Charge Transfer Dynamics in Complexes of Light-Absorbing CdS Nanorods and Redox Catalysts

The use of photoexcited electrons and holes in semiconductor nanocrystals as reduction and oxidation reagents is an intriguing way of harvesting photon energy to drive chemical reactions. This dissertation describes research efforts to understand the photoexcited charge transfer kinetics in complexes of colloidal CdS nanorods coupled with either a water oxidation or reduction catalyst. The first project focuses on the charge transfer interactions between photoexcited CdS nanorods and a mononuclear water oxidation catalyst derived from the [Ru(bpy)(tpy)Cl]+ parent structure. The second project details the electron transfer kinetics in complexes of CdS nanorods coupled with [FeFe]-hydrogenase, which catalyzes H+ reduction. These complexes photochemically produce H2 with quantum yields of up to 20%. Kinetics of electron transfer from CdS nanorods to hydrogenase play a critical role in the overall photochemical reactivity, as the quantum efficiency of electron transfer defines the upper limit on the quantum yield of H 2 generation. Insights from these time-resolved spectroscopic studies are used to discuss the intricate kinetic pathways involved in photochemical H2 generation and the mechanism for electron transfer from photoexcited nanorods to hydrogenase in photocatalytic complexes.