Sensitive detection of monosultap using a BSA-Cu nanocluster-based turn-off-on fluorescent sensor

Monosultap (Mon) poses significant environmental and human health risks due to its widespread and irregular use. However, due to the lack of intrinsic fluorophores and identifiable sites in monosultap, there were few fluorescence analytical methods achieved sensitive detection of monosultap. Hence, we present a BSA-Cu nanocluster-based turn-off-on fluorescent sensor for sensitive detection of monosultap. The sensor exhibits fluorescence quenching ("turn-off") in the presence of DTAB-CuTPyP. The competitive binding of monosultap with DTAB-CuTPyP switches the sensor to the "turn-on" state. Under optimized conditions, the sensor demonstrates a linear response to monosultap concentrations ranging from 0.33 × 10⁻ 2 to 3.33 × 10⁻ 2  mg/kg, with a detection limit of 0.098 mg/kg, which is below the permissible exposure limit (approximately 1 mg/kg). In addition, the co-existence of nine interference pesticides does not affect the sensor's ability to detect monosultap. This fluorescence restoration mechanism enables sensitive monosultap detection and provides a guide for detecting trace pesticides in food.