In situ investigation of organic ligand displacement processes on ZnO powder surface.

A variety of surface processes require removal or replacement of surface-bound chemical functional groups to achieve the properties required by a specific application. In the case of ZnO powder, a number of applications require manipulation of surface-bound species including ethoxy, acetoxy, acetylacetate, or 1,1,1,5,5,5-hexafluoroacetylacetate. The displacement of the surface species formed by these compounds on ZnO powder surfaces by a gas-phase reagent is described by a model that takes into account stability of surface species predicted by density functional theory and the strength of binding of the second layer on top of the first, provided by the ΔH of sublimation. This simple model is tested by infrared spectroscopy following the adsorption of one compound and its displacement by the other. A correlation between the enthalpic driving force and the percentage of the displaced species observed experimentally is found. This simple approach can be improved and generalized further to include other surface-bound species and other materials.