Construction of ratiometric fluorescence determination of ethylene thiourea in foods based on the nanocomposite combining with sulfur quantum dots and gold clusters

Abstract

A nanocomposite-based dual-emission fluorescent probe was constructed to detect ethylene thioureas (ETU). The nanocomposite SQDs@GSH-AuNCs was formed by the combination of sulfur quantum dots (SQDs) and glutathione stabilized gold clusters (GSH-AuNCs). After the combination, the fluorescence intensities at 450 nm and 570 nm decreased due to the aggregation fluorescence quenching effect. However, the addition of ETU resulted in a partial recovery of fluorescence at 570 nm. A possible reason was the occurrence of a ligand reaction between the zero- and one-valence gold and ETU to form a complex, which weakened the aggregation fluorescence quenching effect. Under the optimal reaction conditions, the concentration of ETU in the range of 2.5 μM to 100 μM had a good linear relationship with the ratio of fluorescence intensity (I570/I450), and the detection limit was 2.08 μM. The experimental results showed that the method had high selectivity and sensitivity, and had a good recovery of ETU in agricultural products. In addition, the hydrolysis process of mancozeb (Mz) was simulated, and by the use of SQDs@GSH-AuNCs, the conditions for promoting and inhibiting the hydrolysis of Mz to produce ETU were analyzed and obtained, which provided an experimental basis for the storage of Mz and a new method for analyzing the hydrolysis process of Mz.