Lanthanum-functionalized gold nanoparticles for coordination–bonding recognition and colorimetric detection of methyl parathion with high sensitivity

A novel and sensitive colorimetric sensor for determination of methyl parathion (MP) was developed based on a lanthanum (La 3+ ) functionalized gold nanoparticles (Au NPs-La) probe. In this assay, a new type of crosslinking molecule-La 3+ , possessing strong coordination effect on oxygen-containing functional groups, was first applied in the Au NPs-based colorimetric assay. On account of the oxygen-containing thiophosphate, MP could combine with La 3+ and induce the aggregation of Au NPs-La probes through coordination–bonding interactions, resulting in a variation of the solution color from red to blue. Further, the color change was in situ monitored with ultraviolet visible (UV–vis) spectrophotometer for the quantitative detection of MP. In contrast with the commonly designed Au NPs-based colorimetric assays, a novel Au NPs-La probe, which equipped with the same type of binding sites with Au NPs and analyte molecules, was explored and used for optical detection of MP. Under optimized conditions, the colorimetric assay exhibited a linear correlation to the concentration of MP in the range from 0.5   nM to 0.5   μM with a detection limit of 0.1   nM (S/N   =   3). The developed sensor is simple, without using complicated instruments, and has enormous potential applications in rapid and on-site monitoring for MP in real samples.