CHEM01200604009 Sreejith Kaniyankandy - Homi Bhabha ...

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increases from 33.3% to 61.8% in presence of BQ. However, the 9ps component show
considerable decrease in contribution while >300ps component shows negligible changes.
Sample τ 1 (ps) τ 2 (ps) τ 3 (ps)
GO 0.9 ±0.2 (33.3%) 9 ± 2 (38.5%) >300 (28.2%)
GO-PY 0.9 ±0.2 (33%) 9 ± 2 (39%) >300 (28%)
GO-BQ 0.85 ±0.2 (61.8%) 10 ± 2 (9.8%) >300 (28.4%)
Table 6.1: Life times of the transient absorption signal of graphene oxide at 670 nm after exciting at 400
nm laser light in absence of any quencher (GO), in presence of electron quencher (GO-BQ) and in presence
of hole quencher (GO-PY).
From our experimental observation we can suggest that that BQ can interact with the
photo-excited electron before trapping and can facilitate faster recombination, as a result we
see that the reduction of 9 ps and > 400 ps components which are primarily attributed to
trapped electrons in different trap depth. We have observed that the contribution of > 400 ps
component has not been changed much from 28.2% (without BQ) to 28.4 % (in presence of
BQ) which earlier was attributed to the component due to the deeper trapped states. So it
clear that BQ cannot quench the electrons effectively which are deeply trapped in GO. This
observation clearly ascertains the significant roles of electron traps in the relaxation
dynamics of photoexcited charge carriers in chemically synthesized GO. However, in
presence of hole quencher (Py) the kinetics at 670 nm of GO did not show any difference
(Figure 6.6 c), which indicates that transient absorption mostly dominated by electron trap
states. From the above investigation it is evident that trapping dynamics of charge carrier