The Metal-Enhanced Fluorescence of CdTe Quantum Dots under the Excitation of Femto Second Laser

This paper presents an investigation on the fluorescent properties of semiconductor CdTe quantum dots (QDs) self-assembled on the surface of PVP (polyvinylpyrrolidone) capped silver nanoparticles (NPs) film by ligand field effect under the two photons excitation of 800nm femto second laser. A significant enhancement by 4.5-fold in the integrated fluorescence intensities, red shift of fluorescence peak and obvious decrease of lifetime were observed in the CdTe QDs assembled on the Ag NPs film in comparison with the pure CdTe QDs on the glass. The fluorescence enhanced factor is larger on the solid film than in the liquid. The fluorescence enhancement factor and red shift were found to depend on the Ag NPs concentration. The fluorescence enhancement was contributed to high localized electromagnetic field generated by the surface plasma on the Ag NPs and the change of surface trap state of CdTe QDs originating from plasma oscillations in the Ag NPs.