Metal-enhanced fluorescence of lanthanide chelates near silver nanostructured films

Metal-enhanced fluorescence (MEF) from lanthanide chelates in close proximity to silver films was studied. Different thicknesses of silver films (20 and 50 nm) were deposited onto quartz substrates using magnetron sputtering, while silver island films were prepared using a previously published procedure. Obviously enhanced emissions from the lanthanide chelates were observed on the silver films. The effect of using different concentrations of aqueous solutions polyvinyl alcohol (PVA) on MEF was also investigated. Fluorescence close to a 20-nm-thick silver film showed that the enhancement of emission is a function of the thickness of the PVA film, reaching a maximum (～2.5-fold increase in intensity) at 83 nm. In conclusion, the MEF induced by the silver films is caused by an electric field effect arising from surface plasmon resonance.