CHEM01200604009 Sreejith Kaniyankandy - Homi Bhabha ...

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Electron quencher (benzoquinone in this case) leads to a fast separation of electrons
from the conduction band. Since the smaller quantum dots have significant surface area due
to smaller radius, the diffusion of the electrons to the surface is expected to take place within
the pulse width. Therefore the probability of quenching is expected to be high. Our previous
studies in fact demonstrate this by monitoring the formation of the lowest exciton state or
cooling dynamics. For quenching studies the concentration of the quencher is ~100 times the
concentration of QD therefore it is expected for the electron quenching to be efficient. In the
present case there is a drastic quench of the bleach in the presence of the electron quencher
(>50%), Since the quenching is expected to be complete and relaxation on quenching gives
only the slower recombination components we can safely conclude by comparing the
dynamics in the presence and absence of quencher that the slow lifetime component comes
from the recombination of the electron injected in graphene after the photoexcitation of the
QD. The studies in the presence of quencher in this case only an electron quencher were used
as we are monitoring the bleach which contains information on the electron dynamics.
Table 6.4. Fits of the time traces monitored at 460nm (Exciton Bleach in presence of electron quencher).