Photothermal effect-enhanced peroxidase-like performance for sensitive detection of organophosphorus pesticides on a visual test strip

Pesticides pose a serious risk to public health, even in trace amounts. The sensitive, rapid, visual, and on-site detection of pesticides in a real sample remains a challenge. Herein, we report a visual and rapid organophosphorus pesticide (OP) sensing device with excellent sensitivity, ease of application, and specificity based on a photothermal effect-based peroxidase (POD) mimetic. The ultrathin MIL-101-NH2(Fe) (Fe-MOF) shell-coated Au nanobipyramide (NBP) not only possesses POD-like activity, but also exhibits excellent photothermal effect under near-infrared (NIR) light. The results reveal that the excellent photo-to-thermal conversion of the Au NBPs can rapidly heat the MIL-101-NH2(Fe) shell, which subsequently induces a markedly enhanced POD-like activity. Using paraoxon-ethyl as model OP, the combination of the OP inhibition effect on the biocatalytic activity of acetylcholinesterase with the inhibition effect of thiocholine on the colorimetric assays of the POD-mimicking Fe-MOF leads to a significant improved selectivity for OP sensing. In particular, the NIR light irradiation increased the OP detection sensitivity by 100 times. Importantly, based on this detection strategy, a visual test strip with high sensitivity was developed and enabled real-time detection through a simple color analysis software on a smartphone. The successful detection of OP residues in fruit peel using this test strip further confirmed its application potential in real sample analysis.