Dependence of fluorescence on coupling from coupled Au nanoparticle - semiconductor quantum dot assemblies

Enhanced nonlinear fluorescence is observed in distributed CdS nanocrystals and Au nanoparticles composite thin film. Well-defined spacings between the semiconductor quantum dots (SQDs) and the metal nanoparticles are considered. The samples are excited with the second harmonic generation of a mode-locked Ti-sapphire laser, and fluorescence spectra are measured. An approximately two-fold increase in linear fluorescence intensity is observed. Similar samples were prepared with Au nanorods (plasmon frequency ~ 750 nm, 25 nm cross-section diameter) to match the excitation wavelength with the resonant plasmon frequency of the Au nanorods. Preliminary results have shown a 10x enhancement of fluorescence.