The structure of water and methanol adsorbed on silica gel by FT-NIR spectroscopy

Abstract

The NIR adsorption spectra were analyzed quantitatively on the fundamental, combination and first overtone region of OH vibrations of silanol groups, water and methanol adsorbed on mesoporous silica gels. Adsorbed methanol constitutes first layer of about 3 molecules/um⁻² and second layer, the structure of which is similar to that of bulk methanol liquid. Adsorbed water consists of a first layer of about 3 molecules/nm⁻2, the second layer of about 9 molecules/nm⁻² and the third layer has a structure similar to the that of bulk water. The molecular configuration at the interface is discussed.