Synthesis of Ag-colloids in sol-gel derived SiO2-coatings on glass

Abstract

Abstract. Ag colloid-containing coatings on soda lime glass and fused silica are prepared via the sol-gel process. To incorporate Ag +-ions in the coatings homogeneously, they are stabilized by a functionalised silane (aminosilane) and then mixed with the basic sol prepared from 3-glycidoxypropyl trimethoxysilane (GPTS) and tetraethoxysilane (TEOS). Crack-free and transparent coatings with a thickness of 0.5 to 1.2/zm, are obtained by heat treatment between 120~ and 600~ The Ag-colloid formation was monitored by UV-VIS spectroscopy as a function of temperature. The investigations reveal that the substrate has a deciding influence on the Ag-colloid formation caused by alkali diffusion from the substrate into the coating. High resolution transmission electron microscopy (HRTEM) investigations prove that poly-crystalline AgxOy-nanoparticles are formed during thermal densification in the coatings and that this change is accompanied by a vanishing of the yellow colour of the coatings. A post-heat treatment in a reducing atmosphere (90% N2, 10% Ha) turns back the yellow colour and single-crystalline Agcolloids can be detected by HRTEM. A suitable choice of the temperature and time conditions allows the control of the colloid size during heat treatment in a reducing atmosphere. For comparison, ion-exchange experiments have been carried out which showed that a spontaneous Ag-colloid formation was achieved in the soda lime substrate at 400~ Since Ag containing SiO2-coatings remained colourless after thermal treatment between 400~ and 600~ in air, on soda lime substrates, a remarkable diffusion of Ag + into the substrate was excluded.

Optical Nonlinearities of Colloidal Metal Quantum Dot - Glass Composites for Nanophotonics

“…mixing selected metal powder with molten glass, is that the linear and nonlinear properties occur in a well-defined space in an optical device, and by using focused ion beams, point quantum confinement may be accomplished. Although several other methods, such as ion-exchange [23], sol-gel [24], electrolytic colouration, etc., also exist for introducing the metal into the insulating substrates, the ion implantation has the following advantages of being a generally applicable process; (a) it can be performed at an ambient temperature, (b) it has no side diffusion problem, (c) it offers an accurate control of the total number of ions being added to the target and (4) it offers a predictable depth distribution in the target matrix determined by the incident ion beam energy. Ion implantation in glassy structures yields in the precipitation of metal colloids at a reasonably higher local concentration because of the large specific volume and more open structure of the glassy state relative to that of the crystalline counterpart.…”

Chemical composition and barrier properties of Ag nanoparticle-containing sol–gel films in oxidizing and reducing low-temperature plasmas

“…Silver doped silica-like coatings can be easily prepared using tetraethyl orthosilicate (TEOS), AgNO 3 and HNO 3 as the main precursors [1][2][3] and it is known that the siloxane bridges (Si-O-Si) form the inorganic backbone of the coating if it is prepared using the sol-gel method [4]. Hydrolysis and polymerization reactions of TEOS could be achieved in the presence of water by controlling the pH of the solution to a sufficient level [4].…”

“…Hydrolysis and polymerization reactions of TEOS could be achieved in the presence of water by controlling the pH of the solution to a sufficient level [4]. Uniform TEOS coatings have been reported to be obtained after annealing at 60°C-120°C and the Ag nanoparticles are known to be formed inside the coating with thermal treatment up to 600°C either in air [1,2] or in reducing atmospheres [3]. In addition to thermal treatments also UV curing of sol-gel films [10] and γ-radiation exposure of mesoporous silica immersed in Ag + ions containing bath [11,12] have been found to be successful methods for the preparation of embedded Ag nanoparticles and nanoclusters in the silica-like coatings.…”

“…Mennig et al [3] observed that after drying at 120°C in air colloidal Ag was formed within the film matrix and that at higher temperatures (400-500°C) in a reducing atmosphere (N 2 /H 2 )…”

“…Some of these amino silanes have also been found to be suitable stabilisers for Ag nanoparticles in sol-gel coatings [3].…”