CHEM01200604009 Sreejith Kaniyankandy - Homi Bhabha ...

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which is also neutral; therefore, we do not expect much change due to surface modifier.
Therefore the changes observed in the absorption are due to the interaction between the TiO 2
and alizarin molecule only.
3.3.3. Femtosecond Transient Absorption Studies
A (m O.D.)
5
4
3
2
1
0
A
500 600 700 800
Wavelength (nm)
0.1ps
0.2 ps
0.4 ps
A (m O.D.)
3
2
1
0
B
500 600 700 800
Wavelength (nm)
1 ps
2 ps
4 ps
A (m O.D.)
5
4
3
2
1
0
C
500 600 700 800
Wavelength (nm)
10 ps
50 ps
100 ps
Figure 3.4: Transient absorption spectra of B- TiO 2 -Alizarin in toluene after 400nm excitation.
To gain information of the interfacial electron transfer dynamics between alizarin and
TiO 2 we have carried out femtosecond transient absorption study by exciting the samples at
400 nm and following the dynamics using probe light in the wavelength range 470-900 nm.
We have shown the time resolved transient absorption spectra in Figure 3.4. The spectrum
shows a prominent peak in the region 500-600nm, which can be assigned to the cation radical
of alizarin [3.3]. Also the spectrum shows a broad featureless band in the wavelength range
700-900nm which can be attributed to injected electron into the conduction band of TiO 2 .