Using silicon-coated gold nanoparticles to enhance the fluorescence of CdTe quantum dot and improve the sensing ability of mercury (II)

Abstract

The effect of silicon-coated gold nanoparticles with different gold core diameter and silica shell thickness on the fluorescence emission of CdTe quantum dots (QDs) was investigated. For gold nanoparticles with a diameter of 15nm, silica coating can only results in fluorescence recover of the bare gold nanoparticle-induced quenching of QDs. However, when the size of gold nanoparticle is increased to 60nm, fluorescence enhancement of the QDs could be obtained by silica coating. Because of the isolation of the silica shell-reduced quenching effect and local electric field effect, the fluorescence of QDs gets intense firstly and then decreases. The maximum fluorescence enhancement takes place as the silica shell has a thickness of 30nm. This enhanced fluorescence from silicon-coated gold nanoparticles is demonstrated for sensing of Hg2+. Under optimal conditions, the enhanced fluorescence intensity decreases linearly with the concentration of Hg2+ ranging from 0 to 200ng/mL. The limit of detection for Hg2+ is 1.25ng/mL. Interference test and real samples detection indicate that the influence from other metal ions could be neglected, and the Hg2+ could be specifically detected.