The band around 3,446 cm -1 is due to –OH stretching
vibration of the silanol or adsorbed water molecules on the
silica surface. The bending vibration of the trapped water
molecules in the silica matrix was detected as an intense
peak at 1,637 cm -1. This band could not be completely
removed by heating, but its intensity however, decreased
[17]. The strong band at *1,095 cm -1 corresponds to the
asymmetric vibration of the siloxane bond, Si–O–Si. This
bond forms the backbone of the silica matrix. The presence
of an absorption band at 801 cm -1 is assigned to the
stretching vibration of Si–O–Si bond [13]. The band
observed at 474 cm -1 is due to the bending vibration of the
Si–O–Si bond [15]. The presence of a band ca.972 cm -1
indicates the Si–O stretching vibration of the silanol group