A New Sensing Method For Pesticide Residues Sensitized By Carbon-based Nanomaterials

Imidacloprid is the first neonicotinoid insecticide,and trichlorfon is a commonly used organophosphorus insecticide.Long-term exposure to these two pesticides at low doses will cause damage to human health,and the residues of these two pesticides in bananas,cabbages and other fruits and vegetables are at high risk.Therefore,this paper is based on carbon based nanomaterials with excellent fluorescence or electrochemical performance,synthesizing different types of carbon based nanomaterials to achieve effective amplification of detection signals,for high selection and sensitivity detection of imidacloprid and trichlorfon in agricultural products.The following research work was mainly carried out:Establish a new sensing method for the determination of imidacloprid using graphene quantum dots（GQDs）—carbon quantum dots（C-dots）energy transfer fluorescence quenching method.Under optimized experimental conditions,there is a good linear relationship between the concentration of imidacloprid and the quenching intensity of C-dots,with a detection limit of 8.23 mol/L×10^-10mol/L,compared with other imidacloprid analysis methods,this method has higher sensitivity.The method was applied to the detection of imidacloprid residues in practical samples such as bananas,with a recovery rate of 93.0%～105.6%.The results were satisfactory.GO/Au NPs/β-CD thin film modified electrode sensors were prepared by introducing graphene（GE）,gold nanoparticles（Au NPs）andβ-cyclodextrin（β-CD）on the surface of glassy carbon electrode by cyclic voltammetry.The reduction current of imidacloprid in B-R buffer at pH 5.02 was effectively amplified,and the reduction current had a good linear relationship with the concentration of imidacloprid.The detection limit of this method is 1.33×10^-10mol/L,and the sensitivity of this method is significantly improved compared with the previous imidacloprid fluorescence analysis method.Moreover,this method has high sensitivity,and has been applied to the detection of actual samples such as bananas.The recovery rate is 92.0%～110.0%,and the results are satisfactory.A molecularly imprinted polymer（MIP）modified electrode sensor was prepared by electro polymerization on the surface of a multi walled carbon nanotube loaded silver（MWCNs/Ag）modified gold electrode,using trichlorfon as a template molecule and o-phenylenediamine as a functional monomer.After eluting trichlorfon,the sensor retains imprinted holes that specifically recognize trichlorfon molecules,which can achieve specific recognition ability for trichlorfon molecules.Both MWCNs/Ag and trichlorfon can sensitize the electrochemical luminescence signals of Luminol-hydrogen peroxide（H₂O₂）system,so the sensor shows high sensitivity.The concentration of trichlorfon was positively correlated with the electrochemical luminescence intensity of the sensor,and the detection limit of trichlorfon was3.90×10^-13mol/L.The sensor was applied to the detection of trichlorfon residues in agricultural products,and the recovery rate was 95.7%～101.4%,and the results were satisfactory.