Distance-Dependent Fluorescence Quenching Efficiency of Gold Nanodisk: Effect of Aspect Ratio-Dependent Plasmonic Absorption

The fluorescence quenching efficiency of an emitter close to a gold nanodisk is investigated by theoretical calculation based on the modified quasi-static approximation and fluorescence energy transfer under dipole?Cdipole coupling. The calculation results show that the surface plasmon resonance (SPR) absorption is the key factor to affect the quenching efficiency. Because of the asymmetric shape of the gold disk, the light absorption depends on both particle volume and aspect ratio (AR). Thus, the AR cannot control the quenching efficiency of gold nanodisk alone. Whether the disk volume is fixed or not may bring different changing way of AR-controlled quenching efficiency. Increasing the AR leads to the quenching efficiency of perpendicular mode start to decrease at a farther distance when the disk volume is changed, but start to decrease at a nearer distance when the volume is fixed. At a given wavelength, one can find a distinct peak in the AR-dependent quenching efficiency curve of parallel mode when the volume is fixed, which is absent from the quenching efficiency curve when the volume is changed. All these tunable quenching efficiency characteristics have been explained by the changing of intensity, shift, and bandwidth of SPR absorption.