Surface-enhanced fluorescence on SiO2-coated silver island films

Fluorescence is one of the molecular spectroscopic properties that is enhan ced by placing the molecule on the rough surface of a coinage metal. The su rface-enhanced fluorescence (SEF) can be directly observed in steady-state fluorescence experiments, The observations are the results of a delicate ba lance between the enhanced emission and the quenching due to energy transfe r to nonradiative surface plasmons, In the present report, SiO2-coated silv er films were fabricated at varying dielectric thickness. The surface of th e films was analyzed with the use of atomic force microscopy (AFM) and Xray photoelectron spectroscopy (XPS), AFM confirms the surface roughness and X PS analysis indicates that the SiO2 coverage was successful. SEF and SERS ( surface-enhanced Raman scattering) were observed on active 6, 10, and 14 nm silver films coated with SiO2. Similar results were obtained with a 6 nm s ilver film coated with 6 nm SiO. The SEF work was carried out on fluorescen t molecules with different quantum yield, and the typical enhancement facto r obtained for the fluorescent signal was approximately 10, Both the SiO2 a nd SiO overlayers provide stable surfaces with well-defined hydrophilic pro perties, Such stable constructions have applicability towards the advanceme nt of SERS and SEF as routine analytical techniques in bio- and chemical se nsors.