Conductive Polymer Films Of Electrochemical Synthesis Applied In PH Sensors

Ion Sensitive Field Effect Transistor(ISFET)technology is a combination of electrochemistry and microelectronics having ion-sensitive properties of electrode and characteristics of field effect transistor which is important for researching.In this paper,the polymer films based on electrochemical synthesis were used as p H-sensitive material and we studied p H-sensitive electrodes and sensors which combined with electrical signal amplification characteristics of field effect transistor.The general operational amplifier taking field effect transistor LF358 as the input stage were fabricated and that was separate extension gate field effect transistor(SEGFET)p H sensor.Polyaniline(PANI)and polypyrrole(PPy)films were synthesized on silicon wafers by cyclic voltammetry and made into p H-sensitive electrodes.Experimental results show that when 20 ml aniline is dissolved in 400 ml 1mol/L sulfuric acid solution,scanning voltage is-0.4～1.2 V,scaning rate is 10 mv/s,scaning cycle is 40,PANI film synthesized has the highest sensitivity 51.05 mv/p H at 25℃ in the p H range of 2～10 of buffer solution.The response time is about 6 min and hysteresis voltage is 6 mv;The sensitivity of PPy film is 47.15 mv/p H at 25℃ when 10 ml pyrrole is dissolved in 200 ml 1mol/L sulfuric acid solution,scanning voltage is-0.4～1.2 V,scaning rate is 10 mv/s,scaning cycle is 20.The response time is about 5 min and hysteresis voltage is 2 mv.From scanning electron micrograph(SEM)we observe that PANI film surface has larger porosity with stronger adsorption and PPy film is dense with strong mechanical properties.Analysis of infrared spectra confirm that the synthetic material are PANI and PPy.Aniline and pyrrole were modified by copolymerization.The experimental results show that when the volume ratio of pyrrole to aniline is 2:1 in 300 ml 1 mol/L sulfuric acid solution,the scanning voltage is-0.4～1.2 V,the scanning rate is 10 mv/s,the scanning period is 20,PANI / PPy film has the highest sensitivity 55.90 mv/p H at 25℃ in the p H range of 2～10 of buffer solution with potential response time 5.5 min and hysteres voltage 6 mv.The sensitivity of PANI/PPy film is up to 60.09 mv/p H at 25℃ when the triethanolamine(0.02mol/L)is added under the optimum ratio and polymerization parameters with p H response range of 4～7.The scanning electron microscopy show that surface of copolymer films is convex and veined with dense density.The infrared spectra show that PANI and PPy copolymers are formed.The polymer membrane based on the conductive polymer have a good potential response to p H with a faster response time and good stability and its sensitivity is enhanced remarkably by copolymerization and change of electrolyte composition.In this paper,we explored the use of polymers as p H sensitive materials and achieved some valuable conclusions,which make a new attempt for the research of p H sensors in the future.