Quantification of outermost OH group on silica glass surface by high-resolution elastic recoil detection analysis

High-resolution elastic recoil detection analysis (HERDA) has been conducted to quantify outermost OH group on a silica glass surface. The results of HERDA showed that the surface number density of OH groups (silanol number) can be measured with a good reproducibility by heating the sample in vacuum to remove the surface adsorbates. The measured silanol number depends on the temperature and is in good agreement with the result reported for porous silicas. Furthermore, by investigating the relationship between the contact angle of water and the silanol number, it was confirmed that the contact angle increases with decreasing silanol number.