Plasmon regulated exciton dynamics and emission behavior of single Au@SiO₂-quantum-dot hybrid

Controlling photon emissions from semiconductor quantum dots (QDs) is crucial for the development of nanophotonic devices. Integrating plasmonic metal nanostructures with QDs effectively tunes their spontaneous emission, fluorescence intensity, blinking behavior, and decay rates. However, the underlying mechanism of plasmonic manipulation remains unclear. We fabricate well-defined hybrid nanostructures consisting of an Au nanoparticle and a single CdZnSeS/ZnS QD, separated by silica shells with precisely controlled thicknesses. Using single-molecule fluorescence lifetime imaging and second-order photon correlation (g²(τ)) measurements, we comprehensively study the plasmonic effects on the photophysical properties of QDs. With localized surface plasmon manipulation, the optimized Au@SiO₂-single QD hybrids exhibit a significant enhancement in photoluminescence intensity, non-blinking behavior, and multi-photon emission. Meanwhile, the radiative recombination rate of QD excitons increases sharply, such that the accelerated radiative decay rate becomes comparable to the nonradiative Auger rate. This significantly boosts multiple exciton radiative recombination, leading to improved photon emission properties of the QDs. Our findings are helpful in understanding the mechanism of plasmon-exciton interactions and could potentially aid in controlling photon emission in nanoscale photonic devices.