Development of gold nanoclusters based direct fluorescence restoration approach for sensitive and selective detection of pesticide

Pesticide contamination of drinking water is of high concern due to their hazardous effects on ecosystems. Several detection methods are available which are associated with many drawbacks, e.g. slow response time and laborious procedural techniques. This limits their practicability. Therefore, there is a dire need to develop quick, simpler but equally sensitive and practical methods for pesticide detection. Herein, we report a highly sensitive assay using fluorescent AuNCs for the detection of a pesticide i.e., 2-methyl-4-chlorophenoxyacetic acid (MCPA). For this purpose, three different fluorescent Au nanoclusters stabilized by histidine (His-AuNCs), lysozyme (Lys-AuNCs) and RNase (RNase-AuNCs) were systematically studied as optical probes for the detection of MCPA using a turn-on assay. The fluorescence of these AuNCs was initially quenched with Cu 2+ ions followed by the quantitative recovery of their fluorescent signals in the presence of MCPA. The sensitivity and selectivity of these clusters for MCPA were in a linear dynamic range, i.e., 110–180 nM, 100–170 nM and 90–160 nM in case of His-AuNCs, Lys-AuNCs and RNase-AuNCs, respectively. Also, the aforesaid clusters were having a different limit of detection (LOD) by each type, i.e., highest by His-AuNCs (21.87), intermediate by Lys-AuNCs (12.97) and lowest by RNase-AuNCs (9.26 nM). Hence, the RNase-AuNCs are found to be the most sensitive, whereas His-AuNCs are least sensitive for the detection of MCPA. These findings offer a rapid, sensitive and selective assay for MCPA detection and have potential implications for the on-site, real-time monitoring of noxious pollutants.