Nitric oxide (NO) is not only a toxic air pollutant generated in most combustion processes, resulting in the formation of ozone and acid rain, but also an important signaling molecule involved in many physiological and pathological processes within mammalian body of which the effect can be beneficial and/or detrimental [1]. Therefore, it is necessary to develop a reliable and sensitive sensor to fulfill the above mentioned environmental and biochemical concerns. In this study, 3,4-ethylenedioxythiophene (EDOT) and 3-thiophenecarboxylic acid (3-T acid) were in-situ oxidativelly copolymerized on a gold interdigitated electrode and the resulted films were used as a resistive type gas sensor. The effects of the composition, ie. the ratio of [3-T acid]/[EDOT], and the acid/base treatment on the sensor response were investigated. Our preliminary results showed that as the ratio of [3-T acid]/[EDOT] was increased from 0 to 3, the sensor response to the exposure of 50 ppm NO gas was increased from nearly none to a slightly higher value of 0.6 %. However, the sensor response can be dramatically increased from 0.6 % to 9.7 % if the in-situ synthesized film is to be treated with hydrochloric acid and ammonia sequentially during which the in-situ copolymer film is reduced. In addition, the selectivity of the NO gas sensor is significantly improved toward CO gas, in which there is essentially no response toward CO gas, which is in sharp contrast in observation with that of the NO gas sensor made from commercial Baytron^® film. Further studies on the effects of acid/base treatment duration and film thickness on the sensor response to NO gas are in progress.

References

[1]       Y. C. Hou, A. Janczuk, and P. G. Wang, Curr. Pharm 5 (1999) 417–471.

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