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PubMed ID: 29369611, Single-atom B or N substitutional doping in single-layer suspended graphene, realized by low-energy ion implantation, is shown to induce a dampening or enhancement of the characteristic interband ? plasmon of graphene through a high-resolution electron energy loss spectroscopy study using scanning transmission electron microscopy. A relative 16% decrease or 20% increase in the ? plasmon quality factor is attributed to the presence of a single substitutional B or N atom dopant, respectively. This modification is in both cases shown to be relatively localized, with data suggesting the plasmonic response tailoring can no longer be detected within experimental uncertainties beyond a distance of approximately 1 nm from the dopant. Ab initio calculations confirm the trends observed experimentally. Our results directly confirm the possibility of tailoring the plasmonic properties of graphene in the ultraviolet waveband at the atomic scale, a crucial step in the quest for utilizing graphene's properties toward the development of plasmonic and optoelectronic devices operating at ultraviolet frequencies. © 2018 American Chemical Society., Engineering and Physical Sciences Research Council Engineering and Physical Sciences Research Council Danmarks Grundforskningsfond, SuperSTEM is the UK Engineering and Physical Sciences Research Council (EPSRC) National Research Facility for Advanced Electron Microscopy. T.P.H. gratefully acknowledges the EPSRC Doctoral Prize Fellowship which funded this research in part. F.S.H. and Q.M.R. thank Dr J. C. Idrobo for useful discussions. The Center for Nanostructured Graphene is sponsored by the Danish National Research Foundation, Project DNRF103.

Gate-controlled supercurrent (GCS) in superconducting nanobridges has recently attracted attention as a means to create superconducting switches. Despite the clear advantages for applications, the microscopic mechanism of this effect is still under debate. In this work, we realize GCS for the first time in a highly crystalline superconductor epitaxially grown on an InAs nanowire. We show that the supercurrent in the epitaxial Al layer can be switched to the normal state by applying similar to +/- 23 V on a bottom gate insulated from the nanowire by a crystalline hBN layer. Our extensive study of the temperature and magnetic field dependencies suggests that the electric field is unlikely to be the origin of GCS in our device. Though hot electron injection alone cannot explain our experimental findings, a very recent non-equilibrium phonons based picture is compatible with most of our results.

The moisture uptake of wood is influenced by accessible hydroxyl groups acting as sorption sites and the water-available cell wall space. To what extent do these mechanisms control the moisture uptake in wood need to be addressed. For this purpose, we modified sorption site density and cell wall space by wood treatments with acetic anhydride or formaldehyde and investigated their effects on moisture uptake. Chemical changes at the cell wall level caused by the treatments were first determined by confocal Raman imaging. Following this, the deuterium exchange method was used to gravimetrically measure the hydroxyl accessibility, while the moisture uptake and the consequent swelling of the wood were determined by dynamic measurements of mass and dimensions within the hygroscopic range. The results showed that the effectiveness in reducing the moisture content of untreated wood across the hygroscopic range differed between the anhydride and formaldehyde-modified wood. We also observed a poor correlation of accessible hydroxyl concentration in formaldehyde-modified wood with weight percentage gain and water uptake. Moreover, the dynamic mass and dimensions analysis indicated that the reduction in swelling in formalized wood was affected by an unidentified mechanism in addition to reduced moisture content.

* Ack:ssa mutta ei silti mukaan raportointiin | openaire: EC/H2020/788489/EU//BioELCell Technical lignins are widely available as side streams from pulping and biorefining processes. The aromatic structure of such lignins could be exploited in coating formulations to provide antioxidant or UV-blocking functionalities to packaging films. In this study, six technical lignins sourced from different plant species by given isolation/modification methods were compared for their composition, molar mass, and functional groups. The lignins were then used to prepare thin spin-coated films from aqueous ammonia media. All the lignins formed ultrathin (

Vitrimer materials, which are permanently cross-linked but reshapable polymers, are a class of materials of growing interest due to their potential in recycling and sustainable development. More precisely, vitrimers derived from commodity polymers could have a drastic impact on plastic consumption in the upcoming years. Here, the development of a polystyrene-based vitrimer harnessing the recently discovered hemiacetal ester exchange reaction of carboxylic acid is presented. 1,4-Cyclohexanedimethanol divinyl ether was reacted with 4-vinylbenzoic acid (VBA) to form a divinyl species containing two hemiacetal ester functions. This dimer was then copolymerized with styrene, butyl acrylate, and VBA to form a cross-linked material presenting pendent acid groups. This material exhibited three distinct behaviors at different temperature regimes: below 80 °C, despite the exchange reactions able to occur at this temperature, the cross-linked material behaved as a frozen material due to the hydrogen bonding formed by the carboxylic acid pendent groups. Between 80 and 130 °C, the vitrimer behavior was demonstrated by rheological creep experiments. At higher temperatures, the dissociation of the hemiacetal ester groups led to the loss of the covalent cross-linking.

Liquid–liquid phase separation of biomacromolecules is crucial in various inter- and extracellular biological functions. This includes formation of condensates to control, e.g., biochemical reactions and structural assembly. The same phenomenon is also found to be critically important in protein-based high-performance biological materials. Here, we use a well-characterized model triblock protein system to demonstrate the molecular level formation mechanism and structure of its condensate. Large-scale molecular modeling supported by analytical ultracentrifuge characterization combined with our earlier high magnification precision cryo-SEM microscopy imaging leads to deducing that the condensate has a bicontinuous network structure. The bicontinuous network rises from the proteins having a combination of sites with stronger mutual attraction and multiple weakly attractive regions connected by flexible, multiconfigurational linker regions. These attractive sites and regions behave as stickers of varying adhesionstrength. For the examined model triblock protein construct, the β-sheet-rich end units are the stronger stickers, while additional weaker stickers, contributing to the condensation affinity, rise from spring-like connections in the flexible middle region of the protein. The combination of stronger and weaker sticker-like connections and the flexible regions between the stickers result in a versatile, liquid-like, self-healing structure. This structure also explains the high flexibility, easy deformability, and diffusion of the proteins, decreasing only 10–100 times in the bicontinuous network formed in the condensate phase in comparison to dilute protein solution. The here demonstrated structure and condensation mechanism of a model triblock protein construct via a combination of the stronger binding regions and the weaker, flexible sacrificial-bond-like network as well as its generalizability via polymer sticker models provide means to not only understand intracellular organization, regulation, and cellular function but also to identify direct control factors for and to enable engineering improved protein and polymer constructs to enhance control of advanced fiber materials, smart liquid biointerfaces, or self-healing matrices for pharmaceutics or bioengineering materials.

International audience; Metal fluorides with 3D open structures, pyrochlore (pyr) or hexagonal tungsten bronze (HTB), are promising materials as positive electrodes for rechargeable batteries or catalysts. Herein, we have developed a two-step synthesis procedure to obtain new anhydrous mixed-metal-cation fluorides crystallizing in the pyrochlore structure. The first step consists of preparing mixed-metal ammonium fluorides (NH4)M2+Fe3+F6 (M = Mn, Fe, Co Ni) using different synthesis strategies. For M = Mn, three allotropic varieties of (NH4)Mn2+Fe3+F6 are obtained; two phases adopt the expected pyrochlore network with either the cubic Fm3̅m or the orthorhombic Pnma space group, and the third phase exhibits a 3D network with narrow pseudotriangular cavities. 57Fe Mössbauer spectrometry indicates that the crystal structures are governed by the Fe3+/Mn2+ cationic order or disorder. The second step is a topotactic oxidation of pyr-(NH4)M2+Fe3+F6 under a molecular F2 flow. To better understand the reaction mechanism, the topotactic oxidation was followed by thermogravimetry, XRD, FTIR, and Mössbauer spectrometry. The successful synthesis of the first anhydrous pyr-M3+0.5Fe0.5F3 provides a new route to prepare anhydrous mixed-metal fluorides pyrochlore with empty cavities of the open framework.

This study evaluates the techno-economic feasibility of five solar-powered concepts for the production of autotrophic microorganisms for food and feed production; the main focus is on three concepts based on hydrogen-oxidizing bacteria (HOB), which are further compared to two microalgae-related concepts. Two locations with markedly different solar conditions are considered (Finland and Morocco), in which Morocco was found to be the most economically competitive for the cultivation of microalgae in open ponds and closed systems (1.4 and 1.9 € kg–1, respectively). Biomass production by combined water electrolysis and HOB cultivation results in higher costs for all three considered concepts. Among these, the lowest production cost of 5.3 € kg–1 is associated with grid-assisted electricity use in Finland, while the highest production cost of >9.1 € kg–1 is determined for concepts using solely photovoltaics and/or photoelectrochemical technology for on-site electricity production and solar-energy conversion to H2 by water electrolysis. All assessed concepts are capital intensive. Furthermore, a sensitivity analysis suggests that the production costs of HOB biomass can be lowered down to 2.1 € kg–1 by optimization of the process parameters among which volumetric productivity, electricity strategy, and electricity costs have the highest cost-saving potentials. The study reveals that continuously available electricity and H2 supply are essential for the development of a viable HOB concept due to the capital intensity of the needed technologies. In addition, volumetric productivity is the key parameter that needs to be optimized to increase the economic competitiveness of HOB production.

openaire: EC/H2020/760876/EU//INNPAPER This paper demonstrates a high-throughput approach to fabricate nanocellulose films with multifunctional performance using conventionally existing unit operations. The approach comprises cast-coating and direct interfacial atmospheric plasma-assisted gas-phase modification along with the microscale patterning technique (nanoimprint lithography, NIL), all applied in roll-to-roll mode, to introduce organic functionalities in conjunction with structural manipulation. Our strategy results in multifunctional cellulose nanofibrils (CNF) films in which the high optical transmittance (∼90%) is retained while the haze can be adjusted (2-35%). Concomitantly, the hydrophobic/hydrophilic balance can be tuned (50-21 mJ/m2 with the water contact angle ranging from ∼20 up to ∼120°), while intrinsic hygroscopicity of CNF films is not significantly compromised. Therefore, a challenge to produce multifunctional bio-based materials with properties defined by various high-performance applications conjoined to the lack of efficient processing strategies is elucidated. Overall, economically and ecologically viable strategy, which was realized by facile and upscalable unit operations using the R2R technology, is introduced to expand the properties' spaces and thus offer a vast variety of interesting applications for CNF films.

openaire: EC/H2020/788489/EU//BioElCell Chitin nanofibrils (NCh, ∼10 nm lateral size) were produced under conditions that were less severe compared to those for other biomass-derived nanomaterials and used to formulate high internal phase Pickering emulsions (HIPPEs). Pre-emulsification followed by continuous oil feeding facilitated a "scaffold" with high elasticity, which arrested droplet mobility and coarsening, achieving edible oil-in-water emulsions with internal phase volume fraction as high as 88%. The high stabilization ability of rodlike NCh originated from the restricted coarsening, droplet breakage and coalescence upon emulsion formation. This was the result of (a) irreversible adsorption at the interface (wettability measurements by the captive bubble method) and (b) structuring in highly interconnected fibrillar networks in the continuous phase (rheology, cryo-SEM, and fluorescent microscopies). Because the surface energy of NCh can be tailored by pH (protonation of surface amino groups), emulsion formation was found to be pH-dependent.Emulsions produced at pH from 3 to 5 were most stable (at least for 3 weeks). Although at a higher pH NCh was dispersible and the three-phase contact angle indicated better interfacial wettability to the oil phase, the lower interdroplet repulsion caused coarsening at high oil loading. We further show the existence of a trade-off between NCh axial aspect and minimum NCh concentration to stabilize 88% oil-in-water HIPPEs: only 0.038 wt % (based on emulsion mass) NCh of high axial aspect was required compared to 0.064 wt % for the shorter one. The as-produced HIPPEs were easily textured by taking advantage of their elastic behavior and resilience to compositional changes. Hence, chitin-based HIPPEs were demonstrated as emulgel inks suitable for 3D printing (millimeter definition) via direct ink writing, e.g., for edible functional foods and ultralight solid foams displaying highly interconnected pores and for potential cell culturing applications.

12 pags., 8 figs., We have investigated different approaches to handling parallel-tempering Monte Carlo (PTMC) simulations in the isothermal-isobaric ensemble of molecular cluster/nanoparticle systems for predicting structural phase diagram transitions. We have implemented various methodologies that consist of treating pressure implicitly through its effect on the volume. Thus, the main problem in the simulations under nonzero pressure becomes the volume definition of the finite nonperiodic system, and we considered approaches based on the particles' coordinates. Various volume models, namely container-volume, particle-volume, average-volume, ellipsoids-volume, and convex hull-volume, were employed, and the required corrections for each of them in the Monte Carlo computations were introduced. Finally, we explored the effects of volume/pressure changes for all models on structural phase transitions of a test system, such as the small "icelike" (HO) water cluster. The temperature and pressure dependence of the cluster's heat capacity and energy-volume Pearson correlation coefficient were studied, phase diagrams were constructed using a multiple-histogram method, and attempts were made to identify phase transitions to particular cluster structures. Our results show significant differences between the employed volume models, and we discuss all pressure-induced, such as solid-solid-, solid-liquid-, and liquid-gas-like, phase transformations in the present study., This work has been supported by MINECO grants No. FIS2017-83157-P, COST Actions CM1405(MOLIM), and CA18212(MDGAS), the Ministry of Education, Youth and Sports of the Czech Republic from the National Programme of Sustainability (NPS II) project “IT4Innovations excellence in science-LQ1602” and from the Large Infrastructures for Research, Experimental Development, and Innovations project “e-Infrastructure CZ-LM2018140”. The calculations were performed on the HPC resources of the IT4Innovations National Supercomputing Center, VSB-Technical University of Ostrava (grants no. OPEN-7-48, DD-15-32, and DD-16-16), the Centro de Calculo (IFF/SGAI-CSIC), and CESGA.

International audience; Ligand-induced chirality in asymmetric CdSe/CdS core–shell nanocrystals (NCs) has been extensively applied in chiral biosensors, regioselective syntheses and assemblies, circularly polarized luminescence (CPL), and chiroptic-based devices due to their excellent physiochemical properties, such as the tunable quantum confinement effects, surface functionality, and chemical stability. Herein, we present CdSe/CdS NCs with various morphologies such as nanoflowers, tadpoles, and dot/rods (DRs) with chirality induced by surface chiral ligands. The observed circular dichroism (CD) and CPL activities are closely associated with the geometrical characteristics of the nanostructures, such as the shell thickness and the aspect ratio of the CdSe/CdS NCs. Furthermore, in situ observations of the growth of tadpoles with a single tail indicate that the CD response is mainly attributed to the CdS shell, which has a maximum tail length of ∼45 nm (approximately λ/10 of the incident light wavelength). On the other hand, the CPL activity is only related to the CdSe core, and the activity benefits from a thin CdS shell with a relatively high photoluminescence quantum yield (QY). Further theoretical models demonstrated the aspect-ratio-dependent g-factor and QY variations in these asymmetric nanostructures. These findings provide insights into not only the asymmetric synthesis of CdSe/CdS NCs, but also the rational design of CdSe/CdS nanostructures with tunable CD and CPL activities.

Understanding the phenomena at interfaces is crucial for producing efficient and stable flexible organic solar cell modules. Minimized energy barriers enable efficient charge transfer, and good adhesion allows mechanical and environmental stability and thus increased lifetime. We utilize here the inverted organic solar module stack and standard photoactive materials (a blend of poly(3-hexylthiophene) and [6,6]-phenyl C61 butyric acid methyl ester) to study the interfaces in a pilot scale large-area roll-to-roll (R2R) process. The results show that the adhesion and work function of the zinc oxide nanoparticle based electron transport layer can be controlled in the R2R process, which allows optimization of performance and lifetime. Plasma treatment of zinc oxide (ZnO) nanoparticles and encapsulation-induced oxygen trapping will increase the absolute value of the ZnO work function, resulting in energy barriers and an S-shaped IV curve. However, light soaking will decrease the zinc oxide work function close to the original value and the S-shape can be recovered, leading to power conversion efficiencies above 3%. We present also an electrical simulation, which supports the results. Finally, we study the effect of plasma treatment in more detail and show that we can effectively remove the organic ligands around the ZnO nanoparticles from the printed layer in a R2R process, resulting in increased adhesion. This postprinting plasma treatment increases the lifetime of the R2R printed modules significantly with modules retaining 80% of their efficiency for ∼3000 h in accelerated conditions. Without plasma treatment, this efficiency level is reached in less than 1000 h.

We introduce the optimization of the pulping conditions and propose different chemical recovery options for a proven biorefinery concept based on γ-valerolactone (GVL)/water fractionation. The pulping process has been optimized whereby the liquor-to-wood (L:W) ratio could be reduced to 3 L/kg without compromising the pulp properties as raw material for textile fibers production. The recovery of the pulping solvent was performed through combinations of lignin precipitation by water addition, distillation at reduced pressure, and liquid CO2 extraction. With a two-step lignin precipitation coupled with vacuum distillation, more than 90% of lignin and GVL could be recovered from the spent liquor. However, a significant part of GVL remained unrecoverable in the residue, which was a highly viscous liquid with complicated phase behavior. The recovery by lignin precipitation combined with liquid CO2 extraction could recover more than 85% GVL and 90% lignin without forming any problematic residue as in the distillation process. The remaining GVL remained in the raffinate containing a low amount of lignin and other compounds, which can be further processed to isolate the GVL and improve the recovery rate.

Asymmetric aldol addition of simple aldehydes and ketones to electrophiles is a cornerstone reaction for the synthesis of unusual sugars and chiral building blocks. We investigated D-fructose-6-phosphate aldolase from E. coli (FSA) D6X variants as catalysts for the aldol additions of linear and cyclic non-functionalized aliphatic ketones or ethanal as nucleophiles to non-phosphorylated hydroxyaldehydes. Thus, addition of propanone, cyclobutanone, cyclopentanone or ethanal to 3-hydroxypropanal or (S)- or (R)-3-hydroxybutanal catalyzed by FSA D6H and D6Q variants furnished rare deoxysugars in 8-77% isolated yields with high stereoselectivity (97:3 dr and >95% ee). © 2018 American Chemical Society., This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 635595 (CarbaZymes), the Ministerio de Economía y Competitividad (MINECO), the Fondo Europeo de Desarrollo Regional (FEDER) (grant CTQ2015-63563-R to P.C. and CTQ2015-64436-P to T.P.), COST action CM1303 Systems Biocatalysis and funding from the Auvergne council.

Surface recombination of plasma radicals is generally considered to limit film conformality during plasma-assisted atomic layer deposition (ALD). Here, we experimentally studied film penetration into high-aspect-ratio structures and demonstrated that it can give direct information on the recombination probability r of plasma radicals on the growth surface. This is shown for recombination of oxygen (O) atoms on SiO2, TiO2, Al2O3, and HfO2 where a strong material dependence has been observed. Using extended plasma exposures, films of SiO2 and TiO2 penetrated extremely deep up to an aspect ratio (AR) of âˆ900, and similar surface recombination probabilities of r = (6 ± 2) × 10-5 and (7 ± 4) × 10-5 were determined for these processes. Growth of Al2O3 and HfO2 was conformal up to depths corresponding to ARs of âˆ80 and âˆ40, with r estimated at (1-10) × 10-3 and (0.1-10) × 10-2, respectively. Such quantitative insight into surface recombination, as provided by our method, is essential for modeling radical-surface interaction and understanding for which materials and conditions conformal film growth is feasible by plasma-assisted ALD. ©

openaire: EC/H2020/721642/EU//SOLUTION | openaire: EC/H2020/676580/EU//NoMaD | openaire: EC/H2020/740233/EU//TEC1p Nanostructured materials are essential building blocks for the fabrication of new devices for energy harvesting/storage, sensing, catalysis, magnetic, and optoelectronic applications. However, because of the increase of technological needs, it is essential to identify new functional materials and improve the properties of existing ones. The objective of this Viewpoint is to examine the state of the art of atomic-scale simulative and experimental protocols aimed to the design of novel functional nanostructured materials, and to present new perspectives in the relative fields. This is the result of the debates of Symposium I "Atomic-scale design protocols towards energy, electronic, catalysis, and sensing applications", which took place within the 2018 European Materials Research Society fall meeting.

openaire: EC/H2020/788489/EU//BioELCell We study the generation and decay of aqueous foams stabilized by sodium dodecyl sulfate (SDS) in the presence of unmodified cellulose nanofibrils (CNF). Together with the rheology of aqueous suspensions containing CNF and SDS, the interfacial/colloidal interactions are determined by quartz crystal microgravimetry with dissipation monitoring, surface plasmon resonance, and isothermal titration calorimetry. The results are used to explain the properties of the air/water interface (interfacial activity and dilatational moduli determined from oscillating air bubbles) and of the bulk (steady-state flow, oscillatory shear, and capillary thinning). These properties are finally correlated to the foamability and to the foam stability. The latter was studied as a function of time by monitoring the foam volume, the liquid fraction, and the bubble size distribution. The shear-thinning effect of CNF is found to facilitate foam formation at SDS concentrations above the critical micelle concentration (cSDS ≥ cmc). Compared with foams stabilized by pure SDS, the presence of CNF enhances the viscosity and elasticity of the continuous phase as well as of the air/water interface. The CNF-containing foams have higher liquid fractions, larger initial bubble sizes, and better stability. Due to charge screening effects caused by sodium counter ions and depletion attraction caused by SDS micelles, especially at high SDS concentrations, CNF forms aggregates in the Plateau borders and nodes of the foam, thus slowing down liquid drainage and bubble growth and improving foam stability. Overall, our findings advance the understanding of the role of CNF in foam generation and stabilization.

The performance of thermoelectric materials has been improved in the past few years by a significant reduction of the thermal conductivity, but this parameter has now reached its (amorphous) limit, which makes the enlargement of the power factor (PF) critical. Here we present a new concept, based on a hybrid system formed by a porous thermoelectric solid permeated by a liquid with an inert salt dissolved (electrolyte), which can be designed to significantly enhance the PF. The concept is demonstrated in an Sb-doped SnO2 porous film permeated with different inert salts (X+(BF4)−, X+ = Li+, Na+, K+) dissolved in 3-methoxypropionitrile (3-MPN). A 61.9% average decrease in the electrical resistivity without a significant variation of the Seebeck coefficient was found in the case of 1 M LiBF4 in 3-MPN. As a result, the PF was remarkably increased 3.4 times. On the other hand, 1-butyl-3-methylimidazolium (BMI+Y–, Y– = I–, BF4–) ionic liquids were also employed as electrolytes. Using the BMII ionic liquid, the electrical resistivity showed a more significant average decrease of 82.5%; however, the absolute value of the Seebeck coefficient was reduced by 35%, finally resulting in an average enhancement of 2.4 times of the PF. The large enhancements achieved are attributed to the modification of the electrostatic environment of the porous solid by the ions in the electrolyte at the solid–liquid interface. These results establish a new strategy for the significant improvement of the PF which is not restricted to certain materials and can be potentially applied widely.

International audience; Understanding the effect of liquid viscosity in nanoconfinement is of paramount importance from both the fundamental and practical points of view. In particular, unexpected dynamic phenomena are ubiquitous in a broad range of nanofluidic applications. In this work, we used state-of-the-art high-pressure (P,V,T) calorimetry for direct observation of pressure, volume, temperature, and thermal effects during controlled intrusion/extrusion of liquids in nanoporous materials. It was discovered that the liquid extrusion pressure and the accompanying thermal effects can be controlled by changing solely the liquid viscosity. Such knowledge allowed us to propose the {nanoporous material + nonwetting liquid} system as a self-recovering nanobumper and to clarify the parameters for its optimization. Experimental results were interpreted in terms of confined classical nucleation theory as the slowdown of bubble expansion in the nanopores because of the high liquid viscosity. The present results are of practical value for designing energy storage/dissipation devices based on intrusion/extrusion cycles, as well as of fundamental importance for understanding the effect of viscosity in nanoconfined liquids.

Journal of the American Chemical Society, 139 (48), ISSN:0002-7863, ISSN:1520-5126

The crystallization kinetics of sodium dodecyl sulfate (SDS)-water micellar solutions, under linear cooling conditions, were experimentally investigated using optical microscopy, differential scanning calorimetry, and infrared spectroscopy. Cooling rates were systematically varied, from 0.1 to 50 °C min–1, encompassing environmental to near-“isothermal” temperature changes, between 22 and −5 °C, for a reference concentration of 20% SDS-H2O. The cooling rate was shown to determine the dominant crystal morphologies, with platelets and needles predominating at the lowest and highest rates, respectively. The results were rationalized in terms of isothermal crystallization data and the time–temperature cooling profile. Rates 0.1, 5.0, and 10 °C min–1 yield morphologies and kinetics analogous to those of isothermal quenches at the corresponding crystallization temperature window. Nontrivial deviations were observed for intermediate rates (0.5, 1.0 °C min–1), due to commensurate changes in temperature and crystallization mechanism, accompanied by solute depletion. The polythermal metastable zone width was estimated, and the non-isothermal nucleation described by the Nývlt equation, while the Avrami and Kissinger models described overall crystallization kinetics. Our measurements quantify the impact of temperature gradients in the crystallization of ubiquitous SDS micellar solutions, for a range of practically relevant profiles incurred during manufacturing and storage.

8 págs.; 9 figs., We describe the conditions for optimal formation of laser-induced periodic surface structures (LIPSS) over poly(3-hexylthiophene) (P3HT) spin-coated films. Optimal LIPSS on P3HT are observed within a particular range of thicknesses and laser fluences. These conditions can be translated to the photovoltaic blend formed by the 1:1 mixture of P3HT and [6,6]-phenyl C-butyric acid methyl ester (PCBM) when deposited on an indium tin oxide (ITO) electrode coated with (poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). Solar cells formed by using either a bilayer of P3HT structured by LIPSS covered by PCBM or a bulk heterojunction with a P3HT:PCBM blend structured by LIPSS exhibit generation of electrical photocurrent under light illumination. These results suggest that LIPSS could be a compatible technology with organic photovoltaic devices. Copyright © 2016 American Chemical Society, This work has been supported by Spanish Ministry of Economy under the projects CTQ 2013-43086-P, MAT2014-59187-R, and MAT2015-66443-C02-1-R. J.C. acknowledges the China Scholarship Council for funding her research (File NO. 201207040083). E.R. and A.R-R thank MINECO for the tenure of a Ramón y Cajal contract (No. RYC-2011-08069) and FPI (BES-2013-062620) contracts, respectively. P.M.-B. and D.M.G. acknowledge financial support by TUM.solar in the frame of the Bavarian Collaborative Research Project “Solar technologies go Hybrid” (SolTec), by the GreenTech Initiative (Interface Science for PhotovoltaicsISPV) of the EuroTech Universities and by the Nanosystems Initiative Munich (NIM). We thank Daniel Hermida and Wim Bras for outstanding support during beamtime in DUBBLE at ESRF. Fruitful comments of A. Urbina are gratefully acknowledged.

We describe a photochemical method to introduce a single alcohol function directly on cucurbit[n]urils (n = 5, 6, 7, 8) with conversions of the order 95-100% using hydrogen peroxide and UV light. The reaction was easily scaled up to 1 g for CB[6] and CB[7]. Spin trapping of cucurbituril radicals combined with MS experiments allowed us to get insights about the reaction mechanism and characterize CB[5], CB[6], CB[7], and CB[8] monofunctional compounds. Experiments involving 18O isotopically labeled water indicated that the mechanism was complex and showed signs of both radical and ionic intermediates. DFT calculations allowed estimating the Bond Dissociation Energies (BDEs) of each hydrogen atom type in the CB series, providing an explanation of the higher reactivity of the "equatorial" C-H position of CB[n] compounds. These results also showed that, for CB[8], direct functionalization on the cucurbituril skeleton is more difficult because one of the methylene hydrogen atoms (Hb) has its BDE lowering within the series and coming close to that of Hc, thus opening the way to other types of free radicals generated on the CB[8] skeleton leading to several side products. Yet CB[5]-(OH)1 and CB[8]-(OH)1, the first CB[8] derivative, were obtained in excellent yields thanks to the soft method presented here.

The photoelectrochemical characterization of silicon carbide (SiC) electrodes is important for enabling a wide range of potential applications for this semiconductor. However, photocorrosion of the SiC surface remains a key challenge, because this process considerably hinders the deployment of this material into functional devices. In this report, we use cyclic voltammetry to investigate the stability of n-type 6H-SiC photoelectrodes in buffered aqueous electrolytes. For measurements in pure Tris buffer, photogenerated holes accumulate at the interface under anodic polarization, resulting in the formation of a porous surface oxide layer. Two possibilities are presented to significantly enhance the stability of the SiC photoelectrodes. In the first approach, redox molecules are added to the buffer solution to kinetically facilitate hole transfer to these molecules, and in the second approach, water oxidation in the electrolyte is induced by depositing a cobalt phosphate catalyst onto the semiconductor surface. Both methods are found to effectively suppress photocorrosion of the SiC electrodes, as confirmed by atomic force microscopy and X-ray photoelectron spectroscopy measurements. The presented study provides straightforward routes to stabilize n-type SiC photoelectrodes in aqueous electrolytes, which is essential for a possible utilization of this material in the fields of photocatalysis and multimodal biosensing., Matthias Sachsenhauser acknowledges support of the IGSSE and of the Technische Universitat Munchen - Institute for Advanced Study, funded by the German Excellence Initiative. Ian D. Sharp was supported by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993.

Understanding the mechanisms of charge transfer across the semiconductor/electrolyte interface is a basic prerequisite for a variety of practical applications. In particular, electrically active surface states located in the semiconductor band gap are expected to play an important role, but direct experimental evidence of surface states has proven to be challenging, and further experimental studies are required to verify their influence on the exchange of charge carriers between semiconductor and electrolyte. Due to its wide band gap, chemical stability, and controllable surface termination, silicon carbide (SiC) provides an excellent model system for this purpose. In this report, we provide a fundamental electrochemical study of n-type 6H-SiC and 4H-SiC electrodes in aqueous electrolytes containing the ferricyanide/ferrocyanide redox couple. Cyclic voltammetry and impedance spectroscopy measurements are performed over a wide range of potentials to determine the energetic positions of the SiC band edges and to investigate the electron-transfer kinetics between SiC and the ferricyanide molecules. For both polytypes, a broad distribution of surface states with energy levels close to the conduction band is found to mediate electron transfer, resulting in deviations of the observed charge transport characteristics from the predictions of well-established models. Moreover, a detailed evaluation of the impedance data allows for explicit correlation of the charge-transfer resistance associated with the ferricyanide reduction reaction with the potential-dependent distribution of surface states. In addition to the relevance of our studies for advancing the implementation of SiC in biosensing, electrocatalytic, and photocatalytic applications, the presented methodology can also be adopted for fundamental electrochemical investigations of other semiconductor electrodes., M.S. acknowledges support of the IGSSE and of the Technische Universitat Munchen-Institute for Advanced Study, funded by the German Excellence Initiative. I.D.S. was supported by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under award no. DESC0004993.

International audience; This study investigates the use of hydrate formation to separate the CO2 from a CO2−CH4 gas mixture in the presence of water-soluble additivestetrahydrofuran (THF) and/or sodium dodecyl sulfate (SDS)at low concentrations. The influence of additive concentration and process operating conditions on the gas enclathration kinetics, the quantity of gas removed, and the selectivity of the separation are studied under quiescent hydrate-forming conditions in a batch reactor. Gas consumption and enclathration occur at high rates only when the two additives are used in combination. Similarly to what has been observed with pure CO2, the proposed mechanism is that a mixed hydrate of structure sII containing THF forms first, which triggers the formation of CO2−CH4 binary gas hydrate of structure sI. However, the gas separation was found not to be selective enough to the CO2 for envisaging any practical application.

International audience; Coprecipitations of Ce(III) nitrates and Ca chlorides have been performed in basic medium at pH > 12 using NaOH, H2O2, and HF as fluorinating agent. Powders have been annealed under air at 600 C during 12 h. Oxides and oxyfluorides with Ce1-xCaxO2-x and Ce1-xCaxO2-x-y/2Fy formulas have been obtained. The Ce/Ca and F/Ca atomic ratios have been determined by elemental analysis (microprobe analysis and F titration with specific electrode), leading one to conclude that the higher is the Ca content, the higher is the F rate. The F/Ca atomic ratio is always lower than 1, but the F content strongly increases with the Ca rate, demonstrating the affinity of fluorine for Ca atoms. XRD data analysis confirmed that Ce-Ca-based oxides and oxyfluorides crystallize with the fluorite-type structure (SG: Fmm) and the a-cell parameter follows Vegard's law both for oxide and for oxyfluoride series. The solubility limit has been estimated to correspond to a Ca/Ce atomic ratio between 0.35 and 0.40 thanks to an accurate XRD analysis using monochromatic Cu K1 radiation, which allows one to detect the occurrence of CaF2 traces. Taking into account the F-Ce bond distance in tetrahedral coordination (bond valence model Ce-F = 2.50 Å; average bond distances in Ce1-xCaxO2-x-y/2Fy: Ce/Ca-O/F = 2.35 Å), the low value of the F/Ca atomic ratio is governed by steric effects and constrains present in the network...

International audience; Competitive adsorption of dilute quantities of certain organic molecules and water at silicate surfaces strongly influence the rates of silicate dissolution, hydration, and crystallization. Here, we determine the molecular-level structures, compositions, and site-specific interactions of adsorbed organic molecules at low absolute bulk concentrations on heterogeneous silicate particle surfaces at early stages of hydration. Specifically, dilute quantities (similar to 0.1% by weight of solids) of the disaccharide sucrose or industrially important phosphonic acid species slow dramatically the hydration of low-surface-area (similar to 1 m(2)/g) silicate particles. Here, the physicochemically distinct adsorption interactions of these organic species are established by using dynamic nuclear polarization (DNP) surface-enhanced solid-state NMR techniques. These measurements provide significantly improved signal sensitivity for near-surface species that is crucial for the detection and analysis of dilute adsorbed organic molecules and silicate species on low-surface-area particles, which until now have been infeasible to characterize. DNP-enhanced 2D Si-29{H-1}, C-13{H-1}, and P-31{H-1} heteronuclear correlation and 1D Si-29{C-13} rotational-echo double-resonance NMR measurements establish hydrogen-bond-mediated adsorption of sucrose at distinct nonhydrated and hydrated silicate surface sites and electrostatic interactions with surface Ca2+ cations. By comparison, phosphonic acid molecules are found to adsorb electrostatically at or near cationic calcium surface sites to form Ca(2+)phosphonate complexes. Although dilute quantities of both types of organic molecules effectively inhibit hydration, they do so by adsorbing in distinct ways that depend on their specific architectures and physicochemical interactions. The results demonstrate the feasibility of using DNP-enhanced NMR techniques to measure and assess dilute adsorbed molecules and their molecular interactions on low-surface-area materials, notably for compositions that are industrially relevant.