Bohm ring experiments validates the potential of these crystals for nanoelectronics and quantum transport applications. This work should enable faster and better nanoscale crystal engineering over a range of compound semiconductors for improved device performance. © 2018 American Chemical Society.

  • Self-assembly morphology of block copolymers in sub-10 nm topographical guiding patterns

    Gottlieb S., Rösner B., Evangelio L., Fernández-Regúlez M., Nogales A., García-Gutiérrez M.C., Keller T.F., Fraxedas J., Ezquerra T.A., David C., Perez-Murano F. Molecular Systems Design and Engineering; 4 (1): 175 - 185. 2019. 10.1039/c8me00046h. IF: 2.708

    Force Probe Microscopy and Surface Nanoengineering

    In this paper, we investigate the directed self-assembly of block copolymers in topographical guiding patterns with feature sizes in the range of the block copolymer half-pitch. In particular, we present the self-assembly of an 11.7 nm half-pitch block copolymer in sub-10 nm resolution guiding patterns fabricated by the direct e-beam exposure of hydrogen silsesquioxane (HSQ). One result of this analysis is that the block copolymer self-assembles such that the guiding pattern features form part of the 3-D architecture of the film. We are capable of determining a shift in the block copolymer pitch as a function of the guiding pattern pitch with sub-nanometer accuracy by means of both real-space (AFM, SEM) and reciprocal-space techniques (GISAXS). An interesting result is that the block copolymer self-assembly in the studied structures depends on the guiding pattern pitch rather than on the trench width as in standard graphoepitaxy. We analyze the structures by means of a free energy model and present both theoretical and experimental evidence of a narrower processing window for such kind of guiding patterns than for regular directed self-assembly using wide topographical guiding patterns, and discuss the origin of this effect. We argue that chain deformation in the vicinity of the top cap of the guiding pattern feature is responsible for an increase of the free energy of the ordered state, which leads to a smaller energy difference between the defect-free and defective self-assembly than that for the observed self-assembly morphology. © 2019 The Royal Society of Chemistry.

  • Signal enhancement on gold nanoparticle-based lateral flow tests using cellulose nanofibers

    Quesada-González D., Stefani C., González I., de la Escosura-Muñiz A., Domingo N., Mutjé P., Merkoçi A. Biosensors and Bioelectronics; 141 (111407) 2019. 10.1016/j.bios.2019.111407. IF: 9.518

    Oxide Nanophysics | Nanobioelectronics and Biosensors | Advanced AFM Laboratory

    Lateral flow paper-based biosensors merge as powerful tools in point-of-care diagnostics since they are cheap, portable, robust, selective, fast and easy to use. However, the sensitivity of this type of biosensors is not always as high as required, often not permitting a clear quantification. To improve the colorimetric response of standard lateral flow strips (LFs), we have applied a new enhancement strategy that increases the sensitivity of LFs based on the use of cellulose nanofibers (CNF). CNF penetrate inside the pores of LFs nitrocellulose paper, compacting the pore size only in the test line, particularly near the surface of the strip. This modification retains the bioreceptors (antibodies) close to the surface of the strips, and thus further increasing the density of selectively attached gold nanoparticles (AuNPs) in the top part of the membrane, in the test line area, only when the sample is positive. This effect boosts in average a 36.6% the sensitivity of the LFs. The optical measurements of the LFs were carried out with a mobile phone camera whose imaging resolution was improved by attaching microscopic lens on the camera objective. The characterization of CNF into paper and their effect was analyzed using atomic force microscope (AFM) and scanning electron microscope (SEM) imaging techniques. © 2019 Elsevier B.V.

  • Size-selective encapsulation of C 60 and C 60 -derivatives within an adaptable naphthalene-based tetragonal prismatic supramolecular nanocapsule

    García-Simón C., Monferrer A., Garcia-Borràs M., Imaz I., Maspoch D., Costas M., Ribas X. Chemical Communications; 55 (6): 798 - 801. 2019. 10.1039/c8cc07886f. IF: 6.164

    Supramolecular NanoChemistry and Materials

    A novel naphthalene-based 5·(BArF) 8 capsule allows for the size-selective inclusion of C 60 from fullerene mixtures. Its size selectivity towards C 60 has been rationalized by its dynamic adaptability in solution that has been investigated by molecular dynamics. Additionally, 5·(BArF) 8 encapsulates C 60 -derivatives such as C 60 -PCBM and N-methylpyrrolidine-C 60 . The latter can be separated from C 60 since 5·(BArF) 8 displays distinct affinity for them. © The Royal Society of Chemistry.

  • Solid Materials with Tunable Reverse Photochromism

    Julià-López A., Ruiz-Molina D., Hernando J., Roscini C. ACS Applied Materials and Interfaces; 11 (12): 11884 - 11892. 2019. 10.1021/acsami.8b22335. IF: 8.456

    Nanostructured Functional Materials

    Herein, we report a novel, straightforward, and universal strategy to achieve solid materials with highly tunable reverse photochromism. This was accomplished by means of commercially available spiropyran dyes, which can produce different types of stable merocyanine states (i.e., nonprotonated and protonated forms) displaying distinct reverse photochromic properties (i.e., colors and coloration rates). To finely control the concentration ratio of these species and, as such, tailor the optical performance of the photochromes, we exploited their differential interaction with surrounding media of distinctive nature (i.e., nonvolatile protic and aprotic polar solvents). In this way, solutions displaying different photochromic responses were prepared for individual spiropyrans without requiring chemical derivatization, an approach that can be generalized to other spiro dyes with distinct acid-base properties. To transfer this behavior to the solid state, core-shell capsules of these solutions were prepared, which were then used as ink materials for the fabrication of flexible polymeric films with unprecedented tunability of their photochromic properties that can be employed as rewritable multicolored devices. © 2019 American Chemical Society.

  • Solution-Processed Ultrathin SnS 2 -Pt Nanoplates for Photoelectrochemical Water Oxidation

    Zuo Y., Liu Y., Li J., Du R., Yu X., Xing C., Zhang T., Yao L., Arbiol J., Llorca J., Sivula K., Guijarro N., Cabot A. ACS Applied Materials and Interfaces; 11 (7): 6918 - 6926. 2019. 10.1021/acsami.8b17622. IF: 8.456

    Advanced Electron Nanoscopy

    Tin disulfide (SnS 2 ) is attracting significant interest because of the abundance of its elements and its excellent optoelectronic properties in part related to its layered structure. In this work, we specify the preparation of ultrathin SnS 2 nanoplates (NPLs) through a hot-injection solution-based process. Subsequently, Pt was grown on their surface via in situ reduction of a Pt salt. The photoelectrochemical (PEC) performance of such nanoheterostructures as photoanode toward water oxidation was tested afterwards. Optimized SnS 2 -Pt photoanodes provided significantly higher photocurrent densities than bare SnS 2 and SnS 2 -based photoanodes of previously reported study. Mott-Schottky analysis and PEC impedance spectroscopy (PEIS) were used to analyze in more detail the effect of Pt on the PEC performance. From these analyses, we attribute the enhanced activity of SnS 2 -Pt photoanodes reported here to a combination of the very thin SnS 2 NPLs and the proper electronic contact between Pt nanoparticles (NPs) and SnS 2 . © 2019 American Chemical Society.

  • Spin communication over 30 μm long channels of chemical vapor deposited graphene on SiO2

    Gebeyehu Z.M., Parui S., Sierra J.F., Timmermans M., Esplandiu M.J., Brems S., Huyghebaert C., Garello K., Costache M.V., Valenzuela S.O. 2D Materials; 6 (3, 034003) 2019. 10.1088/2053-1583/ab1874. IF: 7.343

    Physics and Engineering of Nanodevices | Magnetic Nanostructures

    We demonstrate a high-yield fabrication of non-local spin valve devices with room-temperature spin lifetimes of up to 3 ns and spin relaxation lengths as long as 9 μm in platinum-based chemical vapor deposition (Pt-CVD) synthesized single-layer graphene on SiO2/Si substrates. The spin-lifetime systematically presents a marked minimum at the charge neutrality point, as typically observed in pristine exfoliated graphene. However, by studying the carrier density dependence beyond n ∼ 5 × 1012 cm-2, via electrostatic gating, it is found that the spin lifetime reaches a maximum and then starts decreasing, a behavior that is reminiscent of that predicted when the spin-relaxation is driven by spin-orbit interaction. The spin lifetimes and relaxation lengths compare well with state-of-the-art results using exfoliated graphene on SiO2/Si, being a factor two-to-three larger than the best values reported at room temperature using the same substrate. As a result, the spin signal can be readily measured across 30 μm long graphene channels. These observations indicate that Pt-CVD graphene is a promising material for large-scale spin-based logic-in-memory applications. © 2019 IOP Publishing Ltd.

  • Spin States Protected from Intrinsic Electron-Phonon Coupling Reaching 100 ns Lifetime at Room Temperature in MoSe2

    Ersfeld M., Volmer F., De Melo P.M.M.C., De Winter R., Heithoff M., Zanolli Z., Stampfer C., Verstraete M.J., Beschoten B. Nano Letters; 19 (6): 4083 - 4090. 2019. 10.1021/acs.nanolett.9b01485. IF: 12.279

    Theory and Simulation

    We present time-resolved Kerr rotation measurements, showing spin lifetimes of over 100 ns at room temperature in monolayer MoSe2. These long lifetimes are accompanied by an intriguing temperature-dependence of the Kerr amplitude, which increases with temperature up to 50 K and then abruptly switches sign. Using ab initio simulations, we explain the latter behavior in terms of the intrinsic electron-phonon coupling and the activation of transitions to secondary valleys. The phonon-assisted scattering of the photoexcited electron-hole pairs prepares a valley spin polarization within the first few ps after laser excitation. The sign of the total valley magnetization, and thus the Kerr amplitude, switches as a function of temperature, as conduction and valence band states exhibit different phonon-mediated intervalley scattering rates. However, the electron-phonon scattering on the ps time scale does not provide an explanation for the long spin lifetimes. Hence, we deduce that the initial spin polarization must be transferred into spin states, which are protected from the intrinsic electron-phonon coupling, and are most likely resident charge carriers, which are not part of the itinerant valence or conduction band states. © 2019 American Chemical Society.

  • Strain-induced resistance change in V2O3 films on piezoelectric ceramic disks

    Sakai J., Bavencoffe M., Negulescu B., Limelette P., Wolfman J., Tateyama A., Funakubo H. Journal of Applied Physics; 125 (11, 115102) 2019. 10.1063/1.5083941. IF: 2.328

    Oxide Nanophysics

    We prepared a stacked structure consisting of a quasi-free-standing functional oxide thin film and a ceramic piezoelectric disk and observed the effect of the piezoelectric disk deformation on the resistance of the thin film. Epitaxial V2O3 films were grown by a pulsed laser deposition method on muscovite mica substrates, peeled off using Scotch tapes, and transferred onto piezoelectric elements. In this V2O3/insulator/top electrode/piezoelectronic disk/bottom electrode structure, the resistance of the V2O3 film displayed a variation of 60% by sweeping the piezoelectronic disk bias. With support from x-ray diffraction measurements under an electric field, a huge gauge factor of 3 × 103 in the V2O3 film was inferred. The sizeable resistance change in the V2O3 layer is ascribed to the piezo-actuated evolution of c/a ratios, which drives the material towards an insulating phase. A memory effect on the resistance, related to the hysteretic displacement of the piezoelectric material, is also presented. © 2019 Author(s).

  • Subamorphous Thermal Conductivity of Crystalline Half-Heusler Superlattices

    Chavez-Angel E., Reuter N., Komar P., Heinz S., Kolb U., Kleebe H.-J., Jakob G. Nanoscale and Microscale Thermophysical Engineering; 23 (1): 1 - 9. 2019. 10.1080/15567265.2018.1505987. IF: 3.323

    Phononic and Photonic Nanostructures

    The quest to improve the thermoelectric figure of merit has mainly followed the roadmap of lowering the thermal conductivity while keeping unaltered the power factor of the material. Ideally an electron-crystal phonon-glass system is desired. In this work, we report an extraordinary reduction of the cross-plane thermal conductivity in crystalline (TiNiSn):(HfNiSn) half-Heusler superlattices (SLs). We create SLs with thermal conductivities below the effective amorphous limit, which is kept in a large temperature range (120–300 K). We measured thermal conductivity at room temperature values as low as 0.75 W m −1  K −1 , the lowest thermal conductivity value reported so far for half-Heusler compounds. By changing the deposition conditions, we also demonstrate that the thermal conductivity is highly impacted by the way the single segments of the SL grow. These findings show a huge potential for thermoelectric generators where an extraordinary reduction of the thermal conductivity is required but without losing the crystal quality of the system. © 2018, © 2018 Taylor & Francis.

  • Superposition of interface and volume type resistive switching in perovskite nanoionic devices

    Bagdzevicius S., Boudard M., Caicedo J.M., Rapenne L., Mescot X., Rodríguez-Lamas R., Robaut F., Santiso J., Burriel M. Journal of Materials Chemistry C; 7 (25): 7580 - 7592. 2019. 10.1039/c9tc00609e. IF: 6.641

    Nanomaterials Growth Unit

    The microelectronics industry is currently searching for reliable redox-based resistive switching (RS) memories which are filament-free, scale with the electrode size and do not require a high voltage electroforming step. Interface and volume type switching devices are the most promising memristors to achieve these challenging requirements, both for ReRAM (Resistive Random-Access Memories) non-volatile memory and neuromorphic computing applications. Here RS was investigated for the first time in nanoionic memristors based on GdBaCo2O5+δ (GBCO), an oxide with high oxygen mobility. Non-filamentary and non-volatile reproducible RS was obtained when GBCO is sandwiched between Ag and LaNiO3 (LNO) electrodes. The observed bipolar RS could be successfully induced both by voltage sweeps and by pulses, showing asymmetric clock-wise hysteretic R(V) characteristics at room temperature. The temperature dependence of two independent devices in high and low resistance states (HRS and LRS) revealed a gradual decrease of the resistance difference between the two states on cooling from room temperature to 150 K and its increase below 100 K. Similarly, the R(V) switching curves obtained at low temperature showed the disappearance of the hysteresis at 150 K and its reappearance at lower temperatures. The superposition of volume and interface type RS mechanisms have proven to be responsible for the observed non-volatile change of the remnant resistance. The volume-type RS was related to the variation of the GBCO resistivity due to a change in oxygen content. The interface-type RS, on the other hand, was associated to the created electronic and ionic conduction barrier between GBCO and the LNO bottom electrode. © 2019 The Royal Society of Chemistry.

  • Sustainable synthesis of luminescent CdTe quantum dots coated with modified silica mesoporous nanoparticles: Towards new protein scavengers and smart drug delivery carriers

    Oliveira E., Santos H.M., Jorge S., Rodríguez-González B., Novio F., Lorenzo J., Ruiz-Molina D., Capelo J.L., Lodeiro C. Dyes and Pigments; 161: 360 - 369. 2019. 10.1016/j.dyepig.2018.09.047. IF: 4.018

    Nanostructured Functional Materials

    The synthesis and full characterization of a family of sustainable luminescent nanoparticles, CdTeQDs@MNs, made of quantum dots coated by modified mesoporous silica nanoparticles is reported. The presence of the luminescent QDs allows the imaging of the nanoparticles during cell internalization, as well as the visualization of selective release of doxorubicin inside the cell (via pH stimuli). The modified mesoporous silica nanoparticles lead to pore size improvement allowing better encapsulation and controlled release, of different active principles studied such as, small molecules (rhodamine B), drugs (doxorubicin), and isolated proteins such as bovine serum albumin, lysozyme, carbonic anhydrase, ovalbumin, α-lactalbumin, hemoglobin, myoglobin and cytochrome C. Finally, and as a proof-of-concept the efficacy of these novel platforms was demonstrated through the successful extraction and recognition of proteins in raw serum of osteoarthritis and prosthesis patients, without any previous protein depletion. © 2018 Elsevier Ltd

  • Synchronization of Optomechanical Nanobeams by Mechanical Interaction

    Colombano M.F., Arregui G., Capuj N.E., Pitanti A., Maire J., Griol A., Garrido B., Martinez A., Sotomayor-Torres C.M., Navarro-Urrios D. Physical Review Letters; 123 (1, 017402) 2019. 10.1103/PhysRevLett.123.017402. IF: 9.227

    Phononic and Photonic Nanostructures

    The synchronization of coupled oscillators is a phenomenon found throughout nature. Mechanical oscillators are paradigmatic examples, but synchronizing their nanoscaled versions is challenging. We report synchronization of the mechanical dynamics of a pair of optomechanical crystal cavities that, in contrast to previous works performed in similar objects, are intercoupled with a mechanical link and support independent optical modes. In this regime they oscillate in antiphase, which is in agreement with the predictions of our numerical model that considers reactive coupling. We also show how to temporarily disable synchronization of the coupled system by actuating one of the cavities with a heating laser, so that both cavities oscillate independently. Our results can be upscaled to more than two cavities and pave the way towards realizing integrated networks of synchronized mechanical oscillators. © 2019 American Physical Society.

  • Synthesis of a chiral rod-like metal–organic framework from a preformed amino acid-based hexanuclear wheel

    Grancha T., Ferrando-Soria J., Armentano D., Pardo E. Journal of Coordination Chemistry; 72 (8): 1204 - 1221. 2019. 10.1080/00958972.2019.1575371. IF: 1.685

    Supramolecular NanoChemistry and Materials

    We report the two-step synthesis of a chiral rod-like metal-organic framework (MOF). The chemical approach consists on the use of a previously prepared oxamato-based homochiral hexanuclear wheel, the ligand being a derivative of the natural amino acid l-alanine, with formula (Me4N)6{CuII6[(S)-alama])6}·10H2O (1) [where (S)-alama=(S)-N-(ethyl oxoacetate)alanine]. The anionic hexacopper(II) wheels, stabilized by the presence of templating tetramethylammonium counter-cations, disassemble in the presence of cationic square-planar [Ni(cyclam)]2+ complexes to yield, after a supramolecular reorganization process that involves axial coordination of the [Ni(cyclam)]2+ cations through the free carbonyl groups of the copper(II) moieties, a neutral chiral rod-like, three-dimensional (3D) MOF with formula [Ni(cyclam)][Cu(S)-alama]2·16H2O (2). The resulting MOF constitutes one of the few examples where such a high-nuclearity metal complex is used as precursor for the construction of rod-like MOFs. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.

  • Tailor-made metal-nitrogen-carbon bifunctional electrocatalysts for rechargeable Zn-air batteries via controllable MOF units

    Zhang X., Luo J., Lin H.-F., Tang P., Morante J.R., Arbiol J., Wan K., Mao B.-W., Liu L.-M., Fransaer J. Energy Storage Materials; 17: 46 - 61. 2019. 10.1016/j.ensm.2018.11.034. IF: 0.000

    Advanced Electron Nanoscopy

    The majority of chemical syntheses involve the use of catalysts, which play a crucial role in the yield and conversion rates of chemical reactions. In view of the increasing demand for chemical commodities and specialties linked to the growth of the world's population and the living standards, highly efficient and low-cost catalysts are urgently required. The metal-nitrogen-carbon (M-N-C) catalysts family is one of the most promising candidates. In this work, a series of benzene-1,3,5-tricarboxylate linker based metal organic frameworks (MOFs) were used as self-sacrificial templates and tunable platform for designable preparation of M-N-C catalysts. Changing the pillars between the 2D layers and the nature of the metal ions in the pristine MOFs significantly influenced the structure, chemical composition and catalytic activity of the resulting M-N-C catalysts for the oxygen reduction reaction (ORR). Furthermore, the influence of the MOF units on the catalyst performance, the role of the metals in the M-N-C catalysts and the primary catalytically active sites for ORR were explored by a combination of density functional theory (DFT), in-depth structural and chemical/elemental characterizations, and electrochemical studies. Among the prepared catalysts, Co-BTC-bipy-700 exhibited the highest electrocatalytic activity for oxygen reduction reaction (ORR), which showed a larger limiting current density and similar half-wave potentials with less catalyst degradation and much higher methanol tolerance than the commercial Pt/C catalyst. Meanwhile, as a bifunctional electrocatalyst, Co-BTC-bipy-700 catalyst was also employed for oxygen evolution reaction (OER) and demonstrated a lower overpotential (lowered by 140 mV at a current density of 10 mA cm−2) and better durability than IrO2. Furthermore, in terms of device performance, the Zn-air battery enabled by Co-BTC-bipy-700 catalyst reached a maximum specific energy as high as 1009.8 Wh kg−1, which is 76.5% of the theoretical value (1320 Wh kg−1), and demonstrated higher discharge potential and lower charge potential than that based on the Pt/C catalyst. Importantly, the presented strategy for tailor-made M-N-C catalysts by controlling the synthesis of the pristine MOFs could offer a guide map for the future design of M-N-C catalysts family not only for electrochemical reactions but also beyond electrochemistry. © 2018 Elsevier B.V.

  • Template-Free, Surfactant-Mediated Orientation of Self-Assembled Supercrystals of Metal–Organic Framework Particles

    Avci C., Liu Y., Pariente J.A., Blanco A., Lopez C., Imaz I., Maspoch D. Small; 15 (31, 1902520) 2019. 10.1002/smll.201902520. IF: 10.856

    Supramolecular NanoChemistry and Materials

    Mesoscale self-assembly of particles into supercrystals is important for the design of functional materials such as photonic and plasmonic crystals. However, while much progress has been made in self-assembling supercrystals adopting diverse lattices and using different types of particles, controlling their growth orientation on surfaces has received limited success. Most of the latter orientation control has been achieved via templating methods in which lithographic processes are used to form a patterned surface that acts as a template for particle assembly. Herein, a template-free method to self-assemble (111)-, (100)-, and (110)-oriented face-centered cubic supercrystals of the metal–organic framework ZIF-8 particles by adjusting the amount of surfactant (cetyltrimethylammonium bromide) used is described. It is shown that these supercrystals behave as photonic crystals whose properties depend on their growth orientation. This control on the orientation of the supercrystals dictates the orientation of the composing porous particles that might ultimately facilitate pore orientation on surfaces for designing membranes and sensors. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • The Chemistry behind Catechol-Based Adhesion

    Saiz-Poseu J., Mancebo-Aracil J., Nador F., Busqué F., Ruiz-Molina D. Angewandte Chemie - International Edition; 58 (3): 696 - 714. 2019. 10.1002/anie.201801063. IF: 12.257

    Nanostructured Functional Materials

    The adhesion of some marine organisms to almost any kind of surface in wet conditions has aroused increasing interest in recent decades. Numerous fundamental studies have been performed to understand the scientific basis of this behaviour, with catechols having been found to play a key role. Several novel bio-inspired adhesives and coatings with value-added performances have been developed by taking advantage of the knowledge gained from these studies. To date there has been no detailed overview focusing exclusively on the complex mode of action of these materials. The aim of this Review is to present recent investigations that elucidate the origin of the strong and versatile adsorption capacities of the catechol moiety and the effects of extrinsic factors that play important roles in the overall adhesion process, such as pH value, solvent, and the presence of metal ions. The aim is to detail the chemistry behind the astonishing properties of natural and synthetic catechol-based adhesive materials. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • The Imine-Based COF TpPa-1 as an Efficient Cooling Adsorbent That Can Be Regenerated by Heat or Light

    Pérez-Carvajal J., Boix G., Imaz I., Maspoch D. Advanced Energy Materials; (1901535) 2019. 10.1002/aenm.201901535. IF: 24.884

    Supramolecular NanoChemistry and Materials

    Adsorption-based cooling systems, which can be driven by waste heat and solar energy, are promising alternatives to conventional, compression-based cooling systems, as they demand less energy and emit less CO2. The performance of adsorption-based cooling systems relates directly to the performance of the working pairs (sorbent–water). Accordingly, improvement of these systems relies on the continual discovery of new sorbents that enable greater mass exchange while requiring less energy for regeneration. Here, it is proposed that covalent-organic frameworks (COFs) can replace traditional sorbents for adsorption-based cooling. In tests mimicking standard operating conditions for industry, the imine-based COF TpPa-1 exhibits a regeneration temperature below 65 °C and a cooling coefficient of performance of 0.77 – values which are comparable to those reported for the best metal–organic framework sorbents described to date. Moreover, TpPa-1 exhibits a photothermal effect and can be regenerated by visible light, thereby opening the possibility for its use in solar-driven cooling. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • The new FAST module: A portable and transparent add-on module for time-resolved investigations with commercial scanning probe microscopes

    Dri C., Panighel M., Tiemann D., Patera L.L., Troiano G., Fukamori Y., Knoller F., Lechner B.A.J., Cautero G., Giuressi D., Comelli G., Fraxedas J., Africh C., Esch F. Ultramicroscopy; 205: 49 - 56. 2019. 10.1016/j.ultramic.2019.05.010. IF: 2.644

    Force Probe Microscopy and Surface Nanoengineering

    Time resolution is one of the most severe limitations of scanning probe microscopies (SPMs), since the typical image acquisition times are in the order of several seconds or even few minutes. As a consequence, the characterization of dynamical processes occurring at surfaces (e.g. surface diffusion, film growth, self-assembly and chemical reactions) cannot be thoroughly addressed by conventional SPMs. To overcome this limitation, several years ago we developed a first prototype of the FAST module, an add-on instrument capable of driving a commercial scanning tunneling microscope (STM) at and beyond video rate frequencies. Here we report on a fully redesigned version of the FAST module, featuring improved performance and user experience, which can be used both with STMs and atomic force microscopes (AFMs), and offers additional capabilities such as an atom tracking mode. All the new features of the FAST module, including portability between different commercial instruments, are described in detail and practically demonstrated. © 2019

  • The Role of Polarity in Nonplanar Semiconductor Nanostructures

    De La Mata M., Zamani R.R., Martí-Sánchez S., Eickhoff M., Xiong Q., Fontcuberta Morral A., Caroff P., Arbiol J. Nano Letters; 19 (6): 3396 - 3408. 2019. 10.1021/acs.nanolett.9b00459. IF: 12.279

    Advanced Electron Nanoscopy

    The lack of mirror symmetry in binary semiconductor compounds turns them into polar materials, where two opposite orientations of the same crystallographic direction are possible. Interestingly, their physical properties (e.g., electronic or photonic) and morphological features (e.g., shape, growth direction, and so forth) also strongly depend on the polarity. It has been observed that nanoscale materials tend to grow with a specific polarity, which can eventually be reversed for very specific growth conditions. In addition, polar-directed growth affects the defect density and topology and might induce eventually the formation of undesirable polarity inversion domains in the nanostructure, which in turn will affect the photonic and electronic final device performance. Here, we present a review on the polarity-driven growth mechanism at the nanoscale, combining our latest investigation with an overview of the available literature highlighting suitable future possibilities of polarity engineering of semiconductor nanostructures. The present study has been extended over a wide range of semiconductor compounds, covering the most commonly synthesized III-V (GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb) and II-VI (ZnO, ZnTe, CdS, CdSe, CdTe) nanowires and other free-standing nanostructures (tripods, tetrapods, belts, and membranes). This systematic study allowed us to explore the parameters that may induce polarity-dependent and polarity-driven growth mechanisms, as well as the polarity-related consequences on the physical properties of the nanostructures. © 2019 American Chemical Society.

  • Thermal conductivity in disordered porous nanomembranes

    Sledzinska M., Graczykowski B., Alzina F., Melia U., Termentzidis K., Lacroix D., Sotomayor Torres C.M. Nanotechnology; 30 (26, 265401) 2019. 10.1088/1361-6528/ab0ecd. IF: 3.399

    Phononic and Photonic Nanostructures

    In this work we study the effects of disorder on the thermal conductivity of porous 100 nm thick silicon membranes, in which the size, shape and position of the pores were varied randomly. Measurements using two-laser Raman thermometry on both non-patterned and porous membranes revealed more than a 10-fold reduction of the thermal conductivity compared to that of bulk silicon and a six-fold reduction compared to non-patterned membranes for the sample with random pore shapes. Using Monte Carlo methods we solved the Boltzmann transport equation for phonons and compared different possibilities of pore organization and its influence on the thermal conductivity of the samples. The simulations confirmed that the strongest reduction of thermal conductivity is achieved for a distribution of pores with arbitrary shapes that partially overlap. Up to a 15% reduction of the thermal conductivity with respect to the purely circular pores was predicted for a porous membrane with 37% filling fraction. The effect of the pore shape and distribution was further studied. Maps of temperature and heat flux distributions clearly showed that for particular pore placement heat transport can be efficiently blocked and hot spots can be found in narrow channels between pores. These findings have an impact on the fabrication of membrane-based thermoelectric devices, where low thermal conductivity is required. This work shows that for porous membranes with a given filling fraction the thermal conductivity can be further modified by introducing disorder in the shape and placement of the pores. © 2019 IOP Publishing Ltd.

  • Thermal Control of Intermolecular Interactions and Tuning of Fluorescent-State Energies

    Massaro G., Zampini G., Ruiz-Molina D., Hernando J., Roscini C., Latterini L. Journal of Physical Chemistry C; 123 (8): 4632 - 4637. 2019. 10.1021/acs.jpcc.8b09774. IF: 4.309

    Nanostructured Functional Materials

    The prospect of tuning the energy of emitting states through external stimuli opens the possibility of shifting the energy of emitting units on demand and controlling the bimolecular processes they are involved in. To prove this concept, the fluorescence properties of three differently 9,10-substituted anthracene (ANT) derivatives are investigated in a phase-change material (eicosane). The liquid-to-solid transition of the medium leads to an increase of the local dye concentration, a shortening of the intermolecular distances, and the establishment of excited- and ground-state interactions. As a result, a new contribution to the overall luminescence that derives from the downshifted emission (up to 0.7 eV) from excimer-like species is observed. The addition of a second dye (a Pt-porphyrin) reduces the efficiency of excited- and ground-state complexes between fluorophore units, although it does not prevent the formation of multichromophoric aggregates where interactions between Pt-porphyrin and the emissive state of ANT derivatives are observed. The emission of excimer-like species, formed upon solidification of the medium, can be exploited to further down-shift the fluorescence through energy-transfer processes to a suitable energy acceptor, such as rubrene. © 2019 American Chemical Society.

  • Towards Oxide Electronics: a Roadmap

    Coll M., Fontcuberta J., Althammer M., Bibes M., Boschker H., Calleja A., Cheng G., Cuoco M., Dittmann R., Dkhil B., El Baggari I., Fanciulli M., Fina I., Fortunato E., Frontera C., Fujita S., Garcia V., Goennenwein S.T.B., Granqvist C.-G., Grollier J., Gross R., Hagfeldt A., Herranz G., Hono K., Houwman E., Huijben M., Kalaboukhov A., Keeble D.J., Koster G., Kourkoutis L.F., Levy J., Lira-Cantu M., MacManus-Driscoll J.L., Mannhart J., Martins R., Menzel S., Mikolajick T., Napari M., Nguyen M.D., Niklasson G., Paillard C., Panigrahi S., Rijnders G., Sánchez F., Sanchis P., Sanna S., Schlom D.G., Schroeder U., Shen K.M., Siemon A., Spreitzer M., Sukegawa H., Tamayo R., van den Brink J., Pryds N., Granozio F.M. Applied Surface Science; 482: 1 - 93. 2019. 10.1016/j.apsusc.2019.03.312. IF: 5.155

    Nanostructured Materials for Photovoltaic Energy

    [No abstract available]

  • Trimodal waveguide demonstration and its implementation as a high order mode interferometer for sensing application

    Ramirez J.C., Gabrielli L.H., Lechuga L.M., Hernandez-Figueroa H.E. Sensors (Switzerland); 19 (12, 2821) 2019. 10.3390/s19122821. IF: 3.031

    NanoBiosensors and Bioanalytical Applications

    This work implements and demonstrates an interferometric transducer based on a trimodal optical waveguide concept. The readout signal is generated from the interference between the fundamental and second-order modes propagating on a straight polymer waveguide. Intuitively, the higher the mode order, the larger the fraction of power (evanescent field) propagating outside the waveguide core, hence the higher the sensitivity that can be achieved when interfering against the strongly confined fundamental mode. The device is fabricated using the polymer SU-8 over a SiO2 substrate and shows a free spectral range of 20.2 nm and signal visibility of 5.7 dB, reaching a sensitivity to temperature variations of 0.0586 dB/°C. The results indicate that the proposed interferometer is a promising candidate for highly sensitive, compact and low-cost photonic transducer for implementation in different types of sensing applications, among these, point-of-care. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

  • Tunable circular dichroism and valley polarization in the modified Haldane model

    Vila M., Hung N.T., Roche S., Saito R. Physical Review B; 99 (16, 161404) 2019. 10.1103/PhysRevB.99.161404. IF: 3.736

    Theoretical and Computational Nanoscience

    We study the polarization dependence of optical absorption for a modified Haldane model, which exhibits antichiral edge modes in the presence of sample boundaries and has been argued to be realizable in transition metal dichalcogenides or Weyl semimetals. A rich optical phase diagram is unveiled, in which the correlations between perfect circular dichroism, pseudospin andvalley polarization can be tuned independently upon varying the Fermi energy. In particular, perfect circular dichroism and valley polarization are achieved simultaneously. This combination of optical properties suggests some interesting photonic device functionality (e.g., light polarizer) which could be combined with valleytronics applications (e.g., generation of valley currents). © 2019 American Physical Society.

  • Tuning the supramolecular isomerism of MOF-74 by controlling the synthesis conditions

    Gheorghe A., Imaz I., Van Der Vlugt J.I., Maspoch D., Tanase S. Dalton Transactions; 48 (27): 10043 - 10050. 2019. 10.1039/c9dt01572h. IF: 4.052

    Supramolecular NanoChemistry and Materials

    Supramolecular isomerism of metal-organic frameworks (MOFs) is known for several MOF structures, having direct implications on the properties of these materials. Although the synthesis of MOF isomers is mainly serendipitous in nature, achieving controlled formation of a target framework is highly relevant for practical applications. This work discusses the influence of additives and synthesis conditions on the formation of porous isomers containing Zn2+ as nodes and 2,5-dihydroxy-1,4-benzenedicarboxylate (dobdc4-) as a linker. Using solvent mixtures containing strongly coordinated molecules, e.g. N,N′-dimethylformamide (DMF) and N-methylpyrrolidone (NMP), facilitates the formation of porous structures of type [Zn2(dobdc)(S)x]·yS (S = DMF, NMP) which are built from dinuclear Zn2(O)2(CO2)3 secondary building units (SBUs) consisting of two different edge-sharing polyhedra with the Zn2+ ions in a unsaturated coordinative environment. In the presence of water, the Zn2+ dimers are converted to one-dimensional infinite Zn2+ chains, in which the number of Zn2+-linker bonds increases, therefore giving a hydrolytically more stable coordination environment. The full characterization of the isomers as well as their conversion to the most stable isomer is presented. © 2019 The Royal Society of Chemistry.

  • Tuning transport properties in thermoelectric nanocomposites through inorganic ligands and heterostructured building blocks

    Ibáñez M., Genç A., Hasler R., Liu Y., Dobrozhan O., Nazarenko O., De La Mata M., Arbiol J., Cabot A., Kovalenko M.V. ACS Nano; 13 (6): 6572 - 6580. 2019. 10.1021/acsnano.9b00346. IF: 13.903

    Supramolecular NanoChemistry and Materials | Advanced Electron Nanoscopy

    Methodologies that involve the use of nanoparticles as "artificial atoms" to rationally build materials in a bottom-up fashion are particularly well-suited to control the matter at the nanoscale. Colloidal synthetic routes allow for an exquisite control over such "artificial atoms" in terms of size, shape, and crystal phase as well as core and surface compositions. We present here a bottom-up approach to produce Pb-Ag-K-S-Te nanocomposites, which is a highly promising system for thermoelectric energy conversion. First, we developed a high-yield and scalable colloidal synthesis route to uniform lead sulfide (PbS) nanorods, whose tips are made of silver sulfide (Ag2S). We then took advantage of the large surface-to-volume ratio to introduce a p-type dopant (K) by replacing native organic ligands with K2Te. Upon thermal consolidation, K2Te-surface modified PbS-Ag2S nanorods yield p-type doped nanocomposites with PbTe and PbS as major phases and Ag2S and Ag2Te as embedded nanoinclusions. Thermoelectric characterization of such consolidated nanosolids showed a high thermoelectric figure-of-merit of 1 at 620 K. Copyright © 2019 American Chemical Society.

  • Ultrathin Eu- and Er-Doped Y2O3 Films with Optimized Optical Properties for Quantum Technologies

    Scarafagio M., Tallaire A., Tielrooij K.-J., Cano D., Grishin A., Chavanne M.-H., Koppens F.H.L., Ringuedé A., Cassir M., Serrano D., Goldner P., Ferrier A. Journal of Physical Chemistry C; 123 (21): 13354 - 13364. 2019. 10.1021/acs.jpcc.9b02597. IF: 4.309

    Ultrafast Dynamics in Nanoscale Systems

    Atomic layer deposited (ALD) Y2O3 thin films have been thoroughly investigated for optical or electronic applications. The coherent spectroscopy of lanthanide ions doped into this material has also recently attracted increasing interest in the field of quantum technologies for which they are considered promising candidates in quantum memories or as spin-photon interfaces. However, these most demanding applications require a deep control over the local positioning of the ions and their close environment in the crystalline matrix. This study focuses on the structural as well as optical properties of Eu3+ and Er3+ dopants in Y2O3 using photoluminescence (PL), luminescence decay times, and inhomogeneous line width (Γinh) measurements within this particular context. While as-grown ALD films do not provide an ideal host for the emitters, we demonstrate that by optimizing the deposition conditions and using appropriate annealing post treatments narrow inhomogeneous lines can be obtained for the 7F0↔5D0 transition of Eu3+ even for nanoscale films. Furthermore, about 1.5 ms lifetime has been measured for the infrared telecom transition of Er in ultrathin films (<10 nm), which is an order of magnitude higher than in nanoparticles of the same size. These results validate optimized rare-earth-doped ALD Y2O3 films as a suitable platform for photonics applications where few-nanometer-thick films with well-localized emitters are mandatory. This approach provides the first building blocks toward the development of more complex devices for quantum sensing or hybrid structures coupled with other systems such as two-dimensional materials. © 2019 American Chemical Society.

  • Understanding semiconductor nanostructures via advanced electron microscopy and spectroscopy

    Zamani R.R., Arbiol J. Nanotechnology; 30 (26, 262001) 2019. 10.1088/1361-6528/ab0b0a. IF: 3.399

    Advanced Electron Nanoscopy

    Transmission electron microscopy (TEM) offers an ample range of complementary techniques which are able to provide essential information about the physical, chemical and structural properties of materials at the atomic scale, and hence makes a vast impact on our understanding of materials science, especially in the field of semiconductor one-dimensional (1D) nanostructures. Recent advancements in TEM instrumentation, in particular aberration correction and monochromation, have enabled pioneering experiments in complex nanostructure material systems. This review aims to address these understandings through the applications of the methodology for semiconductor nanostructures. It points out various electron microscopy techniques, in particular scanning TEM (STEM) imaging and spectroscopy techniques, with their already-employed or potential applications on 1D nanostructured semiconductors. We keep the main focus of the paper on the electronic and optoelectronic properties of such semiconductors, and avoid expanding it further. In the first part of the review, we give a brief introduction to each of the STEM-based techniques, without detailed elaboration, and mention the recent technological and conceptual developments which lead to novel characterization methodologies. For further reading, we refer the audience to a handful of papers in the literature. In the second part, we highlight the recent examples of application of the STEM methodology on the 1D nanostructure semiconductor materials, especially III-V, II-V, and group IV bare and heterostructure systems. The aim is to address the research questions on various physical properties and introduce solutions by choosing the appropriate technique that can answer the questions. Potential applications will also be discussed, the ones that have already been used for bulk and 2D materials, and have shown great potential and promise for 1D nanostructure semiconductors. © 2019 IOP Publishing Ltd.

  • Unraveling the Impact of Halide Mixing on Perovskite Stability

    Hieulle J., Wang X., Stecker C., Son D.-Y., Qiu L., Ohmann R., Ono L.K., Mugarza A., Yan Y., Qi Y. Journal of the American Chemical Society; 141 (8): 3515 - 3523. 2019. 10.1021/jacs.8b11210. IF: 14.695

    Atomic Manipulation and Spectroscopy

    Increasing the stability of perovskites is essential for their integration in commercial photovoltaic devices. Halide mixing is suggested as a powerful strategy toward stable perovskite materials. However, the stabilizing effect of the halides critically depends on their distribution in the mixed compound, a topic that is currently under intense debate. Here we successfully determine the exact location of the I and Cl anions in the CH 3 NH 3 PbBr 3-y I y and CH 3 NH 3 PbBr 3-z Cl z mixed halide perovskite lattices and correlate it with the enhanced stability we find for the latter. By combining scanning tunneling microscopy and density functional theory, we predict that, for low ratios, iodine and chlorine incorporation have different effects on the electronic properties and stability of the CH 3 NH 3 PbBr 3 perovskite material. In addition, we determine the optimal Cl incorporation ratio for stability increase without detrimental band gap modification, providing an important direction for the fabrication of stable perovskite devices. The increased material stability induced by chlorine incorporation is verified by performing photoelectron spectroscopy on a half-cell device architecture. Our findings provide an answer to the current debate on halide incorporation and demonstrate their direct influence on device stability. © Copyright 2019 American Chemical Society.

  • Upscaling high activity oxygen evolution catalysts based on CoFe2O4 nanoparticles supported on nickel foam for power-to-gas electrochemical conversion with energy efficiencies above 80%

    Urbain F., Du R., Tang P., Smirnov V., Andreu T., Finger F., Jimenez Divins N., Llorca J., Arbiol J., Cabot A., Morante J.R. Applied Catalysis B: Environmental; 259 (118055) 2019. 10.1016/j.apcatb.2019.118055. IF: 14.229

    Advanced Electron Nanoscopy

    We investigate cobalt ferrite nanoparticles (NPs) supported on large-scale electrodes as oxygen evolution reaction (OER) catalysts. Colloidal CoFe2O4 NPs were loaded on low-cost and high surface area nickel foam (NF) scaffolds. The coating process was optimized for large electrode areas, ensuring a proper distribution of the NPs on the NF that allowed overcoming the electrical conductivity limitations of oxide NPs. We were able to produce CoFe2O4-coated NFs having 10 cm2 geometric surface areas with overpotentials below 300 mV for the OER at a current density of 50 mA/cm2. Such impressively low overpotentials suggested using CoFe2O4 NP-based electrodes within a water electrolysis device. In this prototype device, stable operating currents up to 500 mA at remarkably low cell-voltages of 1.62 and 1.53 V, at ambient and 50 °C electrolyte temperatures, respectively, were reached during operation periods of up to 50 h. The high electrochemical energy efficiencies reached at 50 mA/cm2, 75% and 81% respectively, rendered these devices particularly appealing to be combined with low-cost photovoltaic systems for bias-free hydrogen production. Therefore, CoFe2O4 NP-based electrolysers were coupled to low-cost thin-film silicon solar cells with 13% efficiency to complete a system that afforded solar-to-fuel efficiencies above 10%. © 2019 Elsevier B.V.

  • Validity of a single antibody-based lateral flow immunoassay depending on graphene oxide for highly sensitive determination of E. coli O157:H7 in minced beef and river water

    Hassan A.H.A., Bergua J.F., Morales-Narváez E., Mekoçi A. Food Chemistry; 297 (124965) 2019. 10.1016/j.foodchem.2019.124965. IF: 5.399

    Nanobioelectronics and Biosensors

    Considering the health risks of E. coli O157:H7 presence in food and water, an affordable and highly sensitive detection method is crucial. Herein, we report the first use of a single antibody-based fluorescent lateral flow immunoassay (FLFIA) depending on non-radiative energy transfer between graphene oxide and quantum dots for determination of E. coli O157:H7 in beef and river water. FLFIA showed a high sensitivity rate thousand-fold better than the conventional lateral flow (LF). In inoculated minced beef and river water samples, the limits of detection were 178 and 133 CFU g−1 or mL−1, respectively. Besides, it presented a high selectivity in the presence of other possible interfering bacteria. The single antibody approach reduced the assay cost to 60% less than the conventional LF. Alongside, the results could be read by portable LF readers or smartphones. These advantages offer FLFIA as a promising technology for pathogen detection in food and water. © 2019 Elsevier Ltd

  • Versatile Graphene-Based Platform for Robust Nanobiohybrid Interfaces

    Bueno R., Marciello M., Moreno M., Sánchez-Sánchez C., Martinez J.I., Martinez L., Prats-Alfonso E., Guimerà-Brunet A., Garrido J.A., Villa R., Mompean F., García-Hernandez M., Huttel Y., Morales M.D.P., Briones C., López M.F., Ellis G.J., Vázquez L., Martín-Gago J.A. ACS Omega; 4 (2): 3287 - 3297. 2019. 10.1021/acsomega.8b03152. IF: 2.584

    Advanced Electronic Materials and Devices

    Technologically useful and robust graphene-based interfaces for devices require the introduction of highly selective, stable, and covalently bonded functionalities on the graphene surface, whilst essentially retaining the electronic properties of the pristine layer. This work demonstrates that highly controlled, ultrahigh vacuum covalent chemical functionalization of graphene sheets with a thiol-terminated molecule provides a robust and tunable platform for the development of hybrid nanostructures in different environments. We employ this facile strategy to covalently couple two representative systems of broad interest: metal nanoparticles, via S-metal bonds, and thiol-modified DNA aptamers, via disulfide bridges. Both systems, which have been characterized by a multitechnique approach, remain firmly anchored to the graphene surface even after several washing cycles. Atomic force microscopy images demonstrate that the conjugated aptamer retains the functionality required to recognize a target protein. This methodology opens a new route to the integration of high-quality graphene layers into diverse technological platforms, including plasmonics, optoelectronics, or biosensing. With respect to the latter, the viability of a thiol-functionalized chemical vapor deposition graphene-based solution-gated field-effect transistor array was assessed. © Copyright 2019 American Chemical Society.

  • Versatile iron-catechol-based nanoscale coordination polymers with antiretroviral ligand functionalization and their use as efficient carriers in HIV/AIDS therapy

    Solórzano R., Tort O., García-Pardo J., Escribà T., Lorenzo J., Arnedo M., Ruiz-Molina D., Alibés R., Busqué F., Novio F. Biomaterials Science; 7 (1): 178 - 186. 2019. 10.1039/c8bm01221k. IF: 5.251

    Nanostructured Functional Materials

    A novel chemical approach integrating the benefits of nanoparticles with versatility of coordination chemistry is reported herein to increase the effectiveness of well-known HIV antiretroviral drugs. The novelty of our approach is illustrated using a catechol ligand tethered to the known antiretroviral azidothymidine (AZT) as a constitutive building block of the nanoparticles. The resulting nanoscale coordination polymers (NCPs) ensure good encapsulation yields and equivalent antiretroviral activity while significantly diminishing its cytotoxicity. Moreover, this novel family of nanoparticles also offers (i) long-lasting drug release that is dissimilar inside and outside the cells depending on pH, (ii) triggered release in the presence of esterases, activating the antiviral activity in an on-off manner due to a proper chemical design of the ligand and (iii) improved colloidal stabilities and cellular uptakes (up to 50-fold increase). The presence of iron nodes also adds multifunctionality as possible contrast agents. The present study demonstrates the suitability of NCPs bearing pharmacologically active ligands as an alternative to conventional antiretroviral treatments. © The Royal Society of Chemistry.

  • Water adsorption, dissociation and oxidation on SrTiO 3 and ferroelectric surfaces revealed by ambient pressure X-ray photoelectron spectroscopy

    Domingo N., Pach E., Cordero-Edwards K., Pérez-Dieste V., Escudero C., Verdaguer A. Physical Chemistry Chemical Physics; 21 (9): 4920 - 4930. 2019. 10.1039/c8cp07632d. IF: 3.567

    Oxide Nanophysics

    Water dissociation on oxides is of great interest because its fundamental aspects are still not well understood and it has implications in many processes, from ferroelectric polarization screening phenomena to surface catalysis and surface chemistry on oxides. In situ water dissociation and redox processes on metal oxide perovskites which easily expose TiO 2 -terminated surfaces, such as SrTiO 3 , BaTiO 3 or Pb(Zr,Ti)O 3 , are studied by ambient pressure XPS, as a function of water vapour pressure. From the analysis of the O1s spectrum, we determine the presence of different types of oxygen based species, from hydroxyl groups, either bound to Ti 4+ and metal sites or lattice oxygen, to different peroxide compounds, and propose a model for the adsorbate layer composition, valid for environmental conditions. From the XPS analysis, we describe the existing surface redox reactions for metal oxide perovskites, occurring at different water vapour pressures. Among them, peroxide species resulting from surface oxidative reactions are correlated with the presence of Ti 4+ ions, which are observed to specifically promote surface oxidation and water dissociation as compared to other metals. Finally, surface peroxidation is enhanced by X-ray beam irradiation, leading to a higher coverage of peroxide species after beam overexposure and by ferroelectric polarization, demonstrating the enhancement of the reactivity of the surfaces of ferroelectric materials due to the effect of internal electric fields. © 2019 the Owner Societies.

  • Water-mediated photo-induced reduction of platinum films

    Fraxedas J., Zhang K., Sepúlveda B., Esplandiu M.J., De Andrés X.G., Llorca J., Pérez-Dieste V., Escudero C. Journal of Synchrotron Radiation; 26: 1288 - 1293. 2019. 10.1107/S1600577519004685. IF: 2.452

    Magnetic Nanostructures | Force Probe Microscopy and Surface Nanoengineering

    Platinum thin films activated ex situ by oxygen plasma become reduced by the combined effect of an intense soft X-ray photon beam and condensed water. The evolution of the electronic structure of the surface has been characterized by near-ambient-pressure photoemission and mimics the inverse two-step sequence observed in the electro-oxidation of platinum, i.e. the surface-oxidized platinum species are reduced first and then the adsorbed species desorb in a second step leading to a surface dominated by metallic platinum. The comparison with measurements performed under high-vacuum conditions suggests that the reduction process is mainly induced by the reactive species generated by the radiolysis of water. When the photon flux is decreased, then the reduction process becomes slower. © 2019 International Union of Crystallography.

  • Zinc blende and wurtzite CoO polymorph nanoparticles: Rational synthesis and commensurate and incommensurate magnetic order

    Golosovsky I.V., Estrader M., López-Ortega A., Roca A.G., López-Conesa L., Del Corro E., Estradé S., Peiró F., Puente-Orench I., Nogués J. Applied Materials Today; 16: 322 - 331. 2019. 10.1016/j.apmt.2019.06.005. IF: 8.013

    Magnetic Nanostructures

    On the nanoscale, CoO can have different polymorph crystal structures, zinc blende and wurtzite, apart from rock salt, which is the stable one in bulk. However, the magnetic structures of the zinc blende and wurtzite phases remain virtually unexplored. Here we discuss some of the main parameters controlling the growth of the CoO wurtzite and zinc blende polymorphs by thermal decomposition of cobalt (II) acetylacetonate. In addition, we present a detailed neutron diffraction study of oxygen deficient CoO (CoO0.70–0.75) nanoparticles with zinc blende (∼15 nm) and wurtzite (∼30 nm) crystal structures to unravel their magnetic order and its temperature evolution. The magnetic order of the zinc blende nanoparticles is antiferromagnetic and appears at the Néel temperature TN ∼ 203 K. It corresponds to the 3rd type of magnetic ordering in a face-centered cubic lattice with magnetic moments aligned along a cube edge. The magnetic structure in the wurtzite nanoparticles turned out to be rather complex with two perpendicular components. One component is incommensurate, of the longitudinal spin wave type, with the magnetic moments confined in the ab-plane. In the perpendicular direction, this magnetic order is uncorrelated, forming quasi-two-dimensional magnetic layers. The component of the magnetic moment, aligned along the hexagonal axis, is commensurate and corresponds to the antiferromagnetic order known as the 2nd type in a wurtzite structure. The Néel temperature of wurtzite phase is estimated to be ∼109 K. The temperature dependence of the magnetic reflections confirms the reduced dimensionality of the incommensurate magnetic order. Incommensurate magnetic structures in nanoparticles are an unusual phenomenon and in the case of wurtzite CoO it is probably caused by structural defects (e.g., vacancies, strains and stacking faults). © 2019 Elsevier Ltd