| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 91 === Acetone has been in common use as a solvent and as an extracting regent, in industry for several decades. It is easy to evaporate in air. When the concentration of acetone in air is higher than 10,000 ppm, people may experience such symptoms as cephalalgia, nausea and so on. Acetone is harmful to human health. Presently, some investigations show that diabetes is the most command pathological cause of elevated blood ketones. The term ketone bodies collectively include three molecules, acetoacetate, 3-β-hydroxybutyrate and acetone, which are associated with the diabetic state. Therefore, the diabetic patient has a higher acetone concentration in their expiration gas, blood, or spittle than that of a nondiabetic people. In the future, the possibility exists to use an acetone sensor as a means of monitoring the diabetic patient’s condition.
In the aqueous solution system, to find the best preparing and sensing conditions of sputtered lead were the major issues in this study. Theoretically, acetone reduced into alcohol form on the surface of Pb working electrode in a suitable electrolyte. Therefore, the sensor produced the reduction current signal. The best preparing conditions of sputtered lead were at power of 30 W, and at bias voltage of 90 V. The applied potential of the acetone sensor was -2.15 V (vs. Ag/AgCl) in 0.1M sodium tartrate. The best sensitivity of thin film lead electrode was about 3.45µA/cm2ּppm at agitation rate of 100 rpm, and 30℃. The sensitivities increased with temperature. But when the temperature was higher than 40℃, the sensitivity did not increase obviously. The thin film lead electrode has a better performance than other lead electrodes prepared by conventional methods. The sensitivity of electroplating lead and lead foil were about 1.52µA/cm2ּppm and 1.2µA/cm2ּppm respectively. The thin film lead also has the shorter response time than electroplating lead and lead foil. When the thin film lead was used as working electrode, the response time is about 1 second. And the response times of electroplating lead and lead foil were 5 and 4.6 seconds respectively.
In gas phase system, the gas sensing system in this study can detect the concentration of acetone below 100 ppm. Pb/Nafion® was used as working electrode. It was prepared by sputter. The best preparing conditions were at power of 20 W, and at pressure of 0.018 torr. And the effect of bias voltage was not obviously. The applied potential of the acetone gas sensor was —1.25 V in (vs. Ag/AgCl) 0.1 M sodium tartrate. The response current of 50 ppm acetone was about 1.95 mA/cm2 at 200 ml/min. Both the sensitivity and the limiting sensing region are affected by the concentration of sodium tartrate. The gas sensing system has the best sensitivity when the total flow rate was at 200 ml/min. The sputtered method is better than impregnation-reduction method to prepare Pb/Nafion® working electrode. It is because that the former has higher sensitivity than the latter.
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