The Study Of Electrochemical Sensors

This dissertation concerning mainly about electrochemical sensors involves two major aspects: 1. Mini-type electrochemical DO sensor Aiming at the disadvantages of commercial DO sensor in today's market, such as high price and large size, we developed a kind of Clark type DO sensor which has many advantages including low cost, easy operation, suitability for on-site and real-time measurements, convenient maintenance, and adaptability to mass production. The performance of the sensor was also tested under different conditions. With DO concentration ranging from 0 to 8 ppm, the response of sensor to DO has very good linearity in both tap water and 3% NaCl solution, and the error of the sensor is less than ±0.4 ppm. The current of sensor is at μA level, and varies simultaneously with changing DO. Temperature has some influence on the performance of the sensor, but such effect can be removed through further calibration. 2. The study on EMD pH electrodes In this section, EMD pH electrodes were prepared through anodic oxidation of Mn(Ⅱ). The performance of these electrodes was also examined. Electrodes prepared under different electrodeposition conditions have different performance in their pH response. The sensitivity ranges from 53mV to 73mV, and it declines with increasing electrodeposition current or with prolonged electrodeposition time. The morphology of EMD also changes greatly with different electrodeposition conditions. These electrodes have almost the same response time(3 to 6 minutes). An electrode may have longer response time if the pH of the solution increases. Based on the experiments, we assumed a possible mechanism for EMD's pH response, and some phenomenons were explained according to this mechanism. These electrodes have very good resistance to some reductive ions such as Cl-and Br-.