C. Burda et al., Electron shuttling across the interface of CdSe nanoparticles monitored byfemtosecond laser spectroscopy, J PHYS CH B, 103(11), 1999, pp. 1783-1788
The formation and decay of the optical hole (bleach) for 4 nm CdSe nanopart
icles (NPs) with adsorbed electron accepters (1,4-benzoquinone and 1,2-naph
thoquinone) and the rise and decay of the reduced electron accepters formed
after interfacial electron transfer from the CdSe NPs were investigated by
femtosecond laser spectroscopy. The ultrashort (200-400 fs) rise times of
the bleach at the band-gap energy of the CdSe NP as well as of the acceptor
radical anion are found to increase with increasing the excitation energy.
This suggests that the electron transfer from the CdSe NP to the quinone e
lectron acceptor occurs after thermalization of the excited hot electrons.
The decay times of the transient absorption for the electron acceptor radic
al anions are found to be comparable to that of the CdSe NP bleach recovery
time (3 ps). This suggests that the surface quinones shuttle the electron
from the conduction band to the valence band of the excited NP. We contrast
this behavior with the excited-state dynamics of the recently investigated
CdS-MV2+ system in which the electron acceptor does not shuttle the accept
ed electron back to the hole in CdS.