Construction of CuNCs/AgNPs based fluorescent platform for specific enzyme-free detection of trichlorfon

As a common organophosphorus pesticide, trichlorfon (TC) is being extensively used in agriculture due to its high efficiency in plant diseases and insect pest control. However, TC should be monitored in a timely manner due to its severe threat to public health. Currently reported fluorescence methods for TC detection largely depend on enzyme inhibition effect, which suffers from their intrinsic defects such as poor selectivity, complexity, or high cost. Hence, it is of essential value to develop a facile and low-cost fluorescence approach to achieve specific enzyme-free detection of TC.

In this work, L-cysteine protected copper nanoclusters (CuNCs) with good stability were prepared as the fluorescence sensing probe. Under alkaline conditions, TC tends to be hydrolyzed to produce dichloroacetaldehyde, which was directly employed as an effective reducing agent to in-situ synthesize silver nanoparticles (AgNPs). The fluorescence of L-cys-CuNCs was quenched by AgNPs through the inner filter effect (IFE), realizing specific enzyme-free determination of TC. Besides, portable and visual detection of TC was achieved depending on a smartphone sensing platform. This method was further employed to monitor TC in cherry tomatoes, potatoes, and cultivated soil samples with satisfying results, illustrating its high potential in monitoring TC in real samples. Overall, this method possesses the attractive superiorities of simplicity, cost efficiency, and specificity for the detection of TC.

The strategy has the following advantages. (i) Specific enzyme-free detection of TC was achieved based on CuNCs/AgNPs fluorescent platform. (ii) AgNPs, as CuNCs fluorescence quencher, was directly in-situ synthesized using the hydrolysis products of TC, which avoids adding extra reducing agent and provides a possibility for the waste utilization of TC. (iii) A portable and low-cost smartphone sensing platform was constructed for visually specific determination of TC.