基于微型氨气敏感单元的氨氮检测系统研究

Ammonia nitrogen measurement system based on miniaturized ammonia sensing unit

设计并制备了一种具有微池薄液层结构的安培型氨气微传感器,并以此微传感器构建了氨氮检测系统,探索了使用安培型氨气微传感器检测氨氮的方法。该微传感器为采用MEMS工艺制备的微电极芯片。在微传感器的设计中,将传统的薄层电解液与腔体两结构融为一体,省去了腔体结构,有效减小了体积。氨敏感材料选用铂黑,通过电化学方法修饰于微电极表面。薄层电解液选用保湿性较好的LiCl溶液。使用自行设计的氨氮检测系统对不同浓度氨氮样品进行检测,线性范围0.4～5(mg/L),线性相关系数0.992,检测下限0.2(mg/L),达到90%响应信号所需的时间在2 min以内。结果表明,使用安培型氨气微传感器检测氨氮的方法是可行的。微池薄液层的设计使传感器结构简单、便于加工,同时使氨气可以迅速扩散到电极表面,保证了传感器的响应速度。

An amperometric ammonia microsensor based on the thin liquid layer in micro-pool has been designed and prepared. An ammonia nitrogen measurement system utilizing such a microsensor has been constructed. The ammonia nitrogen measurement method using an amperometric ammonia mierosensor was investigated. The mierosensor is a microeleetrode chip fabricated with MEMS technology. The thin electrolyte layer and the reservoir for electrolyte are combined, thus the reservoir is eliminated and the sensor size is reduced. Platinum black is chosen as the sensing material, which is electrodeposited on the bare microelectrodes using electrochemical method. LiCl solution, which is one kind of hygroscopic electrolyte, is chosen as the thin liquid layer. Measurements of ammonia nitrogen samples with various concentrations using the self-designed measurement system were carried out. A linear calibration curve between 0.4 - 5 mg/L with the correlation coefficient of 0. 992 was obtained. A detection limit of 0.2 mg/L was achieved. The 90% response time was within 2 minutes. Measurement results reveal that the proposed ammonia ni- trogen measurement method using the amperometric ammonia microsensor is feasible. The design of the thin liquid layer in micro-pool simplifies the structure and facilitates the fabrication process. Meanwhile, the thin layer of electrolyte reduces the time for ammonia to diffuse to the microeleetrodes, thus a fast response time is achieved.