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A simple and sensitive colorimetric method for the determination of Pb(2+) ions in aqueous samples was developed using 1-(2-mercaptoethyl)-1,3,5-triazinane-2,4,6-trione (MTT) functionalized silver nanoparticles (MTT-AgNPs). The Pb(2+) ion acted as the metal center of the coordination complex, which formed N-Pb(2+)-O coordination bonds with the MTT-AgNPs, shortening the interparticle distance, and inducing aggregation of the MTT-AgNPs. This aggregation resulted in a dramatic color change from yellow to dark blue. Using this methodology, the concentration of Pb(2+) ions in environmental samples could be quantitatively detected with the naked eye or by using UV-vis spectrometry. Also, we found that the selectivity and sensitivity of detection were noticeably improved in the pH range of 7-8, at which a more obvious color change was observed. The absorption ratios (A625/A395) of the modified AgNP solution exhibited a linear correlation with Pb(2+) ion concentrations within the linear range of 0.1-0.6 μg mL(-1), and the limits of detection in tap and pond water were 0.02 and 0.06 μg mL(-1), respectively. This cost-effective sensing system allows for the rapid and facile determination of Pb(2+) ions in aqueous samples.

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