Metal-enhanced fluorescence using aggregated silver nanoparticles

A simple strategy to prepare aggregated Ag nanoparticle composites in solution by self-assembly is developed. Sodium citrate is used as the reduction agent to produce negatively charged Ag nanoparticles which are then aggregated using cationic polyacrylamide (PAM) to form self-assembled Ag-PAM microcomposites. In these microcomposites, the degree of aggregation of Ag nanoparticles can be controlled by changing the Ag/PAM ratio. This special structural feature can be applied in the study of metal-enhanced fluorescence. Confocal laser scanning microscopy and time-resolved fluorescence measurements are used to examine the fluorescence enhancement phenomenon of the Ag-PAM microcomposites. The microcomposites considerably enhanced the fluorescence intensity of fluorescein isothiocyanate isomer (FITC).