电位型聚吡咯pH传感器的制备

电位型聚吡咯pH传感器的制备;聚吡咯; pH传感器; 电化学聚合; 交流阻抗

Preparation of a Potentiometric pH Sensor Based on Polypyrrole

A pH sensor was fabricated from polypyrrole(PPy) on Pt wire. PPy was prepared electrochemically in a 0.1 mol/L Py aqueous solution with or without addition of 0.1 mol/L NaHCO_(3) and characterized by means of (infrared) absorption spectroscopy(IR) and electrochemical impedance spectroscopy(EIS). The Nyquist plots for non-doped PPy in an acid solution(pH=4.01), a neutral solution(pH=6.85), and an (alkali) solution(pH=9.14) were composed of two semicircles in the high and mid frequency regions and a Warburg response arisen by H~( ) diffusion process in the low frequency region. The Nyquist plots for HCO~-_(3)-doped PPy in corresponding pH buffer solutions were composed of two semicircles in the tested frequency (region) and did not show the Warburg response. In the latter case, the charge transfer resistance and the film resistance of PPy were increased apparently. The electrochemically synthesized non-doped PPy as a pH-indicator electrode had satisfactory potentiometric properties:sub-Nernstian response with a slope of 49.32 mV/pH at buffer solutions of pH 3 to 10, excellent linearity, r=-0.997 1, and relatively short response time and small selectivity (coefficient) to conventional positive ions such as K~( ) and Na~( ).