Colorimetric sensing of lead ion using gold nanorod with enhanced sensitivity via catalytic etching

Abstract Lead, a prevalent heavy metal, poses significant risks to human health through various exposure pathways. Herein, we propose an extremely sensitive assay toward lead ion (Pb 2+ ) using gold nanorods (GNRs) as probes based on its catalytic activity on etching gold in the presence of 2‐mercaptoethanol and sodium thiosulfate. In the presence of Pb 2+ , etching predominantly occurs at the two ends of GNRs, leading to the reduction of aspect ratio and the corresponding blueshift of the localized surface plasmon resonance (LSPR). With increasing Pb 2+ concentration over the range of 0–50 μM, the color of GNR solution lightens, ultimately becoming colorless. The wavelength shift (Δλ) of LSPR is highly dependent on Pb 2+ concentration, with a linear regression equation of Δλ = 10.05ln[Pb 2+ ] + 9.59 and an R 2 = 0.995. The assay demonstrates high selectivity for Pb 2+ over other potentially interfering ions such as Cu 2+ because of its special catalytic activity in the etching of GNRs and the complexing ability of 2‐mercaptoethanol and sodium thiosulfate. Validation of the assay was accomplished by analyzing several forest‐derived food samples, affirming the accuracy in real‐world scenarios. The assay we developed holds promise for many applications in environmental protection and food safety.