Preparation Of Nano-material-organic Polymer Composite Film Modified Electrode And Its Application In Analysis Of Prohibited Food Additives

Illegal addition of various prohibited additives has become one of the main problems that endanger food safety.In order to crack down on behaviors that endanger food safety and ensure food safety,high sensitivity,high selectivity and accurate detection of prohibited additives in food samples have become key means.Although there are many methods available for the analysis and detection of prohibited additives in food samples,there are also various shortcomings.Therefore,the further development of new analytical methods and principles to achieve rapid and accurate detection of prohibited additives in food still requires further exploration and research.Recently,various electrochemical sensing methods based on nanomaterials have received widespread attention in the field of food safety due to their low analysis cost,convenient operation,easy realization of miniaturization,and automation.Its main purpose is to realize the orderly and controllable assembly of nanomaterials on the electrode surface,and use the synergistic effect of each component to further improve the electrochemical analysis performance of the modified electrode for prohibited additives.This thesis first reviews and summarizes the application of nanomaterial chemically modified electrodes in the field of food analysis in recent years.Based on this,three kinds of chemically modified electrodes including graphene quantum dots-polypyrrole peroxide-multi-walled carbon nanotube composite film（GQDs-OPPy/MWCNTs/CCE）,multi-walled carbon nanotubes-polypyrrole peroxide-reduced graphene oxide composite film（MWCNTs/Er GO/OPPy/CCE）,and gold nanoparticle/Poly-L-cysteine-polypyrrole peroxide-reduced graphene oxide composite film（Au NPs/PL-cys/OPPy/ERGO/CCE）modified electrodes were fabricated.The above electrodes were also applied to the electrochemical sensing of Rhodamine B,6-Benzylaminopurine and Clenbuterol,respectively.The main contents are as follows:1.Firstly,the multi-walled carbon nanotubes（MWCNTs）have been coated on the surface of the base electrode.Then the polypyrrole film has electrochemically deposited on the surface of MWCNTs by using graphene quantum dots（GQDs）as a dopant.After further electrochemical reduction and overoxidation treatment,a graphene quantum dot-polypyrrole peroxide-multi-wall carbon nanotube composite film modified electrode（GQDs-OPPy/MWCNTs/CCE）was obtained.Based on the investigation of the electrochemical properties and electrode reaction mechanism of rhodamine B on the modified electrode,a new method for the determination of rhodamine B by differential pulse voltammetry（DPV）has been established.Under optimized experimental conditions,when the concentration is in the range of 5.0×10^-8～2.0×10^-5 mol·L^-1,the peak current is proportional to the concentration of Rh B.The detection limit is 1.7×10^-8 mol·L^-1（3S_b）.Compared with electrochemical sensors reported in the literature,the GQDs-OPPy/MWCNTs/CCE modified electrode has a lower detection limit and a wider linear range.The method has been used to the determination of Rhodamine B in pepper,chili and dried fruit samples with satisfactory results.2.A multi-walled carbon nanotubes/overoxidation polypyrrole/graphene oxide composite film（MWCNTs/PPy/GO）modified electrode has been prepared by one-step electrochemical deposition from a solution containing GO,MWCNTs and pyrrole.After further electrochemical reduction and overoxidation treatment,a multi-walled carbon nanotube-overoxidation polypyrrole-reduced graphene oxide composite film（MWCNTs/OPPy/Er GO）modified electrode has been obtained.The result shows that graphene,carbon nanotubes and polypyrrole can be assembled orderly on the surface of the base electrode simultaneously by one-step electrochemical technique,which simplifies the electrode preparation process.The electrochemical behavior of plant hormone6-benzylamino purine（6-BAP）on the modified electrode has been further investigated,and the possible reaction mechanism of 6-BAP on the modified electrode has been explained.Based on this,a new method for determination of 6-BAP by differential pulse voltammetry（DPV）was established.Under the optimum conditions,the dynamic range of 6-BAP is 1.0×10^-8-3.0×10^-5 mol·L^-1,with a detection limit（3S_b）of 3.3×10^-9mol·L^-1.The method has been applied to the determination of 6-BAP in bean sprout water.The recoveries are in the range of 95.2-104%.3.Firstly,an overoxidation polypyrrole poly-reduced grapheme oxide composite film（OPPy/ERGO）modified electrode has been constructed by electrochemical method.And then,poly-L-cysteine（P-L-Cys）has been electrodeposited on this OPPy/ERGO composite film.A poly-L-cysteine-overoxidation polypyrrole-reduced graphene oxide composite film（P-L-Cys/OPPy/ERGO）has been obtained.Finally,the electrode is immersed in the colloid solution of gold nanoparticles,and an Au NPs/P-L-Cys/OPPy/ERGO composite film electrode has been fabricated.The results show that the three-dimensional structure of the basic OPPy/ERGO composite film provides a larger specific surface area and more active sites for loading P-L-Cys.By the adsorption action of poly-L-cysteine,the Au NPs can be assembled orderly on the electrode surface.The mutual cooperation of the components in the composite film further improves the electrochemical activity of the modified electrode,and can realize the effective determination of clenbuterol hydrochloride in pork.The linear range and detection limit（3S_b）of the DPV method for the detection of clenbuterol hydrochloride is7.0×10^-8～7.0×10^-5 mol·L^-1 and 2.3×10^-8 mol·L^-1,respectively.