Highly sensitive assaying study based on three-dimensional graphene/cerium oxide nanoparticle nanozyme for the detecting of organophosphate pesticides in vegetable

As an important chemical pollutant affecting the safety of agricultural products, the on-site and efficient detection of pesticide residues has become a global trend and hotspot in research. Herein, this work present a highly sensitive assaying study based on three-dimensional graphene/cerium oxide nanoparticle nanozyme for the detection of organophosphate pesticides (OPs) in vegetable. The detection mechanism is because OPs can inhibit the activity of alkaline phosphatase (ALP). Cerium oxide nanoparticles exhibited intrinsic biomimetic oxidase activity and catalyzed the oxidation of the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue oxidized oxTMB. Upon the introduction of ALP, L-ascorbic acid-2-phosphate can be dephosphorylated to ascorbic acid, which aroused the disintegration of cerium oxide nanoparticles into Ce ions. This disintegration weakened the enzyme-mimicking activity, thus impeding the oxidation of TMB. The absorbance at 652 nm exhibited a linear relationship with the concentration of phorate in the range of 0.15–50 μg/mL, generating a limit of detection of 0.13 μg/mL, Phorate recovery in the spiked samples for the absorption detection mode was 81.0 %–96.7 %. The relative standard deviations (RSD) of the absorption were in the range of 2.18 %–4.12 %. The results in terms of detecting pesticide residues collected from food samples via this method satisfactorily agree with those obtained via gas chromatography–mass spectrometry. This simple assay is therefore suitable for sensing pesticides in complex samples, especially in combination with other portable platforms.