Sensitive Pb²⁺ probe based on the fluorescence quenching by graphene oxide and enhancement of the leaching of gold nanoparticles

A novel strategy was developed for fluorescent detection of Pb²⁺ in aqueous solution based on the fact that graphene oxide (GO) could quench the fluorescence of amino pyrene (AP)-grafted gold nanoparticles (AP-AuNPs) and Pb²⁺ could accelerate the leaching rate of AuNPs in the presence of S₂O₃^2-. In this system, fluorescence reporter AP was grafted on AuNPs through the Au-N bond. In the presence of GO, the system shows fluorescence quenching because of π-π stacking between AP and GO. With the addition of Pb²⁺ and S₂O₃ ^2-, the system displays fluorescence recovery, which is attributed to the fact that Pb²⁺ could accelerate the leaching of the AuNPs from GO surfaces and release of AP into aqueous solution. Interestingly, the concentration of GO could control the fluorescence "turn-off" or "turn-on" for Pb²⁺ detection. In addition, GO is also an excellent promoter for the acceleration of the leaching of AuNPs and shortening the analytical time to ∼15 min. Under the optimal conditions, the fluorescence Pb²⁺ sensor shows a linear range from 2.0 × 10^-9 to 2.3 × 10^-7 mol/L, with a detection limit of 1.0 × 10^-10 mol/L.