High quality Cu2ZnSnS4 (CZTS) thin films, as an absorber layer for thin films solar cell, were synthesized successfully using a simple and low cost technique, Close-Space Vapor Transport (CSVT). The films were grown on soda-lime glass substrates using a polycrystalline CZTS ingot as source of evaporation material. Influence of substrate temperature on chemical composition, morphological, structural, electrical and optical properties of the CZTS thin films was investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, UV-Vis-NIR spectrophotometer, Hall effect and photoluminescence (PL) measurements. The results from XRD and Raman characterization confirmed the formation of kesterite CZTS thin films with a (112) plane preferred orientation and Raman shift of 338 cm-1, respectively. When the substrate temperature was increased from 460 to 540 °C, the composition of the thin films becomes Cu-, Sn-poor and Zn-rich, wherein the optical band gap values increased from 1.34 to 1.52 eV. PL spectra show the presence of broad emission band at 1.28 eV. All CZTS thin films exhibit p-type conductivity. With substrate temperature of 500 °C, the CZTS thin films show the best properties as an absorber layer in thin film solar cell (Eg = 1.48 eV, p = 3.4 x1017 cm-3, ρ = 2.6 Ω/cm, μ = 6.4 cm/V.s).

Producing wheat gluten gels with tunable mechanical properties via simple sol-gel routes would facilitate their processing into plant protein-rich food products. However, standard gluten is a very elastic mass with a high concentration of proteins in water and is hardly processable except using high shear harsh extrusions. The wheat proteins are responsible for the viscoelastic properties of standard gluten and dough and are among the most complex proteins families, with extremely broad polymorphisms and polydispersities. They are moreover insoluble in water, rendering rational studies difficult. Thanks to a novel protocol for the gluten proteins extraction that we have recently developed, stable ethanolic suspensions of gluten proteins are obtained for a wide range of protein concentrations. In this talk, we will present the viscoelasticity of those suspensions and show that they exhibit a spontaneous and concentration-dependent gelation, which we find to be driven by the slow formation of hydrogen bonds. We successfully rationalize our data using percolation models and relate the viscoelasticity of the gels to their fractal dimension measured by scattering techniques. The novel gluten gels display self-healing properties and their elastic plateaus cover several decades, from 10-2 to 104 Pa. In particular very soft gels as compared to standard hydrated gluten, suitable for processing, can be produced.

he supramolecular organization of wheat gluten proteins is largely unknown due to the intrinsic complexity of this family of proteins and their insolubility in water. We fractionate gluten in a water/ethanol (50/50 v/v) and obtain a protein extract which is depleted in gliadin, the monomeric part of wheat gluten proteins, and enriched in glutenin, the polymeric part of wheat gluten proteins. We investigate the structure of the proteins in the solvent used for extraction over a wide range of concentration, by combining X-ray scattering and multi-angle static and dynamic light scattering. Our data show that, in the ethanol/water mixture, the proteins display features characteristic of flexible polymer chains in a good solvent. In the dilute regime, the protein form very loose structures of characteristic size 150 nm, with an internal dynamics which is quantitatively similar to that of branched polymer coils. In more concentrated regimes, data highlight a hierarchical structure with one characteristic length scale of the order of a few nm, which displays the scaling with concentration expected for a semi-dilute polymer in good solvent, and a fractal arrangement at much larger length scale. This structure is strikingly similar to that of polymeric gels, thus providing some factual knowledge to rationalize the viscoelastic properties of wheat gluten proteins and their assemblies.

Sickle cell anemia is a blood disorder, known to affect the microcirculation and is characterized by painful vaso-occlusive crises in deep tissues. During the last three decades, many scenarios based on the enhanced adhesive properties of the membrane of sickle red blood cells have been proposed, all related to a final decrease in vessels lumen by cells accumulation on the vascular walls. Up to now, none of these scenarios considered the possible role played by the geometry of the flow on deposition. The question of the exact locations of occlusive events at the microcirculatory scale remains open. Here, using microfluidic devices where both geometry and oxygen levels can be controlled, we show that the flow of a suspension of sickle red blood cells around an acute corner of a triangular pillar or of a bifurcation, leads to the enhanced deposition and aggregation of cells. Thanks to our devices, we follow the growth of these aggregates in time and show that their length does not depend on oxygenation levels; instead, we find that their morphology changes dramatically to filamentous structures when using autologous plasma as a suspending fluid. We finally discuss the possible role played by such aggregates in vaso-occlusive events.

I consider the problem of consistent implementation of symmetries at the non-perturbative level in type II string theory compactifed on a Calabi-Yau threefold. After inclusion of all quantum corrections, all continuous isometries of the classical moduli space are broken to discrete subgroups. I show that the naive choice of these subgroups does not generate a consistent group action, which however can be achieved by taking into account various subtle contributions determined by topological data on the Calabi-Yau. In particular, the monodromy transformations of the RR-felds should acquire anomalous terms, which seem to have a similar origin as the Freed-Witten anomaly for open strings ending on D-branes.

One among other remarkable methods to produce multifunctional assemblies with different spatial organizations is the use of liquid–liquid (L–L) interfaces. Herein, a droplet microfluidic-based method is reported as a strategy for the assembly of asymmetrical inorganic nanohybrid structures. As a proof of concept and motivated by their wide applications in different fields, we studied the assembly of two building nanoblocks, which are fluorescent silica (160 nm diameter) and gold nanoparticles (15 nm diameter). In this strategy, droplets of an aqueous solution of citrated gold nanoparticles are generated in a continuous flow of amine functionalized fluorescent silica nanoparticles dispersed in cyclohexane using the microdevice. The electrostatic attraction between the two nanoparticles confined at the water/cyclohexane interface to form a Pickering emulsion allowed their assembly. We show that Janus nanohybrids can only be observed when the residence time in the microdevice was less than 30 min, thus avoiding the formation of solid shells for longer residence times. Transmission and scanning electron microscopies, optical microscopies, and UV–vis spectroscopy were used to characterize the resulting assemblies. The results were compared to experiments in bulk which showed that microfluidics offers a higher control over the assembly and reduces the time for their elaboration. Moreover, an analytical model based on transport of nanoparticles and their adsorption onto interfaces is used to rationalize our observations. Both flow recirculation inside and outside the droplets in the microchannel and the confinement effect seem to be relevant for the enhanced nanoparticle transport to the interfaces.