Highly sensitive colorimetric detection of lead using maleic acid functionalized gold nanoparticles

Highly sensitive colorimetric detection for Pb2+ has been developed using maleic acid (MA) functionalized GNP. The -COOH on MA was used to modify GNP surface whereas the other -COOH functional group have strong affinity to coordination behavior of Pb2+ allowing the selective formation more than other ions. MA-GNPs solution changed from red to blue color after the addition of Pb2+ due to nanoparticle aggregation. The different optical absorption and discriminate of particle size between the MA-GNPs solution with and without Pb2+ were characterized by UV-visible spectroscopy and transmission electron microscopy (TEM), respectively. The color intensity as a function of Pb2+ concentration gave a linear response in the range of 0.0-10.0 mu g L-1 (R-2=0.990). The detection limit was found at 0.5 mu g L-1 by naked eye and can be completed the analysis within 15 min. The MA-GNPs aggregated with Pb2+ showed high selectivity when was compared to other metal ions (As3+, Ca2+, Cd2+, Co2+, Cu2+, Fe3+, Hg2+, Mg2+, Mn2+, Ni2+, Pb2+ and Zn2+) and anions (Cl-, NO3- and SO42-). Our proposed method was also applied for the determination of Pb2+ in real drinking water samples from 5 sources. The result of real water samples were not statistically significant different from the standard methods at the 95% confidence level (pair t-test method). Moreover, we evaluated our proposed method for the determination of trace Pb2+ concentration in real breast milk samples. The recoveries were acceptable and ranged from 101 to 104% for spiked Pb2+ in real breast milk samples. Thus, MA-GNP colorimetric sensing provides a simple, rapid, sensitive, easy-to-use, inexpensive and low detection limit for the monitoring of Pb2+. (C) 2014 Elsevier B.V. All rights reserved.