Staff directory Jordi Fraxedas Calduch

Jordi Fraxedas Calduch

CSIC Scientific Researcher
jordi.fraxedas(ELIMINAR)@icn2.cat
Thermal Properties of Nanoscale Materials

ORCID: 0000-0002-2821-4831

Publications

2024

Bringing satellite and nanotechnologies together: unifying strengths against pollution and climate change
Ferral, Anabella; Bonansea, Matias; Scavuzzo, Carlos Marcelo; Nemina, Francisco; Paci, Maximiliano Burgos; Ramirez, Jessica Casandra; Sepulveda, Borja; Fraxedas, Jordi; Esplandiu, Maria Jose Frontiers In Nanotechnology; 6: 1332820. 2024. 10.3389/fnano.2024.1332820.
Collective motion of Nafion-based micromotors in water
Fraxedas, Jordi; Reguera, David; Esplandiu, Maria Jose Faraday Discussions; 2490: 424 - 439. 2024. 10.1039/d3fd00098b.
Fe/Au galvanic nanocells to generate self-sustained Fenton reactions without additives at neutral pH
Shahnazarova, Gubakhanim; Al Bast, Nour Al Hoda; Ramirez, Jessica C; Nogues, Josep; Esteve, Jaume; Fraxedas, Jordi; Serra, Albert; Esplandiu, Maria J; Sepulveda, Borja Materials Horizons; 11 (9): 2206 - 2216. 2024. 10.1039/d3mh01935g.
Stoichiometric control of electron mobility and 2D superconductivity at LaAlO3-SrTiO3 interfaces
Singh, Gyanendra; Guzman, Roger; Saiz, Guilhem; Zhou, Wu; Gazquez, Jaume; Masoudinia, Fereshteh; Winkler, Dag; Claeson, Tord; Fraxedas, Jordi; Bergeal, Nicolas; Herranz, Gervasi; Kalaboukhov, Alexei Communications Physics; 7 (1): 149. 2024. 10.1038/s42005-024-01644-3.

2023

Band Alignment and Photoresponse of LaFeO3-Based Heterojunctions
Sheng, YW; Mirjolet, M; Villa, M; Gazquez, J; Santiso, J; Klein, A; Fraxedas, J; Fontcuberta, J Physical Review Applied; 19 (2): 24001. 2023. 10.1103/PhysRevApplied.19.024001. IF: 4.600
Interfacial phenomena in nanotechnological applications for water remediation
Esplandiu Egido, María José Reference Module In Chemistry, Molecular Sciences And Chemical Engineering; 2023. 10.1016/B978-0-323-85669-0.00066-0.
Real-time microscopy of the relaxation of a glass
Ruiz-Ruiz, M; Vila-Costa, A; Bar, T; Rodríguez-Tinoco, C; Gonzalez-Silveira, M; Plaza, JA; Alcalá, J; Fraxedas, J; Rodriguez-Viejo, J Nature Physics; 2023. 10.1038/s41567-023-02125-0. IF: 19.500

2022

From radial to unidirectional water pumping in zeta-potential modulated Nafion nanostructures
Esplandiu M.J., Reguera D., Romero-Guzmán D., Gallardo-Moreno A.M., Fraxedas J. Nature Communications; 13 (1, 2812) 2022. 10.1038/s41467-022-30554-7.

Chemically propelled micropumps are promising wireless systems to autonomously drive fluid flows for many applications. However, many of these systems are activated by nocuous chemical fuels, cannot operate at high salt concentrations, or have difficulty for controlling flow directionality. In this work we report on a self-driven polymer micropump fueled by salt which can trigger both radial and unidirectional fluid flows. The micropump is based on the cation-exchanger Nafion, which produces chemical gradients and local electric fields capable to trigger interfacial electroosmotic flows. Unidirectional pumping is predicted by simulations and achieved experimentally by nanostructuring Nafion into microarrays with a fine tune modulation of surrounding surface zeta potentials. Nafion micropumps work in a wide range of salt concentrations, are reusable, and can be fueled by different salt cations. We demonstrate that they work with the common water-contaminant cadmium, using the own capture of this ion as fuel to drive fluid pumping. Thus, this system has potential for efficient and fast water purification strategies for environmental remediation. Unidirectional Nafion pumps also hold promise for effective analyte delivery or preconcentration for (bio)sensing assays. © 2022, The Author(s).

View abstract
Oscillatory patterns in redox gradient materials through wireless bipolar electrochemistry. The dynamic wave-like case of copper bipolar oxidation
Fuentes-Rodríguez L., Pujades E., Fraxedas J., Crespi A., Xu K., Abad L., Casañ-Pastor N. Materials Chemistry Frontiers; 6 (16): 2284 - 2296. 2022. 10.1039/d2qm00482h.

Bipolar electrochemistry allows the development of processes in a wireless manner, with reactions occurring at the induced anodes and cathodes of an immersed conducting material in the electrolyte. As a result, a gradient oxidation state may appear along the main axis field on the surface or bulk of the material depending on the type of reaction available at each induced potential. Redox intercalation gradients have been observed, metal anodization, or deposition, and also reactions at the electrolyte in the nearby environment of the poles induced. The complex oxidation of copper and interconversion between phases formed yields in this work an oscillating redox gradient, thanks to the great resistance change when the oxidized phases are formed. Parallel stripes containing mainly Cu2O, CuO, and Cu(OH)2 with large resistance are formed perpendicular to the electric field, forming a sequence of secondary dipoles in intermediate Cu stripes, that depends on the external voltage applied, and that oscillates in time at the same spatial coordinates. With longer times, copper solubilizes at the larger induced potential zones, probably as Cu(OH)42−. A simple finite element electrostatic model defines the complex potential waves induced in the piece. The resulting dynamics offer an example of the complexity of order in unwired conducting materials in wet media, either in catalysis, bioelectrodes, electronics, photovoltaics, or energy storage. © 2022 The Royal Society of Chemistry.

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2021

Characterization of charge states in conducting organic nanoparticles by X-ray photoemission spectroscopy
Fraxedas J., Vollmer A., Koch N., de Caro D., Jacob K., Faulmann C., Valade L. Materials; 14 (8, 2058) 2021. 10.3390/ma14082058. IF: 3.623

The metallic and semiconducting character of a large family of organic materials based on the electron donor molecule tetrathiafulvalene (TTF) is rooted in the partial oxidation (charge transfer or mixed valency) of TTF derivatives leading to partially filled molecular orbital-based electronic bands. The intrinsic structure of such complexes, with segregated donor and acceptor molecular chains or planes, leads to anisotropic electronic properties (quasi one-dimensional or two-dimensional) and morphology (needle-like or platelet-like crystals). Recently, such materials have been synthesized as nanoparticles by intentionally frustrating the intrinsic anisotropic growth. X-ray photoemission spectroscopy (XPS) has emerged as a valuable technique to characterize the transfer of charge due to its ability to discriminate the different chemical environments or electronic configurations manifested by chemical shifts of core level lines in high-resolution spectra. Since the photoemission process is inherently fast (well below the femtosecond time scale), dynamic processes can be efficiently explored. We determine here the fingerprint of partial oxidation on the photoemission lines of nanoparticles of selected TTF-based conductors. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

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In situ XPS analysis of the electronic structure of silicon and titanium thin films exposed to low-pressure inductively-coupled RF plasma
Fraxedas J., Schütte M., Sauthier G., Tallarida M., Ferrer S., Carlino V., Pellegrin E. Applied Surface Science; 542 (148684) 2021. 10.1016/j.apsusc.2020.148684. IF: 6.707

Carbon contamination of synchrotron and free-electron lasers beamline optics continues to be a major nuisance due to the interaction of the intense photon beams with the surfaces of the optical elements in the presence of residual gases even in ultrahigh vacuum (UHV) conditions. Among the available in situ cleaning strategies, low-pressure radio frequency (RF) plasma treatment has emerged as a useful and relatively simple approach to remove such carbon contamination. However, the irreversible damage that the plasma may induce in such critical surfaces has to be carefully characterized before its general application. In this study, we focus on reducing the amount of carbon from UHV chamber inside surfaces via silicon and titanium coatings using a low-pressure inductively-coupled downstream plasma source and we characterize the surface alterations by in situ X-ray photoemission spectroscopy (XPS). The in situ mirror cleaning is simulated by means of silicon wafers. We observe upward band bending, which translates into lower binding energies of the photoemission lines, that we attribute to the generation of vacancies and trapped charges in the oxide layers. © 2020 Elsevier B.V.

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Superconducting super-organized nanoparticles of the superconductor (BEDT-TTF)2Cu(NCS)(2)
Dominique de Caro, Kane Jacob, Marco Revelli-Beaumont, Christophe Faulmann, Lydie Valade, Marine Tassé, Sonia Mallet-Ladeira, Shuxiang Fan, Tadashi Kawamoto, Takehiko Mori, Jordi Fraxedas Synthetic Metals; 278 (116844) 2021. 10.1016/j.synthmet.2021.116844. IF: 3.266

The synthesis of (BEDT-TTF)2Cu(NCS)2 in the presence of poly(ethylene glycol) leads to super-organized nanoparticles of 2–8 nm size. Samples contain crystalline nanoparticles of the κ-(BEDT-TTF)2Cu(NCS)2 phase. The electrical conductivity at room temperature is about 0.08 S · cm–1, a typical value for nanopowders of tetrathiafulvalene-based conducting compounds. The current-voltage characteristic for an individual nanoparticle aggregate is fitted with a Shockley diode model. A saturation current of 4.1 pA and a threshold voltage of 0.45 V are extracted. N1s and S2p lines in X-ray photoelectron spectroscopy evidence a charge transfer, characteristic for tetrathiafulvalene-based conducting salts. Magnetic susceptibility studies show a superconducting transition at 9.1 K, a characteristic value for the κ-(BEDT-TTF)2Cu(NCS)2 phase. The thermoelectric power of the nanopowder is represented by the average //c and //b values for the single-crystal. Finally, resistivity for the nanopowder is nearly flat in the metallic region.

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2020

Electrophoretic origin of long-range repulsion of colloids near water/Nafion interfaces
Esplandiu M.J., Reguera D., Fraxedas J. Soft Matter; 16 (15): 3717 - 3726. 2020. 10.1039/d0sm00170h. IF: 3.140

One of the most striking properties of Nafion is the formation of a long-range solute exclusion zone (EZ) in contact with water. The mechanism of formation of this EZ has been the subject of a controversial and long-standing debate. Previous studies by Schurr et al. and Florea et al. root the explanation of this phenomenon in the ion-exchange properties of Nafion, which generates ion diffusion and ion gradients that drive the repulsion of solutes by diffusiophoresis. Here we have evaluated separately the electrophoretic and chemiphoretic contributions to multi-ionic diffusiophoresis using differently charged colloidal tracers as solutes to identify better their contribution in the EZ formation. Our experimental results, which are also supported by numerical simulations, show that the electric field, built up due to the unequal diffusion coefficients of the exchanged ions, is the dominant parameter behind such interfacial phenomenon in the presence of alkali metal chlorides. The EZ formation depends on the interplay of the electric field with the zeta potential of the solute and can be additionally modulated by changing ion diffusion coefficients or adding salts. As a consequence, we show that not all solutes can be expelled from the Nafion interface and hence the EZ is not always formed. This study thus provides a more detailed description of the origin and dynamics of this phenomenon and opens the door to the rational use of this active interface for many potential applications. This journal is © The Royal Society of Chemistry.

View abstract
Self-assembly of block copolymers under nonisothermal annealing conditions as revealed by grazing-incidence small-angle X-ray scattering
Fernandez-Regu Lez M., Solano E., Evangelio L., Gottlieb S., Pinto-Gomez C., Rius G., Fraxedas J., Gutierrez-Fernandez E., Nogales A., Garcia-Gutierrez M.C., Ezquerra T.A., Perez-Murano F. Journal of Synchrotron Radiation; 27: 1278 - 1288. 2020. 10.1107/S1600577520009820. IF: 2.251

An accurate knowledge of the parameters governing the kinetics of block copolymer self-assembly is crucial to model the time- and temperature-dependent evolution of pattern formation during annealing as well as to predict the most efficient conditions for the formation of defect-free patterns. Here, the self-assembly kinetics of a lamellar PS-b-PMMA block copolymer under both isothermal and non-isothermal annealing conditions are investigated by combining grazing-incidence small-angle X-ray scattering (GISAXS) experiments with a novel modelling methodology that accounts for the annealing history of the block copolymer film before it reaches the isothermal regime. Such a model allows conventional studies in isothermal annealing conditions to be extended to the more realistic case of non-isothermal annealing and prediction of the accuracy in the determination of the relevant parameters, namely the correlation length and the growth exponent, which define the kinetics of the self-assembly. © 2020 International Union of Crystallography.

View abstract
Water/methanol solutions characterized by liquid μ-jet XPS and DFT—The methanol hydration case
Pellegrin E., Perez-Dieste V., Escudero C., Rejmak P., Gonzalez N., Fontsere A., Prat J., Fraxedas J., Ferrer S. Journal of Molecular Liquids; 300 (112258) 2020. 10.1016/j.molliq.2019.112258. IF: 5.065

The advent of liquid μ-jet setups as proposed by Faubel and Winter – in conjunction with X-ray Photoemission Spectroscopy (XPS) – has opened up a large variety of experimental possibilities in the field of atomic and molecular physics. In this study, we present first results from a synchrotron-based XPS core level and valence band electron spectroscopy study on water (10-4 M aqueous NaCl solution) as well as a water/methanol mixture using the newly commissioned ALBA liquid μ-jet setup. The experimental results are compared with simulations from density functional theory (DFT) regarding the electronic structure of single molecules, pure molecular clusters, and mixed clusters configurations as well as previous experimental studies. We give a detailed interpretation of the core level and valence band spectra for the vapour and liquid phases of both sample systems. The resulting overall picture gives insight into the water/methanol concentrations of the vapour and liquid phases as well as into the local electronic structure of the pertinent molecular clusters under consideration, with a special emphasis on methanol as the simplest amphiphilic molecule capable of creating hydrogen bonds. © 2019 Elsevier B.V.

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2019

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

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

View abstract
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

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.

View abstract
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

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.

View abstract
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

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

View abstract
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

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.

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2018

Facile synthesis of nanoparticles of the molecule-based superconductor κ-(BEDT-TTF)2Cu(NCS)2 [Synthèse aisée de nanoparticules du supraconducteur moléculaire κ-(BEDT-TTF)2Cu(NCS)2]
Cormary B., Faulmann C., de Caro D., Valade L., de Caro P., Ballesteros B., Fraxedas J. Comptes Rendus Chimie; 21 (9): 809 - 813. 2018. 10.1016/j.crci.2018.07.006. IF: 1.877

Well-dispersed roughly spherical nano-objects of the molecule-based superconductor κ-(BEDT-TTF)2Cu(NCS)2 have been prepared in an organic solution by using an easy synthetic route. Long alkyl-chain aconitate esters have been used as growth controlling agents. Nano-objects exhibiting sizes in the 35–120 nm range are made of aggregated individual smaller nanoparticles ranging from 3 to 10 nm. Nanoparticle powders have been studied by X-ray diffraction, high resolution electron microscopy and atomic force microscopy in the conductivity mode. © 2018 Académie des sciences

View abstract
Interfacial Engineering of Metal Oxides for Highly Stable Halide Perovskite Solar Cells
Mingorance A., Xie H., Kim H.-S., Wang Z., Balsells M., Morales-Melgares A., Domingo N., Kazuteru N., Tress W., Fraxedas J., Vlachopoulos N., Hagfeldt A., Lira-Cantu M. Advanced Materials Interfaces; 5 (22, 1800367) 2018. 10.1002/admi.201800367. IF: 4.834

Oxides employed in halide perovskite solar cells (PSCs) have already demonstrated to deliver enhanced stability, low cost, and the ease of fabrication required for the commercialization of the technology. The most stable PSCs configuration, the carbon-based hole transport layer-free PSC (HTL-free PSC), has demonstrated a stability of more than one year of continuous operation partially due to the dual presence of insulating oxide scaffolds and conductive oxides. Despite these advances, the stability of PSCs is still a concern and a strong limiting factor for their industrial implementation. The engineering of oxide interfaces functionalized with molecules (like self-assembly monolayers) or polymers results in the passivation of defects (traps), providing numerous advantages such as the elimination of hysteresis and the enhancement of solar cell efficiency. But most important is the beneficial effect of interfacial engineering on the lifetime and stability of PSCs. In this work, the authors provide a brief insight into the recent developments reported on the surface functionalization of oxide interfaces in PSCs with emphasis on the effect of device stability. This paper also discusses the different binding modes, their effect on defect passivation, band alignment or dipole formation, and how these parameters influence device lifetime. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

View abstract
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. IF: 2.929

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

View abstract
Unraveling the Operational Mechanisms of Chemically Propelled Motors with Micropumps
Esplandiu M.J., Zhang K., Fraxedas J., Sepulveda B., Reguera D. Accounts of Chemical Research; 51 (9): 1921 - 1930. 2018. 10.1021/acs.accounts.8b00241. IF: 20.955

ConspectusThe development of effective autonomous micro- and nanomotors relies on controlling fluid motion at interfaces. One of the main challenges in the engineering of such artificial machines is the quest for efficient mechanisms to power them without using external driving forces. In the past decade, there has been an important increase of man-made micro- and nanomotors fueled by self-generated physicochemical gradients. Impressive proofs of concept of multitasking machines have been reported demonstrating their capabilities for a plethora of applications. While the progress toward applications is promising, there are still open questions on fundamental physicochemical aspects behind the mechanical actuation, which require more experimental and theoretical efforts. These efforts are not merely academic but will open the door for an efficient and practical implementation of such promising devices.In this Account, we focus on chemically driven motors whose motion is the result of a complex interplay of chemical reactions and (electro)hydrodynamic phenomena. A reliable study of these processes is rather difficult with mobile objects like swimming motors. However, pumps, which are the immobilized motor counterparts, emerge as simple manufacturing and well-defined platforms for a better experimental probing of the mechanisms and key parameters controlling the actuation.Here we review some recent studies using a new methodology that has turned out to be very helpful to characterize micropump chemomechanics. The aim was to identify the redox role of the motor components, to map the chemical reaction, and to quantify the relevant electrokinetic parameters (e.g., electric field and fluid flow). This was achieved by monitoring the velocity of differently charged tracers and by fluorescence imaging of the chemical species involved in the chemical reaction, for example, proton gradients. We applied these techniques to different systems of interest. First, we probed bimetallic pumps as counterparts of the pioneering bimetallic swimmers. We corroborated that fluid motion was due to a self-generated electro-osmotic mechanism driven by the redox decomposition of H2O2. In addition, we analyzed by simulations the key parameters that yield an optimized operation. Moreover, we accomplished a better assessment of the importance of surface chemistry on the metal electrochemical response, highlighting its relevance in controlling the redox role of the metals and motion direction.Second, we focused on metallic and semiconductor micropumps to analyze light-controlled motion mechanisms through photoelectrochemical decomposition of fuels. These pumps were driven by visible light and could operate using just water as fuel. In these systems, we found a very interesting competition between two different mechanisms for fluid propulsion, namely, light-activated electro-osmosis and light-insensitive diffusio-osmosis, stemming from different chemical pathways in the fuel decomposition. In this case, surface roughness becomes a pivotal parameter to enhance or depress one mechanism over the other.These examples demonstrate that pumps are practical platforms to explore operating mechanisms and to quantify their performance. Additionally, they are suitable systems to test novel fuels or motor materials. This knowledge is extensible to swimmers providing not only fundamental understanding of their locomotion mechanisms but also useful clues for their design and optimization. © 2018 American Chemical Society.

View abstract

2017

A statistical analysis of nanocavities replication applied to injection moulding
Pina-Estany J., Colominas C., Fraxedas J., Llobet J., Perez-Murano F., Puigoriol-Forcada J.M., Ruso D., Garcia-Granada A.A. International Communications in Heat and Mass Transfer; 81: 131 - 140. 2017. 10.1016/j.icheatmasstransfer.2016.11.003. IF: 3.718

The purpose of this paper is to investigate both theoretically and experimentally how nanocavities are replicated in the injection moulding manufacturing process. The objective is to obtain a methodology for efficiently replicate nanocavities. From the theoretical point of view, simulations are carried out using a submodeling approach combining Solidworks Plastics for a first macrosimulation and Fluent solver for a subsequent nanosimulation. The effect of the four main factors (melt temperature, mould temperature, filling time and cavity geometry) are quantified using an statistical 24 factorial experiment. It is found that the main effects are the cavity length, the mould temperature and the polymer temperature, with standardized effects of 5, 3 and 2.6, respectively. Filling time has a negative 1.3 standardized effect. From the experimental point of view, Focused Ion Beam technique is used for mechanizing nanocavities in a steel mould. The replication achieved in polycarbonate injection is quantified using an Atomic Force Microscope. It is observed how both the geometry and the position of the cavities in the mould affect its replication. © 2016 Elsevier Ltd

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Cryogenic characterisation and modelling of commercial SiC MOSFETs
Woodend L; Gammon P; Shah V; Pérez-Tomás A; Li F; Hamilton D; Myronov M; Mawby P Materials Science Forum; 897 MSF: 557 - 560. 2017. 10.4028/www.scientific.net/MSF.897.557.
Functional dependence of resonant harmonics on nanomechanical parameters in dynamic mode atomic force microscopy
Gramazio F., Lorenzoni M., Pérez-Murano F., Trinidad E.R., Staufer U., Fraxedas J. Beilstein Journal of Nanotechnology; 8 (1, 90) 2017. 10.3762/bjnano.8.90. IF: 3.127

We present a combined theoretical and experimental study of the dependence of resonant higher harmonics of rectangular cantilevers of an atomic force microscope (AFM) as a function of relevant parameters such as the cantilever force constant, tip radius and free oscillation amplitude as well as the stiffness of the sample's surface. The simulations reveal a universal functional dependence of the amplitude of the 6th harmonic (in resonance with the 2nd flexural mode) on these parameters, which can be expressed in terms of a gun-shaped function. This analytical expression can be regarded as a practical tool for extracting qualitative information from AFM measurements and it can be extended to any resonant harmonics. The experiments confirm the predicted dependence in the explored 3-45 N/m force constant range and 2-345 GPa sample's stiffness range. For force constants around 25 N/m, the amplitude of the 6th harmonic exhibits the largest sensitivity for ultrasharp tips (tip radius below 10 nm) and polymers (Young's modulus below 20 GPa). © 2017 Gramazio et al.

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Identifying the nature of surface chemical modification for directed self-assembly of block copolymers
Evangelio L., Gramazio F., Lorenzoni M., Gorgoi M., Espinosa F.M., García R., Pérez-Murano F., Fraxedas J. Beilstein Journal of Nanotechnology; 8 (1, 198) 2017. 10.3762/bjnano.8.198. IF: 3.127

In recent years, block copolymer lithography has emerged as a viable alternative technology for advanced lithography. In chemicalepitaxy- directed self-assembly, the interfacial energy between the substrate and each block copolymer domain plays a key role on the final ordering. Here, we focus on the experimental characterization of the chemical interactions that occur at the interface built between different chemical guiding patterns and the domains of the block copolymers. We have chosen hard X-ray high kinetic energy photoelectron spectroscopy as an exploration technique because it provides information on the electronic structure of buried interfaces. The outcome of the characterization sheds light onto key aspects of directed self-assembly: grafted brush layer, chemical pattern creation and brush/block co-polymer interface. © 2017 Evangelio et al.

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In Situ Determination of the Water Condensation Mechanisms on Superhydrophobic and Superhydrophilic Titanium Dioxide Nanotubes
Macias-Montero M., Lopez-Santos C., Filippin A.N., Rico V.J., Espinos J.P., Fraxedas J., Perez-Dieste V., Escudero C., Gonzalez-Elipe A.R., Borras A. Langmuir; 33 (26): 6449 - 6456. 2017. 10.1021/acs.langmuir.7b00156. IF: 3.833

One-dimensional (1D) nanostructured surfaces based on high-density arrays of nanowires and nanotubes of photoactive titanium dioxide (TiO2) present a tunable wetting behavior from superhydrophobic to superhydrophilic states. These situations are depicted in a reversible way by simply irradiating with ultraviolet light (superhydrophobic to superhydrophilic) and storage in dark. In this article, we combine in situ environmental scanning electron microscopy (ESEM) and near ambient pressure photoemission analysis (NAPP) to understand this transition. These experiments reveal complementary information at microscopic and atomic level reflecting the surface wettability and chemical state modifications experienced by these 1D surfaces upon irradiation. We pay special attention to the role of the water condensation mechanisms and try to elucidate the relationship between apparent water contact angles of sessile drops under ambient conditions at the macroscale with the formation of droplets by water condensation at low temperature and increasing humidity on the nanotubes' surfaces. Thus, for the as-grown nanotubes, we reveal a metastable and superhydrophobic Cassie state for sessile drops that tunes toward water dropwise condensation at the microscale compatible with a partial hydrophobic Wenzel state. For the UV-irradiated surfaces, a filmwise wetting behavior is observed for both condensed water and sessile droplets. NAPP analyses show a hydroxyl accumulation on the as-grown nanotubes surfaces during the exposure to water condensation conditions, whereas the water filmwise condensation on a previously hydroxyl enriched surface is proved for the superhydrophilic counterpart. © 2017 American Chemical Society.

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Petrographic and geochemical evidence for multiphase formation of carbonates in the Martian orthopyroxenite Allan Hills 84001
Moyano-Cambero C.E., Trigo-Rodríguez J.M., Benito M.I., Alonso-Azcárate J., Lee M.R., Mestres N., Martínez-Jiménez M., Martín-Torres F.J., Fraxedas J. Meteoritics and Planetary Science; 52 (6): 1030 - 1047. 2017. 10.1111/maps.12851. IF: 2.391

Martian meteorites can provide valuable information about past environmental conditions on Mars. Allan Hills 84001 formed more than 4 Gyr ago, and owing to its age and long exposure to the Martian environment, and this meteorite has features that may record early processes. These features include a highly fractured texture, gases trapped during one or more impact events or during formation of the rock, and spherical Fe-Mg-Ca carbonates. In this study, we have concentrated on providing new insights into the context of these carbonates using a range of techniques to explore whether they record multiple precipitation and shock events. The petrographic features and compositional properties of these carbonates indicate that at least two pulses of Mg- and Fe-rich solutions saturated the rock. Those two generations of carbonates can be distinguished by a very sharp change in compositions, from being rich in Mg and poor in Fe and Mn, to being poor in Mg and rich in Fe and Mn. Between these two generations of carbonate is evidence for fracturing and local corrosion. © 2017 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals, Inc. on behalf of The Meteoritical Society.

View abstract
Photochemically Activated Motors: From Electrokinetic to Diffusion Motion Control
Zhang K., Fraxedas J., Sepulveda B., Esplandiu M.J. ACS Applied Materials and Interfaces; 9 (51): 44948 - 44953. 2017. 10.1021/acsami.7b15855. IF: 7.504

Self-propelled micro/nanomotors that can transform chemical energy from the surrounding environment into mechanical motion are cutting edge nanotechnologies with potential applications in biomedicine and environmental remediation. These applications require full understanding of the propulsion mechanisms to improve the performance and controllability of the motors. In this work, we demonstrate that there are two competing chemomechanical mechanisms at semiconductor/metal (Si/Pt) micromotors in a pump configuration under visible light exposure. The first propulsion mechanism is driven by an electro-osmotic process stemmed from a photoactivation reaction mediated by H2O2, which takes place in two separated redox reactions at the Si and Pt interfaces. One reaction involves the oxidation of H2O2 at the silicon side, and the other the H2O2 reduction at the metal side. The second mechanism is not light responsive and is triggered by the redox decomposition of H2O2 exclusively at the Pt surface. We show that it is possible to enhance/suppress one mechanism over the other by tuning the surface roughness of the micromotor metal. More specifically, the actuation mechanism can be switched from light-controlled electrokinetics to light-insensitive diffusio-osmosis by only increasing the metal surface roughness. The different actuation mechanisms yield strikingly different fluid flow velocities, electric fields, and light sensitivities. Consequently, these findings are very relevant and can have a remarkable impact on the design and optimization of photoactivated catalytic devices and, in general, on bimetallic or insulating-metallic motors. © 2017 American Chemical Society.

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Preface
Fraxedas J. Applied Surface Science; 391: 1 - 2. 2017. 10.1016/j.apsusc.2016.09.164.

[No abstract available]

View abstract

2016

Evaluating the compressive stress generated during fabrication of Si doubly clamped nanobeams with AFM
Lorenzoni M., Llobet J., Gramazio F., Sansa M., Fraxedas J., Perez-Murano F. Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics; 34 (6, 06KK02) 2016. 10.1116/1.4967930. IF: 1.398

In this work, the authors employed Peak Force tapping and force spectroscopy to evaluate the stress generated during the fabrication of doubly clamped, suspended silicon nanobeams with rectangular section. The silicon beams, released at the last step of fabrication, present a curved shape that suggests a bistable buckling behavior, typical for structures that retain a residual compressive stress. Both residual stress and Young's modulus were extracted from experimental data using two different methodologies: analysis of beam deflection profiles and tip-induced mechanical bending. The results from the two methods are compared, providing an insight into the possible limitations of both methods. © 2016 Author(s).

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Multiscale study of mononuclear CoII SMMs based on curcuminoid ligands
Díaz-Torres R., Menelaou M., Roubeau O., Sorrenti A., Brandariz-De-Pedro G., Sañudo E.C., Teat S.J., Fraxedas J., Ruiz E., Aliaga-Alcalde N. Chemical Science; 7 (4): 2793 - 2803. 2016. 10.1039/c5sc03298a. IF: 9.144

This work introduces a novel family of CoII species having a curcuminoid (CCMoid) ligand, 9Accm, attached, namely [Co(9Accm)2(py)2] (1) and [Co(9Accm)2(2,2′-bpy)] (2), achieved in high yields by the use of a microwave reactor, and exhibiting two different arrangements for the 9Accm ligands, described as "cis"(2) and "trans"(1). The study of the similarities/differences of the magnetic, luminescent and surface behaviors of the two new species, 1 and 2, is the main objective of the present work. The determined single-crystal structures of both compounds are the only CoII-CCMoid structures described in the literature so far. Both compounds exhibit large positive D values, that of 1 (D = +74 cm-1) being three times larger than that of 2 (D = +24 cm-1), and behave as mononuclear Single-Molecule Magnets (SMMs) in the presence of an external magnetic field. Their similar structures but different anisotropy and SMM characteristics provide, for the first time, deep insight on the spin-orbital effects thanks to the use of CASSCF/NEVPT2 calculations implementing such contributions. Further magnetic studies were performed in solution by means of paramagnetic 1H NMR, where both compounds (1 and 2) are stable in CDCl3 and display high symmetry. Paramagnetic NMR appears to be a useful diagnostic tool for the identification of such molecules in solution, where the resonance values found for the methine group (-CH-) of 9Accm vary significantly depending on the cis or trans disposition of the ligands. Fluorescence studies show that both systems display chelation enhancement of quenching (CHEQ) with regard to the free ligand, while 1 and 2 display similar quantum yields. Deposition of 1-2 on HOPG and Si(100) surfaces using spin-coating was studied using AFM; UV photoemission experiments under the same conditions display 2 as the most robust system. The measured occupied density of states of 2 with UV photoemission is in excellent agreement with theoretical DFT calculations. © The Royal Society of Chemistry 2016.

View abstract
Synthesis, characterization, and thermoelectric properties of superconducting (BEDT-TTF)2I3 nanoparticles
Chtioui-Gay I., Faulmann C., De Caro D., Jacob K., Valade L., De Caro P., Fraxedas J., Ballesteros B., Steven E., Choi E.S., Lee M., Benjamin S.M., Yvenou E., Simonato J.-P., Carella A. Journal of Materials Chemistry C; 4 (31): 7449 - 7454. 2016. 10.1039/c6tc01378c. IF: 5.066

The synthesis of (BEDT-TTF)2I3 in the presence of two neutral amphiphilic molecules [N-octylfurfurylimine and 1-octanamine, N-(2-thienylmethylene)] leads to single and aggregated nanoparticles of 2 to 6 nm size. The samples contain highly crystalline nanoparticles of the βCO-(BEDT-TTF)2I3 phase, confirmed by XRD. Temperature dependent resistance and magnetic susceptibility studies evidence the superconducting transition characteristics of the βCO-(BEDT-TTF)2I3 phase. The I-V curve of a single nanoparticle aggregate, measured using AFM, exhibits an expected semiconductor-like behaviour. Thermoelectric studies led to a ZT of 1.47 × 10-3 at 300 K. © The Royal Society of Chemistry 2016.

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2015

Continuous monitoring of tip radius during atomic force microscopy imaging
Fraxedas J., Pérez-Murano F., Gramazio F., Lorenzoni M., Rull Trinidad E., Staufer U. Proceedings of SPIE - The International Society for Optical Engineering; 9636 ( 96360O) 2015. 10.1117/12.2196951. IF: 0.000

We present a continuous tip monitoring method during atomic force microscopy imaging based on the use of higher harmonics, which are generated in the repulsive regime as a result of the nonlinear interactions between the cantilever tip and the surface under study. We have applied this method to commercial rectangular microfabricated silicon cantilevers with force constants in the 45 N/m range and fundamental frequencies in the 300-400 kHz range and with tip radii below 10 nm. We have focused in the resonance of the 2nd flexural mode and the 6th harmonic using polystyrene surfaces. The simultaneous acquisition of topographic and higher harmonic images allows a continuous control of the state of the tip. The experimental results have been rationalized with computer simulations taking into account both the cantilever dynamics and the tip-surface interactions. © 2015 SPIE.

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Creation of guiding patterns for directed self-assembly of block copolymers by resistless direct e-beam exposure
Evangelio L., Fernandez-Regulez M., Borrise X., Lorenzoni M., Fraxedas J., Perez-Murano F. Proceedings of SPIE - The International Society for Optical Engineering; 9423 (942326) 2015. 10.1117/12.2085830. IF: 0.000

We present a novel approach for the creation of guiding patterns to direct the self-assembly of block copolymers. A neutral layer of a brush polymer is directly exposed by electrons, causing the cross-linking of the brush molecules, and thus changing its local affinity. The advantage relies on the achievable resolution and the reduction of the process steps in comparison with deep UV and conventional electron beam lithography, since it avoids the use of a resist. We envision that this method will be highly valuable for the investigation of novel high-chi DSA materials and complex guiding pattern designs, where pattern placement and resolution is becoming critical. © 2015 SPIE.

View abstract
Creation of guiding patterns for directed self-assembly of block copolymers by resistless direct e-beam exposure
Evangelio L., Fernández-Regúlez M., Borrisé X., Lorenzoni M., Fraxedas J., Pérez-Murano F. Journal of Micro/ Nanolithography, MEMS, and MOEMS; 14 (3, 033511) 2015. 10.1117/1.JMM.14.3.033511. IF: 1.428

We present an approach for the creation of guiding patterns to direct the self-assembly of block copolymers. A neutral layer of a brush polymer is directly exposed by electrons, causing the cross-linking of the brush molecules, and thus changing its local affinity. The advantage relies on the achievable resolution and the reduction of the process steps in comparison with deep UV and conventional electron beam lithography, since it avoids the use of a resist. We envision that this method will be highly valuable for the investigation of high-chi directed self-assembly materials and complex guiding pattern designs, where pattern placement and resolution are becoming critical. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE).

View abstract
Spin density wave and superconducting properties of nanoparticle organic conductor assemblies
Winter L.E., Steven E., Brooks J.S., Benjamin S., Park J.-H., De Caro D., Faulmann C., Valade L., Jacob K., Chtioui I., Ballesteros B., Fraxedas J. Physical Review B - Condensed Matter and Materials Physics; 91 (3, 035437) 2015. 10.1103/PhysRevB.91.035437. IF: 3.736

The magnetic susceptibilities of nanoparticle assemblies of two Bechgaard salts (TMTSF)2PF6 and (TMTSF)2ClO4, have been studied vs temperature and magnetic field. In the bulk these materials exhibit a spin density wave formation (TSDW=12K) and superconductivity (Tc=1.2K), respectively. We show from inductive (susceptibility) measurements that the nanoparticle assemblies exhibit ground-state phase transitions similar to those of randomly oriented polycrystalline samples of the parent materials. Resistivity and diamagnetic shielding measurements yield additional information on the functional nanoparticle structure in terms of stoichiometric and nonstoichiometric composition. © 2015 American Physical Society.

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2014

Four Molecular Superconductors Isolated as Nanoparticles
de Caro, D; Faulmann, C; Valade, L; Jacob, K; Chtioui, I; Foulal, S; de Caro, P; Bergez-Lacoste, M; Fraxedas, J; Ballesteros, B; Brooks, J.S.; Steven, E; Winter, L.E. European Journal of Inorganic Chemistry; 2014 (24): 4010 - 4016. 2014. 10.1002/ejic.201402007. IF: 2.965
Hydrophobic coating of mica by stearic acid vapor deposition
Sauthier, G.; Segura, J.J.; Fraxedas, J.; Verdaguer, A. Colloids and Surfaces A: Physicochemical and Engineering Aspects; 443: 331 - 337. 2014. 10.1016/j.colsurfa.2013.11.031. IF: 2.354
Influence of the relative molecular orientation on interfacial charge-transfer Excitons at donor/acceptor Nanoscale heterojunctions
Aghamohammadi, M.; Fernández, A.; Schmidt, M.; Pérez-Rodríguez, A.; Goñi, A.R.; Fraxedas, J.; Sauthier, G.; Paradinas, M.; Ocal, C.; Barrena, E. Journal of Physical Chemistry C; 118 (27): 14833 - 14839. 2014. 10.1021/jp5041579. IF: 4.835
Sub-10 nm resistless nanolithography for directed self-Assembly of block copolymers
Fernández-Regúlez, M.; Evangelio, L.; Lorenzoni, M.; Fraxedas, J.; Pérez-Murano, F. ACS Applied Materials and Interfaces; 6 (23): 21596 - 21602. 2014. 10.1021/am506600m. IF: 5.900
Water adsorption on etched hydrophobic surfaces of L-, D- and DL-valine crystals
Segura, J.J.; Verdaguer, A.; Fraxedas, J. Surface Science; 621: 191 - 196. 2014. 10.1016/j.susc.2013.11.008. IF: 1.870

2013

Aqueous Alteration vs. Shock in Villalbeto de la Pena Polymict Chondritic Breccia
Trigo-Rodriguez, J. M.; Moyano-Cambero, C. E.; Martinez-Jimenez, M.; Fraxedas, J.; Alonso-Azcarate, J. Meteoritics and Planetary Science; 48: a349. 2013. . IF: 2.800
Colloidal solutions of organic conductive nanoparticles
De Caro, D.; Souque, M.; Faulmann, C.; Coppel, Y.; Valade, L.; Fraxedas, J.; Vendier, O.; Courtade, F. Langmuir : the ACS journal of surfaces and colloids; 29: 8983 - 8988. 2013. 10.1021/la401371c. IF: 4.187
Communication: Growing room temperature ice with graphene
Verdaguer, A.; Segura, J.J.; López-Mir, L.; Sauthier, G.; Fraxedas, J. Journal of Chemical Physics; 138 2013. 10.1063/1.4798941. IF: 3.164
Nanoparticles of molecule-based conductors
De Caro, D.; Valade, L.; Faulmann, C.; Jacob, K.; Van Dorsselaer, D.; Chtioui, I.; Salmon, L.; Sabbar, A.; El Hajjaji, S.; Pérez, E.; Franceschi, S.; Fraxedas, J. New Journal of Chemistry; 37: 3331 - 3336. 2013. 10.1039/c3nj00555k. IF: 2.966
Surface screening of written ferroelectric domains in ambient conditions
Segura, J.J.; Domingo, N.; Fraxedas, J.; Verdaguer, A. Journal of Applied Physics; 113 2013. 10.1063/1.4801983. IF: 2.210

2012

Iridium oxohydroxide, a significant member in the family of iridium oxides. Stoichiometry, characterization, and implications in bioelectrodes
Cruz, A.M.; Abad, L.; Carretero, N.M.; Moral-Vico, J.; Fraxedas, J.; Lozano, P.; Subías, G.; Padial, V.; Carballo, M.; Collazos-Castro, J.E.; Casañ-Pastor, N. Journal of Physical Chemistry C; 116: 5155 - 5168. 2012. 10.1021/jp212275q.
Nanocrystalline N-doped ceria porous thin films as efficient visible-active photocatalysts
Jorge, A.B.; Sakatani, Y.; Boissière, C.; Laberty-Roberts, C.; Sauthier, G.; Fraxedas, J.; Sanchez, C.; Fuertes, A. Journal of Materials Chemistry; 22: 3220 - 3226. 2012. 10.1039/c2jm15230d.
Water-mediated height artifacts in dynamic atomic force microscopy
Verdaguer, A.; Santos, S.; Sauthier, G. ; Segura, J.J.; Chiesa, M. ; Fraxedas, J. Physical Chemistry Chemical Physics; 14: 16080. 2012. 10.1039/c2cp43031b.

2011

Defect-induced wetting on BaF2(111) and CaF2(111) at ambient conditions
Cardellach, M.; Verdaguer, A.; Fraxedas, J. Surface Science; 605: 1929 - 1933. 2011. 10.1016/j.susc.2011.07.003.
Dipolar origin of water etching of amino acid surfaces.
Segura, J. J.; Verdaguer, A.; Sacha, G. M.; Fraxedas, J. Physical Chemistry Chemical Physics; 13: 21446 - 21450. 2011. .
Modulation of surface charge transfer through competing long-range repulsive versus short-range attractive interactions
Fraxedas J., García-Gil S., Monturet S., Lorente N., Fernández-Torrente I., Franke K.J., Pascual J.I., Vollmer A., Blum R.-P., Koch N., Ordejón P. Journal of Physical Chemistry C; 115 (38): 18640 - 18648. 2011. 10.1021/jp2050838.

We report a combined experimental and theoretical study of the modulation of surface charge transfer on the tetrathiafulvalene (TTF)/Au(111) interface as a function of coverage in the submonolayer regime by combining low-temperature scanning tunneling microscopy, high-resolution photoemission spectroscopy using synchrotron radiation, and density functional theory (DFT) calculations. The modulation is induced by the competition between long-range repulsive Coulombic interactions and short-range attractive hydrogen-bonding interactions. The system shows the characteristic pattern evolution, from monomeric stripes at low coverages to two-dimensional islands, with the formation of labyrinths in the crossover. © 2011 American Chemical Society.

View abstract
Nanoparticles of organic conductors: synthesis and application as electrode material in Organic Field Effect Transistors.
de Caro, D. ; Jacob, K. ; Hahioui, H. ; Faulmann, C. ; Valade, L. ; Kadoya, T.; Mori, T. ; Fraxedas, J. ; Viaue, L. New Journal of Chemistry; 35: 1315 - 1319. 2011. .
Strong water-mediated friction asymmetry and surface dynamics of zwitterionic solids at ambient conditions: L-alanine as a case study
Segura, J.J.; Verdaguer, A.; Garzn, L.; Barrena, E.; Ocal, C.; Fraxedas, J. Journal of Chemical Physics; 134 2011. 10.1063/1.3571453.
Tetrathia- and tetraselenafulvalene adsorbed on Ag(110): A theoretical study
Martorell, B.; Fraxedas, J.; Clotet, A. Surface Science; 605: 187 - 192. 2011. 10.1016/j.susc.2010.10.018.

2010

A first principle study of the structural, vibrational and electronic properties of tetrathiafulvalene adsorbed on Ag(110) and Au(110) surfaces
Martorell, B.; Clotet, A.; Fraxedas, J. Journal of Computational Chemistry; 31: 1842 - 1852. 2010. 10.1002/jcc.21465.
Evidence of anion-ordering in (TMTSF)2ClO4 electrodeposited on silicon wafers
Savy, J.-P.; de Caro, D.; Valade, L.; Coiffic, J.-C.; Choi, E.S.; Brooks, J.S.; Fraxedas, J. Synthetic Metals; 160: 855 - 858. 2010. 10.1016/j.synthmet.2010.01.034.
High conductivity in hydrothermally grown AgCuO2 single crystals verified using focused-ion-beam-deposited nanocontacts
Muñoz-Rojas, D.; Córdoba, R.; Fernández-Pacheco, A.; De Teresa, J.M.; Sauthier, G.; Fraxedas, J.; Walton, R.I.; Casañ-Pastor, N. Inorganic Chemistry; 49: 10977 - 10983. 2010. 10.1021/ic101420c.
Ionic liquid-stabilized nanoparticles of charge transfer-based conductors
de Caro, D.; Jacob, K.; Faulmann, C.; Legros, J.-P.; Senocq, F.; Fraxedas, J.; Valade, L. Synthetic Metals; 160: 1223 - 1227. 2010. 10.1016/j.synthmet.2010.03.013.
Orbital specific chirality and homochiral self-assembly of achiral molecules induced by charge transfer and spontaneous symmetry breaking
Mugarza A., Lorente N., Ordejón P., Krull C., Stepanow S., Bocquet M.-L., Fraxedas J., Ceballos G., Gambardella P. Physical Review Letters; 105 (11, 115702) 2010. 10.1103/PhysRevLett.105.115702.

We study the electronic mechanisms underlying the induction and propagation of chirality in achiral molecules deposited on surfaces. Combined scanning tunneling microscopy and ab initio electronic structure calculations of Cu-phthalocyanines adsorbed on Ag(100) reveal the formation of chiral molecular orbitals in structurally undistorted molecules. This effect shows that chirality can be manifest exclusively at the electronic level due to asymmetric charge transfer between molecules and substrate. Single molecule chirality correlates with attractive van der Waals interactions, leading to the propagation of chirality at the supramolecular level. Ostwald ripening provides an efficient pathway for complete symmetry breaking and self-assembly of homochiral supramolecular layers. © 2010 The American Physical Society.

View abstract
Two-dimensional wetting: The role of atomic steps on the nucleation of thin water films on BaF2 (111) at ambient conditions
Cardellach, M.; Verdaguer, A.; Santiso, J.; Fraxedas, J. Journal of Chemical Physics; 132 2010. 10.1063/1.3456698.

2009

Amphiphillic organic crystals
Segura, J.J.; Verdaguer, A.; Cobián, M.; Hernández, E.R.; Fraxedas, J. Journal of the American Chemical Society; 131: 17853 - 17859. 2009. 10.1021/ja905961h.
Charging and discharging of graphene in ambient conditions studied with scanning probe microscopy
Verdaguer, A.; Cardellach, M.; Segura, J.J.; Sacha, G.M.; Moser, J.; Zdrojek, M.; Bachtold, A.; Fraxedas, J. Applied Physics Letters; 94 2009. 10.1063/1.3149770.
Influence of the macroscopic shape of the tip on the contrast in scanning polarization force microscopy images
Sacha, G.M.; Cardellach, M.; Segura, J.J.; Moser, J.; Bachtold, A.; Fraxedas, J.; Verdaguer, A. Nanotechnology; 20 2009. 10.1088/0957-4484/20/28/285704.
Neural cell growth on TiO2 anatase nanostructured surfaces
Collazos-Castro, J.E.; Cruz, A.M.; Carballo-Vila, M.; Lira-Cantú, M.; Abad, L.; del Pino, Á.P.; Fraxedas, J.; San Juan, A.; Fonseca, C.; Pêgo, A.P.; Casañ-Pastor, N. Thin Solid Films; 518: 160 - 170. 2009. 10.1016/j.tsf.2009.06.048.

2008

Correlation between charge state of insulating NaCl surfaces and ionic mobility induced by water adsorption: A combined ambient pressure X-ray photoelectron spectroscopy and scanning force microscopy study
Verdaguer, A.; Segura, J.J.; Fraxedas, J.; Bluhm, H.; Salmeron, M. Journal of Physical Chemistry C; 112: 16898 - 16901. 2008. 10.1021/jp805444v.
Full-wafer fabrication by nanostencil lithography of micro/nanomechanical mass sensors monolithically integrated with CMOS
Arcamone, J.; Van Den Boogaart, M.A.F.; Serra-Graells, F.; Fraxedas, J.; Brugger, J.; Pérez-Murano, F. Nanotechnology; 19 2008. 10.1088/0957-4484/19/30/305302.
In situ nanocalorimetry of thin glassy organic films
León-Gutierrez, E.; Garcia, G.; Lopeandía, A.F.; Fraxedas, J.; Clavaguera-Mora, M.T.; Rodríguez-Viejo, J. Journal of Chemical Physics; 129 2008. 10.1063/1.3009766.
Nitrogen doping of ceria
Jorge, A.B.; Fraxedas, J.; Cantarero, A.; Williams, A.J.; Rodgers, J.; Attfield, J.P.; Fuertes, A. Chemistry of Materials; 20: 1682 - 1684. 2008. 10.1021/cm7028678.
Special issue on thin films of molecular organic materials
J. Fraxedas Journal of Physics Condensed Matter; 20: 180301. 2008. .
Thin water films grown at ambient conditions on BaF2 (111) studied by scanning polarization force microscopy
Verdaguer, A.; Cardellach, M.; Fraxedas, J. Journal of Chemical Physics; 129 2008. 10.1063/1.3006098.
Water on surfaces studied by Scanning Probe Microscopies
A.Verdaguer; A. Mugarza; J. Fraxedas Contributions to Science; 4: 141 - 155. 2008. .

2007

Characterization of the anion-ordering transition in (TMTTF) 2 ReO4 by x-ray absorption and photoemission spectroscopies
Subías, G.; Abbaz, T.; Fabre, J.M.; Fraxedas, J. Physical Review B - Condensed Matter and Materials Physics; 76 2007. 10.1103/PhysRevB.76.085103.
Growth and characterization of molecular organic crystals and films
J. Fraxedas Journal of Optoelectronics and Advanced Materials; 9: 1322 - 1328. 2007. .
Long-range repulsive interaction between molecules on a metal surface induced by charge transfer
Fernandez-Torrente, I.; Monturet, S.; Franke, K.J.; Fraxedas, J.; Lorente, N.; Pascual, J.I. Physical Review Letters; 99 2007. 10.1103/PhysRevLett.99.176103.
Monolithic mass sensor fabricated using a conventional technology with attogram resolution in air conditions
J. Verd; A. Uranga; G. Abadal; J. Teva; F. Torres; F. Pérez-Murano; J. Fraxedas; J. Esteve; N. Barniol Applied Physics Letters; 2007. .
Nanowires of molecule-based charge-transfer salts
J.-P. Savy; D. de Caro; Ch. Faulmann; L. Valade; M. Almeida; T. Koike; H. Fujiwara; T. Sugimoto; J. Fraxedas; T. Ondarçuhu; C. Pasquier New Journal of Chemistry; 2007. .

2006

An approach to the origin of transport properties in a series of molecular conductors, based on XPS and spectroscopic studies
L. Valade; D. de Caro; J-P. Savy; I. Malfant; C. Faulmann; M. Almeida; J. Fraxedas; J. S. Brooks Journal of Low Temperature Physics; 142: 141 - 146. 2006. .
Measuring energies at the nanometer-scale of molecular organic materials with an Atomic Force Microscope: TTF-TCNQ as a case study
J. Fraxedas; J. Langer; I. Díez; F. Sanz Journal of Low Temperature Physics; 142: 121 - 126. 2006. .
Monoclinic polymorphs of the Bechgaard-Fabre salts
J. Fraxedas; S. Perruchas; E. Canadell; P. Auban-Senzie; P. Batail Journal of Low Temperature Physics; 142: 397 - 400. 2006. .
Thin films of molecular materials grown on silicon substrates by chemical vapor deposition and electrodeposition
L. Valade; D. de Caro; J.-P. Savy; I. Malfant; C. Faulmann; M. Almeida; J. Fraxedas; J. S. Brooks Journal of Low Temperature Physics; 142: 393 - 396. 2006. .

2004

Transport properties of monocrystalline microwires of EDT-TTF-(CONHMe)2 and (TMTSF)2ClO4
C. Colin; C. R. Pasquier; P. Auban-Senzier; F. Restangno; S. Baudron; P. Batail; J. Fraxedas Synthetic Metals; 146: 273 - 277. 2004. .