Enhanced Charge Transfer from Coinage Metal Doped InP Quantum Dots

This paper describes coinage-metal-doped InP quantum dots (QDs) as a platform for enhanced electron transfer to molecular acceptors relative to undoped QDs. A synthetic strategy is developed to prepare doped InP/ZnSe QDs. First principles DFT calculations show that Ag+ and Cu+ dopants localize photoexcited holes while leaving electrons delocalized. This charge carrier wavefunction modulation is leveraged to enhance electron transfer to molecular acceptors by up to an order of magnitude. Examination of photoluminescence quenching data suggests that larger electron acceptors, such as anthraquinone and methyl viologen, bind to the QD surface in two ways– by direct adsorption to the surface, and by adsorption following displacement of a weakly bound surface cation-ligand complex. Reactions with larger acceptors show the greatest increases in electron transfer between doped and undoped quantum dots, while smaller acceptors show smaller enhancements. Specifically, benzoquinone shows the smallest followed by naphthoquinone, and then methyl viologen and anthraquinone. These results demonstrate the benefits of dopant-induced excited-state carrier localization on photoinduced charge-transfer and highlight design principles for improved implementation of quantum dots in photoredox catalysis.