The Inverse Relationship between Metal-Enhanced Fluorescence and Fluorophore-Induced Plasmonic Current

In this work we investigate the relationship between metal-enhanced fluorescence (MEF) and fluorophore-induced plasmonic current (PC). This is accomplished through measurements of both radiative emission (MEF) and direct electrical current generation between discrete metal nanoparticles upon fluorophore excitation (PC). We have conducted these measurements on silver and gold nanoparticle island films, over a range of nanoparticle sizes and spacing in the films. We have observed an inverse relationship in the magnitude of MEF with PC, where larger and more closely spaced metal nanoparticles are found to result in increased PC and subsequently a decreased MEF. We attribute this effect to the relatively high capacitance and low charging energy of large and closely spaced particles, providing an outlet for plasmon relaxation in the form of electron flow and electrical current generation. These results are significant as they open potential for controlling for and the optimization of both MEF and PC.