Dopamine-functionalized upconversion nanoparticles as fluorescent sensors for organophosphorus pesticide analysis

Organophosphorus pesticide (OP) residues in agricultural products, herbal medicines and environment have attracted increasing concerns because they cause high healthy risk. Herein, a tyrosinase-mediated photoinduced electron transfer system was constructed for OPs analysis by using dopamine-functionalized upconversion nanoparticles (UCNPs) as fluorescent (FL) sensors. Dopamine quinone was produced by tyrosinase-mediated oxidation of dopamine on the surface of UCNPs, which acted as electron accepter to quench the FL emission of UCNPs. The FL quenching was inhibited by OP since it inhibited the activity of tyrosinase. Chlorpyrifos was used as a model analyte to investigate the feasibility of the FL sensor for the analysis of OPs. Under the optimal conditions, chlorpyrifos can be analysed in a wide range of 1.0 ‒ 1000 ng mL^-1, with a detection limit of 0.38 ng mL^-1 (3σ). Some other groups pesticides, including organonitrogen pesticide, organochlorine pesticide and chloronicotinyl insecticide all showed negligible interference. The proposed sensor was successfully used to analyse chlorpyrifos spiked in Balloonflower and Angelica with acceptable recovery values of 95.4-120.0%, demonstrating its application potential for real samples. It exhibits some advantages like low cost, high sensitivity and free of autofluorescent interference and photobleaching.