Microwave-assisted synthesis of high-quality CdTe/CdS@ZnS–SiO2 near-infrared-emitting quantum dots and their applications in Hg2+ sensing and imaging

Highly luminescent, good stable and low toxic N-acetyl- l -cysteine (NAC) capped CdTe/CdS@ZnS–SiO 2 near-infrared (NIR)-emitting quantum dots (QDs) were successfully fabricated in aqueous solution via a microwave irradiation reduction route, in which thiol-capped CdTe/CdS QDs were employed as core templates and ZnCl 2 , NAC and tetraethyl orthosilicate as shell precursors. This presented ZnS-like clusters filled hybrid SiO 2 model not only greatly improved the brightness and stability of original CdTe/CdS QDs, but also tremendously decreased the cytotoxicity towards HeLa cells. Furthermore, it was found that Hg 2+ could effectively selective quench the QD NIR emission based on electron transfer process. On the basis of this fact, a simple, rapid and specific method for trace Hg 2+ determination was proposed. Under optimal conditions, the fluorescence intensity decreased linearly with the concentration of Hg 2+ ranging from 5.0   ×   10 −9 to 1.0   ×   10 −6   M and the limit of detection for Hg 2+ was 1.0   ×   10 −9   M ( S / N   =   3). As practical applications, the novel NIR sensor has been demonstrated to monitor and image Hg 2+ level in milk power and HeLa cells respectively with satisfactory results obtained.