Metal-induced redshift of optical spectra of gold nanoparticles: An instant, sensitive, and selective visual detection of lead ions

Environmental exposure to non-essential lead has become a serious problem in various developing and industrializing countries. There is an urgent need to develop a method offering instrument-free, rapid, highly sensitive, and selective detection of lead. Colorimetric detection of lead using gold nanoparticles (AuNPs) has been reported but these NPs require specific surface modifications and incubation times. In this study, we have developed an approach for instant, highly selective and sensitive detection of Pb2+. The as-synthesized AuNPs did not require any surface modification for the detection of Pb2+. The selectivity was evaluated by taking 300 μM of various metal ions and the assay color was found to change rapidly from red to blue in the presence of Pb2+, whereas the color remained the same for the other metal ions. The present method did not require a long incubation time as the assay color changed as soon as the AuNPs were added into the Pb2+ solution. Therefore, the developed method realized rapid detection of Pb2+. The limit of detection and limit of quantification were calculated to be 18 μM and 53.5 μM, respectively. The detection mechanism was investigated using ultraviolet–visible spectroscopy, dynamic light scattering, Fourier transform infrared spectroscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy.