Etude et Contrôle du dépôt de nano et micro particules sur un substrat polarisé

International audienc

Fonctionnalisations et caractérisations de surfaces par des films polythiophènes et dépôts de particules composites

L objectif de cette thèse est de réaliser des matériaux composites constitués d un assemblage de polymères et de particules sur un substrat conducteur. L association de deux éléments de nature différente permet alors de conférer des propriétés spécifiques à ce nouveau matériau dont les applications potentielles concernent différents secteurs industriels tels que les microtechniques, l optique, l électronique Dans un premier temps, la surface de substrats d or à été fonctionnalisée par des films de polymère (polybithiophènes et polytris) [5-(2,2 -bithiophène)] méthanol), obtenus par électropolymérisation. L influence de plusieurs paramètres sur la formation des films éléctropolymérisés a été étudiée : nature et concentration du monomère, composition de la solution (sel de fond), vitesse de formation du film Différentes techniques de caractérisation des films obtenus (microscopies optique et électronique, ellipsométrie spectroscopique, AFM) ont été employées afin de caractériser la morphologie et l épaisseur de ces films. Le suivi in situ de la formation de films électropolymérisés a également été étudié par réflectométrie laser à angle fixe couplée à la voltamétrie cyclique. Ainsi une corrélation entre les morphologies des films obtenus et les signaux réflectométriques a pu être réalisée. Les résultats obtenus ont été appuyés par la détermination des indices de réfraction et des épaisseurs par ellipsométrie spectroscopique ainsi que par des mesures d absorbance par spectrophotométrie UV-Visible des nanoparticules inorganiques (silice) absorbées sur des microparticules organiques (latex) a été réalisé sur une surface métallique non fonctionnalisée. Les particules de latex de taille micrométrique permettent de contrôler leur transport sur la surface et les particules nanométriques apportent la fonctionnalité souhaitée. Le dépôt électrophorétique des particules a été étudié en fonction de différents paramètres physico-chimiques (Ph, concentration et nature d additifs organiques, polarisation ) Selon les conditions expérimentales, le dépôt des particules composites peut être réversible ou irréversible. De plus la désorption des nanoparticules est observée dans certains cas. Après avoir sélectionné les conditions expérimentales afin d avoir un dépôt optimal de particules composites (sans désorption des nanoparticules), l assemblage des particules composites sur le substrat métallique fonctionnalisé par le film de polymère a été étudié. Lors de leur dépôt électrophorétique, les particules s absorbent préférentiellement autour des agrégats de films polymères.The objective of this study was to synthesize composite materials made of polymer and particles on a conductive substrates. The combination of two elements of different nature allowed to obtain specific properties of the new material. This application for composite material are of potential interest to various industrial sectors :micro-engineering, optics, electronics Initially, the surface of gold substrates was functionalized with polymer films (polybithiophene and polytris [5-(2,2 -bithiophène)] méthanol]), obtained by electropolymerization. The influence of different parameters on the formation of electropolymerized films was studied : the nature and concentration of the monomer, composition of electrolyte, scan rate of film formation Different techniques (optical and scanning electron microscopy, spectroscopic ellipsometry, AFM) were used to characterize the morphology and thickness of these films. The in situ formation of electropolymerized films was also studied, using a fixed angle laser reflectometer coupled with cyclic voltammetry. A correlation between the morphologies of the films and reflectometry signals was achieved. The results obtained were supported by measuring the refractive index and thickness of the films by spectroscopic ellipsometry and absorbance by UV-Visible spectrophotometry. Secondly, the assembly of composites particles, consisting of inorganic nanoparticles (silica) absorbed onto organic microparticles (latex) was performed on a metal surface. Micrometer-sized latex particles allowed to control their transport to the surface and the nanoparticles provided the desired functionality. The electrophoretic deposition of particles was studied as a function of different physicochemical parameters (pH, concentration and nature of organic additives, polarization ). The deposition of the composite particles may be reversible or irreversible, depending on experimental conditions. Furthermore, desorption of nanoparticles is observed in some cases. After selecting the experimental conditions for optimum deposition of composites particles (without desorption of nanoparticles), the assembly of these particles on the functionalized metal substrate by polymer film was studied. During their electrophoretic deposition, the particles absord mainly around clusters of polymer films.BESANCON-BU Sciences Staps (250562103) / SudocSudocFranceF

Nanodecoding by dewetting

Films of a block copolymer fluid are deposited on surfaces bearing nano-stripes of different wettability (see figure). The dewetting process of the fluid decodes the underlying pattern, opening trenches as narrow as 70 nm in the film, and creating fluid nanoribbons as narrow as 300 nm. The fluid ribbons are stabilized by the internal organization of the copolymer in the confined space of the ribbon

Silica-Supported Alginates From Djiboutian Seaweed as Biomass-Derived Materials for Efficient Adsorption of Ni(II)

International audienceThe development of environmentally friendly, reusable and highly performant adsorbent materials for the removal of heavymetal ions is a big challenge in the field of wastewater treatment. Therefore, in this study, ecofriendly composite materialsbased on alginates extracted from Sargassum sp (Alg.S) and Turbunaria (Alg.T) and supported on different silica parti-cles were prepared and used as adsorbents for Ni(II) ions removal from aqueous solutions. These composites efficientlyextract Ni(II) ions, i.e. the optimal adsorption amount of Ni 2+ reaches 251 mg.g−1 at pH 5 for one composite, surpassingthe adsorption capacities of other adsorbents reported so far in the literature. The kinetic data fit well with a pseudo-secondorder model. Furthermore, the adsorption in a binary system containing both Ni(II) and Pb(II) was also studied. The effectof pH, concentration, and other parameters on the adsorption capacity as well as on kinetics were systematically examined.These results demonstrate that ours composites show great potential as low-cost bio-adsorbents to remove Ni(II) ions fromaqueous solutions

Inkjet printable ZnO/PEDOT:PSS heterojunction for thin flexible semi-transparent optoelectronic sensors

Flexible sensors play an increasing role in printed electronics and are of interest for optoelectronic applications in flexible robotics and industrial automation. Thus, we have investigated the hybrid inorganic-organic junction between ZnO and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate). A thin ITO (indium tin oxide) layer on PET (polyethylene terephthalate) foils was used as substrate electrode. ZnO was deposited from a nanoparticle (NP) suspension by electrophoretic deposition. For comparison, we have used three different methods for the deposition of PEDOT:PSS, namely (i) drop casting, (ii) dip-coating, (iii) inkjet printing. For the resulting ZnO-PEDOT:PSS junctions, current-voltage characteristics were recorded using miBot micromanipulators, and analysed applying adapted models of thermionic emission, according to Cheung and Cheung, as well as Norde. For dip-coated samples we obtained barrier heights of (0.78±0.01) eV and (0.73±0.02) eV, respectively, while inkjet printed and drop casted structures show smaller values (0.53 eV to 0.66 eV, respectively). Thus, dip-coating can be used for a rapid upper estimation of the ZnO-PEDOT:PSS barrier heights for developing inkjet printable optoelectronic sensors. When using low concentrated PEDOT:PSS suspensions, we observed negative photoresponse of the junction; this is consistent with the formation of a ZnO-NPs and PEDOT:PSS nanocomposite which we obtained on porous semi-transparent ZnO-NP films

Flexible and conductive multilayer films based on the assembly of PEDOT:PSS and water soluble polythiophenes

International audienceFlexible conductive polyelectrolyte multilayer films built upon anionic poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and cationic poly(3-hexylthiophene)-based conjugated polyelectrolytes (P3HT-R) containing imidazolium, pyridinium and phosphonium ionic groups were prepared using electrostatic layer-by-layer assembly. Adsorbed amount of each polyelectrolyte strongly increases when divalent cations (Ba2+) are employed as electrolyte and when the rinsing step is avoided during the build-up. The electrical properties of these (P3HT-R/PEDOT:PSS)n multilayer films were then investigated using the van der Pauw method leading to an average conductivity of ∼2 S m−1. Semiconducting behavior of these organic coatings was demonstrated by the direct relationship between the conductivity and the temperature. (P3HT-R/PEDOT:PSS)n multilayer films exhibited p-type semiconducting behavior as showed by Seebeck measurements. Finally, these films were successfully deposited onto flexible polymer sheets and their conductivity was found to be not affected by applying a bending stress

Ultracompact x-ray dosimeter based on scintillators coupled to a nano-optical antenna

International audienceWe show that nano-optical antennas are capable of controlling the luminescence induced by the absorption of x rays into matter. The x-ray-excited luminescence from a tiny scintillation cluster coupled to a horn nano-optical antenna is highly directed and determined by the antenna’s geometrical parameters. Directionality is sufficiently high to efficiently outcouple the x-ray-excited luminescence to a narrow single-mode optical fiber, thus enabling ultracompact fiber-integrated x-ray sensors. Our nano-optically driven approach offers the possibility of x-ray profiling and dosimetry in ultra-confined environments, opening up new avenues in the fields of x-ray imaging, as well as medical and industrial endoscopy. With this study, to the best of our knowledge, nano-optical antennas make a first key contribution to the development of x-ray sensing protocols and architectures

Media 1: Fiber-integrated optical nano-tweezer based on a bowtie-aperture nano-antenna at the apex of a SNOM tip

Originally published in Optics Express on 21 April 2014 (oe-22-8-10072