New precursors to form gold nanoparticles in silica monoliths by direct laser-irradiation

PosterInternational audienc

Progressive multi-layer drop-casting of CdSe nanoparticles for photocurrent down shifing monitoring

We investigated the spectroscopic photocurrent response of photovoltaic devices versus an increasing number of drop-casted CdSe nanoparticles onto planar and nanocones silicon p-i-n junctions. For all samples, a strong enhancement of the photocurrent in the UV range was detected as well as a constant increase of the photocurrent up to 20% (16%) for a planar (nanocones) junction in the range 600-800 nm. The analysis of the photocurrent versus the number of drop casted nanoparticles layers allows us to evidence a down-shifting mechanism in the U-V range and an adaptative index effect below the threshold of absorption

Porous Gold Films Fabricated by Wet-Chemistry Processes

Porous gold films presented in this paper are formed by combining gold electroless deposition and polystyrene beads templating methods. This original approach allows the formation of conductive films (2 × 106 (Ω·cm)−1) with tailored and interconnected porosity. The porous gold film was deposited up to 1.2 μm on the silicon substrate without delamination. An original zirconia gel matrix containing gold nanoparticles deposited on the substrate acts both as an adhesion layer through the creation of covalent bonds and as a seed layer for the metallic gold film growth. Dip-coating parameters and gold electroless deposition kinetics have been optimized in order to create a three-dimensional network of 20 nm wide pores separated by 20 nm thick continuous gold layers. The resulting porous gold films were characterized by GIXRD, SEM, krypton adsorption-desorption, and 4-point probes method. The process is adaptable to different pore sizes and based on wet-chemistry. Consequently, the porous gold films presented in this paper can be used in a wide range of applications such as sensing, catalysis, optics, or electronics

CO2 laser-induced precipitation of CdSxSe1−x nanoparticles in a borosilicate glass: A new approach for the localized growth of quantum dots

International audienceA novel method allowing the local growth of semiconductor nanoparticles in dense silicate glasses is presented. In this method combining a continuous middle-infrared laser irradiation and a heat-treatment in open air, a transparent melt-quenched borosilicate glass containing CdSxSe1−x nanocrystals was annealed at a temperature below the softening point. Simultaneously, a continuous infrared laser irradiation at 10.6 μm was applied, acting as a thermal addition. Resonant Raman, photoluminescence and absorption spectra reveal the local growth of CdSxSe1−x nanoparticles, with a homogeneous composition and average particle radii ranging from 1.9 to 5.5 nm. These results demonstrate the feasibility of coupling a laser irradiation with an appropriate heat-treatment in order to achieve the spatial organization of nanostructures in vitreous materials

CO2 laser–induced precipitation of semiconductor nanoparticles in a dense glass

International audienceNanostructures based on II-VI semiconductor nanocrystallites (NCs) embedded in glass have been studied for many years. Among these systems, the pseudo-binary CdSxSe1-x nanostructures are of particular interest, owing to their optical absorption and emission spectra that cover the entire visible spectral region. Laser irradiation methods have been shown to allow the local growth of several types of NCs in various kinds of matrices. Unfortunately, in the case of the CdSxSe1-x doped silicate glasses, a near-infrared fs laser irradiation, instead of nucleating NCs, leads to permanent refractive index changes in micro-size regions within the glass and may even provoke glass damages at the highest pulse energies. A novel method allowing the local growth of semiconductor nanoparticles in dense silicate glasses is presented. In this method, combining a continuous middle-infrared laser irradiation and a heat-treatment in open air, a transparent melt-quenched borosilicate glass containing CdSxSe1-x nanocrystals was annealed at a temperature below the softening point. Simultaneously, a continuous infrared laser irradiation at 10.6 µm was applied, acting as a thermal addition. Spectroscopic studies reveal the local growth of CdSxSe1-x nanoparticles, with a homogeneous composition and average particle radii ranging from 1.9 to 5.5 nm. These results demonstrate the feasibility of coupling a laser irradiation with an appropriate heat-treatment in order to achieve the spatial organization

H2-induced copper and silver nanoparticle precipitation inside sol-gel silica optical fiber preforms

Ionic copper- or silver-doped dense silica rods have been prepared by sintering sol-gel porous silica xerogels doped with ionic precursors. The precipitation of Cu or Ag nanoparticles was achieved by heat treatment under hydrogen followed by annealing under air atmosphere. The surface plasmon resonance bands of copper and silver nanoparticles have been clearly observed in the absorption spectra. The spectral positions of these bands were found to depend slightly on the particle size, which could be tuned by varying the annealing conditions. Hence, transmission electron microscopy showed the formation of spherical copper nanoparticles with diameters in the range of 3.3 to 5.6 nm. On the other hand, in the case of silver, both spherical nanoparticles with diameters in the range of 3 to 6 nm and nano-rods were obtained

Kinetics of gelation and densification of nanoporous silica xerogels: a structural and textural study

International audienc

Building nanoparticles in a matrix with a laser: several examples

OralInternational audienc

Control of gallium incorporation in sol–gel derived CuIn(1−x)GaxS2 thin films for photovoltaic applications

International audienceIn this paper, we report the elaboration of Cu(In,Ga)S2 chalcopyrite thin films via a sol–gel process. To reach this aim, solutions containing copper, indium and gallium complexes were prepared. These solutions were thereafter spin-coated onto the soda lime glass substrates and calcined, leading to metallic oxides thin films. Expected chalcopyrite films were finally obtained by sulfurization of oxides layers using a sulfur atmosphere at 500 °C. The rate of gallium incorporation was studied both at the solutions synthesis step and at the thin films sulfurization process. Elemental and X-ray diffraction (XRD) analyses have shown the efficiency of monoethanolamine used as a complexing agent for the preparation of CuIn(1−x)GaxS2 thin layers. Moreover, the replacement of diethanolamine by monoethanolamine has permitted the substitution of indium by isovalent gallium from x = 0 to x = 0.4 and prevented the precipitation of copper derivatives. XRD analyses of sulfurized thin films CuIn(1−x)GaxS2, clearly indicated that the increasing rate of gallium induced a shift of XRD peaks, revealing an evolution of the lattice parameter in the chalcopyrite structure. These results were confirmed by Raman analyses. Moreover, the optical band gap was also found to be linearly dependent upon the gallium rate incorporated within the thin films: it varies from 1.47 eV for x = 0 to 1.63 eV for x = 0.4

Synthesis and nonlinear optical properties of zirconia-protected gold nanoparticles embedded in sol–gel derived silica glass

International audienceA new approach to dope a silica glass with gold nanoparticles (GNPs) is presented. It consisted in embedding zirconia-coated GNPs in a silica sol to form a doped silica gel. Then, the sol-doped nanoporous silica xerogel is densified leading to the formation of a glass monolith. The spectral position and shape of the surface plasmon resonance (SPR) reported around 520 nm remain compatible with small spherical GNPs in a silica matrix. The saturable absorption behavior of this gold/zirconia-doped silica glass has been evidenced by Z-scan technique. A second-order nonlinear absorption coefficient β of about −13.7 cmGW−1 has been obtained at a wavelength near the SPR of the GNPs