Boosting the Photocatalytic Activity of InP QDs through Surface Ligand-Mediated Charge Transfer

Abstract

Quantum dots (QDs) have proven to be promising photocatalysts owing to their size-tunable optical properties and efficient generation of charge carriers. However, their performance is strongly influenced by surface ligands, which govern charge carrier dynamics. In this study, green-emitting InP/ZnS quantum dots (G-InP/ZnS QDs) are synthesised and ligand exchanged to compare the effects of organic and inorganic surface ligands in determining the efficiency of charge transfer and thereby their photocatalytic activity. To evaluate their photocatalytic efficiency, a carbon–carbon (C–C) bond-forming reaction was employed as a test reaction in which the reactants are 1-phenylpyrrolidine and phenyl-trans-styryl sulfone. Systematic optimisation of reaction parameters, including irradiation time, catalyst concentration, and light intensity, led to the identification of optimal conditions for maximum product formation. Under these conditions, inorganic ligand-capped QDs exhibited superior photocatalytic activity, giving a higher yield of product compared to the conventional organic ligand-capped QDs. Control experiments confirmed the photocatalytic nature of the reaction, with negligible product formation found in the dark or in the absence of catalyst or in the presence of only heat. The enhanced catalytic activity of inorganic ligand-capped QDs is attributed to effective charge extraction and charge transfer processes between the QD surface and reactants, via the conductive ligands. Overall, this study highlights the critical role of surface ligand engineering in modulating charge carrier dynamics and demonstrates its direct impact on improving the photocatalytic efficiency of QD-based photocatalysis.