Fluorescence Enhancement of CdTe Nanocystals Induced by Ag/TiO₂Core-shell Nanoparticles

Abstract

Metal-enhanced fluorescence from CdTe nanocrystals placed in close proximity to novel synthesized Ag/TiO2 core/shell nanoparticles films is studied.The Ag/TiO2 core-shell nanoparticles are synthesized in the aqueous solutions by colloid chemistry method.Transmission electron microscopy images show that mostly Ag/TiO2 core/shell nanoparticles are clearly core/shell structure and ball-shaped.The deep black cores are Ag nanoparticles and the light-colored shell are titania.In addition,the UV-Vis absorption spectra of Ag nanoparticles have a surface Plasmon absorption at 409 nm arising from the particles.A similar surface plasmon absorption due to Ag nanoparticles is observed for the titania-coated Ag nanoparticles at a wavelength longer than for the Ag nanoparticles.This absorption shift is caused by a high refractive index of the titania shell and strongly suggests a complete coverage of Ag nanoparticles with titania.The as-prepared Ag/TiO2 core-shell nanoparticles are assembled with the CdTe nanocrystals and spin-coated on the quartz glass.Significantly enhanced fluorescence emissions are observed,implying that enhanced fluorescence from Ag/TiO2 core/shell nanoparticles films is mostly due to an electric field enhancement effect.The current work is available for the applications in light emitting device,fluorescence imaging,and biological detection.