Particulate assemblies of CdS and TiO 2 prepared by Langmuir–Blodgett technique with octadecylamine/methylstearate mixed films

Abstract

Langmuir–Blodgett (LB) technique has been applied to fabrications of various nanoparticulate assemblies such as monolayer and multilayer of CdS particles, in-plane mixed monolayer and alternate multilayer of CdS/TiO 2 particles on the solid substrate. We examined the most favorable conditions for yielding uniform and dense packing of the particles in a 2-dimensional arrangement, followed by structural characterization of the as-deposited particulate layers. As a result, it was found for the CdS particulate films that charge density of cationic Langmuir monolayer markedly influences the amount of particles embedded on the substrate and that multilayer LB deposition enables stepwise control of thickness for the particulate assemblies. For the composite CdS/TiO 2 particulate films, desired in-plane mixing ratio and alternating layer structure of two kinds of particles were achieved, on which basis the possibilities of fabricating a variety of heteroparticulate layers are pointed out. In addition, photocatalytic activities of TiO 2 and CdS/TiO 2 particulate films fabricated by the LB technique were evaluated in terms of decomposition of both oleic acid cast film and stearic acid (SA) LB film by irradiating with UV light. The results exhibited that when the bilayer of TiO 2 particulate film is employed in place of the monolayer film, the photodecomposition rate of SA is sufficiently accelerated and that the alternate CdS/TiO 2 particulate layer is less active for the oxidative decomposition.