Detection of Hg2+ and F- Ions by Using Fluorescence Switching of Quantum Dots in an Au-Cluster-CdTe QD Nanocomposite

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 Au-25 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 x 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 x 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.