Studies And Application Of Electrocatalysis Activity Of Two Kinds Of Chemically Modified Electrodes

In electroanalytical chemistry, the general reaction between the electrode and solution interface are electron transfer in non-homogeneous solution. Electrodes such as mercury, precious metals and graphite were widely used in electrochemical studies in the past years. However> those electrode reactions are all single electron transfer and the majority of ions in solution are transferred slowly on the electrode. In the Voltammetry studies, the problem of the traditional electrode is that the current value decreased with the growth of time due to the changes of the activity of the electrode surface. So, how to make the electrode to be selective, and provide faster response has been a problem need to be solved for many electrochemical workers.Chemical Modification Electrode (CME) which focuses on the electrode surface is a revolutionary change in electrochemical field. Chemically modified electrodes are designed by immobilizing excellent chemical properties of molecules, ions, fixed polymer on the electrode surface through chemical modification. The resulting micro-structure endows the electrodes with particular chemical and electrochemical properties so as to achieve higher selective reactions which have high specificity, excellent selectivity and efficiency. In this paper, two kinds of methods are used to modify the electrodes to produce two novel electrochemical sensors.In the paper, works were done as followings:1.Glassy carbon(GC) electrode is modified with an electropolymerized film of Iron(II)-Tetra(5,6-dihydro-l,4-dithijn)porphyrazine (FePz(dtn)₄ ). The polymer film modified electrode is used to electrochemically detect the ascorbic acid (AA). In cyclic voltammetric measurements, polymer film showed excellent electrocatalytic activity as the oxidation potential for AA is positively shifted compared to that at the bare electrode. The oxidation peak current increased linearly with the concentration of AA in the electrolytic solution. The linear range was from 5 to 300μg·mL^-1, and the limit is 1.3μg·mL^-1. The modified electrode had good sensitivity, selectivity and stability.2. A novel hydrogen peroxide biosensor was fabricated by self-assembling of horseradish peroxidase (HRP), gold nanoparticles (nano-Au) and electropolymerized PVP on the gold electrode. The performance and conditions such as pH and potential influencing the resulting biosensor were studied in detail by means of CV and chronoamperometry. Under optimized conditions, the immobilized HRP exhibited direct electrochemical behavior toward the reduction of hydrogen peroxide (H₂O₂). The linear range is from 3.5×10^-7 to 3.15×10^-6 mol.L^-1 with the correlation coefficient -0.996.