论文部分内容阅读
A real time sensor system is an essential device for monitoring the concentration levels of SO2 and NO2 in atmosphere.In this study,an adsorption sensor system with high sensitivity and selectivity for SO2 and NO2 is made by coating conductive polymers such as PEDOT(poly(3,4-ethylenedioxythiophene)) and polypyrrole and porous materials such as MWCNT,activated carbon,and graphene on a quartz crystal microbalance(QCM) surface.The sensor materials are dissolved or dispersed to required concentration levels in specific solvents and then coated on the QCM surface by a spinner of 3000 rpm.The amount of coating is controlled by the coating time and the number of coating.Each coating time is maintained as 10 s.The QCM used in this work has its natural frequency of 8 MHz.The maximum concentration levels of gases are about 60 ppm.All sensing materials on the QCM surface are characterized experimentally by SEM and AFM.Furthermore their performances for sensing have been assessed by measuring their sensitivity and selectivity for two gases.Among various sensor materials,conductive polymers,PEDOT and polypyrrole,have high sensitivity for both gases but their selectivities are not so good.On the other hand,polystyrene has high selectivity for SO2 but it has low sensitivity comparing with other materials.According to these results,two effects are controversial but it is proven that this problem can be overcome when an array adsorption sensor system is devised.