Study On Preparation Super-Micro PH Sensors By Electro-Chemistry Modification Iridium And Carbon Fiber

pH is one of the key physicochemical parameters of solution, so pH determination is very significant to many fields, such as industry, agriculture, medicine, environment, chemistry, life process and etc. At present, the most popular pH electrode is mainly glass electrode. But because of its own shortage such as high inherent resistance, low mechanical strength, easy to be broken, existence acid or alkali error, unable to determine F- solution, hard to miniaturize and need to be activated before using, the glass electrode is restricted in practical application. And the Metal/Metal oxide pH electrode can overcome the glass electrode shortcomings, attracting more and more human's attention.Ir/IrO_x, Ag/IrO_x and CF/IrO_x pH electrodes were prepared by electrochemical method in different electrolyte and matrix. They showed good pH response characteristics. Ir/IrO_x-pH electrode: linear range pH2¹3, electrode slope -58mV/pH, response time less than 1min; Ag/IrO_x-pH electrode: linear range pH2¹2, electrode slope -73 mV/pH, response time less than 30s; CF/IrO_x-pH electrode: linear range pH2¹2, electrode slope -79mV/pH, response time about 20s. The author had separately prepared exposed Ag/AgCl reference electrode, entired-solid SiC reference electrode and improved Fe³⁺/Fe²⁺oxidation/reduction reference electrode. And they all had good reproduction, reversibility, long service life, slight temperature effect and so on. They improved the electrolysis Ag/AgCl electrode's preparation technology and avoided the shortcomings of Ag/AgCl electrode such as photosensitivity, temperature hysteresis etc. So they could take the SCE and Ag/AgCl reference electrode as substitutes and they were suitable to be used in the situation of high temperature and pressure.This article reported the glass electrode's surface adsorption function during determination pH in high polymer and colloidal solutions, made the comparison with the IrO_x-pH electrode in the same solution and drew up theΔpH relational graph of the two electrodes. The result indicated that the difference between the two electrodes in aqueous solution wasΔpH≤0.1 and in high polymer colloid the difference wasΔpH≤0.3. The author initially explained mechanism of the glass electrode's surface adsorption.Author studied the electrode's surface topography, -OH in oxide film and hydration process using SEM, FT-IR. Using EDX, XPS, author analyzed that the proportion of Ir and O element was 1:2 or 2:3, the Ir element valence state was +4 or +3, and the existing form of O element was O^2-, -OH, H₂O.This article used the positive ion film(PIF) to modify the electrode's surface, which improved the electrode's ability to resist the oxidation/reduction anion's disturbance. At the same time PIF could protect the electrode's surface, which further enhanced the electrode to bear chemical corrosion and mechanical external force.Using IrO_x-pH electrode and compound pH glass electrode, the author separately determined pH of liquid, solid as well as the high polymer solution and the result was satisfying according to the compound glass electrode. The CF/IrO_x compound ultra-micro pH electrode was separately used in animal and the result was anastomotic with the literature. So this article established a new method of pH online determination which was simple, fast and accurate and had a broad application prospect.