Dépôts organosiliciés par torche plasma micro-onde à la pression atmosphérique (de l échelle micrométrique à l échelle nanométrique)

Un procédé de dépôt CVD à l air libre, utilisant une torche micro-onde à injection axiale (TIA), a été développé pour le dépôt de films organosiliciés sur substrats de silicium monocristallins. Les effets et interactions de plusieurs paramètres de réglages de la TIA sur les propriétés physico-chimiques des films ont été déterminés par la mise en oeuvre d un plan d expériences de Rechtschaffner. L analyse des résultats a permis d établir des modèles expérimentaux ou fonctions de transfert liant les variables de dépôt aux propriétés des films. Suite aux analyses mathématique, graphique puis statistique des résultats du plan, complétées par la vérification expérimentale des modèles, plusieurs points d intérêt particuliers interactions, corrélation inter-réponses ont été discutés. Les résultats dégagés ont mis en exergue une influence considérable de la température de surface du substrat. Par la suite, l effet de cette température de surface sur les propriétés structurales et microstructurales des dépôts a été étudié. Pour ce faire, une analyse minutieuse des bandes associées aux vibrations des liaisons Si-O et OH a été mis en oeuvre, notamment par un travail de décomposition spectral de FTIR. Ainsi, des informations sur l organisation atomique dans le volume du matériau, notamment sur la conformation des liaisons Si-O-Si (angle et disparité angulaire) et sur la stoechiométrie ont été extraites. A plus grande échelle, des indications sur la densité, la porosité, et les contraintes au sein des films ont également été obtenues. Les résultats rapportés ont été utilisés pour expliciter les mécanismes de croissance du matériau. La caractérisation du jet plasma par spectroscopie d émission optique a permis d extraire des températures de gaz et d appuyer les hypothèses émises. Enfin, la construction d un nanocapteur à lecture en fluorescence à partir de nanostructures siliciées auto-organisées sur des substrats de Si(100) et Si(100)/Pt patternés par nanoindentation puis fonctionnalisées par chimie-click a été initiée.A new open air CVD process assisted by a microwave axial injection torch (TIA) has been developed for the deposition of organosilicon coatings on monocristalline silicon substrates. Both main effects of deposition parameters and first-order interactions on the physical & chemical properties of the films have been investigated from a Rechtschaffner design of experiments (DOE). Response equations relating the responses with the deposition variables have been obtained. After the mathematical, graphical and statistical analysis of the results, several correlations settings/responses and response/response have been discussed and possible mechanisms that contribute to these relations have been suggested. These results have demonstrated that the substrate temperature plays a major role on the responses. Therafter the effects of the substrate temperature on the structural and microstructural properties of the coatings have been studied more in detail. That way, a thorough FTIR spectroscopy study has been performed through the deconvolution of the IR-absorption spectral curves into elementary profiles. This works has allowed to determinate the kind and the contribution of structural components and estimate the structural arrangement of the constituent atoms. In addition, results have been used to explicit growth mechanisms of the coatings. OES characterization of the plasma has corroborated the emitted assumptions. Finally we have reported on the first steps of a lab-on-chip building through the clickchemistry functionalization of self-organized networked SiOxHyCz nano-islands on Si(100) and Pt/Si(100) substrates patterned by nano-indentation.LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

Skin Whitening Cosmetics: Feedback and Challenges in the Development of Natural Skin Lighteners

With the public’s growing interest in skin whitening, lightening ingredients only used under dermatological supervision until recently, are more and more frequently incorporated into cosmetic formulas. The active agents that lighten skin tone are either natural or synthetic substances, and may act at various levels of melanogenesis. They are used to treat various skin pigmentation disorders or simply to obtain a lighter skin tone as whiter skin may be synonymous of wealth, health, youth, and/or beauty in different cultures. However, recent studies demonstrated the adverse effects of some of these ingredients, leading to their interdiction or restricted use under the European Directive and several other international regulations. After an overview of skin whitening practices and the associated risks, this article provides insight into the mechanisms involved in melanin synthesis and the biological assays available to attest the lightening activity of individual ingredients. The legislation dealing with the use of skin lighteners is then discussed. As traditional depigmenting agents such as hydroquinone and corticosteroids are of safety concern, the potential of natural extracts has been investigated more and more; finally, a synthesis of three years of research in our laboratory for such plant extracts will be given

Tailoring the mechanical properties of SiOxHyCz films deposited by atmospheric pressure microwave plasma torch with a Rechtschaffner design of experiments : a pragmatic statistical approach

International audienceSiOxHyCz micrometer thick films are deposited from an argon/hexamethyldisiloxane (HMDSO) mixture on Si (100) substrate by plasma enhanced chemical vapor deposition (PECVD) process using a Torche à Injection Axiale (TIA) at atmospheric pressure. Both main effects of deposition parameters and first-order interactions on the hardness and elastically modulus are investigated from a Rechtschaffner design of experiments (DOEs). This screening design, based on series of two and three-level saturated design, allows the reduction of the total number of experiments by a factor 1.5 in the present work, without compromising the quality of the results. First conclusions demonstrate that torch-substrate distance and HMDSO flow rates are the main influent factors affecting the mechanical behavior of the deposited films, which is basically explained by their indirect effects both on the precursor dissociation in plasma phase and on film growth mechanisms. Additionally, the use of a desirability approach enables to converge towards a multi-criteria optimum of deposition conditions for the expected mechanical properties

New method for screening anti-Leishmania compounds in plants extracts by HPTLC-bioautography

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A thorough FT-IR spectroscopy study on micrometric silicon oxide films deposited by atmospheric pressure microwave plasma torch

International audienceSiOxHyCz micrometer thick films are deposited from an argon/hexamethyldisiloxane mixture on Si (100) substrate by plasma enhanced chemical vapour deposition process using an axial injection torch at atmospheric pressure. Results highlight a similar effect of low and high substrate temperatures both on the deposition process and on the microstructure of the deposited films. Mesoscopically, scanning electron microscopy analyses reveal that particles are promptly produced in the gas phase and incorporated to the film. Microscopically, a detailed infrared analysis in transmission mode demonstrates a high carbon contamination in the low and high temperature intervals resulting in a lower stoichiometry. This work allows to define an optimum growth window for the substrate temperature, leading to smooth, particle-free and carbon-free films: [60 ◦ C; 90 ◦ C]

Development of a Natural Anti-Age Ingredient Based on Quercus pubescens Willd. Leaves Extract—A Case Study

Consumers pay more and more attention not just to the safety and health aspects of ingredients entering their cosmetics’ formulations, but also to their potency, origin, processing, ethical value and environmental footprint. Sustainability of the supply chain, preservation of biodiversity, as well as greener extraction techniques are hence very popular with consumers. Consumers are primarily concerned by the efficacy of the cosmetic products they use and continuously scrutinize product labels, so marketing arguments need to be based on rigorous testing and reliable results to support claims (anti-age, anti-pollution, etc.) displayed on the product’s packaging. As a result, the increasing demand for natural ingredients with assessed bioactivities has profoundly modified the strategies adopted by cosmetic professionals to innovate in terms of actives. Sourcing and developing new natural cosmetic actives is a long-term procedure that is thoroughly described in the present paper, via the example of the design of both liquid and solid ingredients based on Quercus pubescens Willd. leaves extract, for which anti-age properties were assessed by a combination of in vitro assays

Effects of the substrate temperature on the deposition of thin SiOx films by atmospheric pressure microwave plasma torch (TIA)

International audienceThe effect of surface temperature on the deposition of silicon oxide (SiOx) films with a non-thermal microwave axial injection torch (TIA) was investigated in an open air reactor. Argon was used as plasma gas and hexamethyldisiloxane (Si2O2C6H18) as silicon precursor. The parametric study reported here focuses on the influence of the substrate temperature on the morphological and chemical properties of the films deposited in the interval [0 °C-130 °C]. A similar effect of low and high surface temperature on the deposition process and on the microstructure of the deposited films was highlighted. Macroscopically, particles were promptly produced in the gas phase and incorporated to the film, which generates high surface roughness. Microscopically, FTIR results have shown a high carbon contamination of the deposited films at low and high temperatures, resulting in understoichiometric SiOx films. They have also demonstrated that an optimum growth window for smooth and particle free SiOx was to keep the surface temperature between 30 and 60 °C. Simple reaction mechanisms for powder formation and continuous silicon oxide thin films growth are suggested for each temperature ranges

Influence of the V/II ratio on the growth of groupe III nitride quantum dots deposited on silicon substrate by plasma enhanced chemical vapor deposition

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