Highly Sensitive and Selective Fluorescence “Turn-On” Detection of Pb (II) Based on Fe(3)O(4)@Au–FITC Nanocomposite

New nanocomposites, Fe(3)O(4)@Au–FITC, were prepared and explored to develop a fluorescent detection of Pb(2+). The Fe(3)O(4)@AuNPs–FITC nanocomposites could be etched by Pb(2+) in the presence of Na(2)S(2)O(3), leading to fluorescence recovery of FITC quenched by Fe(3)O(4)@Au nanocomposites. With the increase of Pb(2+) concentration, the fluorescence recovery of Fe(3)O(4)@AuNPs–FITC increased gradually. Under optimized conditions, a detection limit of 5.2 nmol/L of Pb(2+) with a linear range of 0.02–2.0 µmol/L were obtained. The assay demonstrated negligible response to common metal ions. Recoveries of 98.2–106.4% were obtained when this fluorescent method was applied in detecting Pb(2+) spiked in a lake-water sample. The above results demonstrated the high potential of ion-induced nanomaterial etching in developing robust fluorescent assays.