Determination of the Generation Efficiency and Reductive Reactivity of the Upconverted Hot Electrons from Mn-Doped Quantum Dots under Weak Visible Light

Hot electrons generated via Mn-mediated Auger upconversion in Mn-doped quantum dots (QDs) have been shown to be highly effective for reduction reactions that require high reduction potentials and long-range electron transfer. Due to their high energy, these electrons can drive reduction reactions in the solution phase through multiple pathways, including interfacial hot electron transfer on the QD surface and reduction by presolvated and solvated electrons within the solvent. Despite their demonstrated ability to drive challenging reactions, the efficiency of generating upconverted hot electrons under continuous-wave (cw) visible light excitation remains largely unknown. Here, we quantified the quantum yield of hot electron generation from Mn-doped CdSSe/ZnS QDs under continuous white light (455 nm) in aqueous media using the reductive dechlorination of monochloroacetate (MCA) as a hot electron-selective reaction. We found that the quantum yield for hot electron upconversion can reach 35–40% at an excitation intensity of ∼0.1 W/cm2, highlighting the high efficiency of Mn-doped QDs as a source of hot electrons. Furthermore, we observed a dependence of the product yield on the photoexcitation history, suggesting a possible excitation-induced surface charge affecting the local concentration of reactants near the QDs, thereby altering the reaction kinetics. These findings provide important insights into the design of more efficient Mn-doped QD structures and reaction conditions for hot electron-enabled photocatalysis using visible light-driven hot electron sources.