The adsorption of diethyldithiophosphate on cuprous sulphide

The adsorption of diethyldithiophosphate (DTP) from its aqueous solutions has been studied on cuprous sulphide (chalcocite) surfaces by measuring the characteristic changes in the positions and relative integrated intensities of C 1s, P 2p, S 2p, O 1s and Cu 2p3/2 XPS lines and by observing the changes in the in situ internal reflection IR (infrared) spectra at various stages of adsorption. A multistage model is suggested for DTP adsorption on a freshly formed chalcocite surface. During adsorption components preadsorbed on the surface are removed. The DTP ions are initially distributed on the surface without any special orientation but later form islands. The degree of orientation increases with coverage and later, a well oriented close packed monolayer is found. When the adsorption continues beyond this stage the additionally deposited molecules form a randomly oriented layer on the close packed oriented monomolecular layer.