The Effect of Local Dielectric Environment on the Fluorescence Quenching Efficiency of Gold Nanoshell

By using the theory of quasi-static electrodynamics and fluorescence resonance energy transfer (FRET), local dielectric constant-dependent fluorescence quenching of gold nanoshell has been studied. Because the bonding plasmon coupling mode has stronger resonance light absorption, the bonding plasmon coupling mode-induced FRET has a greater quenching efficiency than that of anti-bonding plasmon coupling mode. Both the bonding and anti-bonding plasmon coupling mode-induced fluorescence quenching are greatly dependent on the local dielectric constant. The quenching efficiency corresponding to anti-bonding plasmon coupling mode increases as the inner core dielectric constant is increased, whereas the quenching efficiency corresponding to bonding plasmon coupling mode increases as the outer surrounding dielectric constant is increased. The corresponding physical origin could be illustrated as follows. The anti-bonding and bonding plasmon coupling modes are primarily composed of the cavity and surface plasmon, respectively. As the result of the increasing outer surrounding/inner core dielectric constant-induced shifting and widening of bonding/anti-bonding plasmonic absorption peak, the corresponding wavelength region with high quenching efficiency value also red shifts and broadens as the dielectric constant of outer surrounding/inner core is increased. Thus, the fluorescence quenching efficiency of gold nanoshell could be fine tuned by altering the local dielectric environment.