DNA-Templated Ag Nanocluster/CdSe@ZnS Quantum Dot-Based Platform for Colorimetric and Fluorescence Detection of Organophosphorus Pesticide

The agriculture and environmental industries have employed organophosphorus pesticides (OPs) chemicals as insecticides extensively in previous decades, leading to persistent life-threatening issues. Therefore, developing a platform for the efficient identification of OPs is significant for environmental protection and human health. In this study, a strategy for the colorimetric and fluorescence detection of OPs by combining quantum dots (QDs) with DNA-templated silver nanoclusters (DNA-AgNCs) was proposed. Technically, the fluorescence of DNA-AgNCs will be enhanced once guanine (G)-rich sequences get close to the DNA-AgNCs to form hybrid complexes DNA-AgNCs/G, while quenching of fluorescence can be attributed to the hydrolysate (thiocholine) of acetylthiocholine (ATch) that was caused by acetylcholinesterase (AchE). Based on the fact that OPs can irreversibly inhibit the catalytic activity of AchE and slow down the fluorescence quenching of DNA-AgNCs/G, thus, OPs detection can be achieved by evaluating the fluorescence intensity of DNA-AgNCs/G. Additionally, a dual-mode detection system (colorimetric and fluorescent) is achieved through an ion-exchange reaction between QDs and DNA-AgNCs/G. The concentration of OPs is quantified by monitoring fluorescence changes in the QDs and poly(9,9-dioctylfluorene) (PFO) polymer dots (Pdots) system, with PFO Pdots serving as a stable internal reference. Using trichlorfon as a model, the limit of detection (LOD) was 2.55 pg/mL, while an excellent linear relationship with the trichlorfon concentrations in the range of 5 × 100–5 × 105 pg/mL was obtained. Additionally, visual detection (as low as 1.06 pg/mL) can be realized readily, taking advantage of the ion-exchange reaction between DNA-AgNCs and QDs.