Fluorescent Detection of Lead in Environmental Water and Urine Samples Using Enzyme Mimics of Catechin-Synthesized Au Nanoparticles

A facile, cost-effective, and sensitive fluorescent method for Pb2+ ion detection had been developed using catechin synthesized gold nanoparticles (C-Au NPs). The Pb-catechin complexes and Pb-Au alloys that formed on the C-Au NPs surfaces allowed NPs to exhibit percaidasemimicking catalytic activity in the H2O2-mediated oxidation of Amplex UltraRed (AUR). In 5 mM Tris-acetate buffers at pH 7.0, the H2O2-AUR-C-Au NP probe was highly selective (>100-fold) for Pb2+ ions in the presence of other tested metal ions (K+, Ag+, Na+, Cd2+, Ni2+, Ca2+, Hg2+, Sr2+, Co2+, Cu2+, Ba2+, Fe2+, Mg2+, Cr3+, and Fe3+ ions). The fluorescence intensity (excitation/emission maxima similar to 540/588 nm) of the AUR product was proportional to the concentration of Pb2+ ions in the range of 10 nM-1.0 mu M with a linear correlation (R-2 = 0.99). The H2O2-AUR-C-Au NP probe detected Pb2+ ions with a limit of detection (signal-to-noise ratio: 3) of 1.5 nM. The practicality of the H2O2-AUR-C-Au NP probe was validated for the determination of Pb2+ ion concentration in environmental water and urine samples, demonstrating its advantages of simplicity, selectivity, and sensitivity.