Coupled plasmon effects for the enhancement of fluorescent immunoassays

We present a study of fluoroimmunoassays using Rhodamine-RedX labelled antibodies enhanced by nanoparticle silver island films (SIFs) in the presence of thin metallic layers. Our results show enhancement of the immunoassay signal by up to 10-fold for SIFs on glass and up to 50-fold enhancement for SIFs supported by a metal surface. An explanation for these effects is proposed by considering plasmonic coupling within the system and modification of the fluorophore spontaneous emission rate.