Importance of surface reactions in the photochemistry of zinc sulfide colloids

The photochem. of colloidal ZnS was studied under a variety of exptl. conditions. The time dependence of the photocorrosion was examd. by using time-resolved fluorescence, static fluorescence, and electrospectroscopy for chem. anal. (ESCA) techniques. A qual. model for the semiconductor and its electrolyte interface is developed to explain the exptl. observations where elemental Zn, S, and SO42- formed on the surface act as e-/h+ recombination centers. The photocorrosion products were identified as SO42-, SO32-, and S. The importance of the surface chem. in the photochem. 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.