On the electrochemical behaviors andthe microfabricated sensor of trichloroethylene

• Main Authors: Min-Hua Chen, 陳敏華
• Other Authors: Tse-Chuan Chou
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/79987181892898852812

博士 === 國立成功大學 === 化學工程學系碩博士班 === 92 === 　　Trichloroethylene (TCE) is a widely used organic solvent and degreasing agent in industry. However, the contamination of soil and groundwater with persistent organic pollutants is a matter of increasing concern such as TCE. There are many investigations implying the TCE is a carcinogenic material which causes serious health problems. Furthermore, how to control the concentration of TCE is a very important goal. In this study, the electrochemical reduction behaviors of TCE by using a Pb and an electrodeposited Pb modified electrodes in organic electrolyte were developed. Based on the data, a new amperometric TCE sensor can be designed with high performance, good sensitivity, short response time, nice reusability and long stability to monitor the concentration of TCE. 　　A novel conjugated polyacetylene chloride containing a chloric side chain which is synthesized from the TCE with an organic electrolyte by electropolymerization method. UV-Vis spectrum of the monomer shows an absorption maximum (λmax) around 315 nm due to the π-conjugation which exists in the monomer. The 1H NMR and GC-Mass spectra show that the main product is an acetylene chloride. Additionally, the phase transition temperature of polyacetylene chloride at 325 ˚C was examined by differential scanning calorimeter (DSC). 　　An amperometric TCE sensor by using a Pb electrode in an organic electrolyte was developed. The optimal pretreating and sensing conditions were found to be 1.0 M pretreatment HNO3 concentration, 30 min pretreatment time, -2.10 V (vs. Ag/Ag+ with 0.1 M tetrabutylammonium perchlorate (TBAP) in AN) sensing potential, 250 rpm agitation rate in a 0.025 M tetrabutylammonium tetrafluoroborate (TBAT) organic electrolyte. The response time and the sensitivity were 10 s and 7.15 μA/cm2-ppm, respectively. Additionally, at least 4 months stability for the prepared working electrode was also obtained. The correlation of the sensing response current, id, and TCE concentration, CL, is id=7.15CL in the range from 50 to 250 ppm TCE. The rate constant of (TCE) at mass-transfer control was found to be 4.868�~10-3 (cm-s)-1. 　　The TCE sensor by using an electrodeposited a Pb modified graphite electrode in an organic electrolyte was studied. The best electrodeposition conditions of the prepared working electrode were 20 mA/cm2 electrodeposition current density, 25 ˚C electrodeposition temperature and 2 hrs. Additionally, the optimal sensing conditions were -2.10 V sensing potential (vs. Ag/Ag+ with 0.1 M tetrabutylammonium perchlorate (TBAP) in acetonitrile (AN) solution), 100 rpm agitation rate, and at 25 ˚C with 0.01 M tetrabutylammonium tetrafluoroborate (TBAT) electrolyte concentration in AN solution were obtained in this system. Under the optimal sensing conditions, the results indicated that the sensitivity and response time were 7.06 μA/cm2-ppm and 15 s (90% response time), respectively. 　　　　　Furthermore, the stability is at least 60 days for prepared electrode. Additionally, the correlation of sensing response current, id, and trichloroethylene (TCE) concentration, CL, is id=7.06CL in the range from 100 to 700 ppm TCE. The rate constant of (TCE) at mass-transfer control was found to be 4.81�~10-3 (cm-s)-1. 　　Electrochemical detection of trichloroethylene with an electrodeposited Pb modified was designed. The optimal conditions for the preparation of the electrodeposited Pb modified electrode were obtained which 0.1 M pretreatment HNO3 concentration, 60 min pretreatment time, 20 mA/cm2 electrodeposition current density, 30 ˚C electrodeposition temperature and 2 hrs. The optimal sensing conditions such as -2.10 V sensing potential (vs. Ag/Ag+ with 0.1 M tetrabutylammonium perchlorate (TBAP) in acetonitrile (AN) solution), 155 rpm agitation rate, and at room temperature with 0.01 M tetrabutylammonium tetrafluoroborate (TBAT) electrolyte concentration in AN solution were obtained in this system. Under the optimal sensing conditions, the results indicated that the sensitivity and the response time were 1.06 μA/cm2-ppm and 20 s (90% response time), respectively. Furthermore, the stability is at least 60 days for prepared electrode. Additionally, the correlation of sensing response current, id, and trichloroethylene (TCE) concentration, CL, is id=1.06CL in the range from 50 to 700 ppm TCE. The rate constant of (TCE) at mass-transfer control was found to be 7.217�~10-4 (cm-s)-1. 　　A novel electrochemical TCE sensor using an electrodeposited Pb modified Pt-Ti thin film electrode was successfully developed and well characterized. The prepared conditions of the electrodeposited Pt-Ti thin film working electrode were obtained as 3�~10-3 torr sputtering pressure, 20 min sputtering deposition time ,30 watts sputtering power, 18.75 mA/cm2 and 2 hrs under room temperature. Optimal sensing conditions were found to be -2.10 V (vs. Ag/Ag+ with 0.1 M tetrabutylammonium perchlorate (TBAP) in acetonitrile (AN) solution) sensing potential, 250 rpm agitation rate. At room temperature, the sensitivity and response time was 2.86μA/cm2-ppm and 15 s (90% response time), respectively. Furthermore, the prepared electrode had over 15 cycles of reusability, and the stability is least 180 days. Additionally, the correlation of sensing response current, id, and trichloroethylene (TCE) concentration, CL, is id=2.86CL in the range from 100 to 700 ppm TCE. The rate constant of (TCE) at mass-transfer control was found to be 2.434�~10-3 (cm-s)-1. 　　In this study, the framework of the TCE sensor with an electrodeposited Pb modified Pt-Ti thin film electrode can be obtained excellent sensing performances such as the sensitivity, the response time, the reusability and the stability. Additionally, the electrodeposited Pb modified Pt-Ti thin film electrode can be combined with microfabrication technique for the design of TCE sensor. Therefore, the electrochemical TCE sensor using an electrodeposited Pb modified Pt-Ti thin film electrode in TBAT organic electrolyte showed promising features for commercial application.