Photocatalytic processes on semiconductor nanocrystals are a promising route to solar energy conversion to chemical fuels. Photoreduction processes are well studied and often excitingly efficient. The necessary concomitant oxidative processes, however, are much slower and have been identified as the bottle neck for increased efficiency of overall photocatalysis. Furthermore, these processes usually use sacrificial reagents rather than sustainable ones (such as H2O oxidation to O2 or redox-cycleable reagents). Here we present or work towards solving this problem. We preapred a ligand that facilitates hole transfer from CdS nanorods through energetic overlap of a dithiocarbamate functional group with the valence band. A conjugated bipyridine chelates Fe(II) and DFT calculations show that this is the eventual destination of the hole in a two-step process. Hole transfer from the CdS valence band to the midgap states provided by the dithiocarbamate and Fe(II) is dipole allowed and occurs at rates much faster than is experimentally known for the CdSe/CdS band-edge radiative recombination. The system was experimentally assembled and characterized via UV-vis absorbance spectroscopy, fluorescence spectroscopy, time-resolved photoluminescence spectroscopy, and energy dispersive X-ray spectroscopy which corroborated the experimental predictions.

Digging out of a hole problem

254th National Meeting (2017)

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