Thierry Devers

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$Research paper thumbnail of Electrical behaviour of fractal nanosized tin dioxide films prepared by electrodeposition for gas sensing applications$

Electrical behaviour of fractal nanosized tin dioxide films prepared by electrodeposition for gas sensing applications

Microelectronics Journal, 2005

ABSTRACT An original electrochemical process to prepare SnO2 gas sensors is detailed and correlat... more ABSTRACT An original electrochemical process to prepare SnO2 gas sensors is detailed and correlated to electrical behaviour under gas environment. In particular conditions, Tin material was electrodeposited on insulating substrate to form a thin film principally composed of a single layer of individual nanoaggregates (5–10 nm in size). After tin electrodeposition, these supported aggregates were oxidised at air or pressurized oxygen to induce the formation of a fractal SnO2 film. From these resulting active films, electrical measurements were carried out in ethanol and 300 ppm CO atmospheres. The results show, a sensitivity of 400% at 227 °C in the ethanol case with a response time of 140 s. When the temperature of electrical measurements increases, response and recovery times decrease. However, the sensing amplitude was not modified (Sensitivity around 4) between 250 and 300 °C. In the case of CO, the sensor presented a typical response with a factor of about 2.5 at 250 °C. A fractal dimension between 1.4 and 1.6 is found for fractal-shaped samples allowing an increase of specific surface in contact with gases. However, its does not effect sensitivity, which depends mainly on grain size.

Structure and atoms mixing in electrodeposited Sn(Au) nanoaggregates

Journal of Crystal Growth, 2005

The tin (Sn) electrochemical deposition on insulating substrates has been performed to elaborate ... more The tin (Sn) electrochemical deposition on insulating substrates has been performed to elaborate a distribution of supported nanoaggregates for gas sensors applications. Depending on current density, the deposit has either the shape of dendrites or of a homogeneous, continuous layer, thinner than 20nm. In this study, fine current densities variation has been investigated to determine growth evolution, especially in the

Comparison of photoprotection efficiency and antiproliferative activity of ZnO commercial sunscreens and CeO2

Materials Letters, 2013

Cerium oxide (CeO 2) nanopowders were successfully synthesized by a simple microwave-hydrothermal... more Cerium oxide (CeO 2) nanopowders were successfully synthesized by a simple microwave-hydrothermal method. The UVB protection of an emulsion containing CeO 2 was evaluated in vitro and compared to the one provided by the same emulsion, zinc oxide (ZnO) instead of CeO 2. CeO 2 offered better protection against UVB radiation. Finally, in vitro cytotoxicity of CeO 2 and various ZnO commercial sunscreens was carried out using NCTC2544 cell line. Assessment of cell viability demonstrated that all tested ZnO commercial sunscreens reduce cell viability in a dose-and time-dependent manner whereas CeO 2 particles did not produce any effects on NCTC2544 growth at the highest concentration tested (80 mg/ml).

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Attenuation of UV absorption by poly(lactic acid)-iron oxide nanocomposite particles and their potential application in sunscreens

Chemical Engineering Journal, 2021

Abstract The topical application of sunscreen and cosmetic products that afford protection from t... more Abstract The topical application of sunscreen and cosmetic products that afford protection from terrestrial ultraviolet radiation to reduce the risk of developing skin cancer is an integral part of modern sun protection. The current sunscreen formulations use inorganic zinc oxide (ZnO) and titanium dioxide (TiO2), that are highly photocatalytic, with the ability to penetrate the skin, and exhibit potential toxicity. In this study, we demonstrate a novel methodology to increase the sun protection factor (SPF) of encapsulated metal oxide (Fe2O3) nanoparticles in poly(lactic acid) (PLA) microspheres as ultraviolet filters for sunscreen applications. The combination of these two materials results in a nanocomposite with increased UV attenuation and without significant cytotoxic effects during in vitro evaluation. A commercial sunscreen formulation was used to show the benefits of the developed nanocomposites by replacing the harmful ZnO particles by the Fe2O3-PLA ones, and a throughout comparison between commercial and the new sunscreen formulation was performed. By adding a small amount of the novel Fe2O3-PLA particles, a remarkable increase in the SPF performance, from 40 (commercial ZnO formulation) to 50 was achieved just by replacing the ZnO particles with 5 wt% of Fe2O3-PLA ones, resulting in a high level of UV protection, coupled with lower dangerous photocatalytic activity when compared with commercial ZnO nanoparticles. The encapsulation of metal oxide nanoparticles by PLA could provide a route to improve the sunscreen efficacy and enhance its SPF by using more environmentally friendly materials.

Biocompatible Bi(OH)3 nanoparticles with reduced photocatalytic activity as possible ultraviolet filter in sunscreens

Materials Research Bulletin, 2018

In this study we investigate readily synthesised Bi(OH)3nanoparticles as a novel, multifunctional... more In this study we investigate readily synthesised Bi(OH)3nanoparticles as a novel, multifunctional ultraviolet filter for sunscreen. The absorbance of Bi(OH)3NPs in the ultraviolet region is comparable to that of both ZnO and TiO2NPs used in commercial sunscreens. In vitro photoprotection results show that the combination of TiO2/Bi(OH)3is more efficient than TiO2/ZnO over the whole UV range, with an increase in sun protection factor of 28%. The emulsions show rheological properties comparable to those of commercial sunscreens. The combination of TiO2/Bi(OH)3led to insignificant damage on pre-painted steel panels after exterior exposure for twelve weeks. We also demonstrate that the addition of Bi(OH)3NPs reduces the degradation of crystal violet by photocatalytically active TiO2or ZnO NPs under ultraviolet exposure. Finally, assessment of the biocompatibility of Bi(OH)3with HaCaT keratinocytes and Madin-Darby Canine Kidney (MDCK) cells in vitro is described.

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$Research paper thumbnail of {"__content__"=>"Functionalized and grafted TiO, CeO, and SiO nanoparticles-ecotoxicity on Daphnia magna and relevance of ecofriendly polymeric networks.", "sub"=>[{"__content__"=>"2"}, {"__content__"=>"2"}, {"__content__"=>"2"}]}$

{"__content__"=>"Functionalized and grafted TiO, CeO, and SiO nanoparticles-ecotoxicity on Daphnia magna and relevance of ecofriendly polymeric networks.", "sub"=>[{"__content__"=>"2"}, {"__content__"=>"2"}, {"__content__"=>"2"}]}

Environmental science and pollution research international, 2018

Effects of functionalization and grafting of TiO, CeO, and SiO nanoparticles (NPs) were investiga... more Effects of functionalization and grafting of TiO, CeO, and SiO 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.

Multifunctional Fe2O3/CeO2 nanocomposites for free radical scavenging ultraviolet protection

RSC Advances, 2016

In this study we synthesized Fe2O3/CeO2 composite nanoparticles with high ultraviolet absorption ... more

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Titanium doped tin dioxide as potential UV filter with low photocatalytic activity for sunscreen products

Materials Letters, 2016

Titanium doped tin dioxide nanopowders were produced using a simple precipitation method and disp... more Titanium doped tin dioxide nanopowders were produced using a simple precipitation method and displayed the same crystalline structure and decreasing particle size with increasing dopant concentration. Optical absorption studies showed broad absorption in the UV region for each sample and enhanced absorption relative to commercial zinc oxide (ZnO) but significantly less absorption than the uncoated commercial titanium dioxide nanopowder (P-25). Photocatalytic studies showed that the 5%Ti doped sample had the lowest methylene blue (MB) degradation rate of (1.9 70.4) Â 10 À 3 min À 1 , followed by the undoped ((2.6 70.4) Â 10 À 3 min À 1) and 10% Ti-doped ((4.57 0.4) Â 10 À 3 min À 1) samples. All of the nanoparticle samples demonstrated substantially lowered photocatalytic activity compared to commercial ZnO and P-25 reference particles.

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New CeO 2 nanoparticles-based topical formulations for the skin protection against organophosphates

Toxicology Reports, 2015

To reinforce skin protection against organophosphates (OPs), the development of new topical skin ... more To reinforce skin protection against organophosphates (OPs), the development of new topical skin protectants (TSP) has received a great interest. Nanoparticles like cerium dioxide (CeO 2) 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 CeO 2 NPs in formulations for the skin protection (2) the impact of the doping of CeO 2 NPs by calcium; (3) the effect of two methods of dispersion of CeO 2 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 CeO 2 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 CeO 2 NPs with a decreased of toxicological impact but the coating is less film-forming which slightly impacts the reproducibility of the penetration results.

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Novel active topical skin protectant against the penetration of organophosphates

International audienc

Synthesis and Characterization of Ce-doped α-Fe2O3 Nanoparticles for Ultraviolet Protection in Cosmetic Products

Buffer layer effect in nanostructured tin electrodeposition on insulating and conducting substrates

Progress in Solid State Chemistry, 2005

The electroplating techniques for metal aggregates and films deposition commonly use an electric ... more The electroplating techniques for metal aggregates and films deposition commonly use an electric current to reduce metal ions in solution, but are restricted to conducting substrate. This new electrochemical technique permits coating of insulating or conducting substrates with metals having controlled aggregate size and growth speed. The basis of our approach is the progressive outward growth of the metal from an

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Engineering of Bismuth Oxide Nanoparticles to Induce Differential Biochemical Activity in Malignant and Nonmalignant Cells

Particle & Particle Systems Characterization, 2014

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Engineering of Bismuth Oxide Nanoparticles to Induce Differential Biochemical Activity in Malignant and Nonmalignant Cells

Particle & Particle Systems Characterization, 2014

$Figure 3. Graph of ROS and nanoceramic cytotoxicity at 50 pg mL! concentration after 24 h. Surviving fraction and ROS data are presented with uncertainties given as one standard deviation with statistical signifi- cances between the air and the argon samples measured as: 9L cytoxicity p value < 0.005, MDCK cytotoxicity p < 0.0001; 9L ROS p value < 0.01 and MDCK ROS p value < 0.05.$

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Rapid electroplating of insulators

Nature, 2002

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Application of nanostructured Ca doped CeO2 for ultraviolet filtration

Materials Research Bulletin, 2010

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The effects of cerium doping on the size, morphology, and optical properties of α-hematite nanoparticles for ultraviolet filtration

Materials Research Bulletin, 2013

Iron(III) nitrate hexahydrate (Fe(NO 3) 3 Á9H 2 O, Sigma-Aldrich 99%), cerium(III) acetate hydrat... more Iron(III) nitrate hexahydrate (Fe(NO 3) 3 Á9H 2 O, Sigma-Aldrich 99%), cerium(III) acetate hydrate (Ce(CH 3 CO 2) 3 ÁxH 2 O, Sigma-Aldrich !98%) and sodium hydroxide (NaOH, Sigma-Aldrich !97%), were used as the reactants in the synthesis of the Fe (2Àx) Ce x O y nanoparticles. Firstly, stock solutions of 0.25 mol L À1 1 iron nitrate solution and 0.063 mol L À1 cerium acetate solution were added to a conical flask with a magnetic stirrer bar in desirable portions, and after thoroughly mixed, 2 mol L À1 NaOH solution drop-wise at ambient temperature result in a dark-red precipitate. The resulting suspension was then separated by centrifugation for 5 min @ 4400 RPM (Eppendorf 5702) and washed with Milli-Q water. The resulting slurry was then dried in an oven (Binder) at 90 8C for 3 h, followed by calcination for 6 h at 500 8C in a Thermotech tube furnace.

format_quoteIncreased cerium doping beyond solubility limits leads to decreased absorbance, correlating mean particle size with UV absorption.format_quote

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Cerium oxide based particles as possible alternative to ZnO in sunscreens: Effect of the synthesis method on the photoprotection results

Materials Letters, 2012

The aim of this study was to synthesize and characterize Ca-doped CeO2 nanopowder in order to det... more

Preparation of dendritic tin nanoaggregates by electrodeposition

Journal of Non-Crystalline Solids, 2003

We have used a new galvanic technique to obtain tin nanoaggregates on an insulating surface. This... more 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.

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Synthesis and Characterization of Fe Doped CeO2 Nanoparticles for Pigmented Ultraviolet Filter Applications

Journal of Nanoscience and Nanotechnology, 2011

Iron doped CeO2 nanoparticles with doping concentrations between 0 and 30 mol% were synthesized b... more Iron doped CeO2 nanoparticles with doping concentrations between 0 and 30 mol% were synthesized by the co-precipitation method for potential application as a pigmented ultraviolet filtration material. Each sample was calcined in air and in argon. The iron solubility limit in the CeO2 lattice was found to be between 10 and 20 mol%. Raman spectroscopy results revealed that both iron doping and argon calcination increase the concentration of oxygen vacancies in the CeO2 lattice. Iron doping causes a blue-shift of the absorbance spectrum, which can be linked to the decreased crystallite size, as obtained by XRD peak broadening using the Scherrer formula. The undoped samples showed weak ferromagnetic behaviour whereas the doped samples were all paramagnetic.

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