Novel Electrochemical Sensing Based On Silver And Gold Nanomaterials

The electrochemical sensor can convert the interaction of the substance on the surface of the electrode into an electrical signal,which has the advantages of fast response and high detection sensitivity.Silver,gold and other noble metal nanomaterials can improve the performance of electrochemical sensing analysis by increasing the electron transfer rate on the electrode surface and increasing the effective area of the electrode.In this thesis,silver nanocomposites,gold nanoparticles（AuNPs）and gold nanoclusters（AuNCs）were prepared by chemical reduction method,constant potential deposition method and thiol protection method,respectively.The relationship between their preparation method and sensor performance was discussed.Based on this,novel electrochemical sensors were constructed.The main research content is as follows:（1）Silver nanoparticles-carbon nanofibers composites was prepared by chemical reduction in N,N-Dimethylformamide medium and modified on the surface of glassy carbon electrode to develop a novel nitrite electrochemical sensor.The electrochemical sensor was used for detecting nitrite in pickles and ham sausages.The electrochemical sensor had a wide linear range(0.01-11 mmol·L^-1)and good selectivity.（2）AuNPs modified electrode was prepared by constant potential deposition method using glassy carbon electrode（GCE）as a substrate electrode in a solution containing chloroauric acid.The effects of deposition conditions on the surface morphology,effective area,electroactive gold area and interfacial impedance of the electrode were studied in detail.Electrocatalytic behavior of AuNPs/GCE for nitrite,ethanol,hydrogen peroxide and p-nitrophenol were investigated.The relationship between Au NPs electrodeposition conditions and AuNPs/GCE catalytic activity was revealed.The results showed that:the catalytic performance of AuNPs/GCE varied depending on the catalyzed object.In a certain ranges,the catalytic activity of AuNPs/GCE for the oxidation of nitrite and the reduction of hydrogen peroxide increased with the negative shifting of deposition potential and prolonging the deposition time.But with the prolonging deposition time,the accumulation of AuNPs on the electrode surface decreased the catalytic performance.The catalytic activity of Au NPs/GCE for ethanol increased with the negative shifting of deposition potential and prolonging the deposition time,so the electroactive gold area of AuNPs/GCE was the main influencing factors.AuNPs/GCE did not play a catalytic role in the catalytic reduction of p-nitrophenol,which was mainly due to the dependence of the reduction of p-nitrophenol on the electrode material.（3）A novel AuNCs was prepared by thiol protection method in methylene chloride medium and characterized.The effects of the electrode,pulse parameters,the concentration of electrolyte and AuNCs on the electrochemical behavior of AuNCs were studied in detail,and the electrochemical fingerprints of AuNCs were given;a new idea of using the electrochemical fingerprints of AuNCs to calculate the molecular composition of AuNCs was proposed,and this electrochemical fingerprints was used for in-situ monitoring of ligand exchange of AuNCs.A novel electrochemical sensor based on the nanocluster was fabricated.The response mechanism of the sensor is based on the ligand exchange between AuNCs and biothiol,such as,cysteine,homocysteine and glutathione,which results in the change of the electrode interface impedance.The limit of detection of biothiols was 0.05mmol·L^-1.