A fast and solvent-free protocol to introduce amides and amines onto graphene oxide
Solvent-free functionalisation of graphene oxide with amide and amine groups at room temperature
Stefania Sandoval, Amparo Fuertes, Gerard Tobias
Chemical Communications 55, 81, 12196-12199, 2019
Figure: Ammonolysis at room temperature induces the efficient formation of amine and amide groups (N-functionalization) onto the graphene oxide (GO) surface.
We present a new, simple, fast and energy efficient solvent-free protocol that allows the introduction of amides and amines onto graphene oxide (GO) at room temperature. This approach allows the functionalization of GO even with extremely reduced amounts of ammonia (NH3) gas and greatly expands the derivatisation routes to integrate graphene derivatives into devices and composite materials.
Advances towards useful high temperature superconductors: enhanced film thickness and redued anisotropy
Growth of all-chemical high critical current YBa2Cu3O7 thick films and coated conductors
Cornelia Pop, Bohores Villarejo, Flavio Pino, Bernat Mundet, Susagna Ricart, Mariona de Palau, Teresa Puig, Xavier Obradors
Superconductor Science & Technology 32, 015004, 2019
Intrinsic anisotropy versus effective pinning anisotropy in YBa2Cu3O7 thin films and nanocomposites
Elena Bartolome, Ferran Valles, Anna Palau, Víctor Rouco, Nicola Pompeo, Fedor F. Balakirev, Boris Maiorov, Leonardo Civale, Teresa Puig, Xavier Obradors, Enrico Silva
Physical Review B 100, 054502, 2019
Figure: (a) Evolution of the total critical current, Ic (77K) with YBCO film thickness (nm) using different deposition (spin coating and ink jet printing (IJP)) for single crystalline and metallic substrates, up to 1 µm thickness. Dashed lines indicate the slopes corresponding to different critical current densities, (b) Dependence of effective anisotropy factor (geff) and the intrinsic anisotropy factors (determined from resistive measurements in high fields up to 65 T (gHc2,HF), resistive measurements (gHc2,res) and microwave measurements (gMW) as a function of the nanostrain (%) for the pristine films (shown at 0.1 % nanostrain) and a set of nanocomposites with different nanostrain.
High critical currents and reduced anisotropy are fundamental properties also for chemical solution deposited YBa2Cu3O7coated conductors. Thickness in the range of 1 m was achieved through control of nucleation and growth process, and nanocomposites with half effective anisotropy of pristine films were reached. Resistivity measurements up to 65 T and microwave surface impedance were properly combined to achieve this conclusion.
Atomistic insight into nanostructured biomaterials
Long-lived ionic nano-domains can modulate the stiffness of soft interfaces
William Trewby, Jordi Faraudo, Kislon Voitchovsky
Nanoscale 11, 4376-4384, 2019
Protein-surface interactions at the nanoscale: Atomistic simulations with implicit solvent models
David C. Malaspina, Leonor Perez-Fuentes, Carlos Drummond, Delfi Bastos-Gonzalez, Jordi Faraudo
Current Opinion in Colloid & Interface Science 41, 40-49, 2019
Figure: Summary of the systems studied by atomistic MD simulations. Left: different configurations of cations adsorbed onto a lipid membrane linked by hydration water molecules. Center: nanostructures and patterns of adsorbed cations ions over a lipid membrane. Right: example of a protein adsorbed onto an inorganic surface.
Using Supercomputers we perform molecular dynamics simulations of materials at scales of the order of a million of atoms. In this way we obtain unprecedent insight into the way that nanostructuration of biomaterials influence their properties. The examples considered here were how ionic domains modulate the elastic properties of biomembranes or how proteins interact with inorganic nanomaterials.
Carboranes for the synthesis of innovative nanostructures
The Key to Controlling the Morphologies of Quantum Nanocrystals: Spherical Carborane Ligands
Abhishek Saini, Arpita Saha, Clara Viñas, Francesc Teixidor
Chem. Commun. 55, 9817-9820, 2019
Figure: Carboranes for the synthesis of innovative nanostructures application
Spherical boron ligands act as the pathway to achieve rare nanostructures in the Quantum regime, using a simple colloidal synthesis. Quantum Rings and Rods with intense photoluminescent properties can be synthesized in a single step synthesis, opening the door to bulk production of these fascinating nanomaterials, something never achieved before.
Carpet-like Graphene in polycristalline silicon carbide (SiC)
Face dependent footprints of carpet-like graphene films grown on polycrystalline silicon carbide.
Cristina Ramírez, Eugenio García, Esther Barrena, Angel De Pablos, Manuel Belmonte, M. Isabel Osendi, Pilar Miranzo, Carmen Ocal
Carbon 153, 417-427, 2019
Figure: Combination of different local probe and electron microscopies (SFM, KPFM, RAMAN, FESEM images) as well as micro-Raman spectroscopy (purple spectrum) used to determine the dependence of the properties of graphene grown simultaneously on different facets of SiC.
The unique properties of graphene arise from its 2D structure but, in real applications, it cannot stand alone without a support. In this study, large-area, low-defect-density supported graphene is obtained by sublimation of silicon carbide (SiC). Employing polycrystalline SiC we compare graphene simultaneously grown on different facets at exactly the same conditions. We provide a reliable methodology to prepare continuous graphene on SiC components for scaling-up at low cost with controlled thickness, quality and stresses.
Cation arrangement on perovskites films
Spontaneous cationic ordering in chemical solution-grown La2CoMnO6 double perovskite thin films
Hailin Wang, Jaume Gazquez, Carlos Frontera, Matthew F. Chisholm, Alberto Pomar, Benjamin Martinez, Narcis Mestres
NPG Asia Materials 11:44, 2019
Figure: From left to right, Z-contrast image of the LCMO film, ADF image, atomic maps of La M, Co L, and Mn L absorption edges and RGB map produced by overlaying the Co (in red) and Mn (in green) elemental maps. The spectrum image was acquired along the -zone axis for visualizing the B-site ordering.
Double perovskite oxides are of interest because of their physical properties; however, these properties are strongly dependent on the ordered arrangement of cations in the double perovskite structure. We show that the slow growth rates close to thermodynamic equilibrium conditions in chemical solution methods are advantageous promoting spontaneous B-site cationic ordering.
Chemical engineering of ferroelectric BiFe1-xCoxO3 thin films with enhanced photo response
Band Gap Tuning of Solution-Processed Ferroelectric Perovskite BiFe1–xCoxO3 Thin Films
Pamela Machado, Mateusz Scigaj, Jaume Gazquez, Estel Rueda, Antonio Sánchez-Díaz, Ignasi Fina, Martí Gibert-Roca, Teresa Puig, Xavier Obradors, Mariano Campoy-Quiles, Mariona Coll
Chem. Mater. 31, 3, 947–954, 2019
Figure: Solution processed BiFe1-xCoxO3 ferroelectric perovskite thin films are developed as promising photoactive layer. Band gap tuning is achieved by performing compositional tuning while enhancing ferroelectricity and photo response.
The use of ferroelectric oxide perovskites as a stable photoactive layer has opened up a ground-breaking new arena of research in the field of energy. They can be cheaply produced and present an unconventional photovoltaic mechanism that may surpass the power conversion efficiencies dictated in traditional semiconductors. In this work we demonstrate that the band gap of solution processed BiFeO3 can be tuned towards the visible by exploring the novel substitution of Fe by Co, while enhancing ferroelectricity. Non-optimized vertical devices prove enhanced photo response.
Ferroelectrics for photovoltaics is a young field and composition and interface engineering offer immense potential to further improve device performances. Also, it is envisioned many new opportunities arising from better understanding of the cross-coupling mechanism between light absorption, polarization and electronic properties.
Compositional variability in aerinite changes it from blue to brown
First identification and compositional study of brown aerinite directly on polished thin-sections by synchrotron through-the-substrate microdiffraction
Anna Crespi, Oriol Vallcorba, Igors Šics, Jordi Rius
European Journal of Mineralogy 31 (5-6): 999–1005, 2019
Figure: Photomicrograph under transmitted light of a region of the polished thin section containing a broad stripe of pale-blue aerinite and, in the middle, the brown aerinite zone (size is around 100 μm).
Aerinite is the characteristic blue pigment of Pyrenean Romanesque mural paintings. Although structurally solved by X-ray powder diffraction in 2004, the question if aerinite can display other colors is still open. Application of the through-the-substrate microdiffraction technique (jointly developed by ICMAB and ALBA Synchrotron) to a polished thin-section from Tartareu (Lleida) has confirmed that an Fe-Mn-rich zone observed in this thin-section effectively corresponds to brown aerinite with Fe and Mn partially replacing Al and Ca. This unprecedented result also indicates the tolerance of the aerinite structure type to compositional variability.
Correlation of the crystal structure, transport properties and silver mobility in a mixed silver-copper oxide
Charge Delocalization, Oxidation States, and Silver Mobility in the Mixed Silver−Copper Oxide AgCuO2
Abel Carreras, Sergio Conejeros, Agustín Camón, Alberto García, Nieves Casañ-Pastor, Pere Alemany, Enric Canadell
Inorganic Chemistry 58, 7026−7035, 2019
Figure: The crystal structure of AgCuO2 is built from the condensation of CuO2 chains and AgO2 units (top left). As a result of an electron transfer between formally Ag+ and Cu3+ d levels a Fermi surface (top right) with Ag and Cu contribution is created leading to a metallic behavior. Such transfer stabilizes oxidized silver and oxidized copper, and the structure may be described as Ag-O planes with intercalated Cu-O chains in between (center down).
The puzzling structural details of the mixed oxide AgCuO2 are shown to be related to a charge transfer between the AgO2 extended units and the CuO2 chains. As a result the system behaves as a metal and the silver atoms form quite stable chains that can easily slide among the CuO2 chains.
Electroactive conducting electrode materials for neural growth
Electric Field Gradients and Bipolar Electrochemistry effects on Neural Growth. A finite element study on inmersed electroactive conducting electrode materials
Llibertat Abad, Ann M. Rajnicek, Nieves Casañ-Pastor
Electrochimica Acta 317 (2019) 102-111
Figure: Induced dipoles electrochemistry affecting neural growth.
Electric dipoles induced on conducting materials within electrochemical cells, modify neural behaviour in substantial ways. This work evaluates the field gradients and intercalation processes that occur at the poles of the unconnected mixed conducting material serving as neural growth support, and that eventually favour direction and speed of neural growth. Remote control of electrostimulation processes in the neural system may be devised and lower impedance energy storage systems demonstrated.
Electron microscopy reveales rotational polarization domains
Rotational Polarization Nanotopologies in BaTiO3/SrTiO3 Superlattices
Saúl Estandía, Florencio Sánchez, Matthew F. Chisholm, Jaume Gázquez
Nanoscale 11, 21275-21283, 2019
Figure: Scanning transmission electron microscopy HAADF image (left panel) of a 6x (10 u.c. BaTiO3)/(10 u.c. SrTiO3) superlattice and corresponding dipoles map (right panel). Marked regions are zoomed in the bottom images (without angle colour map).
Rotational polarization topologies at the nanoscale have been observed by means of scanning transmission electron microscopy in BaTiO3/SrTiO3 superlattices grown on cubic SrTiO3(001). The transition from a highly homogeneous polarization state to rotational nanodomains is achieved by controlling the superlattice period while maintaining compressive epitaxial strain. The nanodomains prove that nominal tetragonal structure of BaTiO3 allows rotational polar textures.
Exploring Transition-Edge Sensors
Large current-induced broadening of the superconducting transition in Mo/Au transition edge sensors
Lourdes Fabrega, Agustin Camon, Carlos Pobes, Pavel Strichovanec, Raquel Gonzalez-Arrabal
Superconductor Science and Technology 32, 1, 015006, 2019
Figure: Cross-section TEM image of a Mo/Au bilayer deposited on a Si3N4 membrane; room temperature growth is required to prevent strains in the Mo layer and Si3N4 membrane. Columnar morphology is appreciated, as well as a flat, sharp Mo/Au interface, which results in very narrow superconducting transitions.
Transition-Edge Sensors (TESs) are extremely sensitive microcalorimeters, which take advantage of the sharpness of the superconducting transition. Use of proximity Mo/Au bilayers allows tuning critical temperature Tc. Study of superconducting proximity effect reveals a high quality interface and tracks the evolution of Tc with layers thicknesses. Nevertheless, the transition is hugely broadened by current, which can be interpreted as current-driven vortex-antivortex depairing. Both effects have impact on performances of TES-based radiation detectors, in development at the ICMAB.
Ferroelectric capacitors of epitaxial complex oxide on silicon
Epitaxial Integration on Si(001) of Ferroelectric Hf0.5Zr0.5O2 Capacitors with High Retention and Endurance
Jike Lyu, Ignasi Fina, Josep Fontcuberta, Florencio Sánchez
ACS Applied Materials & Interfaces 11, 6, 6224–6229, 2019
Figure: Sketch of the ferroelectric capacitor (left) and polarization retention after poling with voltage pulses of indicated amplitude (right).
Ferroelectric capacitors with epitaxial Hf0.5Zr0.5O2, integrated on Si(001) are reported for the first time, showing a remnant polarization around 20 μC/cm2, and high endurance and retention. The low films roughness and their improved insulating properties makes epitaxial Hf0.5Zr0.5O2 ideal for being integrated in ferroelectric-based devices.
First observation of a single-condensate to two-condensate superconductive transition
Gap suppression at a Lifshitz transition in a multi-condensate superconductor
Gyanendra Singh, Alexis Jouan, Gervasi Herranz, Mateusz Scigaj, Florencio Sánchez, Lara Benfatto, Sergio Caprara, Marco Grilli, Guilhem Saiz, François Couëdo, Cheryl Feuillet-Palma, Jérôme Lesueur, Nicolas Bergeal
Nature Materials 18, 948–954, 2019
Figure: Superconducting phase diagram. We plot the gap energies of the two condensates Δ1(0) and Δ2(0) (left axis) and γ coefficient (right axis), which accounts for the weight of each condensate in the LaAlO3/SrTiO3 quantum well. These magnitudes are plotted as a function of the voltage gate (VG) and are superimposed on the sheet resistance color map.
We report an unprecedented observation of a transition between single-condensate to two-condensate superconductivity. The experiments were done using resonant microwave transport carried out in the Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, enabling continuous and reversible transitions between the two condensate regimes via electrostatic gating of LaAlO3/SrTiO3 quantum wells.
Flexible and lightweight organic molecular metal humidity sensor
On the Sensing Mechanisms of a Hydroresistive Flexible Film Based on an Organic Molecular Metal
Raphael Pfattner, Elena Laukhina, Laura Ferlauto, Fabiola Liscio, Silvia Milita, Anna Crespi, Victor Lebedev, Marta Mas-Torrent. Vladimir Laukhin, Concepció Rovira, Jaume Veciana
ACS Appl. Electron. Mater. 1, 9, 1781–1791, 2019
Figure: Schematic illustration of reversible water uptake shown on top of SEM image taken from the cross section of a bilayer film. Insets: Electronic and structural phase transition of bilayer film with [(BEDT-TTF)5(Br4(H5O2))] as hydroresistive organic molecular metal.
We present the flexible bilayer film polycarbonate/polycrystalline organic molecular conductor as a promising material for humidity sensors which may be applied in a number of monitoring scenarios. The film is capable of monitoring air relative humidity levels from 15 up to 90 % as a well definite reproducible electrical signal.
From nanoparticles to a mesoporous material
Controlled Self‐Assembly of Mesoporous CuO Networks Guided by Organic Interlinking
José Antonio Ayllón, Julio Fraile, Concepción Domingo
Particle and Particle Systems Characterization 36(3):1800453, 2019
Figure: Scheme showing the process to transform a nanoparticle dispersion into a mesoporous material using a polytopic linker.
A simple way of transforming a colloidal dispersion of nanoparticles into a mesoporous solid with noticeable thermal stability is described. The strategy consists into the partial replacement of the shell of monotopic capping ligands, with proper functionalization to impart good dispersability, by rigid polytopic ligands that favor a controlled aggregation.
Laser-based synthesis of hybrid supercapacitors with high storage capacity
Fabrication of graphene-based electrochemical capacitors through reactive inverse matrix assisted pulsed laser evaporation
Ángel Pérez del Pino, Mohamed Ahmed Ramadan, Pablo Garcia Lebière, Raluca Ivan, Constantin Logofatu, Ibraheem Yousef, Enikö György
Applied Surface Science 484, 245-256, 2019
Figure: (a) Assembled device. (b) Galvanostatic charge-discharge curves of symmetric GO-NiO-imidazole device at different current densities. (c) Areal capacitance at different current densities, from galvanostatic charge-discharge data. (d) Areal capacitance at different sweep rates calculated from cyclic voltammetry (CV) data. Inset: CV loop obtained at 100 mV s-1 from asymmetric GO-imi/GO-NiO-imi (-/+) device. (e) Ragone plot of the assembled devices. (f) Capacitance retention and coulombic efficiency (inset) of the devices.
Precursor molecules as citric acid, ascorbic acid and imidazole were added to aqueous dispersions consisting of graphene oxide (GO) platelets and NiO nanoparticles, submitted to UV laser irradiation. The precursor molecules determine the reduction degrees and nitrogen doping of GO platelets transferred to the substrates surface. The nitrogen doped, highly reduced GO/NiO electrodes exhibit enhanced storage capacity and high cycling stability.
Multiwalled carbon nanocapsules for cancer diagnosis and therapy
A simple and versatile one-step filling and end-closing of multi-walled carbon nanotubes with potential application in cancer diagnosis and therapy.
Non-cytotoxic carbon nanocapsules synthesized via one-pot filling and end closing of multi-walled carbon nanotubes
Markus Martincic, Sandra Vranic, Elzbieta Pach, Stefania Sandoval, Belén Ballesteros, Kostas Kostarelos, Gerard Tobias
Carbon 141, 782-793, 2019
Figure: (a) Schematic representation of the synthesis of multiwalled carbon nanocapsules (closed-ended filled carbon nanotubes), (b) BET surface area of empty MWCNTs annealed at different temperatures and (c) flow cytometry using PI/Annexin V staining (alive cells are represented in P18 region, early apoptotic in P19, late apoptotic and/or necrotic cells in P17 and necrotic cells in P16.)
Carbon nanotubes (CNTs) have remarkable properties with applications in a wide range of fields. Moreover, the presence of an inner cavity expands their versatility, allowing their endohedral modification. Among the large variety of materials that can be filled in their interior, the encapsulation of biomedically relevant payloads inside CNTs has taken a great deal of attention. CNTs not only offer protection to the encapsulated cargo from the biological milieu, but also can be externally modified by the attachment of selected biomolecules that can provide an increase in the biocompatibility and selectivity of the material.
Filling of CNTs is typically performed using an excess of the guest material and a large amount of the filler remains external to the walls after synthesis. The non-encapsulated compounds can induce negative side effects when employed in the biomedical field. For this reason, a subsequent washing protocol for the selective elimination of the external material, while preserving the inner compound, must be performed. In this context, we have reported a fast and simple method that allows the formation of a wide variety of multiwalled carbon nanocapsules (closed-ended filled CNTs), clean from external, non-encapsulated material. The proposed methodology consists in thermally annealing open-ended MWCNTs in the presence of a chosen payload at temperatures ranged between 1000 °C and 1200 °C, which leads to their simultaneous filling and end-closing. Once the MWCNTs are filled, the non-encapsulated compounds can be easily removed in a fast manner. This approach has demonstrated to be highly versatile, since several biomedically relevant compounds have been sealed in the cavities of CNTs. In vitro studies of both empty and filled MWCNTs showed that nanocapsules did not induce cellular death after being internalized by cells.
Nano-imprinted organic layers for colloidal quantum-dot solar cells
Nanostructured Back Reflectors for Efficient Colloidal Quantum-Dot Infrared Optoelectronics
Se-Woong Baek, Pau Molet, Min-Jae Choi, Margherita Biondi, Olivier Ouellette, James Fan, Sjoerd Hoogland, F. Pelayo García de Arquer, Agustín Mihi, Edward H. Sargent
Advanced Materials, 31 (33), 1901745, 2019
Figure: a) Schematics of the PDMS imprinting process in CQD devices. b) Surface images and line profile of organic layer scanned by AFM after imprinting. Scale bar: 2 μm c) SEM images of organic hole transporting template after imprinting (left) and d) final metal structure deposited onto the organic template. e) Photograph of the pre-patterned PDMS mold (left) and the final IR CQD device after nano-imprinting (right).
In this work, we introduce a patterned organic layer in colloidal quantum-dot (CDQ) solar cells between the CQD solid and back metal electrode. This organic layer has preferred band alignment and suitable hole mobility, enabling it to act as an efficient hole-transport layer (HTL) instead of conventional 1,2-ethanedithiol (EDT)-treated CQD HTL. In addition, this soft organic layer can be readily molded with soft nano-imprinting lithography and form high quality inverse 2D-photonic structure. The metal coated 2D photonic electrode generates such an efficient light scattering that we achieved a record External Quantum Efficiency (EQE) value of 86 % at 1220 nm. This value is 20 % higher than previous best reports on IR PCE in CQD solar cells.
Observation of a giant topological Hal effect (THE) in an oxide material
Giant topological Hall effect in correlated oxide thin films
Lorenzo Vistoli, Wenbo Wang, Anke Sander, Qiuxiang Zhu, Blai Casals, Rafael Cichelero, Agnès Barthélémy, Stéphane Fusil, Gervasi Herranz, Sergio Valencia, Radu Abrudan, Eugen Weschke, Kazuki Nakazawa, Hiroshi Kohno, Jacobo Santamaria, Weida Wu, Vincent Garcia, Manuel Bibes
Nature Physics 15, 67–72, 2019
Figure: Topological Hall effect (THE) in (Ca,Ce)MnO3. (a) Hall effect at different temperatures. The data are shifted vertically for clarity. (b) Decomposition of the Hall effect into anomalous Hall effect (AHE) and topological Hall effect (THE) using magneto-optical Kerr ellipticity at 15 K.
A topological Hall effect (THE) arises from the interaction of electrons with topological spin distributions, which are robust against fluctuations and noise. ICMAB researchers contributed by detecting THE from magneto-optic spectroscopy. The giant THE observed in (Ca,Ce)MnO3 is dependent on carrier concentration, which can be controlled by electric fields, opening new prospects for applications in electronics.
Probing apical oxygen vacancies in YBa2Cu3O7-x films with atomic resolution in real space
Direct observation of apical oxygen vacancies in the high-temperature superconductor YBa2Cu3O7−x
Steven T. Hartman, Bernat Mundet, Juan-Carlos Idrobo, Xavier Obradors, Teresa Puig, Jaume Gázquez, Rohan Mishra
Physical Review Materials 3, 114806, 2019
Figure: (a) The atomic structure of fully oxygenated YBa2Cu3O7-x. The locations of the three possible oxygen vacancies are marked. (b) ABF image with its contrast inverted to show the atomic columns as bright spots. (c) Panel showing two horizontal intensity profiles measured along the BaO planes showing different concentration of VO. (d) The orbital-projected DOS of the superconducting CuO2 plane with Cu atom directly adjacent to an apical vacancy. The planar Cu 3dz2 states are in gold.
We report on the direct observation of apical oxygen vacancies (VO) in optimally doped YBa2Cu3O7-x films by HR-STEM. DFT calculations evidence that isolated apical and chain VO have similar formation energy,for low vacancy concentrations. Also, apical VO significantly distorts the surrounding lattice and the electronic structure of YBCO. An influence to the superconducting properties is suggested.
Self-assembled metallacarborane corona on a protein molecule
Dual Binding Mode of Metallacarborane Produces a Robust Shield on Proteins
Isabel Fuentes, Jordi Pujols, Clara Viñas, Salvador Ventura, Francesc Teixidor
Chem. Eur. J. 25, 12820-12829, 2019
Figure: Bovine Serum Albumin (BSA)’s volume from Dynamic Light Scattering (DLS) and the representations of Na[COSAN] covering a single BSA core molecule (a) first, (b) second, (c) third and (d) fourth layers.
Metallacarboranes like [Co(C2B9H11)2]-, which self-assemble, have the property to strongly interact with amines. Therefore, they should be able to interact with certain aminoacids that are present in proteins. This paper reports on the stable coating of Bovine Serum Albumin (BSA) by the metallacarborane [Co(C2B9H11)2]- through the anchoring with the amino residues and fulfilling the complementary surface by self-assembling. Many of the protein’s properties are preserved even at higher temperatures than denaturalization.
Self-assembly of magnetic chains from nanoparticles
Spontaneous in-flight assembly of magnetic nanoparticles into macroscopic chains
Lluis Balcells, Igor Stankovic, Zorica Konstantinovic, Aanchal Alagh, Victor Fuentes, Laura López-Mir, Judit Oró, Narcis Mestres, Carlos García , Alberto Pomar, Benjamin Martínez
Nanoscale 11, 14194, 2019
Figure: Spontaneous self-assembly of magnetic nanoparticles into macroscopic chains by using a combination of magnetron sputtering and gas aggregation techniques
We have pushed the capabilities of the cluster gun technique beyond single particle fabrication as magnetic nanoparticles spontaneously self-assembled into macroscopic chains in a controlled and reproducible way. The low-kinetic energy inside a magnetron sputtering vacuum chamber and strong dipolar magnetic interaction are responsible for particles’ agglomeration at very low volume fractions.
Soft litography microstructuring of epitaxial quartz on silicon
Tailoring the crystal growth of quartz on silicon for patterning epitaxial piezoelectric films
Qianzhe Zhang, David Sanchez-Fuentes, Andrés Gomez, Rudy Desgarceaux, Benoit Charlot, Jaume Gazquez, Adrian Carretero-Genevrier, Martí Gich
Nanoscale Advances 1, 3741-3752, 2019
Figure: The systematic study of chemical solution deposition parameters has made possible finding the optimal conditions to prepare structured epitaxial quartz films on silicon by soft lithography.
We gained control over epitaxial growth of quartz on silicon by chemical solution deposition to demonstrate the structuring of those films by soft lithography. The key aspects to obtain the desired microstructure were the surfactant, the concentration of melting agent, the deposition of several layers and relative humidity.
Substituents modulate the transport properties of chiral molecular conductors
Chiral EDT-TTF precursors with one stereogenic centre: substituent size modulation of the conducting properties in the (R-EDT-TTF)2PF6 (R = Me or Et) series
Nabil Mroweh, Pascale Auban-Senzier, Nicolas Vanthuyne, Enric Canadell, Narcís Avarvari
J. Mater. Chem C 7, 12664−12673, 2019
Figure: Depending on the R substituent in the (R-EDT-TTF) donor (center) two different conducting salts with 2:1 stoichiometry, [(R)-1]2PF6 (left) and [(R)-2]2PF6 (right) can be prepared. The different donor layers lead to band formation with considerably different band width resulting with metals ([(R)-1]2PF6, left) or localized semiconductors ([(R)-2]2PF6, right).
Investigation of the influence of chirality on the transport properties requires the preparation of structurally different families of enantiopure conductors. Controlling the substituent bulkiness in the R-EDT-TTF donor leads, with the PF6 anion, to two different series of 2:1 enantiopure conducting salts with either metallic or activated conductivity.
Synchrotron X-rays reveals the structural symmetry from bulk to film
Double-cell superstructure and vacancy ordering in tensile-strained metallic thin films of Pr0.50Ca0.50CoO3 on LaAlO3
Jessica Padilla-Pantoja, Xavier Torrelles, Jaume Gazquez, Juan Rubio-Zuazo, Javier Blasco, Javier Herrero-Martín, Jose Luis García-Muñoz
Physical Review Materials 3, 104407, 9pp, 2019
Figure: (top) Selected synchrotron X-ray diffraction scans at RT from PCCO thin film, showing a double-cell in the film due to the (1/2, 1/2, 1/2) superstructure. (H,K,L) reflections are expressed in the LAO basis. (bottom) High-resolution Z-contrast image of the PCCO/LAO interface. d1 and d2 signal different (Pr/Ca) - (Pr/Ca) distances. Yellow circles in the image Fourier transform mark two superlattice peaks. The arrows mark the O-deficient planes. Scale bar 10 nm. Histogram of the out-of-plane distance values (Δz) between lanthanide neighbors in successive layers.
Pr0.5Ca0.5CoO3 presents in bulk form a singular valence, spin-state and metal-insulator transition. We report a reduction of the structural symmetry from Pnma(bulk) to P212121 (film) revealed by synchrotron X-rays. In contrast to the general tendency reported for strained ferromagnetic Co perovskite films, we show that unexpectedly a nominal tensile strain can also be compatible with the presence of alternating O vacancy planes parallel to the interface.
Topotactic nitridation of transition metal double perovskites
Topochemical nitridation of Sr2FeMoO6
Roberta Ceravola, Carlos Frontera, Judith Oró-Solé, Ashley P.Black, C.Ritter, Ignasi Mata, Elies Molins, Josep Fontcuberta and Amparo Fuertes
Chemical Communications 55, 3105-3108, 2019
Figure: (a) Schematic band filing of Sr2FeMoO6. Fermi level is nearby the bottom of Fe-3dt2g↓-Mo-(4d,5s)↓ bands. (b) In the oxide FeO6 and MoO6 octahedra are regular (top sketch) and the free carriers in the conduction band (bottom sketch) promote long range ferromagnetic order. (c) Schematic band filing of Sr2FeMoO4.9N1.1. (d) Localized states formed around defect-related potential wells (e.g.: nitride sites, Jahn-Teller Fe4+ ions). (e) Magnetoresistance (MR=[r(H)-r(0)]/r(0)) of the oxynitride sample at different temperatures; Inset: logarithm of the resistance (at zero field) as a function of T-1/4.
The topochemical nitridation of cation ordered, tetragonal Sr2FeMoO6 in NH3 at moderate temperatures leads to the cubic, Fm-3m double perovskite oxynitride Sr2FeMoO4.9N1.1where double-exchange interactions determine ferromagnetic order with Tc ≈ 100 K. Substitution of oxide by nitride induces bond asymmetries and local electronically-driven structural distortions, which combined with Fermi level lowering restrict charge itineracy to confined regions and preclude spontaneous long-range magnetic order. Under a magnetic field, ferromagnetic correlations expand, favoring charge delocalization and a negative magnetoresistance is observed.
Towards theranostic albumin-iron oxide nanocages
Insights into preformed HSA corona on iron oxide nanoparticles: structure, effect of particle size, impact on MRI efficiency and metabolization
Carlos Moya, Remei Escudero, David C. Malaspina, Maria de la Mata, Jesús Hernández-Saz, Jordi Faraudo, Anna Roig
ACS Appl. Bio Mater. 2, 7, 3084–3094, 2019
Figure: Excellent accordance between the values obtained from spectroscopy studies and results from molecular dynamics simulation: A) the number of proteins units forming a monolayer of human serum albumin (HSA) corona on the surface of iron oxide nanoparticles of different sizes. HSA corona enhances particle integrity and stability in biological media: B) The hydrodynamic diameter of HSA-nanoparticles is stable up to 25 hours in gastric-like conditions. C) MRI performance of the HSA-nanoparticles is unaltered after their incubation in PBS for 90 days.
The spontaneous protein corona formed on nanoparticles in biological media can be detrimental for their intended biomedical uses. Herein we present a universal route to preform a monolayer of human albumin onto iron oxide nanoparticles guided by molecular dynamic simulations. This well-defined albumin corona acts as a bio-shield against the rapid acidic-dissolution of the iron oxide cores, it increases their colloidal dispersability in PBS (phosphate-buffered saline) and it does not interfere with the nanoparticles' performance as magnetic resonance imaging (T2-MRI) contrast agent. Theranostic drug delivery albumin-nanocages attained by partial dissolution of the inorganic core are proposed as the follow-up of this work.
Unconventional cooperative interactions analyzed by DFT and electrostatic potential surface analysis
Synthesis, X-ray Characterization and Density Functional Theory Studies of N6-benzyl-N6-methyladenine-M(II) Complexes (M=Zn, Cd): The Prominent Role of π-π, C-H···π and Anion-π Interactions
Roser Pons, Cristina Ibánez, Ana B. Buades, Antonio Franconetti, Àngel García-Raso, Juan J. Fiol, Angel Terrón, Elies Molins, Antonio Frontera
Applied Organometallic Chemistry 33, e4906, 2019
Figure: (a) Molecular Electrostatic Potential (MEP) surface (0.002 a.u.) of the zwiterionic complex [Zn(HL)Cl3]·H2O being L= N6-benzyl-N6-methyladenine. MEP values at selected points of the surface are indicated. (b) Lp–π and anion–π assembly. (c) Lp–π complex where only water is considered.
Unconventional cooperative lone pair–π, anion–π and π+–π+ interactions appear in the studied complexes. The energies associated with these assemblies have been computed using density functional theory (DFT) calculations and rationalized by molecular electrostatic potential surface analysis. The protonated adenine ring presents an extended π‐acidic surface adequate for the interaction with electron–rich atoms (O/Cl) or moieties (phenyl ring). However, in another complex, establishes unexpected π+–π+ interactions with an adjacent diprotonated adenine ring promoted by the [Cd3(μ–L)2(μ–Cl)4Cl6]4− anions.
Volume resistive switching in 3-terminal devices
Engineering Oxygen Migration for Homogeneous Volume Resistive Switching in 3-Terminal Devices
Juan Carlos Gonzalez-Rosillo, Rafael Ortega-Hernandez, Benedikt Arndt, Mariona Coll, Regina Dittmann, Xavier Obradors, Anna Palau, Jordi Suñe, Teresa Puig
Advanced Electronic Materials 1800629 (1-8), 2019
Figure: (a) Oxygen ion exchange mechanism between the La0.8Sr0.2MnO3 and the CeO2−x layers proposed to describe the field-induced resistive switching phenomenon. (b) Scheme of the 3-T device. The red region under the gate electrode indicates the active switching region. (c) Cycle evolution of High and Low resistance states in the 3-T device.
This study reports on a robust physical mechanism governing a field-induced volume resistive switching in metallic La1−xSrxMnO3−y perovskites, displaying a metal insulator transition. We show that oxygen migration can be smartly engineered by introducing a CeO2−x capping layer, acting as oxygen reservoir, which is used to validate the phenomenon as a proof-of-concept three-terminal (3-T) device.