ICN2 Publications

2018

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

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

    Theoretical and Computational Nanoscience

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


  • A hexa-quinoline based: C 3-symmetric chemosensor for dual sensing of zinc(ii) and PPi in an aqueous medium via chelation induced

    Sinha S., Chowdhury B., Adarsh N.N., Ghosh P. Dalton Transactions; 47 (19): 6819 - 6830. 2018. 10.1039/c8dt00611c.

    Nanostructured Functional Materials

    A quinoline-based C3-symmetric fluorescent probe (1), N,N′,N′′-((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene))tris(1-(quinolin-2-yl)-N-(quinolin-2-ylmethyl)methanamine), has been developed which can selectively detect Zn2+ without the interference of Cd2+via significant enhancement in emission intensity (fluorescence "turn-ON") associated with distinct fluorescence colour changes and very low detection limits (35.60 × 10-9 M in acetonitrile and 29.45 × 10-8 M in 50% aqueous buffer (10 mM HEPES, pH = 7.4) acetonitrile media). Importantly, this sensor is operative with a broad pH window (pH 4-10). The sensing phenomenon has been duly studied through UV-vis, steady-state, and time-resolved fluorescence spectroscopic methods indicating 1:3 stoichiometric binding between 1 and Zn2+ which is further corroborated by 1H NMR studies. Density functional theoretical (DFT) calculations provide the optimized molecular geometry and properties of the zinc complex, 1[Zn(ClO4)]3 3+, which is proposed to be formed in acetonitrile. The results are in line with the solution-state experimental findings. The single crystal X-ray study provides the solid state structure of the trinuclear Zn2+ complex showing solubility in an aqueous buffer (10 mM HEPES, pH = 7.4). Finally, the resulting trinuclear Zn2+ complex has been utilized as a fluorescence "turn-OFF" sensor for the selective detection of pyrophosphate in a 70% aqueous buffer (10 mM HEPES, pH = 7.4) acetonitrile solvent with a nanomolar detection limit (45.37 × 10-9 M). © 2018 The Royal Society of Chemistry.


  • A liquid-liquid transition in supercooled aqueous solution related to the HDA-LDA transition

    Woutersen S., Ensing B., Hilbers M., Zhao Z., Austen Angell C. Science; 359 (6380): 1127 - 1131. 2018. 10.1126/science.aao7049.

    Theory and Simulation

    Simulations and theory suggest that the thermodynamic anomalies of water may be related to a phase transition between two supercooled liquid states, but so far this phase transition has not been observed experimentally because of preemptive ice crystallization. We used calorimetry, infrared spectroscopy, and molecular dynamics simulations to investigate a water-rich hydrazinium trifluoroacetate solution in which the local hydrogen bond structure surrounding a water molecule resembles that in neat water at elevated pressure, but which does not crystallize upon cooling. Instead, this solution underwent a sharp, reversible phase transition between two homogeneous liquid states. The hydrogen-bond structures of these two states are similar to those established for high- and low-density amorphous (HDA and LDA) water. Such structural similarity supports theories that predict a similar sharp transition in pure water under pressure if ice crystallization could be suppressed. © 2017 The Authors.


  • A multiscale model of the effect of Ir thickness on the static and dynamic properties of Fe/Ir/Fe films

    Cuadrado R., Oroszlány L., Szunyogh L., Hrkac G., Chantrell R.W., Ostler T.A. Scientific Reports; 8 (1, 3879) 2018. 10.1038/s41598-018-21934-5.

    Theory and Simulation

    The complex magnetic properties of Fe/Ir/Fe sandwiches are studied using a hierarchical multi-scale model. The approach uses first principles calculations and thermodynamic models to reveal the equilibrium spinwave, magnetization and dynamic demagnetisation properties. Finite temperature calculations show a complex spinwave dispersion and an initially counter-intuitive, increasing exchange stiffness with temperature (a key quantity for device applications) due to the effects of frustration at the interface, which then decreases due to magnon softening. Finally, the demagnetisation process in these structures is shown to be much slower at the interface as compared with the bulk, a key insight to interpret ultrafast laser-induced demagnetization processes in layered or interface materials. © The Author(s) 2018.


  • A Solar Transistor and Photoferroelectric Memory

    Pérez-Tomás A., Lima A., Billon Q., Shirley I., Catalan G., Lira-Cantú M. Advanced Functional Materials; 28 (17, 1707099) 2018. 10.1002/adfm.201707099.

    Oxide Nanophysics | Nanostructured Materials for Photovoltaic Energy

    This study presents a new self-powered electronic transistor concept “the solar transistor.” The transistor effect is enabled by the functional integration of a ferroelectric-oxide thin film and an organic bulk heterojunction. The organic heterojunction efficiently harvests photon energy and splits photogenerated excitons into free electron and holes, and the ferroelectric film acts as a switchable electron transport layer with tuneable conduction band offsets that depend on its polarization state. This results in the device photoconductivity modulation. All this (i.e., carrier extraction and poling) is achieved with only two sandwiched electrodes and therefore, with the role of the gating electrode being taken by light. The two-terminal solar-powered phototransistor (or solaristor) thus has the added advantages of a compact photodiode architecture in addition to the nonvolatile functionality of a ferroelectric memory that is written by voltage and nondestructively read by light. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


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

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

    Theory and Simulation

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


  • All nanocarbon Li-Ion capacitor with high energy and high power density

    Dubal D.P., Gomez-Romero P. Materials Today Energy; 8: 109 - 117. 2018. 10.1016/j.mtener.2018.03.005.

    Novel Energy-Oriented Materials

    An energy storage device reaching energy densities of 102 Wh/Kg at power densities of 104 W/Kg would mean the possibility of charging such a device in 36 s. The nanocarbon device presented here is closer to that feat than any previously reported system. N-doped Carbon Nanopipes were used as anode and Partially Reduced Graphene Oxide as cathode, with LiPF6 EC/PC electrolyte. This system yields simultaneously high energy and power densities (262 at 450 W/kg and 78 Wh/kg at 9000 W/kg) which are energy/power combinations considerably higher than those of present Li-ion batteries. Our cell exhibits excellent cycle stability (∼91% capacity retention after 4000 cycles “0.01–4 V”). These breakthrough results are based on the kinetic balancing of the nanocarbon electrodes, which can deliver excellent high energy density at high rates and low costs. © 2018 Elsevier Ltd


  • Aqueous production of spherical Zr-MOF beads: Via continuous-flow spray-drying

    Avci-Camur C., Troyano J., Pérez-Carvajal J., Legrand A., Farrusseng D., Imaz I., Maspoch D. Green Chemistry; 20 (4): 873 - 878. 2018. 10.1039/c7gc03132g.

    Supramolecular NanoChemistry and Materials

    Porous metal-organic frameworks (MOFs) are attracting great attention from industry, thanks to their myriad potential applications in areas such as catalysis and gas storage. Zr-MOFs (also known as UiO-type MOFs) are especially promising, owing to their large surface areas, high chemical versatility and remarkable hydrothermal, chemical and thermal stabilities. However, among the challenges currently precluding the industrial exploitation of MOFs is the lack of green methods for their synthesis. Herein we describe a continuous-flow spray-drying method for the simultaneous synthesis and shaping of spherical MOF microbeads in a mixture of water and acetic acid. We used this approach to build two archetypical Zr-MOFs: UiO-66-NH2 and Zr-fumarate. By tuning the concentration of acetic acid in water, we were able to produce, by a scalable process, UiO-66-NH2 and Zr-fumarate beads with SBET and water-sorption values comparable to the literature values obtained with other methods. © 2018 The Royal Society of Chemistry.


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

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

    Nanobioelectronics and Biosensors

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


  • Arrays of suspended silicon nanowires defined by ion beam implantation: Mechanical coupling and combination with CMOS technology

    Llobet J., Rius G., Chuquitarqui A., Borrisé X., Koops R., Van Veghel M., Perez-Murano F. Nanotechnology; 29 (15, 155303) 2018. 10.1088/1361-6528/aaac67.

    Nanoscience Instrument Development Division

    We present the fabrication, operation, and CMOS integration of arrays of suspended silicon nanowires (SiNWs). The functional structures are obtained by a top-down fabrication approach consisting in a resistless process based on focused ion beam irradiation, causing local gallium implantation and silicon amorphization, plus selective silicon etching by tetramethylammonium hydroxide, and a thermal annealing process in a boron rich atmosphere. The last step enables the electrical functionality of the irradiated material. Doubly clamped silicon beams are fabricated by this method. The electrical readout of their mechanical response can be addressed by a frequency down-mixing detection technique thanks to an enhanced piezoresistive transduction mechanism. Three specific aspects are discussed: (i) the engineering of mechanically coupled SiNWs, by making use of the nanometer scale overhang that it is inherently-generated with this fabrication process, (ii) the statistical distribution of patterned lateral dimensions when fabricating large arrays of identical devices, and (iii) the compatibility of the patterning methodology with CMOS circuits. Our results suggest that the application of this method to the integration of large arrays of suspended SiNWs with CMOS circuitry is interesting in view of applications such as advanced radio frequency band pass filters and ultra-high-sensitivity mass sensors. © 2018 IOP Publishing Ltd.


  • Biochemical and MALDI-TOF mass spectrometric characterization of a novel native and recombinant cystine knot miniprotein from Solanum tuberosum subsp. andigenum cv. Churqueña

    Cotabarren J., Tellechea M.E., Tanco S.M., Lorenzo J., Garcia-Pardo J., Avilés F.X., Obregón W.D. International Journal of Molecular Sciences; 19 (3, 678) 2018. 10.3390/ijms19030678.

    Nanostructured Functional Materials

    Cystine-knot miniproteins (CKMPs) are an intriguing group of cysteine-rich molecules that combine the characteristics of proteins and peptides. Typically, CKMPs are fewer than 50 residues in length and share a characteristic knotted scaffold characterized by the presence of three intramolecular disulfide bonds that form the singular knotted structure. The knot scaffold confers on these proteins remarkable chemical, thermal, and proteolytic stability. Recently, CKMPs have emerged as a novel class of natural molecules with interesting pharmacological properties. In the present work, a novel cystine-knot metallocarboxypeptidase inhibitor (chuPCI) was isolated from tubers of Solanum tuberosum, subsp. andigenum cv. Churqueña. Our results demonstrated that chuPCI is a member of the A/B-type family of metallocarboxypeptidases inhibitors. chuPCI was expressed and characterized by a combination of biochemical and mass spectrometric techniques. Direct comparison of the MALDI-TOF mass spectra for the native and recombinant molecules allowed us to confirm the presence of four different forms of chuPCI in the tubers. The majority of such forms have a molecular weight of 4309 Da and contain a cyclized Gln in the N-terminus. The other three forms are derived from N-terminal and/or C-terminal proteolytic cleavages. Taken together, our results contribute to increase the current repertoire of natural CKMPs. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.


  • Bioluminescent nanopaper for rapid screening of toxic substances

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

    Nanobioelectronics and Biosensors

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


  • Bottom-up synthesis of multifunctional nanoporous graphene

    Moreno C., Vilas-Varela M., Kretz B., Garcia-Lekue A., Costache M.V., Paradinas M., Panighel M., Ceballos G., Valenzuela S.O., Peña D., Mugarza A. Science; 360 (6385): 199 - 203. 2018. 10.1126/science.aar2009.

    Physics and Engineering of Nanodevices | Atomic Manipulation and Spectroscopy

    Nanosize pores can turn semimetallic graphene into a semiconductor and, from being impermeable, into the most efficient molecular-sieve membrane. However, scaling the pores down to the nanometer, while fulfilling the tight structural constraints imposed by applications, represents an enormous challenge for present top-down strategies. Here we report a bottom-up method to synthesize nanoporous graphene comprising an ordered array of pores separated by ribbons, which can be tuned down to the 1-nanometer range. The size, density, morphology, and chemical composition of the pores are defined with atomic precision by the design of the molecular precursors. Our electronic characterization further reveals a highly anisotropic electronic structure, where orthogonal one-dimensional electronic bands with an energy gap of ∼1 electron volt coexist with confined pore states, making the nanoporous graphene a highly versatile semiconductor for simultaneous sieving and electrical sensing of molecular species. 2017 © The Authors


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

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

    Nanoscience Instrument Development Division

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


  • Characterization of nanoparticle batch-to-batch variability

    Mülhopt S., Diabaté S., Dilger M., Adelhelm C., Anderlohr C., Bergfeldt T., de la Torre J.G., Jiang Y., Valsami-Jones E., Langevin D., Lynch I., Mahon E., Nelissen I., Piella J., Puntes V., Ray S., Schneider R., Wilkins T., Weiss C., Paur H.-R. Nanomaterials; 8 (5, 311) 2018. 10.3390/nano8050311.

    Inorganic Nanoparticles

    A central challenge for the safe design of nanomaterials (NMs) is the inherent variability of NM properties, both as produced and as they interact with and evolve in, their surroundings. This has led to uncertainty in the literature regarding whether the biological and toxicological effects reported for NMs are related to specific NM properties themselves, or rather to the presence of impurities or physical effects such as agglomeration of particles. Thus, there is a strong need for systematic evaluation of the synthesis and processing parameters that lead to potential variability of different NM batches and the reproducible production of commonly utilized NMs. The work described here represents over three years of effort across 14 European laboratories to assess the reproducibility of nanoparticle properties produced by the same and modified synthesis routes for four of the OECD priority NMs (silica dioxide, zinc oxide, cerium dioxide and titanium dioxide) as well as amine-modified polystyrene NMs, which are frequently employed as positive controls for nanotoxicity studies. For 46 different batches of the selected NMs, all physicochemical descriptors as prioritized by the OECD have been fully characterized. The study represents the most complete assessment of NMs batch-to-batch variability performed to date and provides numerous important insights into the potential sources of variability of NMs and how these might be reduced. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.


  • Composites of laminar nanostructured ZnO and VOx-nanotubes hybrid as visible light active photocatalysts

    Benavente E., Navas D., Devis S., Segovia M., Sotomayor-Torres C., González G. Catalysts; 8 (2, 93) 2018. 10.3390/catal8020093.

    Phononic and Photonic Nanostructures

    A series of hybrid heterostructured nanocomposites of ZnO with V2O5 nanotubes (VOx-NTs) in different mixing ratios were synthesized, with the aim of reducing the recombination of photoinduced charge carriers and to optimize the absorption of visible light. The study was focused on the use of heterostructured semiconductors that can extend light absorption to the visible range and enhance the photocatalytic performance of ZnO in the degradation of methylene blue as a model pollutant. The addition of VOx-NTs in the synthesis mixture led to a remarkable performance in the degradation of the model dye, with hybrid ZnO (stearic acid)/VOx-NTs at a ratio of 1:0.06 possessing the highest photocatalytic activity, about seven times faster than pristine zinc oxide. Diffuse reflectance spectroscopic measurements and experiments in the presence of different trapping elements allowed us to draw conclusions regarding the band positions and photocatalytic degradation mechanism. The photocatalytic activity measured in three subsequent cycles showed good reusability as no significant loss in efficiency of dye degradation was observed. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.


  • Conductance quantization suppression in the quantum Hall regime

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

    Advanced Electronic Materials and Devices

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


  • Crystal structure and mechanism of human carboxypeptidase O: Insights into its specific activity for acidic residues

    Garcia-Guerrero M.C., Garcia-Pardo J., Berenguer E., Fernandez-Alvarez R., Barfi G.B., Lyons P.J., Aviles F.X., Huber R., Lorenzo J., Reverter D. Proceedings of the National Academy of Sciences of the United States of America; 115 (17): E3932 - E3939. 2018. 10.1073/pnas.1803685115.

    Nanostructured Functional Materials

    Human metallocarboxypeptidase O (hCPO) is a recently discovered digestive enzyme localized to the apical membrane of intestinal epithelial cells. Unlike pancreatic metallocarboxypeptidases, hCPO is glycosylated and produced as an active enzyme with distinctive substrate specificity toward C-terminal (C-t) acidic residues. Here we present the crystal structure of hCPO at 1.85-Å resolution, both alone and in complex with a carboxypeptidase inhibitor (NvCI) from the marine snail Nerita versicolor. The structure provides detailed information regarding determinants of enzyme specificity, in particular Arg275, placed at the bottom of the substrate-binding pocket. This residue, located at “canonical” position 255, where it is Ile in human pancreatic carboxypeptidases A1 (hCPA1) and A2 (hCPA2) and Asp in B (hCPB), plays a dominant role in determining the preference of hCPO for acidic C-t residues. Site-directed mutagenesis to Asp and Ala changes the specificity to C-t basic and hydrophobic residues, respectively. The single-site mutants thus faithfully mimic the enzymatic properties of CPB and CPA, respectively. hCPO also shows a preference for Glu over Asp, probably as a consequence of a tighter fitting of the Glu side chain in its S1′ substrate-binding pocket. This unique preference of hCPO, together with hCPA1, hCPA2, and hCPB, completes the array of C-t cleavages enabling the digestion of the dietary proteins within the intestine. Finally, in addition to activity toward small synthetic substrates and peptides, hCPO can also trim C-t extensions of proteins, such as epidermal growth factor, suggesting a role in the maturation and degradation of growth factors and bioactive peptides. © 2018 National Academy of Sciences. All Rights Reserved.


  • Crystallographically Textured Nanomaterials Produced from the Liquid Phase Sintering of BixSb2-xTe3 Nanocrystal Building Blocks

    Liu Y., Zhang Y., Ortega S., Ibáñez M., Lim K.H., Grau-Carbonell A., Martí-Sánchez S., Ng K.M., Arbiol J., Kovalenko M.V., Cadavid D., Cabot A. Nano Letters; 18 (4): 2557 - 2563. 2018. 10.1021/acs.nanolett.8b00263.

    Advanced Electron Nanoscopy

    Bottom-up approaches for producing bulk nanomaterials have traditionally lacked control over the crystallographic alignment of nanograins. This limitation has prevented nanocrystal-based nanomaterials from achieving optimized performances in numerous applications. Here we demonstrate the production of nanostructured BixSb2-xTe3 alloys with controlled stoichiometry and crystallographic texture through proper selection of the starting building blocks and the adjustment of the nanocrystal-to-nanomaterial consolidation process. In particular, we hot pressed disk-shaped BixSb2-xTe3 nanocrystals and tellurium nanowires using multiple pressure and release steps at a temperature above the tellurium melting point. We explain the formation of the textured nanomaterials though a solution-reprecipitation mechanism under a uniaxial pressure. Additionally, we further demonstrate these alloys to reach unprecedented thermoelectric figures of merit, up to ZT = 1.96 at 420 K, with an average value of ZTave = 1.77 for the record material in the temperature range 320-500 K, thus potentially allowing up to 60% higher energy conversion efficiencies than commercial materials. © 2018 American Chemical Society.


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

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

    Nanostructured Functional Materials

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


  • Effect of the channel length on the transport characteristics of transistors based on boron-doped graphene ribbons

    Marconcini P., Cresti A., Roche S. Materials; 11 (5, 667) 2018. 10.3390/ma11050667.

    Theoretical and Computational Nanoscience

    Substitutional boron doping of devices based on graphene ribbons gives rise to a unipolar behavior, a mobility gap, and an increase of the ION/IOFF ratio of the transistor. Here we study how this effect depends on the length of the doped channel. By means of self-consistent simulations based on a tight-binding description and a non-equilibrium Green's function approach, we demonstrate a promising increase of the ION/IOFF ratio with the length of the channel, as a consequence of the different transport regimes in the ON and OFF states. Therefore, the adoption of doped ribbons with longer aspect ratios could represent a significant step toward graphene-based transistors with an improved switching behavior. © 2018 by the authors.


  • Electrochromic Molecular Imprinting Sensor for Visual and Smartphone-Based Detections

    Capoferri D., Álvarez-Diduk R., Del Carlo M., Compagnone D., Merkoçi A. Analytical Chemistry; 90 (9): 5850 - 5856. 2018. 10.1021/acs.analchem.8b00389.

    Nanobioelectronics and Biosensors

    Electrochromic effect and molecularly imprinted technology have been used to develop a sensitive and selective electrochromic sensor. The polymeric matrices obtained using the imprinting technology are robust molecular recognition elements and have the potential to mimic natural recognition entities with very high selectivity. The electrochromic behavior of iridium oxide nanoparticles (IrOx NPs) as physicochemical transducer together with a molecularly imprinted polymer (MIP) as recognition layer resulted in a fast and efficient translation of the detection event. The sensor was fabricated using screen-printing technology with indium tin oxide as a transparent working electrode; IrOx NPs where electrodeposited onto the electrode followed by thermal polymerization of polypyrrole in the presence of the analyte (chlorpyrifos). Two different approaches were used to detect and quantify the pesticide: direct visual detection and smartphone imaging. Application of different oxidation potentials for 10 s resulted in color changes directly related to the concentration of the analyte. For smartphone imaging, at fixed potential, the concentration of the analyte was dependent on the color intensity of the electrode. The electrochromic sensor detects a highly toxic compound (chlorpyrifos) with a 100 fM and 1 mM dynamic range. So far, to the best of our knowledge, this is the first work where an electrochromic MIP sensor uses the electrochromic properties of IrOx to detect a certain analyte with high selectivity and sensitivity. © 2018 American Chemical Society.


  • Energy harvesting from neutralization reactions with saline feedback

    Lima G., Dubal D.P., Rueda-García D., Gómez-Romero P., Huguenin F. Electrochimica Acta; 275: 145 - 154. 2018. 10.1016/j.electacta.2018.04.075.

    Novel Energy-Oriented Materials

    This work proposes an acid-base machine consisting of insertion electrodes for protons and alkaline metal ions placed in electrolytic solutions with different pH values and alkaline ion concentrations to harvest energy from a neutralization reaction. We simulate energy harvesting during acidic wastewater treatment with base (KOH) by using phosphomolybdic acid and nickel hexacyanoferrate as the negative and the positive electrodes, respectively, in aqueous H2SO4 and K2SO4 solutions. In this configuration, the machine harvests energy from a change in the free energy related to changes in the proton and in the potassium ion concentrations after neutralization reactions, with feedback from the saline solution resulting from neutralization. The electrochemical impedance spectroscopy diagrams provide insight into the practical proton and potassium ion electroinsertion reversibility in acidic and neutral media. Based on the charge/discharge curves at pH = 2 and pH = 5.8, the acid-base machine harvests ca. 10 kJ per mol of electro-inserted protons in the first cycles. These results demonstrate that the methodology is viable for sustainable growth—it can harvest energy from wastewater treatment, a practice that can be especially profitable for the industrial sector, which produces great amounts of wastewater. © 2018 Elsevier Ltd


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

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

    Magnetic Nanostructures

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


  • Epoxidation of carbon nanocapsules: Decoration of single-walled carbon nanotubes filled with metal halides

    D’Accolti L., Gajewska A., Kierkowicz M., Martincic M., Nacci A., Sandoval S., Ballesteros B., Tobias G., Da Ros T., Fusco C. Nanomaterials; 8 (3, 137) 2018. 10.3390/nano8030137.

    Electron Microscopy Division

    Methyl(trifluoromethyl)dioxirane (TFDO) can be used for the oxyfunctionalization of SWCNTs filled with NaI and LuCl3 under mild conditions. The chosen metal halides are of interest for theranostics, both for imaging and therapy when in their radioactive form. The applied functionalization methodology does not require metal catalyst, preserves the integrity of the nanotubes during treatment, avoiding the release of the filling material. In this way, epoxidation can be considered as an efficient methodology for the functionalization of carbon nanocapsules, where the traditional harsh oxidation conditions by acids are not applicable. © 2018 2018 by the authors. Licensee MDPI, Basel, Switzerland.


  • First principles analysis of the CDW instability of single-layer 1T-TiSe2 and its evolution with charge carrier density

    Guster B., Canadell E., Pruneda M., Ordejón P. 2D Materials; 5 (2, 025024) 2018. 10.1088/2053-1583/aab568.

    Theory and Simulation

    We present a density functional theory study of the electronic structure of single-layer TiSe2, and focus on the charge density wave (CDW) instability present on this 2D material. We explain the periodicity of the CDW from the phonon band structure of the undistorted crystal, which is unstable under one of the phonon modes at the M point. This can be understood in terms of a partial band gap opening at the Fermi level, which we describe on the basis of the symmetry of the involved crystal orbitals, leading to an energy gain upon the displacement of the atoms following the phonon mode in a 2 × 1 structure. Furthermore, the combination of the corresponding phonons for the three inequivalent M points of the Brillouin zone leads to the 2 × 2 distortion characteristic of the CDW state. This leads to a further opening of a full gap, which reduces the energy of the 2 × 2 structure compared to the 2 × 1 one of a single M point phonon, and makes the CDW structure the most stable one. We also analyze the effect of charge injection into the layer on the structural instability. We predict that the 2 × 2 structure only survives for a certain range of doping levels, both for electrons and for holes, as doping reduces the energy gain due to the gap opening. We predict the transition from the commensurate 2 × 2 distortion to an incommensurate one with increasing wavelength upon increasing the doping level, followed by the appearance of the undistorted 1 × 1 structure for larger carrier concentrations. © 2018 IOP Publishing Ltd.


  • Flexible Graphene Solution-Gated Field-Effect Transistors: Efficient Transducers for Micro-Electrocorticography

    Hébert C., Masvidal-Codina E., Suarez-Perez A., Calia A.B., Piret G., Garcia-Cortadella R., Illa X., Del Corro Garcia E., De la Cruz Sanchez J.M., Casals D.V., Prats-Alfonso E., Bousquet J., Godignon P., Yvert B., Villa R., Sanchez-Vives M.V., Guimerà-Brunet A., Garrido J.A. Advanced Functional Materials; 28 (12, 1703976) 2018. 10.1002/adfm.201703976.

    Advanced Electronic Materials and Devices

    Brain–computer interfaces and neural prostheses based on the detection of electrocorticography (ECoG) signals are rapidly growing fields of research. Several technologies are currently competing to be the first to reach the market; however, none of them fulfill yet all the requirements of the ideal interface with neurons. Thanks to its biocompatibility, low dimensionality, mechanical flexibility, and electronic properties, graphene is one of the most promising material candidates for neural interfacing. After discussing the operation of graphene solution-gated field-effect transistors (SGFET) and characterizing their performance in saline solution, it is reported here that this technology is suitable for μ-ECoG recordings through studies of spontaneous slow-wave activity, sensory-evoked responses on the visual and auditory cortices, and synchronous activity in a rat model of epilepsy. An in-depth comparison of the signal-to-noise ratio of graphene SGFETs with that of platinum black electrodes confirms that graphene SGFET technology is approaching the performance of state-of-the art neural technologies. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • Flexoelectricity in Bones

    Vasquez-Sancho F., Abdollahi A., Damjanovic D., Catalan G. Advanced Materials; 30 (9, 1705316) 2018. 10.1002/adma.201705316.

    Oxide Nanophysics

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


  • Fluorescently labelled nanomaterials in nanosafety research: Practical advice to avoid artefacts and trace unbound dye

    Murray R.A., Escobar A., Bastús N.G., Andreozzi P., Puntes V., Moya S.E. NanoImpact; 9: 102 - 113. 2018. 10.1016/j.impact.2017.11.001.

    Inorganic Nanoparticles

    Fluorescence labelling has become a fundamental tool in nanotoxicological research. There are, however, certain drawbacks when dealing with the labelling of nanomaterials. Very often the leaching of dye from the nanomaterial or the presence of unbound dyes in solution leads to the incorrect quantification and localisation of nanomaterials in cells. In this review article we will discuss possible situations, which may give rise to incorrect quantification of the fluorescence associated with nanomaterials and their consequences in the evaluation of the fate of the nanomaterial and its intracellular dose. Issues related to the labelling strategies, dye photostability, impact of the dye on the properties of the nanomaterial surface, and the presence of unbound dye will be discussed. We will also show how Fluorescence Correlation Spectroscopy can be used to trace the presence of free label in solution. In addition, we will discuss the interaction of fluorescence molecules with metallic nanoparticles which can lead to an enhancement or quenching of fluorescence depending on the distance between the dye and the nanoparticle surface. Finally, we will compare the fluorescence emission originating from quantum dots and organic molecules. © 2017 Elsevier B.V.


  • Growth and Luminescence of Polytypic InP on Epitaxial Graphene

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

    Advanced Electron Nanoscopy

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


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

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

    Phononic and Photonic Nanostructures

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


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

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

    Novel Energy-Oriented Materials

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


  • Impact of the: In situ rise in hydrogen partial pressure on graphene shape evolution during CVD growth of graphene

    Gebeyehu Z.M., Arrighi A., Costache M.V., Sotomayor-Torres C.M., Esplandiu M.J., Valenzuela S.O. RSC Advances; 8 (15): 8234 - 8239. 2018. 10.1039/c7ra13169k.

    Physics and Engineering of Nanodevices | Phononic and Photonic Nanostructures | Force Probe Microscopy and Surface Nanoengineering

    Exposing graphene to a hydrogen post-etching process yields dendritic graphene shapes. Here, we demonstrate that similar dendritic structures can be achieved at long growth times without adding hydrogen externally. These shapes are not a result of a surface diffusion controlled growth but of the competing backward reaction (etching), which dominates the growth dynamics at long times due to an in situ rise in the hydrogen partial pressure. We have performed a systematic study on the growth of graphene as a function of time to identify the onset and gradual evolution of graphene shapes caused by etching and then demonstrated that the etching can be stopped by reducing the flow of hydrogen from the feed. In addition, we have found that the etching rate due to the in situ rise in hydrogen is strongly dependent on the confinement (geometrical confinement) of copper foil. Highly etched graphene with dendritic shapes was observed in unconfined copper foil regions while no etching was found in graphene grown in a confined reaction region. This highlights the effect of the dynamic reactant distribution in activating the in situ etching process during growth, which needs to be counteracted or controlled for large scale growth. © The Royal Society of Chemistry 2018.


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

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

    Nanobioelectronics and Biosensors

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


  • In-line metrology for roll-to-roll UV assisted nanoimprint lithography using diffractometry

    Kreuzer M., Whitworth G.L., Francone A., Gomis-Bresco J., Kehagias N., Sotomayor-Torres C.M. APL Materials; 6 (5, 058502) 2018. 10.1063/1.5011740.

    Phononic and Photonic Nanostructures

    We describe and discuss the optical design of a diffractometer to carry out in-line quality control during roll-to-roll nanoimprinting. The tool measures diffractograms in reflection geometry, through an aspheric lens to gain fast, non-invasive information of any changes to the critical dimensions of target grating structures. A stepwise tapered linear grating with constant period was fabricated in order to detect the variation in grating linewidth through diffractometry. The minimum feature change detected was ∼40 nm to a precision of 10 nm. The diffractometer was then integrated with a roll-to-roll UV assisted nanoimprint lithography machine to gain dynamic measurements in situ. © 2018 Author(s).


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

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

    Atomic Manipulation and Spectroscopy

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


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

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

    Inorganic Nanoparticles

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


  • Large spin relaxation anisotropy and valley-Zeeman spin-orbit coupling in WSe2 /graphene/ h -BN heterostructures

    Zihlmann S., Cummings A.W., Garcia J.H., Kedves M., Watanabe K., Taniguchi T., Schönenberger C., Makk P. Physical Review B; 97 (7, 075434) 2018. 10.1103/PhysRevB.97.075434.

    Theoretical and Computational Nanoscience

    Large spin-orbital proximity effects have been predicted in graphene interfaced with a transition-metal dichalcogenide layer. Whereas clear evidence for an enhanced spin-orbit coupling has been found at large carrier densities, the type of spin-orbit coupling and its relaxation mechanism remained unknown. We show an increased spin-orbit coupling close to the charge neutrality point in graphene, where topological states are expected to appear. Single-layer graphene encapsulated between the transition-metal dichalcogenide WSe2 and h-BN is found to exhibit exceptional quality with mobilities as high as 1×105 cm2 V-1 s-1. At the same time clear weak antilocalization indicates strong spin-orbit coupling, and a large spin relaxation anisotropy due to the presence of a dominating symmetric spin-orbit coupling is found. Doping-dependent measurements show that the spin relaxation of the in-plane spins is largely dominated by a valley-Zeeman spin-orbit coupling and that the intrinsic spin-orbit coupling plays a minor role in spin relaxation. The strong spin-valley coupling opens new possibilities in exploring spin and valley degree of freedom in graphene with the realization of new concepts in spin manipulation. © 2018 American Physical Society.


  • Lipid Monolayer Formation and Lipid Exchange Monitored by a Graphene Field-Effect Transistor

    Blaschke B.M., Böhm P., Drieschner S., Nickel B., Garrido J.A. Langmuir; 34 (14): 4224 - 4233. 2018. 10.1021/acs.langmuir.8b00162.

    Advanced Electronic Materials and Devices

    Anionic and cationic lipids are key molecules involved in many cellular processes; their distribution in biomembranes is highly asymmetric, and their concentration is well-controlled. Graphene solution-gated field-effect transistors (SGFETs) exhibit high sensitivity toward the presence of surface charges. Here, we establish conditions that allow the observation of the formation of charged lipid layers on solution-gated field-effect transistors in real time. We quantify the electrostatic screening of electrolyte ions and derive a model that explains the influence of charged lipids on the ion sensitivity of graphene SGFETs. The electrostatic model is validated using structural information from X-ray reflectometry measurements, which show that the lipid monolayer forms on graphene. We demonstrate that SGFETs can be used to detect cationic lipids by self-exchange of lipids. Furthermore, SGFETs allow measuring the kinetics of layer formation induced by vesicle fusion or spreading from a reservoir. Because of the high transconductance and low noise of the electrical readout, we can observe characteristic conductance spikes that we attribute to bouncing-off events of lipid aggregates from the SGFET surface, suggesting a great potential of graphene SGFETs to measure the on-off kinetics of small aggregates interacting with supported layers. © 2018 American Chemical Society.


  • Local Piezoelectric Behavior of Potassium Sodium Niobate Prepared by a Facile Synthesis via Water Soluble Precursors

    Senes N., Iacomini A., Domingo N., Enzo S., Mulas G., Cuesta-Lopez S., Garroni S. Physica Status Solidi (A) Applications and Materials Science; 2018. 10.1002/pssa.201700921.

    Oxide Nanophysics

    Due to the ever-increasing restrictions connected to the use of toxic lead-based materials, the developing of lead-free piezoceramics has become one of the most urgent tasks. In this context, potassium sodium niobate materials (KNN) have attracted a lot of interest as promising candidates due to their excellent piezo properties. For this reason, many efforts have been addressed to optimize the synthesis process now suffering by several drawbacks including the high volatilization of potassium and sodium at the conventional high temperature treatments and the use of expensive metal precursors. To overcome these issues, a new modified Pechini method to synthesize single phase K0.5Na0.5NbO3 powders, from water soluble metal precursors, is presented. Microstructural and structural parameters are characterized by X-ray diffraction (XRD). Depending on the amount of citric acid added to the starting reagents, two pure single-phase K0.5Na0.5NbO3 (2g citric acid) and K0.3Na0.7NbO3 (0.2g citric acid), respectively, are obtained with a good crystallinity at a moderate temperature of 500°C. The piezo responses of the as calcined systems are tested by piezoresponse force microscopy (PFM). K0.5Na0.5NbO3 exhibits a much higher response with respect to the other phase, which relates to the larger crystallinity and to the chemical composition. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


  • Nanocrystalline silicon optomechanical cavities

    Navarro-Urrios D., Capuj N.E., Maire J., Colombano M., Jaramillo-Fernandez J., Chavez-Angel E., Martin L.L., Mercadé L., Griol A., Martínez A., Sotomayor-Torres C.M., Ahopelto J. Optics Express; 26 (8): 9829 - 9839. 2018. 10.1364/OE.26.009829.

    Phononic and Photonic Nanostructures

    Silicon on insulator photonics has offered a versatile platform for the recent development of integrated optomechanical circuits. However, there are some constraints such as the high cost of the wafers and limitation to a single physical device level. In the present work we investigate nanocrystalline silicon as an alternative material for optomechanical devices. In particular, we demonstrate that optomechanical crystal cavities fabricated of nanocrystalline silicon have optical and mechanical properties enabling non-linear dynamical behaviour and effects such as thermo-optic/free-carrier-dispersion self-pulsing, phonon lasing and chaos, all at low input laser power and with typical frequencies as high as 0.3 GHz. © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.


  • NiSn bimetallic nanoparticles as stable electrocatalysts for methanol oxidation reaction

    Li J., Luo Z., Zuo Y., Liu J., Zhang T., Tang P., Arbiol J., Llorca J., Cabot A. Applied Catalysis B: Environmental; 234: 10 - 18. 2018. 10.1016/j.apcatb.2018.04.017.

    Advanced Electron Nanoscopy

    Nickel is an excellent alternative catalyst to high cost Pt and Pt-group metals as anode material in direct methanol fuel cells. However, nickel presents a relatively low stability under operation conditions, even in alkaline media. In this work, a synthetic route to produce bimetallic NiSn nanoparticles (NPs) with tuned composition is presented. Through co-reduction of the two metals in the presence of appropriate surfactants, 3–5 nm NiSn NPs with tuned Ni/Sn ratios were produced. Such NPs were subsequently supported on carbon black and tested for methanol electro-oxidation in alkaline media. Among the different stoichiometries tested, the most Ni-rich alloy exhibited the highest electrocatalytic activity, with mass current density of 820 mA mg−1 at 0.70 V (vs. Hg/HgO). While this activity was comparable to that of pure nickel NPs, NiSn alloys showed highly improved stabilities over periods of 10,000 s at 0.70 V. We hypothesize this experimental fact to be associated to the collaborative oxidation of the byproducts of methanol which poison the Ni surface or to the prevention of the tight adsorption of these species on the Ni surface by modifying its surface chemistry or electronic density of states. © 2018 Elsevier B.V.


  • On the use of Parylene C polymer as substrate for peripheral nerve electrodes

    De La Oliva N., Mueller M., Stieglitz T., Navarro X., Del Valle J. Scientific Reports; 8 (1, 5965) 2018. 10.1038/s41598-018-24502-z.

    Advanced Electronic Materials and Devices

    Parylene C is a highly flexible polymer used in several biomedical implants. Since previous studies have reported valuable biocompatible and manufacturing characteristics for brain and intraneural implants, we tested its suitability as a substrate for peripheral nerve electrodes. We evaluated 1-year-aged in vitro samples, where no chemical differences were observed and only a slight deviation on Young's modulus was found. The foreign body reaction (FBR) to longitudinal Parylene C devices implanted in the rat sciatic nerve for 8 months was characterized. After 2 weeks, a capsule was formed around the device, which continued increasing up to 16 and 32 weeks. Histological analyses revealed two cell types implicated in the FBR: macrophages, in contact with the device, and fibroblasts, localized in the outermost zone after 8 weeks. Molecular analysis of implanted nerves comparing Parylene C and polyimide devices revealed a peak of inflammatory cytokines after 1 day of implant, returning to low levels thereafter. Only an increase of CCL2 and CCL3 was found at chronic time-points for both materials. Although no molecular differences in the FBR to both polymers were found, the thick tissue capsule formed around Parylene C puts some concern on its use as a scaffold for intraneural electrodes. © 2018 The Author(s).


  • Optical emission of GaN/AlN quantum-wires-the role of charge transfer from a nanowire template

    Müßener J., Greif L.A.T., Kalinowski S., Callsen G., Hille P., Schörmann J., Wagner M.R., Schliwa A., Martí-Sánchez S., Arbiol J., Hoffmann A., Eickhoff M. Nanoscale; 10 (12): 5591 - 5598. 2018. 10.1039/c7nr08057c.

    Advanced Electron Nanoscopy

    We show that one-dimensional (1d) GaN quantum-wires (QWRs) exhibit intense and spectrally sharp emission lines. These QWRs are realized in an entirely self-assembled growth process by molecular beam epitaxy (MBE) on the side facets of GaN/AlN nanowire (NW) heterostructures. Time-integrated and time-resolved photoluminescence (PL) data in combination with numerical calculations allow the identification and assignment of the manifold emission features to three different spatial recombination centers within the NWs. The recombination processes in the QWRs are driven by efficient charge carrier transfer effects between the different optically active regions, providing high intense QWR luminescence despite their small volume. This is deduced by a fast rise time of the QWR PL, which is similar to the fast decay-time of adjacent carrier reservoirs. Such processes, feeding the ultra-narrow QWRs with carriers from the relatively large NWs, can be the key feature towards the realization of future QWR-based devices. While processing of single quantum structures with diameters in the nm range presents a serious obstacle with respect to their integration into electronic or photonic devices, the QWRs presented here can be analyzed and processed using existing techniques developed for single NWs. © 2018 The Royal Society of Chemistry.


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

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

    Nanomaterials Growth Division | Electron Microscopy Division

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


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

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

    Advanced Electron Nanoscopy

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


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

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

    Supramolecular NanoChemistry and Materials

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


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

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

    Nanobioelectronics and Biosensors

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


  • Photothermal Activation of Metal-Organic Frameworks Using a UV-Vis Light Source

    Espín J., Garzón-Tovar L., Carné-Sánchez A., Imaz I., Maspoch D. ACS Applied Materials and Interfaces; 10 (11): 9555 - 9562. 2018. 10.1021/acsami.8b00557.

    Supramolecular NanoChemistry and Materials

    Metal-organic frameworks (MOFs) usually require meticulous removal of the solvent molecules to unlock their potential porosity. Herein, we report a novel one-step method for activating MOFs based on the photothermal effect induced by directly irradiating them with a UV-vis lamp. The localized light-to-heat conversion produced in the MOF crystals upon irradiation enables a very fast solvent removal, thereby significantly reducing the activation time to as low as 30 min and suppressing the need for time-consuming solvent-exchange procedures and vacuum conditions. This approach is successful for a broad range of MOFs, including HKUST-1, UiO-66-NH2, ZIF-67, CPO-27-M (M = Zn, Ni, and Mg), Fe-MIL-101-NH2, and IRMOF-3, all of which exhibit absorption bands in the light emission range. In addition, we anticipate that this photothermal activation can also be used to activate covalent organic frameworks (COFs). © 2018 American Chemical Society.


  • Polydopamine-like Coatings as Payload Gatekeepers for Mesoporous Silica Nanoparticles

    Moreno-Villaécija M.-A., Sedó-Vegara J., Guisasola E., Baeza A., Regí M.V., Nador F., Ruiz-Molina D. ACS Applied Materials and Interfaces; 10 (9): 7661 - 7669. 2018. 10.1021/acsami.7b08584.

    Nanostructured Functional Materials

    We report the use of bis-catecholic polymers as candidates for obtaining effective, tunable gatekeeping coatings for mesoporous silica nanoparticles (MSNs) intended for drug release applications. In monomers, catechol rings act as adhesive moieties and reactive sites for polymerization, together with middle linkers which may be chosen to tune the physicochemical properties of the resulting coating. Stable and low-toxicity coatings (pNDGA and pBHZ) were prepared from two bis-catechols of different polarity (NDGA and BHZ) on MSN carriers previously loaded with rhodamine B (RhB) as a model payload, by means of a previously reported synthetic methodology and without any previous surface modification. Coating robustness and payload content were shown to depend significantly on the workup protocol. The release profiles in a model physiological PBS buffer of coated systems (RhB@MSN@pNDGA and RhB@MSN@pBHZ) showed marked differences in the "gatekeeping" behavior of each coating, which correlated qualitatively with the chemical nature of their respective linker moieties. While the uncoated system (RhB@MSN) lost its payload almost completely after 2 days, release from RhB@MSN@pNDGA was virtually negligible, likely due to the low polarity of the parent bis-catechol (NDGA). As opposed to these extremes, RhB@MSN@pBHZ presented the most promising behavior, showing an intermediate release of 50% of the payload in the same period of time. © 2017 American Chemical Society.


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

    Adarsh N.N., Frias C., Ponnoth Lohidakshan T.M., Lorenzo J., Novio F., Garcia-Pardo J., Ruiz-Molina D. Chemical Engineering Journal; 340: 94 - 102. 2018. 10.1016/j.cej.2018.01.058.

    Nanostructured Functional Materials

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


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

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

    Force Probe Microscopy and Surface Nanoengineering

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


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

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

    Theoretical and Computational Nanoscience

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


  • Raman thermometry analysis: Modelling assumptions revisited

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

    Phononic and Photonic Nanostructures

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


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

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

    Atomic Manipulation and Spectroscopy

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


  • Reconsidering figures of merit for performance and stability of perovskite photovoltaics

    Khenkin M.V., Anoop K.M., Visoly-Fisher I., Galagan Y., Di Giacomo F., Patil B.R., Sherafatipour G., Turkovic V., Rubahn H.-G., Madsen M., Merckx T., Uytterhoeven G., Bastos J.P.A., Aernouts T., Brunetti F., Lira-Cantu M., Katz E.A. Energy and Environmental Science; 11 (4): 739 - 743. 2018. 10.1039/c7ee02956j.

    Nanostructured Materials for Photovoltaic Energy

    The development of hybrid organic-inorganic halide perovskite solar cells (PSCs) that combine high performance and operational stability is vital for implementing this technology. Recently, reversible improvement and degradation of PSC efficiency have been reported under illumination-darkness cycling. Quantifying the performance and stability of cells exhibiting significant diurnal performance variations is challenging. We report the outdoor stability measurements of two types of devices showing either reversible photo-degradation or reversible efficiency improvement under sunlight. Instead of the initial (or stabilized) efficiency and T80 as the figures of merit for the performance and stability of such devices, we propose using the value of the energy output generated during the first day of exposure and the time needed to reach its 20% drop, respectively. The latter accounts for both the long-term irreversible degradation and the reversible diurnal efficiency variation and does not depend on the type of process prevailing in a given perovskite cell. © 2018 The Royal Society of Chemistry.


  • Reduction of Thermal Conductivity in Nanowires by Combined Engineering of Crystal Phase and Isotope Disorder

    Mukherjee S., Givan U., Senz S., De La Mata M., Arbiol J., Moutanabbir O. Nano Letters; 18 (5): 3066 - 3075. 2018. 10.1021/acs.nanolett.8b00612.

    Advanced Electron Nanoscopy

    Nanowires are a versatile platform to investigate and harness phonon and thermal transport phenomena in nanoscale systems. With this perspective, we demonstrate herein the use of crystal phase and mass disorder as effective degrees of freedom to manipulate the behavior of phonons and control the flow of local heat in silicon nanowires. The investigated nanowires consist of isotopically pure and isotopically mixed nanowires bearing either a pure diamond cubic or a cubic-rhombohedral polytypic crystal phase. The nanowires with tailor-made isotopic compositions were grown using isotopically enriched silane precursors 28SiH4, 29SiH4, and 30SiH4 with purities better than 99.9%. The analysis of polytypic nanowires revealed ordered and modulated inclusions of lamellar rhombohedral silicon phases toward the center in otherwise diamond-cubic lattice with negligible interphase biaxial strain. Raman nanothermometry was employed to investigate the rate at which the local temperature of single suspended nanowires evolves in response to locally generated heat. Our analysis shows that the lattice thermal conductivity in nanowires can be tuned over a broad range by combining the effects of isotope disorder and the nature and degree of polytypism on phonon scattering. We found that the thermal conductivity can be reduced by up to ∼40% relative to that of isotopically pure nanowires, with the lowest value being recorded for the rhombohedral phase in isotopically mixed 28Six 30Si1-x nanowires with composition close to the highest mass disorder (x ∼ 0.5). These results shed new light on the fundamentals of nanoscale thermal transport and lay the groundwork to design innovative phononic devices. © 2018 American Chemical Society.


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

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

    Supramolecular NanoChemistry and Materials

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


  • Role of Tungsten Doping on the Surface States in BiVO4 Photoanodes for Water Oxidation: Tuning the Electron Trapping Process

    Shi Q., Murcia-López S., Tang P., Flox C., Morante J.R., Bian Z., Wang H., Andreu T. ACS Catalysis; 8 (4): 3331 - 3342. 2018. 10.1021/acscatal.7b04277.

    Advanced Electron Nanoscopy

    The nanostructured BiVO4 photoanodes were prepared by electrospinning and were further characterized by XRD, SEM, and XPS, confirming the bulk and surface modification of the electrodes attained by W addition. The role of surface states (SS) during water oxidation for the as-prepared photoanodes was investigated by using electrochemical, photoelectrochemical, and impedance spectroscopy measurements. An optimum 2% doping is observed in voltammetric measurements with the highest photocurrent density at 1.23 VRHE under back side illumination. It has been found that a high PEC performance requires an optimum ratio of density of surface states (NSS) with respect to the charge donor density (Nd), to give both good conductivity and enough surface reactive sites. The optimum doping (2%) shows the highest Nd and SS concentration, which leads to the high film conductivity and reactive sites. The reason for SS acting as reaction sites (i-SS) is suggested to be the reversible redox process of V5+/V4+ in semiconductor bulk to form water oxidation intermediates through the electron trapping process. Otherwise, the irreversible surface reductive reaction of VO2 + to VO2+ though the electron trapping process raises the surface recombination. W doping does have an effect on the surface properties of the BiVO4 electrode. It can tune the electron trapping process to obtain a high concentration of i-SS and less surface recombination. This work gives a further understanding for the enhancement of PEC performance caused by W doping in the field of charge transfer at the semiconductor/electrolyte interface. © 2018 American Chemical Society.


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

    del Valle J., Santos D., Delgado-Martínez I., de la Oliva N., Giudetti G., Micera S., Navarro X. Journal of Tissue Engineering and Regenerative Medicine; 12 (4): e1991 - e2000. 2018. 10.1002/term.2629.

    Advanced Electronic Materials and Devices

    Segregation of regenerating motor and sensory axons may be a good strategy to improve selective functionality of regenerative interfaces to provide closed-loop commands. Provided that extracellular matrix components and neurotrophic factors exert guidance effects on different neuronal populations, we assessed in vivo the potential of separating sensory and motor axons regenerating in a bicompartmental Y-type tube, with each branch prefilled with an adequate combination of extracellular matrix and neurotrophic factors. The severed rat sciatic nerve was repaired using a bicompartmental tube filled with a collagen matrix enriched with fibronectin (FN) and brain-derived neurotrophic factor (BDNF) encapsulated in poly-lactic co-glycolic acid microspheres (FN + MP.BDNF) in one compartment to preferentially attract motor axons and collagen enriched with laminin (LM) and nerve growth factor (NGF) and neurotrophin-3 (NT-3) in microspheres (LM + MP.NGF/NT-3) in the other compartment for promoting sensory axons regeneration. Control animals were implanted with the same Y-tube with a collagen matrix with microspheres (MP) containing PBS (Col + MP.PBS). By using retrotracer labelling, we found that LM + MP.NGF/NT-3 did not attract higher number of regenerated sensory axons compared with controls, and no differences were observed in sensory functional recovery. However, FN + MP.BDNF guided a higher number of regenerating motor axons compared with controls, improving also motor recovery. A small proportion of sensory axons with large soma size, likely proprioceptive neurons, was also attracted to the FN + MP.BDNF compartment. These results demonstrate that muscular axonal guidance can be modulated in vivo by the addition of fibronectin and BDNF. Copyright © 2017 John Wiley & Sons, Ltd.


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

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

    Supramolecular NanoChemistry and Materials

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


  • Simultaneous Local Heating/Thermometry Based on Plasmonic Magnetochromic Nanoheaters

    Li Z., Lopez-Ortega A., Aranda-Ramos A., Tajada J.L., Sort J., Nogues C., Vavassori P., Nogues J., Sepulveda B. Small; 2018. 10.1002/smll.201800868.

    Magnetic Nanostructures

    A crucial challenge in nanotherapies is achieving accurate and real-time control of the therapeutic action, which is particularly relevant in local thermal therapies to minimize healthy tissue damage and necrotic cell deaths. Here, a nanoheater/thermometry concept is presented based on magnetoplasmonic (Co/Au or Fe/Au) nanodomes that merge exceptionally efficient plasmonic heating and simultaneous highly sensitive detection of the temperature variations. The temperature detection is based on precise optical monitoring of the magnetic-induced rotation of the nanodomes in solution. It is shown that the phase lag between the optical signal and the driving magnetic field can be used to detect viscosity variations around the nanodomes with unprecedented accuracy (detection limit 0.0016 mPa s, i.e., 60-fold smaller than state-of-the-art plasmonic nanorheometers). This feature is exploited to monitor the viscosity reduction induced by optical heating in real-time, even in highly inhomogeneous cell dispersions. The magnetochromic nanoheater/thermometers show higher optical stability, much higher heating efficiency and similar temperature detection limits (0.05 °C) compared to state-of-the art luminescent nanothermometers. The technological interest is also boosted by the simpler and lower cost temperature detection system, and the cost effectiveness and scalability of the nanofabrication process, thereby highlighting the biomedical potential of this nanotechnology. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


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

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

    Supramolecular NanoChemistry and Materials

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


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

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

    Nanostructured Functional Materials

    One new lead(II) coordination supramolecular complex (CSC) (1D), [Pb2(L)2(I)4]n, L = C4H6N2 (1-methyl imidazole), has been synthesized under different experimental conditions. Micrometric crystals (bulk) or nano-sized materials have been obtained depending on using the branch tube method or sonochemical irradiation. All materials have been characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD) and FT-IR spectroscopy. Single crystal X-ray analyses on complex 1 showed that Pb2+ ion is 4-coordinated. Topological analysis shows that the complex 1 is 2,3,5C2 net. Finally, the role of reaction time and temperature on the growth and final morphology of the structures obtained by sonochemical irradiation have been studied. © 2017 Elsevier B.V.


  • Sonochemical Synthesis of Optically Tuneable Conjugated Polymer Nanoparticles

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

    Nanostructured Functional Materials

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


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

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

    Nanostructured Functional Materials

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


  • Spin Proximity Effects in Graphene/Topological Insulator Heterostructures

    Song K., Soriano D., Cummings A.W., Robles R., Ordejón P., Roche S. Nano Letters; 18 (3): 2033 - 2039. 2018. 10.1021/acs.nanolett.7b05482.

    Theory and Simulation | Theoretical and Computational Nanoscience

    Enhancing the spin-orbit interaction in graphene, via proximity effects with topological insulators, could create a novel 2D system that combines nontrivial spin textures with high electron mobility. To engineer practical spintronics applications with such graphene/topological insulator (Gr/TI) heterostructures, an understanding of the hybrid spin-dependent properties is essential. However, to date, despite the large number of experimental studies on Gr/TI heterostructures reporting a great variety of remarkable (spin) transport phenomena, little is known about the true nature of the spin texture of the interface states as well as their role on the measured properties. Here, we use ab initio simulations and tight-binding models to determine the precise spin texture of electronic states in graphene interfaced with a Bi2Se3 topological insulator. Our calculations predict the emergence of a giant spin lifetime anisotropy in the graphene layer, which should be a measurable hallmark of spin transport in Gr/TI heterostructures and suggest novel types of spin devices. © 2018 American Chemical Society.


  • Strong Quantum Confinement Effects and Chiral Excitons in Bio-Inspired ZnO-Amino Acid Cocrystals

    Muhammed M.A.H., Lamers M., Baumann V., Dey P., Blanch A.J., Polishchuk I., Kong X.-T., Levy D., Urban A.S., Govorov A.O., Pokroy B., Rodríguez-Fernández J., Feldmann J. Journal of Physical Chemistry C; 122 (11): 6348 - 6356. 2018. 10.1021/acs.jpcc.8b01567.

    Elucidating the underlying principles behind band gap engineering is paramount for the successful implementation of semiconductors in photonic and optoelectronic devices. Recently it has been shown that the band gap of a wide and direct band gap semiconductor, such as ZnO, can be modified upon cocrystallization with amino acids, with the role of the biomolecules remaining unclear. Here, by probing and modeling the light-emitting properties of ZnO-amino acid cocrystals, we identify the amino acids' role on this band gap modulation and demonstrate their effective chirality transfer to the interband excitations in ZnO. Our 3D quantum model suggests that the strong band edge emission blue-shift in the cocrystals can be explained by a quasi-periodic distribution of amino acid potential barriers within the ZnO crystal lattice. Overall, our findings indicate that biomolecule cocrystallization can be used as a truly bio-inspired means to induce chiral quantum confinement effects in quasi-bulk semiconductors. © 2018 American Chemical Society.


  • Strongly anisotropic spin relaxation in graphene-transition metal dichalcogenide heterostructures at room temperature

    Benítez L.A., Sierra J.F., Savero Torres W., Arrighi A., Bonell F., Costache M.V., Valenzuela S.O. Nature Physics; 14 (3): 303 - 308. 2018. 10.1038/s41567-017-0019-2.

    Physics and Engineering of Nanodevices

    A large enhancement in the spin-orbit coupling of graphene has been predicted when interfacing it with semiconducting transition metal dichalcogenides. Signatures of such an enhancement have been reported, but the nature of the spin relaxation in these systems remains unknown. Here, we unambiguously demonstrate anisotropic spin dynamics in bilayer heterostructures comprising graphene and tungsten or molybdenum disulphide (WS2, MoS2). We observe that the spin lifetime varies over one order of magnitude depending on the spin orientation, being largest when the spins point out of the graphene plane. This indicates that the strong spin-valley coupling in the transition metal dichalcogenide is imprinted in the bilayer and felt by the propagating spins. These findings provide a rich platform to explore coupled spin-valley phenomena and offer novel spin manipulation strategies based on spin relaxation anisotropy in two-dimensional materials. © 2017 The Author(s).


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

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

    Theoretical and Computational Nanoscience

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


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

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

    Oxide Nanophysics | Force Probe Microscopy and Surface Nanoengineering

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


  • Supported Mn3O4 Nanosystems for Hydrogen Production through Ethanol Photoreforming

    Barreca D., Bigiani L., Monai M., Carraro G., Gasparotto A., Sada C., Martí-Sanchez S., Grau-Carbonell A., Arbiol J., Maccato C., Fornasiero P. Langmuir; 34 (15): 4568 - 4574. 2018. 10.1021/acs.langmuir.8b00642.

    Advanced Electron Nanoscopy

    Photoreforming promoted by metal oxide nanophotocatalysts is an attractive route for clean and sustainable hydrogen generation. In the present work, we propose for the first time the use of supported Mn3O4 nanosystems, both pure and functionalized with Au nanoparticles (NPs), for hydrogen generation by photoreforming. The target oxide systems, prepared by chemical vapor deposition (CVD) and decorated with gold NPs by radio frequency (RF) sputtering, were subjected to a thorough chemico-physical characterization and utilized for a proof-of-concept H2 generation in aqueous ethanolic solutions under simulated solar illumination. Pure Mn3O4 nanosystems yielded a constant hydrogen production rate of 10 mmol h-1 m-2 even for irradiation times up to 20 h. The introduction of Au NPs yielded a significant enhancement in photocatalytic activity, which decreased as a function of irradiation time. The main phenomena causing the Au-containing photocatalyst deactivation have been investigated by morphological and compositional analysis, providing important insights for the design of Mn3O4-based photocatalysts with improved performances. © 2018 American Chemical Society.


  • Synthesis and Caracterization of Mesoporous FePO4 as Positive Electrode Materials for Lithium Batteries

    Salamani A., Merrouche A., Telli L., Gómez-Romero P., Huertas Z.C. Surface Engineering and Applied Electrochemistry; 54 (1): 55 - 63. 2018. 10.3103/S106837551801012X.

    Novel Energy-Oriented Materials

    Mesoporous iron phosphates were synthesized using sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) as surfactants. The material synthesized in the presence of SDS was not applied as a positive electrode active material of a lithium battery. The results show that the obtained FePO4 has a mesoporous structure with a specific surface area of 70 m2 g−1 and a dominant pore diameter of 3 nm. Those mesoporous were characterized by different microstructural and electrochemical analyzes. Among the materials studied under different conditions, those calcined at 450°C preserve mesoporous structures and exhibit the best electrochemical performance when used as active materials of the positive electrodes of lithium batteries. Effectively, a relatively high specific capacity of 135 and 122 mAh g−1 was registered at C/20 collected experimentally by the samples synthesized in the presence of SDS and CTAB, respectively. © 2018, Allerton Press, Inc.


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

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

    Novel Energy-Oriented Materials

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


  • Template-Assisted Scalable Nanowire Networks

    Friedl M., Cerveny K., Weigele P., Tütüncüoglu G., Martí-Sánchez S., Huang C., Patlatiuk T., Potts H., Sun Z., Hill M.O., Güniat L., Kim W., Zamani M., Dubrovskii V.G., Arbiol J., Lauhon L.J., Zumbühl D.M., Fontcuberta Morral A.I. Nano Letters; 18 (4): 2666 - 2671. 2018. 10.1021/acs.nanolett.8b00554.

    Advanced Electron Nanoscopy

    Topological qubits based on Majorana Fermions have the potential to revolutionize the emerging field of quantum computing by making information processing significantly more robust to decoherence. Nanowires are a promising medium for hosting these kinds of qubits, though branched nanowires are needed to perform qubit manipulations. Here we report a gold-free templated growth of III-V nanowires by molecular beam epitaxy using an approach that enables patternable and highly regular branched nanowire arrays on a far greater scale than what has been reported thus far. Our approach relies on the lattice-mismatched growth of InAs on top of defect-free GaAs nanomembranes yielding laterally oriented, low-defect InAs and InGaAs nanowires whose shapes are determined by surface and strain energy minimization. By controlling nanomembrane width and growth time, we demonstrate the formation of compositionally graded nanowires with cross-sections less than 50 nm. Scaling the nanowires below 20 nm leads to the formation of homogeneous InGaAs nanowires, which exhibit phase-coherent, quasi-1D quantum transport as shown by magnetoconductance measurements. These results are an important advance toward scalable topological quantum computing. © 2018 American Chemical Society.


  • The Misfit Dislocation Core Phase in Complex Oxide Heteroepitaxy

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

    Nanomaterials Growth Division

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


  • The photothermal effect in MOFs: Covalent post-synthetic modification of MOFs mediated by UV-Vis light under solvent-free conditions

    Espín J., Garzón-Tovar L., Boix G., Imaz I., Maspoch D. Chemical Communications; 54 (33): 4184 - 4187. 2018. 10.1039/c8cc01593g.

    Supramolecular NanoChemistry and Materials

    Here, we report the covalent post-synthetic modification (CPSM) of MOFs using the photothermal effect. Specifically, we subjected mixtures of a photothermally active MOF and another reagent to irradiation with a UV-Vis lamp. This caused the MOF to heat up, which in turn caused the other reagent to melt and subsequently react with the functional groups on the walls of the MOF pores. We have exploited this dual function of MOFs as both heater and host for CPSMs to achieve rapid formation of amides from the reaction of representative MOFs (UiO-66-NH2 or MIL-101-NH2-(Al)) with anhydrides under solvent-free conditions. In addition, this approach enables more complex CPSMs in MOFs such as the formation of amides in UiO-66-NH2 by using an aldehyde through a cascade reaction. © 2018 The Royal Society of Chemistry.


  • Thermoelectric spin voltage in graphene

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

    Physics and Engineering of Nanodevices

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


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

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

    Advanced Electronic Materials and Devices

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


  • Towards flexible solid-state supercapacitors for smart and wearable electronics

    Dubal D.P., Chodankar N.R., Kim D.-H., Gomez-Romero P. Chemical Society Reviews; 47 (6): 2065 - 2129. 2018. 10.1039/c7cs00505a.

    Novel Energy-Oriented Materials

    Flexible solid-state supercapacitors (FSSCs) are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics. In this study, we review the state-of-the-art advancements in FSSCs to provide new insights on mechanisms, emerging electrode materials, flexible gel electrolytes and novel cell designs. The review begins with a brief introduction on the fundamental understanding of charge storage mechanisms based on the structural properties of electrode materials. The next sections briefly summarise the latest progress in flexible electrodes (i.e., freestanding and substrate-supported, including textile, paper, metal foil/wire and polymer-based substrates) and flexible gel electrolytes (i.e., aqueous, organic, ionic liquids and redox-active gels). Subsequently, a comprehensive summary of FSSC cell designs introduces some emerging electrode materials, including MXenes, metal nitrides, metal-organic frameworks (MOFs), polyoxometalates (POMs) and black phosphorus. Some potential practical applications, such as the development of piezoelectric, photo-, shape-memory, self-healing, electrochromic and integrated sensor-supercapacitors are also discussed. The final section highlights current challenges and future perspectives on research in this thriving field. © 2018 The Royal Society of Chemistry.


  • Triphenyl Phosphite as the Phosphorus Source for the Scalable and Cost-Effective Production of Transition Metal Phosphides

    Liu J., Meyns M., Zhang T., Arbiol J., Cabot A., Shavel A. Chemistry of Materials; 30 (5): 1799 - 1807. 2018. 10.1021/acs.chemmater.8b00290.

    Advanced Electron Nanoscopy

    Transition metal phosphides have great potential to optimize a number of functionalities in several energy conversion and storage applications, particularly when nanostructured or in nanoparticle form. However, the synthesis of transition metal phosphide nanoparticles and its scalability is often limited by the toxicity, air sensitivity, and high cost of the reagents used. We present here a simple, scalable, and cost-effective "heating up" procedure to produce metal phosphides using inexpensive, low-toxicity, and air-stable triphenyl phosphite as source of phosphorus and chlorides as metal precursors. This procedure allows the synthesis of a variety of phosphide nanoparticles, including phosphides of Ni, Co, and Cu. The use of carbonyl metal precursors further allowed the synthesis of Fe2P and MoP nanoparticles. The fact that minor modifications in the experimental parameters allowed producing nanoparticles with different compositions and even to tune their size and shape shows the high potential and versatility of the triphenyl phosphite precursor and the presented method. We also detail here a methodology to displace organic ligands from the surface of phosphide nanoparticles, which is a key step toward their application in energy conversion and storage systems. © 2018 American Chemical Society.


  • Tunable Magnetism in Nanoporous CuNi Alloys by Reversible Voltage-Driven Element-Selective Redox Processes

    Quintana A., Menéndez E., Isarain-Chávez E., Fornell J., Solsona P., Fauth F., Baró M.D., Nogués J., Pellicer E., Sort J. Small; 14 (21, 1704396) 2018. 10.1002/smll.201704396.

    Magnetic Nanostructures

    Voltage-driven manipulation of magnetism in electrodeposited 200 nm thick nanoporous single-phase solid solution Cu20Ni80 (at%) alloy films (with sub 10 nm pore size) is accomplished by controlled reduction-oxidation (i.e., redox) processes in a protic solvent, namely 1 m NaOH aqueous solution. Owing to the selectivity of the electrochemical processes, the oxidation of the CuNi film mainly occurs on the Cu counterpart of the solid solution, resulting in a Ni-enriched alloy. As a consequence, the magnetic moment at saturation significantly increases (up to 33% enhancement with respect to the as-prepared sample), while only slight changes in coercivity are observed. Conversely, the reduction process brings Cu back to its metallic state and, remarkably, it becomes alloyed to Ni again. The reported phenomenon is fully reversible, thus allowing for the precise adjustment of the magnetic properties of this system through the sign and amplitude of the applied voltage. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


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

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

    Advanced Electron Nanoscopy

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


  • Ultrathin Hierarchical Porous Carbon Nanosheets for High-Performance Supercapacitors and Redox Electrolyte Energy Storage

    Jayaramulu K., Dubal D.P., Nagar B., Ranc V., Tomanec O., Petr M., Datta K.K.R., Zboril R., Gómez-Romero P., Fischer R.A. Advanced Materials; 30 (15, 1705789) 2018. 10.1002/adma.201705789.

    Novel Energy-Oriented Materials

    The design of advanced high-energy-density supercapacitors requires the design of unique materials that combine hierarchical nanoporous structures with high surface area to facilitate ion transport and excellent electrolyte permeability. Here, shape-controlled 2D nanoporous carbon sheets (NPSs) with graphitic wall structure through the pyrolysis of metal–organic frameworks (MOFs) are developed. As a proof-of-concept application, the obtained NPSs are used as the electrode material for a supercapacitor. The carbon-sheet-based symmetric cell shows an ultrahigh Brunauer–Emmett–Teller (BET)-area-normalized capacitance of 21.4 µF cm−2 (233 F g−1), exceeding other carbon-based supercapacitors. The addition of potassium iodide as redox-active species in a sulfuric acid (supporting electrolyte) leads to the ground-breaking enhancement in the energy density up to 90 Wh kg−1, which is higher than commercial aqueous rechargeable batteries, maintaining its superior power density. Thus, the new material provides a double profits strategy such as battery-level energy and capacitor-level power density. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • Uniformly coated highly porous graphene/MnO2 foams for flexible asymmetric supercapacitors

    Drieschner S., Seckendorff M.V., Corro E.D., Wohlketzetter J., Blaschke B.M., Stutzmann M., Garrido J.A. Nanotechnology; 29 (22, 225402) 2018. 10.1088/1361-6528/aab4c2.

    Advanced Electronic Materials and Devices

    Supercapacitors are called to play a prominent role in the newly emerging markets of electric vehicles, flexible displays and sensors, and wearable electronics. In order to compete with current battery technology, supercapacitors have to be designed with highly conductive current collectors exhibiting high surface area per unit volume and uniformly coated with pseudocapacitive materials, which is crucial to boost the energy density while maintaining a high power density. Here, we present a versatile technique to prepare thickness-controlled thin-film micro graphene foams (μGFs) with pores in the lower micrometer range grown by chemical vapor deposition which can be used as highly conductive current collectors in flexible supercapacitors. To fabricate the μGF, we use porous metallic catalytic substrates consisting of nickel/copper alloy synthesized on nickel foil by electrodeposition in an electrolytic solution. Changing the duration of the electrodeposition allows the control of the thickness of the metal foam, and thus of the μGF, ranging from a few micrometers to the millimeter scale. The resulting μGF with a thickness and pores in the micrometer regime exhibits high structural quality which leads to a very low intrinsic resistance of the devices. Transferred onto flexible substrates, we demonstrate a uniform coating of the μGFs with manganese oxide, a pseudocapacitively active material. Considering the porous structure and the thickness of the μGFs, square wave potential pulses are used to ensure uniform coverage by the oxide material boosting the volumetric and areal capacitance to 14 F cm-3 and 0.16 F cm-2. The μGF with a thickness and pores in the micrometer regime in combination with a coating technique tuned to the porosity of the μGF is of great relevance for the development of supercapacitors based on state-of-the-art graphene foams. © 2018 IOP Publishing Ltd.


  • Unravelling the Elusive Antiferromagnetic Order in Wurtzite and Zinc Blende CoO Polymorph Nanoparticles

    Roca A.G., Golosovsky I.V., Winkler E., López-Ortega A., Estrader M., Zysler R.D., Baró M.D., Nogués J. Small; 14 (15, 1703963) 2018. 10.1002/smll.201703963.

    Magnetic Nanostructures

    Although cubic rock salt-CoO has been extensively studied, the magnetic properties of the main nanoscale CoO polymorphs (hexagonal wurtzite and cubic zinc blende structures) are rather poorly understood. Here, a detailed magnetic and neutron diffraction study on zinc blende and wurtzite CoO nanoparticles is presented. The zinc blende-CoO phase is antiferromagnetic with a 3rd type structure in a face-centered cubic lattice and a Néel temperature of TN (zinc-blende) ≈225 K. Wurtzite-CoO also presents an antiferromagnetic order, TN (wurtzite) ≈109 K, although much more complex, with a 2nd type order along the c-axis but an incommensurate order along the y-axis. Importantly, the overall magnetic properties are overwhelmed by the uncompensated spins, which confer the system a ferromagnetic-like behavior even at room temperature. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • Unveiling BiVO4 nanorods as a novel anode material for high performance lithium ion capacitors: Beyond intercalation strategies

    Dubal D.P., Jayaramulu K., Zboril R., Fischer R.A., Gomez-Romero P. Journal of Materials Chemistry A; 6 (14): 6096 - 6106. 2018. 10.1039/c8ta00549d.

    Novel Energy-Oriented Materials

    Energy storage is increasingly demanded in many new niches of applications from wearables to unmanned autonomous vehicles. However, current energy storage systems are unable to fulfill the power requirements (high energy at high power) needed for these novel applications. Recently, Li-ion capacitors (LICs) have been spotted as hybrid devices with the potential to display high energy and high power. Nevertheless, it is still a great challenge to achieve high performance LICs due to the unmatched kinetic properties and capacity between anode and cathode materials. Herein, we are presenting our first seminal report on the use of BiVO4 nanorods as a new anode material for LICs coupled with a partially reduced graphene oxide (PRGO) cathode. The BiVO4 nanorods show an excellent reversible capacity of 877 mA h g-1 (ultrahigh volumetric capacity of 4560 mA h cm-3) at 1.1 A g-1 with a great capacity retention (in half-cell design), which is the highest value reported so far for metal vanadates. Later on, a LIC was constructed with BiVO4 as the anode and PRGO as the cathode electrode, delivering a high energy density of 152 W h kg-1 and a maximum power density of 9.6 kW kg-1 compared to that for hard carbon and intercalation (such as Li4Ti5O12 and Li3VO4) based anode materials. Additionally, the BiVO4//PRGO LIC exhibits a good cyclability of 81% over 6000 cycles. Thus, this investigation opens up new opportunities to develop different LIC systems. © 2018 The Royal Society of Chemistry.


  • Wide and ultra-wide bandgap oxides: Where paradigm-shift photovoltaics meets transparent power electronics

    Pérez-Tomás A., Chikoidze E., Jennings M.R., Russell S.A.O., Teherani F.H., Bove P., Sandana E.V., Rogers D.J. Proceedings of SPIE - The International Society for Optical Engineering; 10533 ( 105331Q) 2018. 10.1117/12.2302576.

    Oxide Nanophysics

    Oxides represent the largest family of wide bandgap (WBG) semiconductors and also offer a huge potential range of complementary magnetic and electronic properties, such as ferromagnetism, ferroelectricity, antiferroelectricity and high-temperature superconductivity. Here, we review our integration of WBG and ultra WBG semiconductor oxides into different solar cells architectures where they have the role of transparent conductive electrodes and/or barriers bringing unique functionalities into the structure such above bandgap voltages or switchable interfaces. We also give an overview of the state-of-the-art and perspectives for the emerging semiconductor β- Ga2O3, which is widely forecast to herald the next generation of power electronic converters because of the combination of an UWBG with the capacity to conduct electricity. This opens unprecedented possibilities for the monolithic integration in solar cells of both self-powered logic and power electronics functionalities. Therefore, WBG and UWBG oxides have enormous promise to become key enabling technologies for the zero emissions smart integration of the internet of things. © Copyright 2018 SPIE.