Small peak at 1640 cm-1 and
intense peak between 3400 and 3200 cm-1 is due to stretching vibrations
of adsorbed water and –OH groups from nanopowder. After TiO2 surface
modification with APTES, a characteristic peak appears at 1540 cm-1.
It is ascribed to –NH2 groups from aminosilane (spectra 3 and 4). Small
peak at 1120 cm-1 indicates the formation of C-N bonds. Another peak
at 3000 - 2923 cm-1 is referred to the presence of –CH2- groups, what
is an evidence of efficient TiO2 surface modification with APTES.