Increasing the Enhancement Factor in Plasmon-Enhanced Fluorescence with Shell-Isolated Nanoparticles

Three central experimental variables are looked at to increase the observed enhancement factor in plasmon-enhanced fluorescence: nanoparticle size, nanoparticle aggregation, and the sample temperature. The rise in emission intensity is demonstrated here in carefully chosen experimental conditions. First, it is shown that shell-isolated nanoparticles of gold (Au-SHINs) with a core of 100 nm produce a higher enhancement factor than smaller Au-SHINs (with a core of 40 nm) in solution and on Langmuir–Blodgett (LB) films. The enhancement factor is further increased by aggregation of the Au-SHINs in solution, and the findings are supported by finite-difference time-domain (FDTD) computations. Second, the enhancement factor (110-fold) of plasmon-enhanced fluorescence achieved with large Au-SHINs on an LB film of eosin decyl ester (EOSDEC) increases dramatically at low temperatures (170 fold). High enhancement factors are underpinned by a close matching of the plasmon extinction and fluorescence emission.