Preparation And Detection Of Typical Contaminants In Food By Self-assembly Of Carbon-based 1D/2D Nano-hybrid Materials

Pesticide residues and mycotoxins are two typical contaminants in agricultural products,which pose a serious threat to human health and social environment,and have become a major safety problem in the world.Therefore,it is of great meaning to develop rapid and sensitive detection ways for pesticide residues and mycotoxins to protect human health and social environment.In recent years,the use of electrochemical sensors to detect contaminants in agricultural products has been more and more studied.Among them,the selection of modification materials is crucial to improve the performance of electrochemical sensing,and carbon-based nanohybrid materials have attracted much attention because of their excellent electrochemical performance.Preparation by self-assembly method in this paper.the series carbon one-dimensional/two-dimensional（1D/2D）nanohybrid material,the experimental research show that the nanohybrid material due to the excellent electrical conductivity,high specific surface area of pesticide residue isoproturon（ISO）,paraquat（PQ）and mycotoxins ochratoxin A（OTA）has high catalytic activity.The electrochemical sensor was constructed by functionalized modification of the glassy carbon electrode（GCE）with this kind of nanohybrid material,which was used for the detection of pesticide residues and mycotoxins in a variety of agricultural products,showing good sensing performance.The main research content of this paper is divided into three parts,and the results are as follows:（1）1D carboxylated multi-walled carbon nanotubes（MWCNTS-COOH）and 2D graphene oxide（GO）were self-assembled with the aid of ultrasound to construct ISO electrochemical sensor,which realized the rapid and sensitive detection of ISO by square wave voltammetry（SWV）.The sensor displays a relatively wide linear range from 0.30 to15.0μmol/L,limit of detection（LOD）of 0.10μmol/L,as well as good repeatability,high reproducibility,excellent selectivity,and long-term stability.The sensor has also been successfully employed in various real samples such as tomato,and lettuce analyses.The obtained recoveries are in the range of 97.33%～105.0%with low RSD（less than 2.5%）,which is very close to the results of the HPLC,showing the proposed electrochemical sensor has great potential in practical applications.（2）Using simple self-assembly method will 1 D high conductive graphene（Gr）and2D MWCNTs-COOH group of Nafion（Nf）was modified,the Nf-Gr-MWCNTs-COOH nano hybrid material,the coordination effect of these elements can produce sensitive sensors,and using the simple,high selectivity and sensitivity of square wave voltammetry（SWV）used for paraquat（PQ）detection.The sensor has a wide linear range（0.01～15μmol/L）and low LOD（0.005μmol/L）.And the sensor has good repeatability,reproducibility,high selectivity,long-term stability and good anti-pollution.It has been successfully applied to black tea,corn,lettuce,wolfberry and plum samples with recovery of 96.00%～106.0%and relative standard deviation less than 3.0%.It shows that the electrochemical sensor has a good application prospect.（3）1D MWCNTS-COOH were coated with 2D titanium carbide（2D Ti₃C₂）by a simple self-assembly method as a modified material for glassy carbon electrode and used for OTA detection.Physical characterizations and electrochemical techniques revealed that MWCNTs-COOH can not only prevent the restacking of 2D Ti₃C₂ nanosheets but also facile its electro transfer,leading to a nanohybrid with a high specific surface and good electrocatalytic activity to OTA.The electrochemical sensor shows a good linear response to OTA in a concentration range from 0.09μmol L to 10μmol/L and LOD of 0.028μmol/L.The proposed sensor was impelled six successive times to detect OTA,a good repeatability with RSD of 3.72%was obtained,indicating the constructed sensor possessed good anti-fouling property in the detection of OTA.Moreover,satisfactory recoveries between91.8%and 103.2%were obtained in the real sample analysis of grape and beer,showing that the developed sensing technique is reliable for the screening of trace OTA in food resources.