Colorimetric and fluorescent probes for the rapid detection of profenofos in farmland system

•A dual-modal optical sensor was designed to detect profenofos for the first time.•The advantages of the method are simple, low-cost, and good accuracy and precision.•The proposed method was successfully used to profenofos detection in real samples. Colorimetric and fluorescent sensors were developed for the detection of profenofos. The colorimetric assay relied on the aggregation of cysteine modified gold nanoparticles (Au-cys) composite caused by the hydrogen bond and Au-S bond between profenofos and Au-cys. The further addition of S, N-doped carbon quantum dots (CDs) (fluorescence quantum yield up to 98%) into the Au-cys system depended on the change of fluorescence intensity of Au-cys-CDs owing to the inner filter effect between Au-cys and CDs. Under the optimal conditions, the sensor exhibits good linearity within 0.2–1.2 mg L−1 and 20–320 μg L−1, and limit of detection of 21.7 μg L−1 and 5.5 μg L−1 in colorimetry and fluorescence mode, respectively. The developed sensor did not only possess favorable selectivity and sensitivity, but also feasibility of usage in the actual detection of profenofos in farmland system samples.