Coordinated carbon dots-Fe featuring synergistically enhanced peroxidase-like activity at neutral pH for specific and background-free detection of dichlorvos

Abstract

Nanozyme-based assays present favorable prospects in sensitive determination of pesticides in food samples yet are constrained with little or even no catalytic activities at neutral pH, lack of selectivity, and interference by sample color. Here, a facile and novel photothermal system for rapid, specific, sensitive, and background-free detection of dichlorvos was developed based on peroxidase-like activity of coordinated carbon dots-Fe (CDs-Fe). CDs-Fe was prepared and fabricated based on the redox and coordination chemistry between CDs and Fe species. Catalytic mechanism investigations illustrate that CDs-Fe with outstanding peroxidase-like activity at neutral pH comes from the synergistic effect of •OH production and electron transfer process. More interestingly, dichlorvos can specifically complex with CDs-Fe through electrostatic attraction and π-π stacking interactions, which then cement substrates affinity and improve electron transfer efficiency to enhance the catalytic activity. Oxidized 3,3′,5,5′-tetramethylbenzidine (oxTMB) presents photothermal effect by absorption of near-infrared (808 nm) laser-driven light, which eliminates the color interference from real samples. Accordingly, a background-free photothermal strategy was established. Furthermore, a portable hydrogel kit was fabricated by embedding CDs-Fe and TMB into agarose hydrogel for on-site rapid detection of dichlorvos. A good relationship was observed in the range of 5.00–650 μg L−1 with a satisfactory detection limit at 4.85 μg L−1, and a good recovery (90.56–107.0 %) with excellent anti-interference capacity was achieved for real sample analysis. The work presents a novel nanozyme enhancement strategy for specific and background-free detecting dichlorvos in food samples.