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The efficient light-driven fuel production from homogeneous photocatalytic systems is one promising avenue towards an alternative energy economy. However, electron transfer from a conventional photosensitizer to a catalyst is short-range and necessitates spatial proximity between them. Here we show that energetic hot electrons generated by Mn-doped semiconductor quantum dots (QDs) allow for long-range sensitization of Ni(cyclam)-based molecular catalysts, enabling photocatalytic reduction of CO 2 to CO without requiring chemical linkages between the QDs and catalyst molecules. Our results demonstrate the potential of hot electron sensitization in simplifying the design of hybrid catalyst systems while improving photocatalytic activity. 

The utility of colloidal semiconductor quantum dots as a source of photons and charge carriers for photonic and photovoltaic applications has created a large field of research focused on tailoring and broadening their functionality beyond what an exciton can provide. One approach towards expanding the range of characteristics of photons and charge carriers from quantum dots is through doping impurity ions ( e.g. Mn 2+ , Cu + , and Yb 3+ ) in the host quantum dots. In addition to the progress in synthesis enabling fine control of the structure of the doped quantum dots, a mechanistic understanding of the underlying processes correlated with the structure has been crucial in revealing the full potential of the doped quantum dots as the source of photons and charge carriers. In this review, we discuss the recent progress made in gaining microscopic understanding of the photophysical pathways that give rise to unique dopant-related luminescence and the generation of energetic hot electrons via exciton-to-hot electron upconversion.