Inner filter effect-based upconversion nanosensor for rapid detection of thiram pesticides using upconversion nanoparticles and dithizone–cadmium complexes

•A chemical nanosensor was developed for the determination of thiram.•The detection was achieved by a fluorescence inner filter effect.•The dithizone-Cd2+ complex as a bridging ligand was able to ultra-sensitive detection of thiram.•The proposed nanosensor has good sensitivity with a LOD of 6.75 ng/mL.