IMPORTANCE OF SURFACE-REACTIONS IN THE PHOTOCHEMISTRY OF ZNS COLLOIDS

The photochemistry of colloidal ZnS has been studied under a variety of experimental conditions. The time dependence of the photocorrosion has been examined by using time-resolved fluorescence, static fluorescence, and electron spectroscopy for chemical analysis (ESCA) techniques. A qualitative model for the semiconductor and its electrolyte interface is developed to explain the experimental observations where elemental Zn, S, and SO42- formed on the surface act as e-/h+ recombination centers. The photocorrosion products have been identified as SO42-, SO32-, and S. The importance of the surface chemistry in the photochemistry is shown via the correlation between the growth in the emission intensities and the formation of the photocorrosion products on the surface of the dried colloids. © 1990 American Chemical Society.