Preparation of Size-Quantized CdS and ZnS Particles in Nanophase Reactors Provided by Binary Liquids Adsorbed at Layered Silicates

Abstract

Liquid sorption measurements of hexadecylpyridinium montmorillonite (HDPM) dispersions in ethanol (1)-cyclohexane (2) and methanol (1)-cyclohexane (2) binary mixtures established the formation of a 0.5- to 5-nm-thick alcohol (1)-rich adsorption layer at the organoclay complex interfaces. This adsorption layer was used as a nanophase reactor for the in situ generation of size-quantized cadmium sulfide and zinc sulfide semiconductor particles from cadmium (or zinc) acetate and equivalent amounts of H 2 S. The volumes of the nanophase reactor in ethanol (1)-cyclohexane (2) at 1 :2 = 0.05 :99.95 were determined, by adsorption excess isotherm and X-ray diffraction measurements, to be 0.692 cm 3 /(g of HDPM) and 0.746 cm 3 /(g of HDPM), respectively. Adsorption excess isotherm and X-ray diffraction measurements gave corresponding values of 0.170 cm 3 /(g of HDPM) and 0.231 cm 3 /(g of HDPM) in methanol (1)-cyclohexane (2) at 1 :2 = 0.01 :99.99. As expected, smaller sized semiconductor particles were generated in the smaller nanophase reactor, provided by the methanol-rich adsorption layer. Further reduction of semiconductor particles was accomplished by decreasing the concentration of their parent ions in the nanophase reactor. Incorporation of semiconductor nanocrystallites into HDPM manifested themselves in increased viscosity of the suspension. Information on the fractal dimensions of the semiconductor-clay organocomplex suspensions and that on the radius of gyration of the nanoparticles has been determined by small-angle X-ray scattering measurements. The use of selectively adsorbed polar liquids at the solid binary polar-apolar liquid mixture interfaces as versatile nanophase reactors is discussed.