Studies On Improved Screen Printed Electrode And Multifunctional Gold And Nanocomposite Electrochemical Sensor

Food safety issues are receiving increasing attention.Foodborne pathogens,viruses and other chemical hazards are important factors influencing food safety.How to establish a faster,more accurate and sensitive detection method is the direction that researchers are committed to.Among many rapid detection methods,electrochemical sensors have attracted wide attention in various fields due to their high specificity,high efficiency,and low cost.However,electrochemical sensors still need to be continuously improved to achieve better performance.At present,the research on improving electrochemical performance is mainly devoted to the modification procedure of electrodes,the modification method and the selection of modified materials,such as the preparation of novel nanomaterials for modification.These studies have indeed achieved some improvement and improvement,but they cannot fundamentally improve electrode performance.There is also a part of research that is aimed at improving the properties of the electrode itself,so that the improvement of the solid electrode from the beginning to the printed electrode fundamentally solves the cumbersome process of physical and chemical treatment of each electrode.However,there are still some problems in the screen-printed electrode itself,such as the small area of the working electrode,which is absolutely sensitive and relatively insensitive.After several years of data query and research,it is found that the surface area of the working electrode is a very important factor affecting the performance of the electrode,but related research reports are rare.Therefore,this study started from the working electrode itself of the screen-printed electrode,and carried out improved design and performance test research.At the same time,by preparing different nano-gold and its composite materials,combined with different modification methods,three representative food harmful factors were used as detection objects,and three electrochemical sensors were developed to promote the improvement of electrochemical sensor detection performance.It also provides research models for such tests to facilitate the development of electrochemical sensors in the field of food safety.The main contents of this study are as follows:1.Improvement of screen-printed working electrode based on gold nanoparticles modification of different surface area E.coli O157:H7 electrochemical immunosensorIn this study,four screen printed electrodes（SPCE）with different working electrode areas（working electrode diameters of 2 mm,2.5 mm,3 mm,and 3.5 mm）were prepared.In order to explore its performance and select the best,firstly,chloroauric acid（HAuCl₄）was reduced to gold nanoparticles（AuNPs）by Cyclic Voltammetry（CV）and uniformly deposited on screen-printed carbon electrodes surface,and characterized by CV to evaluates the four electrodes to select the best.The results showed that SPCE with the largest working electrode area had the best performance,so it was selected for direct detection of Escherichia coli O157:H7（E.coli O157:H7）.The performance of the electrochemical immunosensor was characterized by CV and Electrochemical impedance spectroscopy（EIS）.The immunosensor was quantified by the CV method,and the oxidation peak current change value(ΔI_pa)was linear with the logarithm of the E.coli O157:H7 solution concentration,and the linear range was 1.19×10³ CFU·mL^-11 to 1.19×10⁹ CFU·mL^-1.The minimum detection limit is 5.94×10² CFU·mL^-1.At the same time,the immunosensor has relatively good specificity,reproducibility and stability.The actual sample analysis of the milk powder samples was carried out by this method,and the recovery rate was between 91.5%and 105.8%.2.Study on hydrogen peroxide sensor based on stabilized polyaniline and gold-platinum composite metal nanoparticles for screen-printed electrodes with different surface area working electrodesDue to the good electrochemical performance of nano-gold,the composite Au@Pt was prepared to detect hydrogen peroxide（H₂O₂）.The Au@Pt/PANI/SPCE modified electrode was prepared by the polyaniline modified electrode obtained by the potentiostatic method to detect hydrogen peroxide.At the same time,the SPCEs of four different working electrode areas were compared to make modified electrodes under the same conditions,and the results showed that the working electrode area showed the best performance.Then,the hydrogen peroxide was detected by Amperometric i-t detection（Amperometric i-t Curve,i-t）.The result was a linear range of 0.02 mM to 12 mM,detection limit of 2.9μM,and sensitivity of 749.8μA?mM^-1?cm^-2.The sensor has good reproducibility and specificity.In addition,it can be repeatedly tested 54 times with excellent stability.By using this method to analyze the actual sample of milk samples,there is a good recovery rate（between 99.5%and104.2%）,indicating that the sensor is basically free of protein interference.3.Electrochemical Immunosensors for H5 and H7 Subtype Avian Influenza Viruses by functionalized rGO Composite Gold Palladium NanoparticlesBased on the results of the previous chapter,Au@Pt has a large specific surface area and can have good catalytic performance for H₂O₂.Therefore,in this chapter,by preparing another nano-gold composite Au@Pd,it is found that the prepared Au@Pd has better catalytic ability than Au@Pt,and the best Au@Pd is obtained by changing the molar ratio of the soluntion by H₂PdCl₄ to HAuCl₄.The immunological probe rGO-NR-Au@Pd-Ab2-BSA was prepared by combining it with graphene nanomaterials to detect the H5 subtype avian influenza virus,and the linear range of2^-7 to 2^-16 HA unit/50μL was linear.Relationship,detection limit is 2^-16 HA unit/50μL,and has good specificity,reproducibility and stability.The recovery rate of the actual sample analysis by this method was good,which were 105.4%,101.9%,104.6and 98%,respectively.At the same time,the low concentration of H7 subtype avian influenza virus was detected,and it was linear in the concentration range of 2^-13,2^-14,2^-15,2^-16 HA unit/50μL,detection limit is 2^-16 HA unit/50μL and had good specificity.