Fabrication And Application Of Photoelectrochemical Sensing Interface For Hydrogen Peroxide

The electric conductive polymers are a polymer with conjugated bonds. Its conductivity can be changed from insulator into a conductor via the aid of chemical or electrochemical "doping". The poly(thionine) is a conducting polymer, which is prepared by electrochemical oxidation of thionine on the surface of electrode. Moreover, the poly(thionine) is a light-sensitive material, as a photic acceptor, it can oxidize the reducing agent as electron donor to produce the light-current, while it was excitated to a high energy level by light. We found hydrogen peroxide (H2O2) can employed as an electron donor in the photoelectrochemical reaction of poly(thionine), composing to a new photoelectrochemical system. The H2O2 is an important chemical product, but also an intermediate of O2 reduction and enzyme-catalyzed reaction. So, the substrate, the product or the enzyme activity could be determined indirectly by measuring of H2O2 in the enzymatic reaction. In the paper, a photoelectrochemical sensing interface for H2O2 was fabricated by electro-polymerizing thionine, and the activity of glucose, choline oxidase and uricase were determined indirectly by this methed. The main works are shown as follows:1. The photoelectrochemical system was fabricated by electro-polymerizing thionine, and it's electrochemical and photoelectrochemical behavior was investigated. The experimental results showed that poly(thionine) had a symmetrical redox peaks with two-electron and two-proton shift process in acidic solution. Its anode peak potential and cathodic peak potential was ?0.124 and ?0.198 V, respectively. And the separation of peak potentials (ΔEp) was 74 mV, the apparent potential E0 ' was ?0.161 V. In the dark, adding H2O2 to the electrolyte, poly(thionine) was oxidized with anode peak current decreasing and the cathodic peak current increasing. In light excitation, the energy level of poly(thionine) enhanced to excite state; it can get two electrons from H2O2. As the poly(thionine) reduced to ground state, the working electrode produced a light-current when a bias voltage of +0.4 V was applied to the electrode. With the increase in the amount of H2O2, the current gradually increased. And a linear relationship exist in 2×10-6 ~ 3×10-4 mol/L was obtained with a linear correlation coefficient of 0.9925 and the detection limit of 1.8μmol/L.2. As basis of the photoelectrochemical sensing interface for H2O2, the activity of glucose, choline oxidase and uricase were determined indirectly. In the reaction of catalyzing glucose to generate H2O2 by glucose oxidase, the current increases according to the concentration of glucose oxidase. The linear range is 2.0~30 U/mL, the linear relationship is y = 0.032x +7.287, the linear correlation coefficient is 0.9880 and the detection limit is 1.8 U/mL (S/N=3), RSD is 2.77%. Choline oxidase, the linear range of detection is 2.4~40 U/L, the linear relationship is y = 132.0x +2.385, linear correlation coefficient is 0.9815, detection limit is 0.8 U/L (S/N=3), RSD is 3.02%. Uricase, the linear range of the biological activity is 8.2~80 U/L, the linear relationship is y = 71.13x + 2.313, linear correlation coefficient is 0.9975, detection limit is 2.7 U/L (S/N=3), RSD is 2.68%.