Ligand Exchange Reprograms Blinking Dynamics and Photon Statistics in Single InP/ZnS Quantum Dots.

Ligand exchange is widely used in quantum dot (QD) processing, but its impact on the photophysical properties of QDs remains poorly understood. Using single-particle intensity-lifetime analysis, blinking statistics, and photon correlations, we demonstrate that replacing oleic acid (OA) with 3-mercaptopropionic acid (MPA) alters the dominant blinking mechanism in single InP/ZnS QDs. OA-capped QDs exhibit separated lifetime-intensity clusters that are characteristic of charging-induced Auger blinking. After MPA exchange, the lifetime-intensity relationship becomes continuous and approximately linear. Long-lived bright periods also become less probable, consistent with a shift toward trap-assisted band-edge-carrier blinking. Concurrently, MPA exchange shortens exciton and biexciton lifetimes while increasing the normalized zero-delay coincidence probability, indicating different responses of the single-exciton and biexciton relaxation channels. These concurrent yet distinct changes demonstrate that ligand exchange does not simply alter the average emission intensity but rebalances the competing radiative, Auger-mediated, and trap-assisted relaxation pathways at the single-QD level.