FTIR Results and Discussion. The IR spectrum of the pure P25 TiO2 specimen shown in Figure 7 shows
î(OH) stretching bands in the region between 3740 and 3300 cm -1. The sharp bands observed between 3630 and
3680 cm-1 and the broader bands at 3500 and 3420 cm-1 have been reported in the literature9 and are attributed
to hydroxyl groups on different sites and to varying interactions between hydroxyl groups on TiO2. Ammonia
readily interacts with the most acidic hydroxyl groups and remains on the surface of the particles even after
evacuation of the reaction chamber as evidenced by the significant reduction of the IR intensity of the î(OH) band
upon exposure of the pure P25 TiO2 to ammonia and the concomitant appearance of î(NH) stretching bands at 3346
and 3400 cm-1. The intensities of the bands at 3500 and 3420 cm-1, which have been attributed to a monodentate
hydroxyl group and a bridging hydroxyl group, respectively, were reduced completely by the ammonia. The
residual intensity of the band in the 3630-3680 cm-1 region of the spectrum is attributed to weak Lewis and
Brønsted sites from which the ammonia desorbed after evacuation of the chamber.10