Fluorescence quenching of nanoemitters within metallic nanoholes

The spontaneous emission rate of a dipole is strongly modified by metallic nano-structures that confine electromagnetic fields at the nanoscale. Metallic nanoholes (MNHs) are particularly attractive for single-molecule detection, as they simultaneously reduce observation volume and enhance fluorescence. While prior work has emphasized field enhancement, the mechanisms of fluorescence quenching remain less explored. In this study, we analyze dipole-metal coupling in MNHs through numerical simulations and experimental validation. Radiative and nonradiative decay rates, quantum yield, and fluorescence lifetime were calculated for dipoles of varying orientations and lateral offset distances inside nanoholes of different diameters. Fluorescence lifetime imaging of HPTS-doped PVA films confirmed the simulations, with deviations at small diameters attributed to fabrication-induced sidewall tapering. These findings clarify quenching dynamics in MNHs and inform nanophotonic design for biosensing and quantum emitter applications.