Branched mercapto acid capped CdTe quantum dots as fluorescence probes for Hg2+ detection

Herein, we report the synthesis of CdTe quantum dots prepared by colloidal synthesis route using the branched mercapto acid, 3 Mercaptoisobutyric acid (3-MIBA) as capping agent. The as synthesized 3-MIBA capped CdTe quantum dot (CdTe@3-MIBA) was used as fluorescent probe to detect Hg2+. Further, the performance was linear in the range 1.5-100 nM with a limit of detection of 1.5 +/- 0.5 nM. The results demonstrated that fluorescence quenching of CdTe@3-MIBA by mercury follow different routes: (i) strong affinity of Hg towards S causes depassivation of capping agents thus resulting in aggregation of quantum dots (ii) excitonic electron transfer from the lowest unoccupied molecular orbital (LUMO) of CdTe@3-MIBA to the LUMO of Hg2+ thus preventing emission.