Silanol groups, interpretation bands

The above interpretation can also explain the IR spectra of the HYUS sanples. Indeed, the HYUS-8 sample shows two bands at 3555 and 3635 cm, a considerable amount of silanol groups, and hydroxyl vibrating at 3675 and--3695 cm (Fijg. 4a). After pyridine is adsorbed the bands at 3555 and 3635 cm disappear, while the other two bands remain and a new band at 3615 cm is now clearly visible (Fig. 4b. If the difference spectrum is obtained a band at 3600-3610 cm (Fig. 4c) again indicates the presence of strongly acid hydroxyl groups. ... 

NH3 desorption on porous glass. The addition of NH3 had no effect on the IR band of surface silanol groups until enough NH3 had been added to cover 1% of the surface. Thus, the Mossbauer and IR results provide additional evidence for the complexity of surface acid site measurement and interpretation. 

Additionally, with high pH values a negative absorption band occurs at 980 cm The band is assigned to the bending vibration of protonated silanol groups (Si—OH). It can be interpreted as deprotonation of Si—OH at the surfaces of the silica abrasive and/ or the silica film resulting in Si—0 . Similar behaviour has been found with different types of silica abrasives, for example Stober-sols. 

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