Page 190 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

Reactive Oxygen Species Generation on Nanoparticulate Material 175

0.120 Water uptake by TiO at 60% RH
2

0.115
Mass (g) ∆M H 2 O

0.110

Mass of dehydrated TiO 2
0.105
0 10 20 30 40 50 60 70 80 90
M
Time (min)
Figure 5.18 The rehydration of anhydrous TiO 2 is a relatively slow
process which takes place over several hours.

presence of a humid atmosphere with water peak in the IR spectrum is
1
clearly visible near 3500 cm .
In a typical photolysis experiment (Figure 5.19), there is convincing
.
1
FTIR evidence for the formation of Ti(III)OH (e 2 ) and Ti(IV)OH (h tr )
tr

Ti(IV)OD
Absorbance (a.u.) a
Ti(IV)OH
Ti(III)OD
Ti(III)OH

b
Vacuum

3800 3600 3400 3200 3000 2800 2600 2400
Wave numbers
.
Figure 5.19 Surface functional groups, >Ti(III)OH and >Ti(IV)OH groups
reflecting the trapping of electrons and holes after illumination under a
vacuum.