Comparison of chemical cleaning methods of glass in preparation for silanization

The uniform deposition of a silane monolayer upon glass has been shown to require small amounts of water along with hydroxyl groups in an isolated or geminal configuration on the substrate surface. In order to expose these groups, organic compounds at the surface must be removed. We present a qualitative evaluation of eight chemical methods commonly used to clean glass microscope slides in preparation for silanization. Mean contact angle of deionized water was measured before covalent attachment of (3-mercaptopropyl)triethoxysilane to assess the efficacy of each procedure. Contact angles were also measured after silanization as a means of determining the uniformity and reproducibility of the silane monolayer. The results indicate that a 1:1 methanol/HC1 wash followed by a bath in concentrated H2SO4 removes surface contaminants most effectively and allows for a very even silanization of the glass surface.