Polyelectrolyte Multilayer Template Assisted in-Situ Synthesis of the Inorganic Nanostructures

Abstract

Apstract:Multilayers formed from weak polyions of polyallylamine (PAH) and polyacrylic acid (PAA), possessing ion-exchangeable carboxylic groups were used to bind the metal cations within the film. By subsequent wet chemical reaction process of the incorporated metal ions, pure zinc sulfide (ZnS) with a narrow size distribution was formed within the PEMs. The size and concentration of the inorganic nanoparticles in polyion matrix were controlled by the concentration of metal -binding carboxylic acid groups as determined by the multilayer assembly pH. Furthermore, the metal cation loading and reaction methodology could be repeatedly cycled to increase the size and volume density of the nanoparticles. Furthermore, the polyelectrolyte multilayer films were used as templates for the ceramic (TiO 2 ) thin film fabrication with a modified sol-gel reaction. Since the multilayer assembly is performed from the polyion aqueous solutions, the multilayers contain some water that, after infiltration of the organometallic precursor, enables in-situ reaction of hydrolysis and condensation reaction. After calcination, nanocrystalline TiO 2 thin films with thickness, controllable by the number of the polyion layers in the matrix, were formed. With the in-situ synthesis approach of inorganic nanstructures in polyelectrolyte multilayer matrix, the ability of obtaining the control over the film thickness and size of the inorganic particles has enabled the tuning of the optical properties of as fabricated inorganic-organic composite films, as well as nanocrystalline ceramic films.