Thierry Devers

Preparation of dendritic tin nanoaggregates by electrodeposition

We have used a new galvanic technique to obtain tin nanoaggregates on an insulating surface. This study describes the morphology and the size of these nanoaggregates and the operating parameters. The nanoaggregates show a dendritic structure composed of polycrystalline grains with grain size down to 20 nm. The microstructural characterization has been achieved by scanning and atomic force microscopes. Potential curves allow one to describe the onset of nucleation.

New CeO2 nanoparticles-based topical formulations for the skin protection against organophosphates

To reinforce skin protection against organophosphates (OPs), the development of new topical skin protectants (TSP) has received a great interest. Nanoparticles like cerium dioxide (CeO2) known to adsorb and neutralize OPs are interesting candidates for TSP. However, NPs are difficult to disperse into formulations and they are suspected of toxicological issues. Thus, we want to study: (1) the effect of the addition of CeO2 NPs in formulations for the skin protection (2) the impact of the doping of CeO2 NPs by calcium; (3) the effect of two methods of dispersion of CeO2 NPs: an O/W emulsion or a suspension of a fluorinated thickening polymer (HASE-F) grafted with these NPs. As a screening approach we used silicone membranes as a skin equivalent and Franz diffusion cells for permeation tests. The addition of pure CeO2 NPs in both formulations permits the penetration to decrease by a 3–4-fold factor. The O/W emulsion allows is the best approach to obtain a film-forming coating with a good reproducibility of the penetration results; whereas the grafting of NPs to a thickener is the best way to obtain an efficient homogenous suspension of CeO2 NPs with a decreased of toxicological impact but the coating is less film-forming which slightly impacts the reproducibility of the penetration results.

Multifunctional Fe2O3/CeO2 nanocomposites for free radical scavenging ultraviolet protection

In this study we synthesized Fe2O3/CeO2 composite nanoparticles for application as multifunctional ultraviolet (UV) filters. The precipitation of small ceria (CeO2) nanoparticles onto the surface of larger hematite (α-Fe2O3) nanoparticles, results in stronger and more selective absorbance in the (UV) region. Through UV photocatalyst experiments, we show that the addition of these nanocomposite particles significantly reduces the degradation of crystal violet by P25 by scavenging the photogenerated OH˙ radicals.

Functionalized and grafted TiO2, CeO2, and SiO2 nanoparticles—ecotoxicity on Daphnia magna and relevance of ecofriendly polymeric networks

Effects of functionalization and grafting of TiO2, CeO2, and SiO2 nanoparticles (NPs) were investigated, and toxicity of pristine, functionalized, and grafted NP towards Daphnia magna was measured. Surface functionalization of NP with amine groups decreased hydrophobicity of NP. When NPs were hydrophilic, they were less toxic than hydrophobic NP towards D. magna. Grafting agents influenced toxicity: no toxicity of NP was observed when bio-based and hydrogenated synthetic polymers were used, whereas perfluorinated polymers induced a higher toxicity.

Consistent BCS modulated signals for GNSS applications

In this study, the authors propose reliable sequences of binary coded symbol (BCS) modulation, and their characteristics and performances for Global Navigation Satellite System (GNSS) application are described. A BCS sequence vector is formed by eight variable length sub-chips of alternated + 1 and −1 (or −1 and + 1) values. A judicious choice of the sub-chips lengths of the BCS sequence permitted to propose several BCS sequences that provide high performances in terms of multipath mitigation, resistance to the noise and interferences rejection. An overview of the essential characteristics and the resulting autocorrelation functions (ACFs) and power spectral densities of the proposed BCS sequences were introduced. The latter ACFs have a sharp main peak due to the increase in the number of transitions of the BCS sequences within a chip interval, which corresponds to a larger slope of the discrimination function, and consequently a reduced range of search in the delay locked loop with a minimum calculation load. The theoretical and simulation results indicate that the proposed BCS sequences are more consistent compared to the conventional signals adopted by the GNSS navigation systems.