Opposite changing dual-emission luminescence of gold nanoparticles by sulfhydryl to develop a pesticide biosensing strategy

Abstract

As the merit of ratiometric assay is impregnable due to potentially interfering processes, a ratiometric method for pesticide detection was developed. By adjusting glutathione : HAuCl₄ to an appropriate ratio, dual-emission luminescent ultra-small gold nanoparticles (AuNPs) with a high emission at 800 nm and a low emission at 600 nm were synthesized. Interestingly, the sulfhydryl-containing compounds were found to result in completely opposite changes to strengthen the 600 nm emission and weaken the 800 nm emission. Therefore, dual-emitted AuNPs were engaged to develop a ratiometric pesticide biosensing strategy. In the presence of acetylcholinesterase (AChE), acetylthiocholine can be hydrolyzed into thiocholine, whose newly generated sulfhydryl can interact with AuNPs, resulting in the opposite change of the dual emissions. While adding pesticide as an AChE inhibitor, the catalytic activity of AChE is inhibited and less thiocholine was produced. The biosensing system shows an obvious sensitivity to the pesticide with a limit of detection (LOD) of 0.2 nM for aldicarb and 0.07 nM for chlorpyrifos. Therefore, this simple assay is suitable for AChE activity and pesticide detection, even in vegetable samples.