Detection of Hg²⁺ and F^-ions by using fluorescence switching of quantum dots in an Au-cluster-CdTe QD nanocomposite

Abstract

A single probe of an Au nanocluster–CdTe quantum dots nanocomposite has been developed by using tripeptide-capped CdTe quantum dots (QD) and bovine serum albumin (BSA) protein-conjugated Au25 nanocluster (NC) for detection of both Hg²⁺ ion and F^- ion. The formation of Au-NC–CdTe QD nanocomposite has been confirmed by TEM, steady state and time resolved spectroscopy, CD and FTIR studies. A significant signal off (74 % PL quenching at 553 nm) phenomenon of this nanocomposite is observed in presence of 6.56×10^-7 M Hg²⁺ ion, due to salt-induced aggregation. However, a dramatic PL enhancement (128 %) of the Au-NC–CdTe QD nanocomposite is observed in presence of 8.47×10^-7 M F^- anion. The calculated limit of detections (LOD) of Hg²⁺ ion concentration and F− ion concentration are found to be 9 and 117 nM, respectively, which are within the safety range set by the United States Environment Protection Agency. Thus, the simple Au-NC–CdTe QD optical-based sensor is very useful to detect both toxic cations and anions.