Label-free upconversion luminescence nanosensor based on LRET for rapid detection of cyanazine

A straightforward and highly selective upconversion luminescence (UCL) nanosensor was designed for the detection of cyanazine (CZ) pesticide residues in food and environmental samples, based on the luminescence resonance energy transfer (LRET) mechanism. Without any modification, the LRET system employed upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs) as the energy donor and acceptor respectively to achieve efficient quenching of UCL. CZ specifically induced the aggregation and detachment of AuNPs from UCNPs, leading to the termination of LRET and achieving the “off-on” process of UCL. According to the changes in UCL, the linear range of the nanosensor for CZ detection was 0.1–8.0 μM, with a detection limit of 0.098 μM. Finally, the nanosensor was successfully applied to detect CZ spiked in lake water, tap water, and corn. The recovery rates were in the range of 98.99–101.42%, and the relative standard deviations (RSD) were below 3%. The proposed nanosensor exhibits excellent application prospects in complex sample matrices.