CHEM01200604009 Sreejith Kaniyankandy - Homi Bhabha ...

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previous section we have discussed the growth of the bleach kinetics of pure CdTe QD at 610
nm shown in inset of Figure 4.2 and also depicted in Figure 4.4a can be fitted with a growth
kinetics can be fitted with time constant of 500 fs. However the kinetic trace at 610 nm in
presence of BQ (Inset, Figure 4.4b) can be fitted with a growth time of 200 fs. Here BQ is
expected to separate out the hot electrons from the conduction band so it is expected that the
growth of bleach signal will be specifically monitor the cooling dynamics of the hot holes.
Here in presence of BQ the electrons will be de-coupled from the holes, as a result we will be
monitoring only hole dynamics.
0.0
b
a
(mOD)
-1.0
-2.0
-3.0
c
(mOD)
0
-1
-2
b
c
a
-3
-1 0 1 2 3 4 5
Time Delay (ps)
0 200 400 600
Time Delay (ps)
Figure 4.4: Normalized kinetic traces of a) CdTe, b) CdTe with BQ and c) CdTe with
BA at 610 nm (1S exciton position). Inset: Same kinetic traces at shorter time scale.
Figure 4.4c is the bleach kinetics of CdTe at 610 nm in presence of hole quencher (BA) can
be fitted with 700 fs growth kinetics. This time constant can be attributed to cooling