Suchergebnisse

Antimonene, a novel group 15 two-dimensional material, is attracting great attention due to its outstanding physical and chemical properties. Despite its thermodynamic stability, the pronounced covalent character of the interlayer interactions imposes severe limitations on its exfoliation into mono- and few-layer. Here, we develop a systematic study of liquid phase exfoliation (LPE) with the aim to optimize antimonene production in terms of concentration and dimensional anisotropy, investigating the most relevant experimental factors affecting the exfoliation: pre-processing of pristine antimony, solvent selection based on Hansen solubility parameters and ultrasound conditions. Moreover, exhaustive characterization by means of turbidimetry, XRD, Raman spectroscopy, XPS, AFM, SEM, XEDS and TEM has been carried out. Indeed, we achieved concentration values of ca. 0.368 g L−1 (∼yield of 37 wt%), up to ∼30 times higher compared to the highest value so far reported, with ca. 50% of the nanolayers with heights between 2 and 10 nm and lateral dimensions in the 40–300 nm range. Furthermore, it has been demonstrated that the yield of the process can be enhanced up to ∼90 wt% by recycling the sediment to perform a maximum of 7 cycles. Moreover, we have illustrated the usefulness of this approach by characterizing the electrochemical behaviour of antimonene as a catalyst for the hydrogen evolution reaction (HER). This study provides important insights into the LPE and electrochemical properties of antimonene, allowing its large-scale production and paving the way for its application in fields of utmost importance such as energy storage and conversion or catalysis ; The work has been supported by the European Union (ERC-2018-StG 804110-2D-PnictoChem to G. A.) and the Spanish MICINN (MAT2016-77608-C3-1-P and PCI2018-093081) and MINECO (Structures of Excellence María de Maeztu MDM-2015-0538 and FIS2017-82415-R). G. A. acknowledges support from the Generalitat Valenciana (CIDEGENT/2018/001) and the Deutsche Forschungsgemeinschaft (DFG; FLAG-ERA AB694/2-1). R. S.-G. acknowledges the Spanish MINECO for an FPU fellowship. J. J. P. and W. S. P. acknowledge financial support from the Spanish MINECO through Grant FIS2016-80434-P, the Fundación Ramón Areces, and the European Union Seventh Framework Programme under FLAG-ERA agreement No. 604391. W. S. P. was funded by the CNPq Fellowship programme (Pós-doutorado júnior) under grant 405107/2017-0 and acknowledges the computer resources and assistance provided by the Centro de Computación Científica of the Universidad Autónoma de Madrid and the RES

PUBLISHED ; Export Date: 15 September 2016 ; Here we demonstrate that liquid phase exfoliation can be used to convert layered crystals of nickel hydroxide into Ni(OH)2 nanosheets in relatively large quantities and without the need for ion intercalation. While other procedures require harsh synthesis conditions and multiple reaction steps, this method involves ultrasonication of commercially available powders in aqueous surfactant solutions and so is relatively mild and potentially scalable. Such mild exfoliation is possible because the surface energy of Ni(OH)2, as measured by inverse gas chromatography, is relatively low at ?70 mJ m?2, similar to other layered materials. TEM, AFM, XPS and Raman spectroscopy show the exfoliated nanosheets to be relatively thin (mean ?10 monolayers thick) and of good quality. Size selection by liquid cascade centrifugation allowed the production of samples with mean nanosheet lengths ranging from 55 to 195 nm. Optical measurements on dispersions showed the optical absorption coefficient spectra to be relatively invariant with nanosheet size while the scattering coefficient spectra varied strongly with size. The resultant size-dependence allows the extinction spectra to be used to estimate nanosheet size as well as concentration. We used the exfoliated nanosheets to prepare thin film electrodes for use in supercapacitors and as oxygen evolution catalysts. While the resultant capacitance was reasonably high at ?1200 F cm?3 (20 mV s?1), the catalytic performance was exceptional with currents of 10 mA cm?2 observed at overpotentials as low as 297 mV, close to the state of the art. ; This work was primarily funded by Science Foundation Ireland through the PI program (11/PI/1087). The research leading to these results has also received funding from the European Union Seventh Framework Program under grant agreement no. 604391 Graphene Flagship, the European Research Council (SEMANTICS) and the Science Foundation Ireland (SFI) funded centre AMBER (SFI/12/RC/2278)

We acknowledge funding from Science Foundation Ireland via the AMBER research centre (SFI/12/RC/2278) and a PI award (11/PI/1087). We are grateful for financial support from the European research Council (SEMANTICS) and the European Union Seventh Framework Programme under grant agreements n?604391 and n?696656 Graphene Flagship.

2D materials have opened a new field in materials science with outstanding scientific and technological impact. A largely explored route for the preparation of 2D materials is the exfoliation of layered crystals with weak forces between their layers. However, its application to covalent crystals remains elusive. Herein, a further step is taken by introducing the exfoliation of germanium, a narrow-bandgap semiconductor presenting a 3D diamond-like structure with strong covalent bonds. Pure α-germanium is exfoliated following a simple one-step procedure assisted by wet ball-milling, allowing gram-scale fabrication of high-quality layers with large lateral dimensions and nanometer thicknesses. The generated flakes are thoroughly characterized by different techniques, giving evidence that the new 2D material exhibits bandgaps that depend on both the crystallographic direction and the number of layers. Besides potential technological applications, this work is also of interest for the search of 2D materials with new properties ; The authors acknowledge the financial support from the Spanish Ministry of Science and Innovation, through the "María de Maeztu" Programme for Units of Excellence in R&D (CEX2018-000805-M and CEX2019-000919-M) and MINECO-FEDER projects PID2019-111742GB-C31, PID2019-111742GB-C32, PCI2018-093081, PID2019-109539GB-C43, MAT2015-666888-C3-3R, MICINN projects FIS2017-82415-R, RTI2018- 097895-B-C43 and PID2019-111742GA-I00, the Comunidad Autónoma de Madrid through S2018/NMT-4321 (NanomagCOST-CM), the Generalitat Valenciana (CIDEGENT/2018/001 grant and iDiFEDER/2018/061 co-financed by FEDER) and the Deutsche Forschungsgemeinschaft (DFG, FLAG-ERA AB694/2-1), the European Union Seventh Framework Programme under Grant agreement No. 604391 Graphene Flagship. The authors thank the European Research Council (ERC Starting Grant 2D-PnictoChem 804110 to G.A.). W.S.P. acknowledges the computer resources and assistance provided by the Centro de Computación Científica of the Universidad Autónoma de Madrid and the computer resources at MareNostrum and technical support provided by Barcelona Supercomputing Center (FI-2019-2-0007)

Development of novel 2D materials with singular and thrilling properties has aroused large interest due to the novel unexpected applications that can be derived from there. In this sense, coordination polymers (CPs) have appeared as matching candidates thanks to their rational chemical design and the added-value properties given by the presence of metal ions. This is the case of switchable spin-crossover systems that have been proposed as excellent candidates for data storage or sensing, among others. Here we report the delamination of crystals of the 2D spin-crossover (SCO) {[Fe(L1)2](ClO4)2}∝ (1) CP by liquid-phase exfoliation (LPE) in water. The application of this top-down technique results in the formation of flakes with controlled thicknesses, down to 1–2 nm thick (mostly mono- and bilayer), that retain the chemical composition and SCO interconversion of the bulk material. Moreover, these flakes can be handled as stable colloidal dispersions for many days. This allows for a controlled transfer to solid substrates and the formation of thermochromic polymeric films as a proof-of-concept of device. These first results will definitely open new venues and opportunities for the investigation and future integration of these original switchable 2D materials in devices. ; This work was supported by projects MAT2015-70615-R, CTQ2015-65439-R, and FIS2015-64886-C5-3-P from the Spanish Government funds and by European Regional Development Fund (ERDF). Funded by the CERCA Program/Generalitat de Catalunya. ICN2 is supported by the Severo Ochoa program from Spanish Ministry of Economy, Industry and Competitiveness (MINECO, Grant SEV-2013-0295). Funded by the project 2014-SGR-301 (Generalitat de Catalunya). This work was supported by the Fonds National de la Recherche Scientifique-FNRS (PDR T.0102.15) and COST actions CM1305 and CA15128. M. M. D is a chargé de recherches from the F.R.S.-FNRS. S.S.-G. acknowledges the support from MINECO BES-2015-071492 grant. R.R. and P.O. acknowledge support from EU H2020-EINFRA-5-2015 MaX Center of Excellence (Grant 676598). ; Peer reviewed

Hybrids between biopolymeric materials and low-cost conductive carbon-based materials are interesting materials for applications in electronics, potentially reducing the need for materials that generate environmentally harmful electronic waste. Herein we investigate a scalable ball-milling method to form graphene nanoplatelets (GNPs) by milling graphite flakes with aqueous dispersions of proteins or protein nanofibrils (PNFs). Aqueous GNP dispersions with high concentrations (up to 3.2 mg mL(-1)) are obtained under appropriate conditions. The PNFs/proteins help to exfoliate graphite and stabilize the resulting GNP dispersions by electrostatic repulsion. PNFs are prepared from hen egg white lysozyme (HEWL) and beta-lactoglobulin (BLG). The GNP dispersions can be processed into free-standing films having an electrical conductivity of up to 110 S m(-1). Alternatively, the GNP dispersions can be drop-cast on PET substrates, resulting in mechanically flexible films having an electrical conductivity of up to 65 S m(-1). The drop-cast films are investigated regarding their thermoelectric properties, having Seebeck coefficients of about 50 mu V K-1. By annealing drop-cast films and thus carbonizing residual PNFs, an increase of electrical conductivity, coupled with a modest decrease in Seebeck coefficient, is obtained resulting in materials displaying power factors of up to 4.6 mu W m(-1) K-2. ; Funding Agencies|China Scholarship CouncilChina Scholarship Council; FormasSwedish Research Council Formas [2019-00679]; COST (European Cooperation in Science and Technology)European Cooperation in Science and Technology (COST) [CA18112]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Energy AgencySwedish Energy Agency [46519-1]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

Abstract
The existence of a phase transition between two distinct liquid phases in single-component network-forming liquids (e.g. water, silica, silicon) has elicited considerable scientific interest. The challenge, both for experiments and simulations, is that the liquid–liquid phase transition (LLPT) occurs under deeply supercooled conditions, where crystallization occurs very rapidly. Thus, early evidence from numerical equation of state studies was challenged with the argument that slow spontaneous crystallization had been misinterpreted as evidence of a second liquid state. Rigorous free-energy calculations have subsequently confirmed the existence of a LLPT in some models of water, and exciting new experimental evidence has since supported these computational results. Similar results have so far not been found for silicon. Here, we present results from free-energy calculations performed for silicon modeled with the classical, empirical Stillinger-Weber–potential. Through a careful study employing state-of-the-art constrained simulation protocols and numerous checks for thermodynamic consistency, we find that there are two distinct metastable liquid states and a phase transition. Our results resolve a long-standing debate concerning the existence of a liquid–liquid transition in supercooled liquid silicon and address key questions regarding the nature of the phase transition and the associated critical point.

This review focuses on the combination of elemental detection techniques with liquid-phase microextraction (LPME), namely, single drop microextraction, hollow fiber based liquid-phase microextraction, dispersive liquid-liquid microextraction, and related techniques. General features of different microextraction procedures, historical overview and automation of LPME are described and compared, along with examples of new developments and applications presented to demonstrate its potential for trace and ultra-trace metal analysis. Furthermore, potential applications and an outlook on the combination of LPME and elemental detection techniques for inorganic analysis are presented. ; The authors would like to thank the Spanish Ministry of Economy and Competitiveness and European Union (FEDER funds) (project n. CTQ2016-79991-R) for the financial support. P. Baile also thanks Ministry of Education, Culture and Sports for her FPU grant (FPU14/04589).

6 pags., 5 figs. ; In phase-change memory devices, a material is cycled between glassy and crystalline states. The highly temperature-dependent kinetics of its crystallization process enables application in memory technology, but the transition has not been resolved on an atomic scale. Using femtosecond x-ray diffraction and ab initio computer simulations, we determined the time-dependent pair-correlation function of phase-change materials throughout the melt-quenching and crystallization process. We found a liquid–liquid phase transition in the phase-change materials AgInSbTe and GeSb at 660 and 610 kelvin, respectively. The transition is predominantly caused by the onset of Peierls distortions, the amplitude of which correlates with an increase of the apparent activation energy of diffusivity. This reveals a relationship between atomic structure and kinetics, enabling a systematic optimization of the memory-switching kinetics. ; F.Q., A.K., M.N., and K.S.T. gratefully acknowledge financial support from the German Research Council through the Collaborative Research Center SFB 1242 project 278162697 ("Non-Equilibrium Dynamics of Condensed Matter in the Time Domain"), project C01 ("Structural Dynamics in Impulsively Excited Nanostructures"), and individual grant So408/9-1, as well as the European Union (7th Framework Programme, grant no. 280555 GO FAST). M.J.S., R.M., and M.W. acknowledge financial support from the German Research Council through the Collaborative Research Center SFB 917 ("Nanoswitches") and individual grant Ma-5339/2-1. M.J.S., I.R., and R.M. also acknowledge the computational resources granted by JARA-HPC from RWTH Aachen University under project nos. JARA0150 and JARA0183. M.T., A.M.L., and D.A.R. were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, through the Division of Materials Sciences and Engineering under contract no. DE-AC02-76SF00515. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. J.L. acknowledges support from the Swedish Research Council. J.S. acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities through research grant UDiSON (TEC2017-82464-R). P.Z. gratefully acknowledges funding by the Humboldt Foundation

Large blue rectangular crystals of the 2D layered coordination polymer 1 have been obtained. The interest for this complex is two-fold. First, complex 1 is made of 2D layers packing along the (0–11) direction favored by the presence of lattice and coordinated water molecules. And second, nanostructures that could be derived by delamination are potentially suitable for catalytic purposes. Therefore it represents an excellent example to study the role of interlayer solvent molecules on the ultrasound-assisted delamination of functionally-active 2D metal-organic frameworks in water, a field of growing interest. With this aim, ultrasound-assisted delamination of the crystals was optimized with time, leading to stable nanosheet colloidal water suspensions with very homogeneous dimensions. Alternative bottom-up synthesis of related nanocrystals under ultrasound sonication yielded similar shaped crystals with much higher size dispersions. Finally, experimental results evidence that the nanostructures have higher catalytic activities in comparison to their bulk counterparts, due to larger metallic center exposition. These outcomes confirm that the combination of liquid phase exfoliation and a suitable synthetic design of 2D coordination polymers represents a very fruitful approach for the synthesis of functional nanosheets with an enhancement of catalytic active sites, and in general, with boosted functional properties. ; This work was supported by grant RTI2018-098027-B-C21 from the Spanish Government funds and by the European Regional Development Fund (ERDF). The ICN2 is funded by the CERCA programme/Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa Centres of Excellence programme, funded by the Spanish Research Agency (AEI, grant no. SEV-2017-0706). Noemí Contreras Pereda's project that gave rise to these results received the support of a fellowship from "laCaixa" Foundation (ID 100010434). The fellowship code is LCF/BQ/ES17/11600012. Renhao Dong acknowledgements the financial support from ERC Starting Grant (FC2DMOF, No. 852909) and DFG project (SPP 1928, COORNETs). ; Peer reviewed

AbstractMembraneless organelles (MLOs) are likely assembled via liquid–liquid phase separation (LLPS). The liquid‐like MLOs afford multifold peculiarities including high dynamics, reversibility and responsiveness. It is common to see fast, drastic, and reversible formation and dissolution events of MLOs, as well as transition into more stable glassy or gel‐like states, which suggests a metastable assembly state. Moreover, the alteration of metastability of LLPS is linked with cellular pathology. Here, we review the "metastability" related to MLOs driven by liquid phase separation, from multifaceted regards including energy state, molecular interactions, molecular structure, phase transition, as well as the associations with diseases. This review can help to advance the insight into properties and pathogenesis associated with LLPS of biological matter.

Description d'une méthode expérimentale permettant de ramener à une commune mesure les effets chimiques des rayons alpha en phase liquide et en phase gazeuse dans le cas de polymérisation du chlorure de vinyle. Le nombre de chaînes réactionnelles initiées est sensiblement le même.

PUBLISHED ; Export Date: 5 August 2015 ; Here we demonstrate the production of large quantities of gallium sulfide (GaS) nanosheets by liquid exfoliation of layered GaS powder. The exfoliation was achieved by sonication of the powder in suitable solvents. The variation of dispersed concentration with solvent was consistent with classical solution thermodynamics and showed successful solvents to be those with Hildebrand solubility parameters close to 21.5 MPa1/2. In this way, nanosheets could be produced at concentrations of up to ~0.2 mg/ml with lateral sizes and thicknesses of 50-1000 nm and 3-80 layers, respectively. The nanosheets appeared to be relatively defect free although oxygen was observed in the vicinity of the edges. Using controlled centrifugation techniques, it was possible to prepare dispersions containing size-selected nanosheets. Spectroscopic measurements showed the optical properties of the dispersions to vary strongly with nanosheet size, allowing the elucidation of spectroscopic metrics for in-situ estimation of nanosheet size and thickness. These techniques allow the production of nanosheets with controlled sizes which will be important for certain applications. To demonstrate this, we prepared films of GaS nanosheets of three different sizes for use as hydrogen evolution electrocatalysts. We found a clear correlation between performance and size showing small nanosheets to be more effective. This is consistent with the catalytically active sites residing on the nanosheet edges. ; The research leading to these results has received funding from the European Union Seventh Framework Programme under grant agreement n°604391 Graphene Flagship. We have also received support from the Science Foundation Ireland (SFI) funded centre AMBER (SFI/12/RC/2278). In addition, JNC acknowledges the European Research Council (SEMANTICS) and SFI (11/PI/1087) for financial support. CB acknowledges the German research foundation DFG (BA 4856/1-1). HCN, EMcG, AS-A and VN acknowledge ERC 2DNanoCaps, SFI PIYRA and FP7 MoWSeS. GSD, NCB and SW acknowledge SFI for PI_10/IN.1/I3030. NMcE acknowledges SFI (14/TIDA/2329). STEM experiments were performed at SuperSTEM, the EPSRC UK national facility for aberration-corrected STEM.