ICN2 Publications


  • 1D ferromagnetic edge contacts to 2D graphene/h-BN heterostructures

    Karpiak B., Dankert A., Cummings A.W., Power S.R., Roche S., Dash S.P. 2D Materials; 5 (1, 014001) 2018. 10.1088/2053-1583/aa8d2b.

    Theoretical and Computational Nanoscience

    We report the fabrication of one-dimensional (1D) ferromagnetic edge contacts to two-dimensional (2D) graphene/h-BN heterostructures. While aiming to study spin injection/detection with 1D edge contacts, a spurious magnetoresistance signal was observed, which is found to originate from the local Hall effect in graphene due to fringe fields from ferromagnetic edge contacts and in the presence of charge current spreading in the nonlocal measurement configuration. Such behavior has been confirmed by the absence of a Hanle signal and gate-dependent magnetoresistance measurements that reveal a change in sign of the signal for the electron- and hole-doped regimes, which is in contrast to the expected behavior of the spin signal. Calculations show that the contact-induced fringe fields are typically on the order of hundreds of mT, but can be reduced below 100 mT with careful optimization of the contact geometry. There may be an additional contribution from magnetoresistance effects due to tunneling anisotropy in the contacts, which needs further investigation. These studies are useful for optimization of spin injection and detection in 2D material heterostructures through 1D edge contacts. © 2017 IOP Publishing Ltd.

  • Addressing the Environment Electrostatic Effect on Ballistic Electron Transport in Large Systems: A QM/MM-NEGF Approach

    Feliciano G.T., Sanz-Navarro C., Coutinho-Neto M.D., Ordejón P., Scheicher R.H., Rocha A.R. Journal of Physical Chemistry B; 122 (2): 485 - 492. 2018. 10.1021/acs.jpcb.7b03475.

    Theory and Simulation

    The effects of the environment in nanoscopic materials can play a crucial role in device design. Particularly in biosensors, where the system is usually embedded in a solution, water and ions have to be taken into consideration in atomistic simulations of electronic transport for a realistic description of the system. In this work, we present a methodology that combines quantum mechanics/molecular mechanics methods (QM/MM) with the nonequilibrium Green's function framework to simulate the electronic transport properties of nanoscopic devices in the presence of solvents. As a case in point, we present further results for DNA translocation through a graphene nanopore. In particular, we take a closer look into general assumptions in a previous work. For this sake, we consider larger QM regions that include the first two solvation shells and investigate the effects of adding extra k-points to the NEGF calculations. The transverse conductance is then calculated in a prototype sequencing device in order to highlight the effects of the solvent. © 2017 American Chemical Society.

  • Architecting Graphene Oxide Rolled-Up Micromotors: A Simple Paper-Based Manufacturing Technology

    Baptista-Pires L., Orozco J., Guardia P., Merkoçi A. Small; 14 (3, 1702746) 2018. 10.1002/smll.201702746.

    Nanobioelectronics and Biosensors

    A graphene oxide rolled-up tube production process is reported using wax-printed membranes for the fabrication of on-demand engineered micromotors at different levels of oxidation, thickness, and lateral dimensions. The resultant graphene oxide rolled-up tubes can show magnetic and catalytic movement within the addition of magnetic nanoparticles or sputtered platinum in the surface of graphene-oxide-modified wax-printed membranes prior to the scrolling process. As a proof of concept, the as-prepared catalytic graphene oxide rolled-up micromotors are successfully exploited for oil removal from water. This micromotor production technology relies on an easy, operator-friendly, fast, and cost-efficient wax-printed paper-based method and may offer a myriad of hybrid devices and applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei/1.

  • Bioluminescent nanopaper for rapid screening of toxic substances

    Liu J., Morales-Narváez E., Orozco J., Vicent T., Zhong G., Merkoçi A. Nano Research; 11 (1): 114 - 125. 2018. 10.1007/s12274-017-1610-7. IF: 7.354

    Nanobioelectronics and Biosensors

    Environmental pollution is threatening human health and ecosystems as a result of modern agricultural techniques and industrial progress. A simple nanopaper-based platform coupled with luminescent bacteria Aliivibrio fischeri (A. fischeri) as a bio-indicator is presented here, for rapid and sensitive evaluation of contaminant toxicity. When exposed to toxicants, the luminescence inhibition of A. fischeri-decorated bioluminescent nanopaper (BLN) can be quantified and analyzed to classify the toxicity level of a pollutant. The BLN composite was characterized in terms of morphology and functionality. Given the outstanding biocompatibility of nanocellulose for bacterial proliferation, BLN achieved high sensitivity with a low cost and simplified procedure compared to conventional instruments for laboratory use only. The broad applicability of BLN devices to environmental samples was studied in spiked real matrices (lake and sea water), and their potential for direct and in situ toxicity screening was demonstrated. The BLN architecture not only survives but also maintains its function during freezing and recycling processes, endowing the BLN system with competitive advantages as a deliverable, ready-to-use device for large-scale manufacturing. The novel luminescent bacteria-immobilized, nanocelullose-based device shows outstanding abilities for toxicity bioassays of hazardous compounds, bringing new possibilities for cheap and efficient environmental monitoring of potential contamination. © 2018, Tsinghua University Press and Springer-Verlag GmbH Germany.

  • Characterization of Carbon-Contaminated B4C-Coated Optics after Chemically Selective Cleaning with Low-Pressure RF Plasma

    Moreno Fernández H., Rogler D., Sauthier G., Thomasset M., Dietsch R., Carlino V., Pellegrin E. Scientific Reports; 8 (1, 1293) 2018. 10.1038/s41598-018-19273-6.

    Boron carbide (B4C) is one of the few materials that is expected to be most resilient with respect to the extremely high brilliance of the photon beam generated by free electron lasers (FELs) and is thus of considerable interest for optical applications in this field. However, as in the case of many other optics operated at light source facilities, B4C-coated optics are subject to ubiquitous carbon contaminations. Carbon contaminations represent a serious issue for the operation of FEL beamlines due to severe reduction of photon flux, beam coherence, creation of destructive interference, and scattering losses. A variety of B4C cleaning technologies were developed at different laboratories with varying success. We present a study regarding the low-pressure RF plasma cleaning of carbon contaminated B4C test samples via inductively coupled O2/Ar, H2/Ar, and pure O2 RF plasma produced following previous studies using the same ibss GV10x downstream plasma source. Results regarding the chemistry, morphology as well as other aspects of the B4C optical coating before and after the plasma cleaning are reported. We conclude that among the above plasma processes only plasma based on pure O2 feedstock gas exhibits the required chemical selectivity for maintaining the integrity of the B4C optical coatings. © 2018 The Author(s).

  • Conductance quantization suppression in the quantum Hall regime

    Caridad J.M., Power S.R., Lotz M.R., Shylau A.A., Thomsen J.D., Gammelgaard L., Booth T.J., Jauho A.-P., Bøggild P. Nature Communications; 9 (1, 659) 2018. 10.1038/s41467-018-03064-8.

    Conductance quantization is the quintessential feature of electronic transport in non-interacting mesoscopic systems. This phenomenon is observed in quasi one-dimensional conductors at zero magnetic field B, and the formation of edge states at finite magnetic fields results in wider conductance plateaus within the quantum Hall regime. Electrostatic interactions can change this picture qualitatively. At finite B, screening mechanisms in narrow, gated ballistic conductors are predicted to give rise to an increase in conductance and a suppression of quantization due to the appearance of additional conduction channels. Despite being a universal effect, this regime has proven experimentally elusive because of difficulties in realizing one-dimensional systems with sufficiently hard-walled, disorder-free confinement. Here, we experimentally demonstrate the suppression of conductance quantization within the quantum Hall regime for graphene nanoconstrictions with low edge roughness. Our findings may have profound impact on fundamental studies of quantum transport in finite-size, two-dimensional crystals with low disorder. © 2018 The Author(s).

  • Dual-Fluorescent Nanoscale Coordination Polymers via a Mixed-Ligand Synthetic Strategy and Their Use for Multichannel Imaging

    Nador F., Wnuk K., García-Pardo J., Lorenzo J., Solorzano R., Ruiz-Molina D., Novio F. ChemNanoMat; 4 (2): 183 - 193. 2018. 10.1002/cnma.201700311.

    Nanostructured Functional Materials

    Two rationally designed strategies for covalent bonding of fluorescent dyes in coordination polymer nanoparticles aiming to achieve bifunctional fluorescent nanostructures have been developed. The first strategy was based on the synthesis of the coordination polymers structured as nanoparticles by coordination of CoII ions to two different catechol ligands containing free functional chemical groups (dopamine and 3,4-dihydroxybenzaldehyde), and a bis(imidazole)-based ligand (1,4-bis(imidazole-1-ylmethyl)benzene, bix). Subsequently, different dyes, namely fluorescein isothiocyanate (FITC), 1-pyrenebutanoic acid hydrazide (PBH) or Alexa Fluor® 568 (A568), could be sequentially attached to the surface of the nanoparticles. The second strategy was focused on the prefunctionalization of catechol ligands with the corresponding dyes and, afterwards, the coordination with the metal ions in presence of bix. In vitro studies demonstrated the internalization of the bifunctional nanoparticles and the persistence of the fluorescent properties after cell uptake without dye leaching. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Enhanced Ultrafast Nonlinear Optical Response in Ferrite Core/Shell Nanostructures with Excellent Optical Limiting Performance

    Perumbilavil S., López-Ortega A., Tiwari G.K., Nogués J., Endo T., Philip R. Small; 14 (6, 1701001) 2018. 10.1002/smll.201701001.

    Magnetic Nanostructures

    Nonlinear optical nanostructured materials are gaining increased interest as optical limiters for various applications, although many of them suffer from reduced efficiencies at high-light fluences due to photoinduced deterioration. The nonlinear optical properties of ferrite core/shell nanoparticles showing their robustness for ultrafast optical limiting applications are reported. At 100 fs ultrashort laser pulses the effective two-photon absorption (2PA) coefficient shows a nonmonotonic dependence on the shell thickness, with a maximum value obtained for thin shells. In view of the local electric field confinement, this indicates that core/shell is an advantageous morphology to improve the nonlinear optical parameters, exhibiting excellent optical limiting performance with effective 2PA coefficients in the range of 10−12 cm W−1 (100 fs excitation), and optical limiting threshold fluences in the range of 1.7 J cm−2. These values are comparable to or better than most of the recently reported optical limiting materials. The quality of the open aperture Z-scan data recorded from repeat measurements at intensities as high as 35 TW cm−2, indicates their considerably high optical damage thresholds in a toluene dispersion, ensuring their robustness in practical applications. Thus, the high photostability combined with the remarkable nonlinear optical properties makes these nanoparticles excellent candidates for ultrafast optical limiting applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Flexoelectricity in Bones

    Vasquez-Sancho F., Abdollahi A., Damjanovic D., Catalan G. Advanced Materials; 2018. 10.1002/adma.201705316.

    Oxide Nanophysics

    Bones generate electricity under pressure, and this electromechanical behavior is thought to be essential for bone's self-repair and remodeling properties. The origin of this response is attributed to the piezoelectricity of collagen, which is the main structural protein of bones. In theory, however, any material can also generate voltages in response to strain gradients, thanks to the property known as flexoelectricity. In this work, the flexoelectricity of bone and pure bone mineral (hydroxyapatite) are measured and found to be of the same order of magnitude; the quantitative similarity suggests that hydroxyapatite flexoelectricity is the main source of bending-induced polarization in cortical bone. In addition, the measured flexoelectric coefficients are used to calculate the (flexo)electric fields generated by cracks in bone mineral. The results indicate that crack-generated flexoelectricity is theoretically large enough to induce osteocyte apoptosis and thus initiate the crack-healing process, suggesting a central role of flexoelectricity in bone repair and remodeling. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • Growth and Luminescence of Polytypic InP on Epitaxial Graphene

    Mukherjee S., Nateghi N., Jacobberger R.M., Bouthillier E., de la Mata M., Arbiol J., Coenen T., Cardinal D., Levesque P., Desjardins P., Martel R., Arnold M.S., Moutanabbir O. Advanced Functional Materials; 28 (8, 1705592) 2018. 10.1002/adfm.201705592.

    Advanced Electron Nanoscopy

    Van der Waals epitaxy is an attractive alternative to direct heteroepitaxy where the forced coherency at the interface cannot sustain large differences in lattice parameters and thermal expansion coefficients between the substrate and the epilayer. Herein, the growth of monocrystalline InP on Ge and SiO2/Si substrates using graphene as an interfacial layer is demonstrated. Micrometer-sized InP crystals are found to grow with interfaces of high crystalline quality and with different degrees of coalescence depending on the growth conditions. Some InP crystals exhibit a polytypic structure, consisting of alternating zinc-blende and wurtzite phases, forming a type-II homojunction with well (barrier) width of about 10 nm. The optical properties, investigated using room temperature nano-cathodoluminescence, indicate the signatures of the direct optical transitions at 1.34 eV across the gap of the zinc-blende phase and the indirect transitions at ≈1.31 eV originating from the alternating zinc-blende and wurtzite phases. Additionally, the InP nanorods, found growing mainly on the graphene/SiO2/Si substrate, show optical transition across the gap of the wurtzite phase at ≈1.42 eV. This demonstration of InP growth on graphene and the correlative study between the structure and optical properties pave the way to develop hybrid structures for potential applications in integrated photonic and optoelectronic devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Heterostructured layered hybrid ZnO/MoS2 nanosheets with enhanced visible light photocatalytic activity

    Benavente E., Durán F., Sotomayor-Torres C., González G. Journal of Physics and Chemistry of Solids; 113: 119 - 124. 2018. 10.1016/j.jpcs.2017.10.027.

    Phononic and Photonic Nanostructures

    A series of novel heterostructured hybrid layered ZnO and MoS2 nanosheets composites were successfully prepared with different MoS2 contents. Among all the prepared materials, ZnO/MoS2 (1:0.05) composite showed enhanced photocatalytic activity for methylene blue degradation under direct solar light compared with pristine ZnO. The MoS2 component played a key role for the visible light activity of the composite system at longer wavelengths. The kinetic equations of photocatalytic reaction and possible photocatalytic degradation mechanism were investigated. The results indicated that it belongs to the zero order kinetic and the photogenerated electrons are transferred from hybrid layered ZnO to the MoS2 nanosheets, facilitating an interfacial electron transfer suppressing the recombination of charge carriers during the photocatalytic degradation. © 2017 Elsevier Ltd

  • Hybrid Graphene-Polyoxometalates Nanofluids as Liquid Electrodes for Dual Energy Storage in Novel Flow Cells

    Dubal D.P., Rueda-Garcia D., Marchante C., Benages R., Gomez-Romero P. Chemical Record; 2018. 10.1002/tcr.201700116.

    Novel Energy-Oriented Materials

    Solid Hybrid materials abound. But flowing versions of them are new actors in the materials science landscape and in particular for energy applications. This paper presents a new way to deliver nanostructured hybrid materials for energy storage, namely, in the form of nanofluids. We present here the first example of a hybrid electroactive nanofluid (HENFs) combining capacitive and faradaic energy storage mechanisms in a single fluid material. This liquid electrode is composed of reduced graphene oxide and polyoxometalates (rGO-POMs) forming a stable nanocomposite for electrochemical energy storage in novel Nanofluid Flow Cells. Two graphene based hybrid materials (rGO-phosphomolybdate, rGO-PMo12 and rGO-phosphotungstate, rGO-PW12) were synthesized and dispersed with the aid of a surfactant in 1M H2SO4 aqueous electrolyte to yield highly stable hybrid electroactive nanofluids (HENFs) of low viscosity which were tested in a home-made flow cell under static and continuous flowing conditions. Remarkably, even low concentration rGO-POMs HENFs (0.025wt%) exhibited high specific capacitances of 273F/g(rGO-PW12) and 305F/g(rGO-PMo12) with high specific energy and specific power. Moreover, rGO-POM HENFs show excellent cycling stability (∼95%) as well as Coulombic efficiency (∼77-79%) after 2000 cycles. Thus, rGO-POM HENFs effectively behave as real liquid electrodes with excellent properties, demonstrating the possible future application of HENFs for dual energy storage in a new generation of Nanofluid Flow Cells. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • In situ monitoring of PTHLH secretion in neuroblastoma cells cultured onto nanoporous membranes

    de la Escosura-Muñiz A., Espinoza-Castañeda M., Chamorro-García A., Rodríguez-Hernández C.J., de Torres C., Merkoçi A. Biosensors and Bioelectronics; 107: 62 - 68. 2018. 10.1016/j.bios.2018.01.064.

    Nanobioelectronics and Biosensors

    In this work, we propose for the first time the use of anodic aluminum oxide (AAO) nanoporous membranes for in situ monitoring of parathyroid hormone-like hormone (PTHLH) secretion in cultured human cells. The biosensing system is based on the nanochannels blockage upon immunocomplex formation, which is electrically monitored through the voltammetric oxidation of Prussian blue nanoparticles (PBNPs). Models evaluated include a neuroblastoma cell line (SK-N-AS) and immortalized keratinocytes (HaCaT) as a control of high PTHLH production. The effect of total number of seeded cells and incubation time on the secreted PTHLH levels is assessed, finding that secreted PTHLH levels range from approximately 60 to 400 ng/mL. Moreover, our methodology is also applied to analyse PTHLH production following PTHLH gene knockdown upon transient cell transfection with a specific silencing RNA (siRNA). Given that inhibition of PTHLH secretion reduces cell proliferation, survival and invasiveness in a number of tumors, our system provides a powerful tool for the preclinical evaluation of therapies that regulate PTHLH production. This nanoporous membrane – based sensing technology might be useful to monitor the active secretion of other proteins as well, thus contributing to characterize their regulation and function. © 2018 Elsevier B.V.

  • In-Situ Scrutiny of the Relationship between Polymorphic Phases and Properties of Self-Assembled Monolayers of a Biphenyl Based Thiol

    Paradinas M., Munuera C., Buck M., Ocal C. Journal of Physical Chemistry B; 122 (2): 657 - 665. 2018. 10.1021/acs.jpcb.7b05958.

    Atomic Manipulation and Spectroscopy

    Two polymorphic phases of ω-(4′-methylbiphenyl-4-yl) butane-1-thiol (BP4) molecules formed on Au(111) were investigated by multidimensional atomic force microscopy, combining conductivity measurements, electrostatic characterization, friction force mapping, and normal force spectroscopy. Based on the same molecular structure but differing in molecular order, packing density, and molecular tilt, the two phases serve as a test bench to establish the structure-property relationships in self-assembled monolayers (SAMs). From a detailed analysis of the charge transport and electrostatics, the contributions of geometrical and electronic effects to the tunneling are discussed. © 2017 American Chemical Society.

  • Inter-laboratory comparison of nanoparticle size measurements using dynamic light scattering and differential centrifugal sedimentation

    Langevin D., Lozano O., Salvati A., Kestens V., Monopoli M., Raspaud E., Mariot S., Salonen A., Thomas S., Driessen M., Haase A., Nelissen I., Smisdom N., Pompa P.P., Maiorano G., Puntes V., Puchowicz D., Stępnik M., Suárez G., Riediker M., Benetti F., Mičetić I., Venturini M., Kreyling W.G., van der Zande M., Bouwmeester H., Milani S., Rädler J.O., Mülhopt S., Lynch I., Dawson K. NanoImpact; 10: 97 - 107. 2018. 10.1016/j.impact.2017.12.004.

    Inorganic Nanoparticles

    Nanoparticle in vitro toxicity studies often report contradictory results with one main reason being insufficient material characterization. In particular the characterization of nanoparticles in biological media remains challenging. Our aim was to provide robust protocols for two of the most commonly applied techniques for particle sizing, i.e. dynamic light scattering (DLS) and differential centrifugal sedimentation (DCS) that should be readily applicable also for users not specialized in nanoparticle physico-chemical characterization. A large number of participants (40, although not all participated in all rounds) were recruited for a series of inter-laboratory comparison (ILC) studies covering many different instrument types, commercial and custom-built, as another possible source of variation. ILCs were organized in a consecutive manner starting with dispersions in water employing well-characterized near-spherical silica nanoparticles (nominal 19 nm and 100 nm diameter) and two types of functionalized spherical polystyrene nanoparticles (nominal 50 nm diameter). At first each laboratory used their in-house established procedures. In particular for the 19 nm silica particles, the reproducibility of the methods was unacceptably high (reported results were between 10 nm and 50 nm). When comparing the results of the first ILC round it was observed that the DCS methods performed significantly worse than the DLS methods, thus emphasizing the need for standard operating procedures (SOPs). SOPs have been developed by four expert laboratories but were tested for robustness by a larger number of independent users in a second ILC (11 for DLS and 4 for DCS). In a similar approach another SOP for complex biological fluids, i.e. cell culture medium containing serum was developed, again confirmed via an ILC with 8 participating laboratories. Our study confirms that well-established and fit-for-purpose SOPs are indispensable for obtaining reliable and comparable particle size data. Our results also show that these SOPs must be optimized with respect to the intended measurement system (e.g. particle size technique, type of dispersant) and that they must be sufficiently detailed (e.g. avoiding ambiguity regarding measurand definition, etc.). SOPs may be developed by a small number of expert laboratories but for their widespread applicability they need to be verified by a larger number of laboratories. © 2017 Elsevier B.V.

  • Optimisation of growth parameters to obtain epitaxial Y-doped BaZrO3 proton conducting thin films

    Magrasó A., Ballesteros B., Rodríguez-Lamas R., Sunding M.F., Santiso J. Solid State Ionics; 314: 9 - 16. 2018. 10.1016/j.ssi.2017.11.002.

    Nanomaterials Growth Division | Electron Microscopy Division

    We hereby report developments on the fabrication and characterization of epitaxial thin films of proton conducting Y-doped BaZrO3 (BZY) by pulsed laser deposition (PLD) on different single crystal substrates (MgO, GdScO3, SrTiO3, NdGaO3, LaAlO3 and sapphire) using Ni-free and 1% Ni-containing targets. Pure, high crystal quality epitaxial films of BZY are obtained on MgO and on perovskite-type substrates, despite the large lattice mismatch. The deposition conditions influence the morphology, cell parameters and chemical composition of the film, the oxygen partial pressure during film growth being the most determining. Film characterization was carried out using X-ray diffraction, transmission electron and atomic force microscopies, wavelength dispersive X-ray spectroscopy and angle-resolved X-ray photoelectron spectroscopy. All films show a slight tetragonal distortion that is not directly related to the substrate-induced strain. The proton conductivity of the films depends on deposition conditions and film thickness, and for the optimised conditions its total conductivity is slightly higher than the bulk conductivity of the target material (3 mS/cm at 600 °C, in wet 5% H2/Ar). The conductivities are, however, more than one order of magnitude lower than the highest reported in literature and possible reasoning is elucidated in terms of local and extended defects in the films. © 2017 Elsevier B.V.

  • Passivation layers for nanostructured photoanodes: Ultra-thin oxides on InGaN nanowires

    Neuderth P., Hille P., Schörmann J., Frank A., Reitz C., Martí-Sánchez S., De La Mata M., Coll M., Arbiol J., Marschall R., Eickhoff M. Journal of Materials Chemistry A; 6 (2): 565 - 573. 2018. 10.1039/c7ta08071a.

    Advanced Electron Nanoscopy

    An experimental strategy for systematically assessing the influence of surface passivation layers on the photocatalytic properties of nanowire photoanodes by combining photocurrent analysis, photoluminescence spectroscopy and high resolution transmission electron microscopy with a systematic variation of sample structure and the surrounding electrolyte is demonstrated. Following this approach we can separate the impact on recombination and transport processes of photogenerated carriers. We apply this strategy to analyze the influence of ultra-thin TiO2, CeO2 and Al2O3 coatings deposited by atomic layer deposition on the photoelectrochemical performance of InxGa1-xN/GaN nanowire (NW) photoelectrodes. The passivation of surface states results in an increase of the anodic photocurrent (PC) by a factor of 2.5 for the deposition of 5 nm TiO2. In contrast, the PC is reduced for CeO2- and Al2O3-coated NWs due to enhanced defect recombination in the passivation layer or increased band discontinuities. Furthermore, photoelectrochemical oxidation of the InxGa1-xN/GaN NW photoelectrode is attenuated by the TiO2 layer and completely suppressed for a layer thickness of 7 nm or more. Due to efficient charge transfer from the InxGa1-xN NW core a stable TiO2-covered photoanode with visible light excitation is realized. © 2018 The Royal Society of Chemistry.

  • Phosphatidylserine-liposomes promote tolerogenic features on dendritic cells in human type 1 diabetes by apoptotic mimicry

    Rodriguez-Fernandez S., Pujol-Autonell I., Brianso F., Perna-Barrull D., Cano-Sarabia M., Garcia-Jimeno S., Villalba A., Sanchez A., Aguilera E., Vazquez F., Verdaguer J., Maspoch D., Vives-Pi M. Frontiers in Immunology; 9 (FEB, 253) 2018. 10.3389/fimmu.2018.00253.

    Supramolecular NanoChemistry and Materials

    Type 1 diabetes (T1D) is a metabolic disease caused by the autoimmune destruction of insulin-producing β-cells. With its incidence increasing worldwide, to find a safe approach to permanently cease autoimmunity and allow β-cell recovery has become vital. Relying on the inherent ability of apoptotic cells to induce immunological tolerance, we demonstrated that liposomes mimicking apoptotic β-cells arrested autoimmunity to β-cells and prevented experimental T1D through tolerogenic dendritic cell (DC) generation. These liposomes contained phosphatidylserine (PS)-the main signal of the apoptotic cell membrane-and β-cell autoantigens. To move toward a clinical application, PS-liposomes with optimum size and composition for phagocytosis were loaded with human insulin peptides and tested on DCs from patients with T1D and control age-related subjects. PS accelerated phagocytosis of liposomes with a dynamic typical of apoptotic cell clearance, preserving DCs viability. After PS-liposomes phagocytosis, the expression pattern of molecules involved in efferocytosis, antigen presentation, immunoregulation, and activation in DCs concurred with a tolerogenic functionality, both in patients and control subjects. Furthermore, DCs exposed to PS-liposomes displayed decreased ability to stimulate autologous T cell proliferation. Moreover, transcriptional changes in DCs from patients with T1D after PS-liposomes phagocytosis pointed to an immunoregulatory prolife. Bioinformatics analysis showed 233 differentially expressed genes. Genes involved in antigen presentation were downregulated, whereas genes pertaining to tolerogenic/anti-inflammatory pathways were mostly upregulated. In conclusion, PS-liposomes phagocytosis mimics efferocytosis and leads to phenotypic and functional changes in human DCs, which are accountable for tolerance induction. The herein reported results reinforce the potential of this novel immunotherapy to re-establish immunological tolerance, opening the door to new therapeutic approaches in the field of autoimmunity. © 2018 Rodriguez-Fernandez, Pujol-Autonell, Brianso, Perna-Barrull, Cano-Sarabia, Garcia-Jimeno, Villalba, Sanchez, Aguilera, Vazquez, Verdaguer, Maspoch and Vives-Pi.

  • Photoluminescent lateral flow based on non-radiative energy transfer for protein detection in human serum

    Zamora-Gálvez A., Morales-Narváez E., Romero J., Merkoçi A. Biosensors and Bioelectronics; 100: 208 - 213. 2018. 10.1016/j.bios.2017.09.013.

    Nanobioelectronics and Biosensors

    A new paper-based lateral flow immunoassay configuration was engineered and investigated. The assay is intended for the detection of a model protein in human serum, that is, human immunoglobulin G, with the aim to demonstrate a virtually universal protein detection platform. Once the sample is added in the strip, the analyte is selectively captured by antibody-decorated silica beads (Ab-SiO2) onto the conjugate pad and the sample flows by capillarity throughout the strip until reaching the test line, where a sandwich-like immunocomplex takes place due to the presence of antibody-functionalized QDs (Ab-QDs) onto the test line. Eventually, GO is added as a revealing agent and the photoluminescence of those sites protected by the complex Ab-SiO2/Antigen/Ab-QDs will not be quenched, whereas those photoluminescent sites directly exposed are expected to be quenched by GO, including the control line, made of bare QDs, reporting that the assay occurred successfully. Hence, the photoluminescence of the test line is modulated by the formation of sandwich-like immunocomplexes. The proposed device achieves a limit of detection (LOD) of 1.35 ng mL−1 in standard buffer, which is lower when compared with conventional lateral flow technology reported by gold nanoparticles, including other amplification strategies. Moreover, the resulting device was proven useful in human serum analysis, achieving a LOD of 6.30 ng mL−1 in this complex matrix. This low-cost disposable and easy-to-use device will prove valuable for portable and automated diagnostics applications, and can be easily transferred to other analytes such as clinically relevant protein biomarkers. © 2017

  • Pt(IV)-based nanoscale coordination polymers: Antitumor activity, cellular uptake and interactions with nuclear DNA

    Adarsh N.N., Frias C., Ponnoth Lohidakshan T.M., Lorenzo J., Novio F., Garcia-Pardo J., Ruiz-Molina D. Chemical Engineering Journal; 2018. 10.1016/j.cej.2018.01.058.

    Nanostructured Functional Materials

    Cisplatin has been for many years the gold standard chemotherapeutic drug for the treatment of a wide range of solid tumors, even though its use is commonly associated with serious side effects including non-selective toxicity, myelosuppression or development of cisplatin resistance, among others complications. Over the last decade, a number of nanoparticle formulations were developed to reduce its side effects and improve the selectivity and efficacy of this drug. In this study, we have developed a novel nanoparticle platform based on nanoscale coordination polymer named (Zn-Pt(IV)-NCPs) which contains a Pt(IV) prodrug, Zn and the linker ligand 1,4-Bis(imidazol-1-ylmethyl)benzene (bix). The main objective has been to gain insights into the mechanism of action of this nanostructured material in comparison with cisplatin and the free Pt(IV) prodrug in order to establish a correlation between nanostructuration and therapeutic activity. Zn-Pt(IV)-NCPs nanoparticles displayed an average size close to 200 nm as determined by DLS, a good stability in physiologic environments, and a controlled drug release of Pt. In vitro studies demonstrated that Pt(IV)-NCPs showed an enhanced cytotoxic effect against cell culture of cervical cancer, neuroblastoma and human adenocarcinoma cells in comparison with free Pt(IV) prodrug. Although no difference in cell uptake of Pt was observed for any of the three cell lines assayed, a higher amount of Pt bound to the DNA was found in the cells treated with the nanostructured Pt(IV) prodrug. These studies suggest that the nanostructuration of the prodrug facilitate its activation and induce a change in the mechanism of action related to an increased interaction with the DNA as corroborated by the studies of direct interaction of the Pt(IV) prodrug, nanostructured or not, with DNA. © 2018 Elsevier B.V.

  • Quantification of nanomechanical properties of surfaces by higher harmonic monitoring in amplitude modulated AFM imaging

    Gramazio F., Lorenzoni M., Pérez-Murano F., Evangelio L., Fraxedas J. Ultramicroscopy; 187: 20 - 25. 2018. 10.1016/j.ultramic.2018.01.013.

    Force Probe Microscopy and Surface Nanoengineering

    The determination of nanomechanical properties is an intensive topic of study in several fields of nanophysics, from surface and materials science to biology. At the same time, amplitude modulation force microscopy is one of the most established techniques for nanoscale characterization. In this work, we combine these two topics and propose a method able to extract quantitative nanomechanical information from higher harmonic amplitude imaging in atomic force microscopy. With this method it is possible to discriminate between different materials in the stiffness range of 1–3 GPa, in our case thin films of PS-PMMA based block copolymers. We were able to obtain a critical lateral resolution of less than 20 nm and discriminate between materials with less than a 1 GPa difference in modulus. We show that within this stiffness range, reliable values of the Young's moduli can be obtained under usual imaging conditions and with standard dynamic AFM probes. © 2018

  • Quantum Hall effect in graphene with interface-induced spin-orbit coupling

    Cysne T.P., Garcia J.H., Rocha A.R., Rappoport T.G. Physical Review B; 97 (8, 085413) 2018. 10.1103/PhysRevB.97.085413.

    Theoretical and Computational Nanoscience

    We consider an effective model for graphene with interface-induced spin-orbit coupling and calculate the quantum Hall effect in the low-energy limit. We perform a systematic analysis of the contribution of the different terms of the effective Hamiltonian to the quantum Hall effect (QHE). By analyzing the spin splitting of the quantum Hall states as a function of magnetic field and gate voltage, we obtain different scaling laws that can be used to characterize the spin-orbit coupling in experiments. Furthermore, we employ a real-space quantum transport approach to calculate the quantum Hall conductivity and investigate the robustness of the QHE to disorder introduced by hydrogen impurities. For that purpose, we combine first-principles calculations and a genetic algorithm strategy to obtain a graphene-only Hamiltonian that models the impurity. © 2018 American Physical Society.

  • Raman thermometry analysis: Modelling assumptions revisited

    Jaramillo-Fernandez J., Chavez-Angel E., Sotomayor-Torres C.M. Applied Thermal Engineering; 130: 1175 - 1181. 2018. 10.1016/j.applthermaleng.2017.11.033.

    Phononic and Photonic Nanostructures

    In Raman thermometry, several assumptions are made to model the heat conduction and to extract the thermal conductivity of the samples from the measured data. In this work, the heat conduction in bulk and mesa-like samples was investigated by numerical simulation and measured by the temperature-induced Raman shift method, to study the range of applicability of these assumptions. The effects of light penetration depth and finite sample size on the accuracy of the thermal conductivity determination were investigated by comparing the results of the finite element method with the usual analytical approximation for bulk samples. We found that the assumptions used in the analytical model can be applied to extract the thermal conductivity in solids if the following conditions are fulfilled: the ratio of light penetration depth to laser spot radius is smaller than 0.5, the ratio of spot radius to sample thickness is smaller than 0.1, and the ratio of spot radius to sample half width is smaller than 0.01. © 2017

  • Real Space Demonstration of Induced Crystalline 3D Nanostructuration of Organic Layers

    Paradinas M., Pérez-Rodríguez A., Barrena E., Ocal C. Journal of Physical Chemistry B; 122 (2): 633 - 639. 2018. 10.1021/acs.jpcb.7b05342.

    Atomic Manipulation and Spectroscopy

    The controlled 3D nanostructuration of molecular layers of the semiconducting molecules C22H14 (pentacene) and N,N′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8) is addressed. A tip-assisted method using atomic force microscopy (AFM) is developed for removing part of the organic material and relocating it in up to six layer thick nanostructures. Moreover, unconventional molecular scale imaging combining diverse friction force microscopy modes reveals the stacking sequence of the piled layers. In particular, we unambiguously achieve epitaxial growth, an issue of fundamental importance in thin film strategies for the nanostructuration of more efficient organic nanodevices. © 2017 American Chemical Society.

  • Reversible Thermochromic Polymeric Thin Films Made of Ultrathin 2D Crystals of Coordination Polymers Based on Copper(I)-Thiophenolates

    Troyano J., Castillo O., Martínez J.I., Fernández-Moreira V., Ballesteros Y., Maspoch D., Zamora F., Delgado S. Advanced Functional Materials; 28 (5, 1704040) 2018. 10.1002/adfm.201704040.

    Supramolecular NanoChemistry and Materials

    A one-pot reaction between Cu(BF4)2·xH2O and 4-mercaptobenzoic acid in acetone or methanol gives rise to the formation of lamellar microcrystals of two Cu(I)-thiophenolate-based coordination polymers (CPs) with the formulas [CuCT] n (1) (CT = 4-carboxy-thiophenolate) and [CuMCT]n (2) (MCT = 4-methoxycarbonyl-thiophenolate). Both 1 and 2 show a reversible luminescent thermochromic behavior upon cooling, changing their color from pale yellow to green to orange in the case of 1, and from pale orange to green in the case of 2. It is shown that the lamellar character of these crystals, which exhibit micrometer lateral dimensions and sub-micrometer/nanometer thicknesses, allows processing them with an organic polymer such as polyvinylidene difluoride (PVDF) to form thermochromic 1@PVDF and 2@PVDF thin films. These thermal stimuli-responsive thin films are freestanding, free of macroscopic defects, and robust under mechanical bending stress, opening up the possibility to use them in, for example, 2D imaging sensor films. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Segregation of motor and sensory axons regenerating through bicompartmental tubes by combining extracellular matrix components with neurotrophic factors

    del Valle J., Santos D., Delgado-Martínez I., de la Oliva N., Giudetti G., Micera S., Navarro X. Journal of Tissue Engineering and Regenerative Medicine; 2018. 10.1002/term.2629.

    Segregation of regenerating motor and sensory axons may be a good strategy to improve selective functionality of regenerative interfaces to provide closed-loop commands. Provided that extracellular matrix components and neurotrophic factors exert guidance effects on different neuronal populations, we assessed in vivo the potential of separating sensory and motor axons regenerating in a bicompartmental Y-type tube, with each branch prefilled with an adequate combination of extracellular matrix and neurotrophic factors. The severed rat sciatic nerve was repaired using a bicompartmental tube filled with a collagen matrix enriched with fibronectin (FN) and brain-derived neurotrophic factor (BDNF) encapsulated in poly-lactic co-glycolic acid microspheres (FN + MP.BDNF) in one compartment to preferentially attract motor axons and collagen enriched with laminin (LM) and nerve growth factor (NGF) and neurotrophin-3 (NT-3) in microspheres (LM + MP.NGF/NT-3) in the other compartment for promoting sensory axons regeneration. Control animals were implanted with the same Y-tube with a collagen matrix with microspheres (MP) containing PBS (Col + MP.PBS). By using retrotracer labelling, we found that LM + MP.NGF/NT-3 did not attract higher number of regenerated sensory axons compared with controls, and no differences were observed in sensory functional recovery. However, FN + MP.BDNF guided a higher number of regenerating motor axons compared with controls, improving also motor recovery. A small proportion of sensory axons with large soma size, likely proprioceptive neurons, was also attracted to the FN + MP.BDNF compartment. These results demonstrate that muscular axonal guidance can be modulated in vivo by the addition of fibronectin and BDNF. © 2018 John Wiley & Sons, Ltd.

  • Self-assembly of polyhedral metal-organic framework particles into three-dimensional ordered superstructures

    Avci C., Imaz I., Carné-Sánchez A., Pariente J.A., Tasios N., Pérez-Carvajal J., Alonso M.I., Blanco A., Dijkstra M., López C., Maspoch D. Nature Chemistry; 10 (1): 78 - 84. 2018. 10.1038/NCHEM.2875.

    Supramolecular NanoChemistry and Materials

    Self-assembly of particles into long-range, three-dimensional, ordered superstructures is crucial for the design of a variety of materials, including plasmonic sensing materials, energy or gas storage systems, catalysts and photonic crystals. Here, we have combined experimental and simulation data to show that truncated rhombic dodecahedral particles of the metal-organic framework (MOF) ZIF-8 can self-assemble into millimetre-sized superstructures with an underlying three-dimensional rhombohedral lattice that behave as photonic crystals. Those superstructures feature a photonic bandgap that can be tuned by controlling the size of the ZIF-8 particles and is also responsive to the adsorption of guest substances in the micropores of the ZIF-8 particles. In addition, superstructures with different lattices can also be assembled by tuning the truncation of ZIF-8 particles, or by using octahedral UiO-66 MOF particles instead. These well-ordered, sub-micrometre-sized superstructures might ultimately facilitate the design of three-dimensional photonic materials for applications in sensing. © 2017 Macmillan Publishers Limited, part of Springer Nature.

  • Single-Crystal-to-Single-Crystal Postsynthetic Modification of a Metal-Organic Framework via Ozonolysis

    Albalad J., Xu H., Gándara F., Haouas M., Martineau-Corcos C., Mas-Ballesté R., Barnett S.A., Juanhuix J., Imaz I., Maspoch D. Journal of the American Chemical Society; 140 (6): 2028 - 2031. 2018. 10.1021/jacs.7b12913.

    Supramolecular NanoChemistry and Materials

    We describe solid-gas phase, single-crystal-to-single-crystal, postsynthetic modifications of a metal-organic framework (MOF). Using ozone, we quantitatively transformed the olefin groups of a UiO-66-type MOF into 1,2,4-trioxolane rings, which we then selectively converted into either aldehydes or carboxylic acids. © 2018 American Chemical Society.

  • Sonochemical synthesis of a novel nanoscale 1D lead(II) [Pb2(L)2(I)4]n coordination Polymer, survey of temperature, reaction time parameters

    Hayati P., Suárez-García S., Gutiérrez A., Molina D.R., Morsali A., Rezvani A.R. Ultrasonics Sonochemistry; 42: 320 - 326. 2018. 10.1016/j.ultsonch.2017.11.033.

    Nanostructured Functional Materials

    One new lead(II) coordination supramolecular complex (CSC) (1D), [Pb2(L)2(I)4]n, L = C4H6N2 (1-methyl imidazole), has 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 complex 1 showed that Pb2+ ion is 4-coordinated. Topological analysis shows that the complex 1 is 2,3,5C2 net. Finally, the role of reaction time and temperature on the growth and final morphology of the structures obtained by sonochemical irradiation have been studied. © 2017 Elsevier B.V.

  • Sonochemical Synthesis of Optically Tuneable Conjugated Polymer Nanoparticles

    Bellacanzone C., Roscini C., del Carmen Ruiz Delgado M., Ponce Ortiz R., Ruiz-Molina D. Particle and Particle Systems Characterization; 35 (2, 1700322) 2018. 10.1002/ppsc.201700322.

    Nanostructured Functional Materials

    The development of novel and simple methodologies for the obtaining of semiconductive polymer nanoparticles with fine-tuned optical properties represents nowadays a challenging research area as it involves a simultaneous chemical modification and nanostructuration of the polymer. Here, starting from poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], this objective is achieved with the one-pot synthesis of oligomers with tunable conjugation length and their nanostructuration, employing a miniemulsion method. Ultrasound irradiation of heterogeneous mixtures leads to the formation of hypochlorous acid that disrupts the electronic conjugation through polymer chain cleavage. Moreover, control over the degree of the electronic conjugation of the oligomers, and therefore of the optical properties, is achieved simply by varying the polymer concentration of the initial solution. Finally, the presence of surfactants during the sonication allows for the formation of nanoparticles with progressive spectral shift of the main absorption (from λmax = 476 to 306 nm) and emission bands (from λmax = 597 to 481 nm). The integration of conducting polymer nanoparticles into polymeric matrices yields self-standing and flexible fluorescent films. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Sonochemical synthesis of two novel Pb(II) 2D metal coordination polymer complexes: New precursor for facile fabrication of lead(II) oxide/bromide micro-nanostructures

    Hayati P., Suárez-García S., Gutierrez A., Şahin E., Molina D.R., Morsali A., Rezvani A.R. Ultrasonics Sonochemistry; 42: 310 - 319. 2018. 10.1016/j.ultsonch.2017.11.037.

    Nanostructured Functional Materials

    Two new lead(II) coordination polymer complexes (CSCs) (2D), [Pb2(L)2(Br)2]n·H2O (1), [Pb2(HL/)(L/)(H2O)2]n·H2O (2), where L = C6H5NO2 (2-pyridinecarboxylic acid) and L/ = C9H6O6 (1,3,5-tricarboxylic acid), have been synthesized under different experimental conditions. Micrometric crystals (bulk) or microsized 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 and 2 shows that Pb2+ ions are 8-coordinated, 7 and 9-coordinated, respectively. Topological analysis shows that the compound 1 and 2 are 4,6L26 and bnn net, respectively. However, neither the shape nor the morphology is maintained, showing the role of sonochemistry to modulate both morphology and dimensions of the resulting crystalline material, independently of whether we have a 2D coordination polymer (CP). Finally, micro structuration of lead(II) bromide oxide and lead(II) oxide have been prepared by calcination of two different lead (II) CPs at 700 °C that were characterized by SEM and XRD. © 2017 Elsevier B.V.

  • Structure evolution of mononuclear tungsten and molybdenum species in the protonation process: Insight from FPMD and DFT calculations

    Zhang N., Yi H., Zeng D., Zhao Z., Wang W., Costanzo F. Chemical Physics; 502: 77 - 86. 2018. 10.1016/j.chemphys.2018.01.009.

    Theoretical and Computational Nanoscience

    In this work, we apply static density functional theory (DFT) calculations, as well as classical and first-principles molecular dynamics (FPMD) simulations, using the free-energy perturbation method to study the protonation ability, active site and structures of W(VI) and Mo(VI) in acidic aqueous solution. Using FPMD simulations, utilizing the pKa's calculation technique, we concluded that the octahedral WO2(OH)2(H2O)2 is the true formula for tungstic acid (H2WO4), and the hydroxyl ligands are the acidic site. This aqueous structure of H2WO4 is analogous to the previously reported structure of molybdic acid (H2MoO4). The FPMD trajectories of the tungstic acid deprotonation show that the mono-protonated monotungstate ion (HWO4 −) may partially exist as a five-coordinated WO3(OH)(H2O)− species except for the four-coordinated WO3(OH)− species. This result is supported by DFT calculations, with an isoenergetic point (ΔE = 1.9 kcal·mol−1) for the WO3(OH)(H2O)− and WO3(OH)− species, when explicit solvent molecules are taken into account. In contrast, for the H2MoO4 acid, FPMD trajectories during the deprotonation process show that two H2O ligands immediately escape from the first coordinated sphere of Mo(VI) to form the four-coordinated MoO3(OH)− species. This difference indicates that structural expansion of W(VI) began in the first protonated step, while that of Mo(VI) only occurs in the second step. In addition, our calculated first and second acid constants for tungstic acid are higher than previously reported values for molybdic acid. This result suggests that WO4 2− is more easily protonated than the MoO4 2− anion in the same acidic solution, which is further confirmed by DFT calculations of hydrated oxoanions and its protonated species, based upon the hydration energy. © 2018 Elsevier B.V.

  • Substrate Dependence of the Freezing Dynamics of Supercooled Water Films: A High-Speed Optical Microscope Study

    Pach E., Rodriguez L., Verdaguer A. Journal of Physical Chemistry B; 122 (2): 818 - 826. 2018. 10.1021/acs.jpcb.7b06933.

    Oxide Nanophysics | Force Probe Microscopy and Surface Nanoengineering

    The freezing of supercooled water films on different substrates was investigated using a high-speed camera coupled to an optical microscope, obtaining details of the freezing process not described in the literature before. We observed the two well known freezing stages (fast dendritic growth and slow freezing of the water liquid left after the dendritic growth), but we separated the process into different phenomena that were studied separately: two-dimensional dendrite growth on the substrate interface, vertical dendrite growth, formation and evolution of ice domains, trapping of air bubbles and freezing of the water film surface. We found all of these processes to be dependent on both the supercooling temperature and the substrate used. Ice dendrite (or ice front) growth during the first stage was found to be dependent on thermal properties of the substrate but could not be unequivocally related to them. Finally, for low supercooling, a direct relationship was observed between the morphology of the dendrites formed in the first stage, which depends on the substrate, and the roughness and the shape of the surface of the ice, when freezing of the film was completed. This opens the possibility of using surfaces and coatings to control ice morphology beyond anti-icing properties. © 2017 American Chemical Society.

  • Synthesis and characterization of porous sulfur/MWCNTs composites with improved performance and safety as cathodes for Li-S batteries

    Fedorkova A.S., Kazda T., Gavalierova K., Gomez-Romero P., Shembel E. International Journal of Electrochemical Science; 13 (1): 551 - 562. 2018. 10.20964/2018.01.67.

    Novel Energy-Oriented Materials

    Sulfur-carbon (S-C-MWCNTs) composites and sulfur-LiFePO4 (S-LFP-MWCNTs) composites were synthesised with MWCNTs additive by sulfur sublimation and solid state reaction. As prepared materials are characterized with scanning electron microscopy, thermogravimetry, FTIR, elemental analysis, XPS, cyclic voltammetry and galvanostatic charge/discharge tests. The composite S-LFP cathode with MWCNTs additive shows improved discharge capacity and performance. It shows an initial discharge capacity of 1167 mAh/g-sulfur, or 70% of theoretical capacity. The discharge capacity measured after 20 cycles for S-LFP-MWCNTs composite cathode was 80% of the initial capacity and remained stable. After 160 charge/discharge tests, the cathode displays a stable capacity of 561 mAh/g-sulfur at the C-rate of 0.2 C. Combination of sulfur, LiFePO4 and MWCNTs prevents aggregation and volume change of the cathode particles and improves the conductivity and electrochemical stability during the long-term cycling. 3-D FTIR spectroscopy measurements confirmed improved chemical stability and safety of sulfur composites also at higher temperatures. © 2018 The Authors.

  • The Misfit Dislocation Core Phase in Complex Oxide Heteroepitaxy

    Bagués N., Santiso J., Esser B.D., Williams R.E.A., McComb D.W., Konstantinovic Z., Balcells L., Sandiumenge F. Advanced Functional Materials; 28 (8, 1704437) 2018. 10.1002/adfm.201704437.

    Nanomaterials Growth Division

    Misfit dislocations form self-organized nanoscale linear defects exhibiting their own distinct structural, chemical, and physical properties which, particularly in complex oxides, hold a strong potential for the development of nanodevices. However, the transformation of such defects from passive into potentially active functional elements necessitates a deep understanding of the particular mechanisms governing their formation. Here, different atomic resolution imaging and spectroscopic techniques are combined to determine the complex structure of misfit dislocations in the perovskite type La0.67Sr0.33MnO3/LaAlO3 heteroepitaxial system. It is found that while the position of the film–substrate interface is blurred by cation intermixing, oxygen vacancies selectively accumulate at the tensile region of the dislocation strain field. Such accumulation of vacancies is accompanied by the reduction of manganese cations in the same area, inducing chemical expansion effects, which partly accommodate the dislocation strain. The formation of oxygen vacancies is only partially electrically compensated and results in a positive net charge q ≈ +0.3 ± 0.1 localized in the tensile region of the dislocation, while the compressive region remains neutral. The results highlight a prototypical core model for perovskite-based heteroepitaxial systems and offer insights for predictive manipulation of misfit dislocation properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Thermoelectric spin voltage in graphene

    Sierra J.F., Neumann I., Cuppens J., Raes B., Costache M.V., Valenzuela S.O. Nature Nanotechnology; 13 (2): 107 - 111. 2018. 10.1038/s41565-017-0015-9.

    Physics and Engineering of Nanodevices

    In recent years, new spin-dependent thermal effects have been discovered in ferromagnets, stimulating a growing interest in spin caloritronics, a field that exploits the interaction between spin and heat currents 1,2 . Amongst the most intriguing phenomena is the spin Seebeck effect 3-5, in which a thermal gradient gives rise to spin currents that are detected through the inverse spin Hall effect 6-8 . Non-magnetic materials such as graphene are also relevant for spin caloritronics, thanks to efficient spin transport 9-11, energy-dependent carrier mobility and unique density of states 12,13 . Here, we propose and demonstrate that a carrier thermal gradient in a graphene lateral spin valve can lead to a large increase of the spin voltage near to the graphene charge neutrality point. Such an increase results from a thermoelectric spin voltage, which is analogous to the voltage in a thermocouple and that can be enhanced by the presence of hot carriers generated by an applied current 14-17 . These results could prove crucial to drive graphene spintronic devices and, in particular, to sustain pure spin signals with thermal gradients and to tune the remote spin accumulation by varying the spin-injection bias. © 2017 The Author(s).

  • Time course study of long-term biocompatibility and foreign body reaction to intraneural polyimide-based implants

    de la Oliva N., Navarro X., del Valle J. Journal of Biomedical Materials Research - Part A; 106 (3): 746 - 757. 2018. 10.1002/jbm.a.36274.

    The foreign body reaction (FBR) against an implanted device is characterized by the formation of a fibrotic tissue around the implant. In the case of interfaces for peripheral nerves, used to stimulate specific group of axons and to record different nerve signals, the FBR induces a matrix deposition around the implant creating a physical separation between nerve fibers and the interface that may reduce its functionality over time. In order to understand how the FBR to intraneural interfaces evolves, polyimide non-functional devices were implanted in rat peripheral nerve. Functional tests (electrophysiological, pain and locomotion) and histological evaluation demonstrated that implanted devices did not cause any alteration in nerve function, in myelinated axons or in nerve architecture. The inflammatory response due to the surgical implantation decreased after 2 weeks. In contrast, inflammation was higher and more prolonged in the device implanted nerves with a peak after 2 weeks. With regard to tissue deposition, a tissue capsule appeared soon around the devices, acquiring maximal thickness at 2 weeks and being remodeled subsequently. Immunohistochemical analysis revealed two different cell types implicated in the FBR in the nerve: macrophages as the first cells in contact with the interface and fibroblasts that appear later at the edge of the capsule. Our results describe how the FBR against a polyimide implant in the peripheral nerve occurs and which are the main cellular players. Increasing knowledge of these responses will help to improve strategies to decrease the FBR against intraneural implants and to extend their usability. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 746–757, 2018. © 2017 Wiley Periodicals, Inc.

  • Ultrasensitive binder-free glucose sensors based on the pyrolysis of in situ grown Cu MOF

    Zhang X., Luo J., Tang P., Morante J.R., Arbiol J., Xu C., Li Q., Fransaer J. Sensors and Actuators, B: Chemical; 254: 272 - 281. 2018. 10.1016/j.snb.2017.07.024. IF: 5.401

    Advanced Electron Nanoscopy

    A non-enzymatic glucose sensor based on carbon/Cu composite materials was developed by the in-situ growth and subsequent pyrolysis of metal-organic frameworks (MOFs) on Cu foam. After pyrolysis, SEM, HRTEM and STEM-EELS were employed to clarify the hierarchical Cu@porous carbon electrode. It is found that the Cu nanoparticles are uniformly embedded in the carbon matrix, carbon matrix in close contact with the pyrolized carbon sheets. The electrocatalytic activity of the Cu@porous carbon matrix electrode for glucose sensing was explored by cyclic voltammetry (CV) and chronoamperometry. The resulting Cu@porous carbon matrix electrode displays ultrahigh sensitivity (10.1 mA cm−2 mM−1), low detection limit (0.6 μM), short response time (less than 2 s) and good stability, indicating that the developed electrode is a promising glucose sensor. © 2017 Elsevier B.V.