Study of grafted silane molecules on silica surface with an atomic force microscope

Atomic force microscopy is employed to study the grafting process on a silica surface of several kind of silane molecules in anhydrous and aqueous solutions: mono- and trichlorosilanes and mono- and triethoxysilanes. A systematic study of the adhesive interaction and the friction behavior is performed. With the anhydrous silane solutions, we show that only the trichlorosilane molecules are able to graft the silica surface, while with the aqueous silane solutions, except for the monoethoxysilane, the silica surface was always grafted. This study provides further support of the use of tribological properties to investigate a surface modification. We show that the influence of the tip velocity on the friction behavior is a powerful way to discriminate between the silica surface and the grafted one.