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Localized surface plasmons can modify linear optical responses of materials located in their vicinity. In particular, rare earth ions luminescence can be enhanced by gold nanoparticles. Luminescence exaltation is a complex phenomenon that depends on multiple parameters, a critical one being the coupling distance between the emitting species and the plasmonic core. An original multilayer nanostructure de-signed to precisely control the distance between the gold cores and the luminescent ions, and to study its effect on the luminescent properties is presented here. Homogeneous silica shells with controlled thicknesses adjustable from 2 to 50 nm and rare earth ion doping rates up to 2x[10.sup.20] Eu/[cm.sup.3] of silica were deposited onto gold nanospheres. These original nanostructures are then incorporated into densified solgel silica composites with high-optical quality. Luminescence properties are studied for increasing gold-europium (III) distances. Strong luminescence quenching is evidenced for coupling distances up to 28 nm. Keywords Gold nanoparticles. Coreshell nanoparticles. Luminescence exaltation. Rare earth. Silica coating. Luminescence quenching, Introduction Gold nanoparticles interact with light and exhibit strong and tunable surface plasmon resonance (SPR). These localized surface plasmons originating from gold nanoparticles in various media can enhance linear and [...]

Anatase TiO2 structure has been widely studied as an electrode for Li-ion battery and as electrocatalyst for water splitting. Inserting guest species into TiO2 has been demonstrated as an effective approach to tune the electronic structure and consequently improves the hydrogen evolution reaction (HER) catalytic activity. In this work, by using mesoporous TiO2 electrodes, we have demonstrated the interplays between HER and Li-ion insertion in Water-in-Salt Electrolyte (WISE). Low C-rates favor the electrocatalytic reaction (HER), but the latter does also depend on the amount of Li in the electrode. Finally, this study guides the experimental conditions for an optimum functioning either in battery environment or in electro-catalysis. [ABSTRACT FROM AUTHOR]

The complexation of vanadium (V) by five dipeptides differing by the nature of the side chains is studied using spectroscopic methods. The result shows that peptides or proteins cannot interact with vanadium by random binding at any peptide linkages as terminal amino and terminal carboxylate may be both required for a vanadium complexation.

Thanks to aqueous sol-gel chemistry, it is now possible to prepare several phase pure TiO2 brookite colloidal systems that significantly differ on nanoparticles size and shape. This TiO2 polymorph is more difficult to be obtained as phase pure material than anatase or rutile. Here we have prepared a set of four different sol-gel brookite syntheses with particles size ranging from 10 to 500 nm and significantly different morphologies as demonstrated by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. We have studied their photocatalytic activities in aqueous solution on phenol and formic acid. The brookite sample with higher specific surface displays better activity for both pollutants abatement than anatase and rutile reference samples and very close to the TiO2 P25 commercial reference. Additional experimental characterization of photogenerated charge carriers and their lifetime is performed using time-resolved microwave conductivity. We could then explain why another efficient brookite material is able to compensate a significantly lower specific surface with a higher photon conversion rate. This study involving a broad set of pure phase brookite samples brings back that phase into the TiO2 polymorphs race for light-enhanced applications. It confirms that size/shape-activity correlation already observed for the anatase polymorph is also valid for the brookite phase. [ABSTRACT FROM AUTHOR]

The preparation of photocatalytic heterostructures of platinum on Bi2WO6 nanoparticles by a wet reduction method is described in this report and compared with other preparation methods. The as-obtained photocatalysts were characterized by XPS and TEM, the results of which confirmed the presence of solely zero-valent metal nanoparticles on the surface of Bi2WO6. The photocatalytic activity of these heterostructures was evaluated by the degradation of Rhodamine B under blue light ( λmax = 445 nm). The deposited noble metal nanoparticles were shown to significantly improve the photocatalytic performance of the bismuth-based material under visible light. Both the preparation mode and the metal loading may impact on the efficiency. The observed photocatalytic enhancement has been attributed to an electron transfer from the semiconductor to the metal, which prevents fast electron/hole recombination. The electrons trapped in the metals may then participate in the multi-electron reduction of O2. [ABSTRACT FROM AUTHOR]

Background Although major concerns exist regarding the potential consequences of human exposure to nanoparticles (NP), no human toxicological data is currently available. To address this issue, we took welders, who present various adverse respiratory outcomes, as a model population of occupational exposure to NP. The aim of this study was to evaluate if welding fume-issued NP could be responsible, at least partially, in the lung alterations observed in welders. Methods A combination of imaging and material science techniques including ((scanning) transmission electron microscopy ((S)TEM), energy dispersive X-ray (EDX), and X-ray microfluorescence (μXRF)), was used to characterize NP content in lung tissue from 21 welders and 21 matched control patients. Representative NP were synthesized, and their effects on macrophage inflammatory secretome and migration were evaluated, together with the effect of this macrophage inflammatory secretome on human lung primary fibroblasts differentiation. Results Welding-related NP (Fe, Mn, Cr oxides essentially) were identified in lung tissue sections from welders, in macrophages present in the alveolar lumen and in fibrous regions. In vitro macrophage exposure to representative NP (Fe2O3, Fe3O4, MnFe2O4 and CrOOH) induced the production of a pro-inflammatory secretome (increased production of CXCL-8, IL-1β, TNF-α, CCL-2, -3, -4, and to a lesser extent IL-6, CCL-7 and -22), and all but Fe3O4 NP induce an increased migration of macrophages (Boyden chamber). There was no effect of NP-exposed macrophage secretome on human primary lung fibroblasts differentiation. Conclusions Altogether, the data reported here strongly suggest that welding-related NP could be responsible, at least in part, for the pulmonary inflammation observed in welders. These results provide therefore the first evidence of a link between human exposure to NP and longterm pulmonary effects. [ABSTRACT FROM AUTHOR]

A one pot synthesis of alumina supported faceted nickel nanoparticles is carried out following a simple, inexpensive, and sustainable pathway. Tailoring the different chemical steps of catalyst preparation allow the faceted morphology to be maintained while reducing the organic leftover. Moreover, this work shows the key role of the halide ions on the nanoparticles shaping that occurs during the reduction step under H2. The predominant role of the {111} facets on the performance of the resulting supported nanocatalysts is also demonstrated. Indeed, catalytic tests in selective hydrogenation of polyunsaturated hydrocarbons performed for both faceted nanocatalysts and reference Ni show a clear selectivity enhancement for the former. The positive impact of {111} faceted Ni catalysts on hydrogenation selectivity is of particular interest to reduce the purification steps after the catalyzed reaction. [ABSTRACT FROM AUTHOR]

The photocatalytic properties of titanium dioxide depend not only on its electronic properties, but also on the material size and shape, which can increase interactions between the reactants and catalyst. Most studies to date show that reducing the particle size down to the nanoscale increases photocatalytic efficiency, as a result of a higher surface to volume ratio and because a larger proportion of the material is actually irradiated by light. We demonstrate that a multiscale shape design, which integrates surface roughness, particle shape, and 1D material processing and orientation, can favor photocatalytic properties in the solid-gas regime, especially mineralization (conversion into CO2), when the hierarchical 1D orientation of the material is combined with unidirectional gas flow. Several materials with hierarchical structure were prepared and characterized. They have been tested for the photocatalytic mineralization of gaseous acetone and compared with commercial catalysts. Our study reveals that a suitable combination of multiscale design and optimization of the material orientation and gas flow favors high mineralization. [ABSTRACT FROM AUTHOR]

The ability to design nanoparticles size and shape through the addition of simple and commercially available organic molecules is of particular interest in the catalytic domain because huge amounts of very fine powders are needed. The origin of this effect is all the more difficult to elucidate because the involved interactions are weak. In this paper, we have investigated the shaping of boehmite AlO(OH) nanoparticles in the presence of polyols like xylitol (C5alditol) by a combined experimental and theoretical approach. Experimental techniques such as XRD, TEM, IEP measurements, adsorption isotherms measurements, and 13C MAS NMR experiments demonstrate that the effect of xylitol has a thermodynamic origin and suggest weak interactions between xylitol and the surface. Furthermore, the strongest proportion of lateral faces ((100), (001), and (101)) that of basal face would be in agreement with a preferential adsorption upon lateral surfaces. These results were refined by a computational approach. DFT calculations of surface energies (taking into account temperature and solvation effects) and of NMR shielding constants corroborate that molecular adsorption mode is preferred over all adsorption modes involving exchanges with surface OH groups. The preferred adsorption on lateral surfaces is attributed to the nest effect induced by hydroxyl groups localized on the concavities of the (001) and (101) surfaces, able to stabilize the xylitol molecule by hydrogen-bonding, whereas the basal (010) surface is almost flat. This combined experimental and computational approach thus provides interesting rationalization for the morphology effects observed. [ABSTRACT FROM AUTHOR]

Acceptability and relevance of nanoparticles in the society is greatly improved using a safer-by-design strategy. However, this is difficult to implement when too late in the development process or when nanoparticles are already on the market (e.g., TiO2). We employ this strategy for emerging nanoparticles of lanthanide oxysulfide of formula (Gd,Ce)2O2S, relevant for photocatalysis as well as for multimodal imaging, as the bandgap of the nanoparticles, related to their Ce content, impacts their ability to absorb visible light. As a first step, we investigated the production of reactive oxygen species (ROS) as a function of cerium content, in abiotic conditions and in vitro using murine macrophage RAW 264.7 cell line. We demonstrate that, at sub-lethal doses, Ce-containing oxysulfide nanoparticles are responsible for a higher ROS intracellular formation than cerium-free Gd2O2S nanoparticles, although no significant inflammatory response or oxidative stress was measured. Moreover, there was no significant loss of cerium as free cation from the nanoparticles, as evidenced by X-ray fluorescence mapping. Based on these results, we propose a risk analysis for lanthanide oxysulfide nanoparticles, leading to a technology assessment that fulfills the safer-by-design strategy. [ABSTRACT FROM AUTHOR]

Abstract: (dipeptide)xV2O5.1.0H2O (0.27

The reaction of vanadate(V) with a series of dipeptides (VaI-GIn, Ala-GIn, Gly-GIn, Gly-Glu, and Ala-Gly) was investigated by UV-visible spectroscopy and multinuclear (51V, 14N, 13C) NMR spectroscopy in solution. It was possible to evaluate the formation constants of the corresponding complexes for which a molecular structure was proposed. Complex formation is favored by the presence of a functionalized or a sterically demanding side chain. The Val-GIn dipeptide which combines both properties exhibits one of the highest formation constant reported so far for dipeptides. [ABSTRACT FROM AUTHOR]

Ab initio calculations have been performed on XeF5− anion at the MP2 and CCSD(T) levels with a large basis set. Four extrema have been optimized and characterized by frequencies analysis. We find the absolute minimum to be of D5h symmetry in accordance with the experimental data; the theoretical vibrational spectrum of this minimum is in good agreement with the experimental one. Three other extrema are found to be higher in energy depending on the angular separation of the Xenon lone pairs as predicted by the VSEPR theory. Finally the characterized transition state has been found to belong to the Xenon pseudorotation pathway. [Copyright &y& Elsevier]

Abstract: TiO2 is a material of great interest for many technological applications among which, as catalyst support. As this specific application requires a good thermal stability of the material, the phase transition between the two most commonly used titania polymorphs, anatase and rutile, has been extensively studied over the past decade. However not much importance has been given to the initial and final particles morphologies. In this study, anatase nanoparticles with an elongated shape were synthesized and their kinetic phase transformation was studied. The thermal treatments were conducted at temperatures ranging from 500 to 700°C. The morphology evolution and the phase transition were characterized by X-ray diffraction and transmission electron microscopy. The phase transformation kinetics is best described by the interface nucleation models. The values of the measured kinetic parameters are significantly lower than those proposed in the literature for isotropic particles, with an activation energy of E a =345kJmol−1. The influence of morphology and, as a consequence, the influence of exposed faces on anatase particles, are presented and discussed. [Copyright &y& Elsevier]

Abstract: This overview features the chemical background on condensation phenomena of the aluminum cation in aqueous solution. The formation of polycationic molecular clusters and nanosized solid phases of aluminum oxy(hydroxi)des is interpreted with illustrative mechanisms, building a bridge between solution chemistry and solid-state chemistry. The formation of the main structural types of aluminosilicates (zeolites, clays, imogolite) is also illustrated through the aqueous chemistry of aluminum and silicates. [Copyright &y& Elsevier]