CHEM01200604009 Sreejith Kaniyankandy - Homi Bhabha ...

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electron transfer times. This reveals that the dynamics observed at the dye cation maxima and
the conduction band electron monitors the same events. The individual contributions to the
electron injection time and BET times are given in the Table 3.1.
0,004
A
0,003
0,002
0,001
0,000
A
0,004
0,003
0,002
0,001
0,000
-2 0 2 4 6 8 10
Delay Time (ps)
0 100 200 300 400 500
Delay Time (ps)
Figure 3.5: Kinetic Decay Traces of B- TiO 2 -Alizarin in toluene after 400nm excitation at λ pr =550nm.
In the present investigation we have observed multi-exponential electron injection in
alizarin/TiO 2 system. There could be several reasons to why this can happen. Some of the
known possibilities are multilayer formation or aggregation of the dyes on TiO 2 surface.
However, in the present investigation we have kept the concentration of alizarin below 10 -4
M, where possibility of aggregation is very remote. Assuming that the dye molecules are
evenly distributed on the surface of TiO 2 we can argue that the concentration is not enough to
form aggregate on the dye surface. We have carried out the ultrafast dynamics study on
surface modified TiO 2 bulk particle (capped with DBS) and did not observe any multiple