Quantum Effect Boosts Energy Transfer in Quantum Dots

Researchers have identified a proton-assisted mechanism that significantly enhances triplet energy transfer between quantum dots and nearby molecules. This discovery, detailed in *Nature Materials*, involves a proton temporarily shifting position to coordinate electron movement. The proton then returns to its original location.

This process, termed proton shuttle-assisted triplet energy transfer (PS-TET), was observed in zinc selenide (ZnSe)-based colloidal quantum dots. These quantum dots were linked to phenol-pyridine dyadic acceptors. When the ZnSe quantum dots absorbed light, they entered an excited state. A hole moved from the ZnSe to the phenol, while a proton simultaneously shifted from phenol to pyridine.

An electron then transferred from the ZnSe to the phenoxyl radical. Concurrently, the proton moved back from pyridinium to its initial site. This sequence of linked steps facilitated the transfer of spin-triplet energy from the ZnSe quantum dots to the phenol-pyridine dyads. The temporary movement of the proton dramatically increased both the speed and efficiency of this energy transfer.

The team also found that adding a trifluoromethyl substituent to pyridine could alter the order of the proton-coupled electron and hole transfer steps. The rate of PS-TET showed minimal change with temperature. This suggests that the proton moves via quantum mechanical tunneling, rather than a conventional heat-driven process. Calculations of proton vibrational wavefunction overlap integrals supported this interpretation.

This quantum-driven shuttle mechanism could offer a new method to tune various technologies. These include solar cells, lasers, and catalytic reactions. Controlling triplet generation efficiency is important for applications like photoredox and environmental catalysis. It is also crucial for optimizing organic optoelectronic devices.