Fluorescence of molecules near small metal particles

Abstract

Small particles and rough surfaces of certain metals are known to give anomalously high electric fields when illuminated with radiation resonant with the plasmon oscillation of these structures. The most widely publicized manifestation of the high field is the surface enhanced Raman effect. Equally dramatic but less well known is the large change in radiative and nonradiative rates for molecules near these structures. A reduction of fluorescence life time of 104 with no loss in quantum efficiency has been reported. This fast radiative rate has been used to give recovery in quantum yield of 103 for heavily quenched fluorophor. We present further studies on the extent to which radiative and non-radiative rates can be controlled using metal particle substrates. Self-quenching, surface treatment, scattering, and the difficult engineering associated with this method are discussed. Prospects for large scale production of substrates and application of the effect to quantitative fluorescence analysis is assessed. The direction of future study required to realize in practice the large demonstrated effects is presented.