Photophysical and photochemical properties of CdS with limited dimensions

Abstract

Laponite, porous Vycor glass and molecular sieves, faujasite X and sodalite, have been used to prepare small particles of CdS with limited dimensions. Laponite limits one dimension of the CdS particles by the interplaner spacing of 11.5 Å. Porous Vycor glass limits two dimensions of the CdS particles to < 40 Å. Molecular sieves were used to limit the particle size to the size of the cavity; however, the particles constructed were larger than the cavity dimensions. The absorption onset and main emission wavelength increase with increasing Cd²⁺ concentration. The spectral properties of PbS are also reported. Methyl viologen and Cu²⁺ quench two different emission bands arising from CdS on laponite in solution. Methyl viologen quenches the high-energy emission, thought to arise from exciton recombination, while Cu²⁺ efficiently quenches a low-energy emission thought to arise from S^2– deficiencies. Methyl viologen shows dynamic-type kinetics, while the static-type kinetics observed from Cu²⁺ gives an estimate of the particle size. The spectroscopic properties of the particles are studied as a function of cadmium concentration and discussed in terms of particle size.