Journal
ACS NANO
Volume 3, Issue 3, Pages 682-690Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn800848y
Keywords
light energy conversion; artificial photosynthesis; photoinduced electron transfer; semiconductor nanocrystals; photocatalysis; reverse micelles; CdSe; viologen radical
Categories
Funding
- Department of Energy, Office of Basic Sciences
- Notre Dame Radiation Laboratory [NDRL 4790]
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Photoinduced charge transfer events between 3 nm diameter CdSe semiconductor nanocrystals and an electron acceptor, MV2+, have been probed in the subpicosecond-microseconds-seconds time scale by confining the reactants in an AOT/heptane reverse micelle. The probe molecule, methyl viologen (MV2+) interacts with the excited CdSe nanoparticle and quenches its emission effectively. The ultrafast electron transfer to MV2+, as monitored from the exciton bleaching recovery of CdSe and the formation of MV+circle radical, is completed with an average rate constant of 2.25 x 10(10) s(-1). Under steady state irradiation (450 nm) the accumulation of MV+circle is seen with a net quantum yield of 0.1. Mediation of the electron transfer through TiO2 nanoparticles is achieved by coupling them with the CdSe-MV2+ system within the reverse micelle. This coupling of two semiconductor nanoparticles increases the quantum yield of MV2+ reduction by a factor of 2. The dual roles of TiO2 as an electron shuttle and a rectifier are elucidated by transient absorption spectroscopy and steady state photolysis. The presence of both TiO2 and MV2+ in the reverse micelle creates a synergistic effect to enhance the electron transfer rate constant by an order of magnitude. The time-resolved events that dictate the production and stabilization of electron transfer product provide an insight into the photocatalytic systems that are potentially important in solar hydrogen production and photocatalytic remediation.
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