電化學壓電晶體液體感測器研製與應用

Abstract

本研究發展一套電極/表面聲波元件(ESAW)系統將超高頻波UHF應用於水溶液化學分析。ESAW系統使用ESAW表面聲波元件為ST-cut石英表面聲波感測元件，此系統應用於水中各種離子濃度偵測及葡萄糖水溶液定量工作。ESAW系統優點是製作成本非常低廉，組裝方法非常容易，而且長時間偵測不會發生訊號能量衰弱現象。建構ESAW系統方法是基於干擾ST-cut石英SAW震盪元件石英晶體表面鄰近電場以產生訊號，製作時以長距離導線及同軸線將放置於水溶液中的各種電極連接到石英SAW震盪元件的金屬外殼。ESAW系統偵測的陽離子包含鹼金族、鹼土族及過渡金屬元素。未經前濃縮步驟，此系統直接測得Cu2+離子偵測極限為7.6 ppm，其靈敏度為2.55 × 105 Hz/(mol/L)。此系統偵測空白訊號標準偏差為10 Hz，信度為99.86 %。ESAW系統亦發展做為葡萄糖生化感測器，其以葡萄糖氧化酶(GOD)催化葡萄糖氧化反應。另外，ESAW系統也應用於葡萄糖與過氧化氫混合溶液系統。ESAW葡萄糖生化感測器在低於10-3M葡萄糖溶液中可測得斜率為9.3 × 102 Hz decade−1 (Hz/logM)的檢量線，且其靈敏度高於QCM葡萄糖生化感測器。 另外，本研究也以AT-cut石英塗佈碳六十C60大環胺醚方式發展QCM微天平之長鏈脂肪酸與膽固醇酯生化感測器。在非離子型界面活性劑的乳化液中以QCM感測器偵測長鏈脂肪酸或膽固醇酯水解產物。進行膽固醇酯水解反應之酵素添加方式包括兩種方式：在待測溶液中加入膽固醇水解酶以及放置碳六十C60固定化膽固醇水解酶濾片。此感測器系統測得膽固醇偵測極限為62 μM，此與目前醫學上光譜分析法偵測極限比較結果是良好的。目前醫學上光譜分析法仍需使用三種酵素反應系統，但本研究研發的膽固醇感測器只需應用使用一種酵素反應系統，再加上碳六十固定化酵素技術，因此大幅降低目前膽固醇定量分析的成本。

An electrochemical electrode/surface acoustic wave (ESAW) system was developed to explore the possibility of the application of UHF waves, 300–3000MHz for chemical analysis in solution. The ESAW system with a ST-cut surface-acoustic wave (SAW)/quartz transducer was prepared for detection of metal ions and glucose in aqueous solutions. The ESAW system has the advantages of very low cost, easy fabrication and detection without quick energy-loss. The ESAW system was an on-line detection system and it was built-up by the interference on the fringing electric field of the ST-cut SAW quartz resonator. A set of electrodes welded with long-distance wires and coaxial cables was used to contact to the metal shell of the 315MHz SAW quartz resonator. The ESAW system was applied to detect various metal ions, e.g., alkaline metal, alkaline-earth metal and transition-metal ions. Without pre-concentration technique, the detection limit of Cu2+ ion with the ESAW detection system was estimated to be 1.2 × 10−4 mol L-1 (i.e. 7.6 ppm, from an analytical sensitivity of 2.55 × 105 Hz/(mol/L) and the standard deviation of the blank signal of 10 Hz with a confidence level of 99.86 %. The ESAW detection system was also applied as a biosensor for glucose to detect the glucose oxidation reaction by glucose oxidase (GOD) in aqueous solutions. The glucose oxidase (GOD) enzyme-catalyzed system was also studied on the detection of glucose / H2O2 mixture. The glucose ESAW biosensor with glucose oxidase exhibited a linear frequency response to the log concentration of glucose with a slope of approximately 9.3 × 102 Hz decade−1 (Hz/logM). The ESAW detection system also showed a good selectivity and a good detection limit of< 10−3M for glucose in aqueous solution. Furthermore, the ESAW detector showed much more sensitive than QCM crystal sensor for glucose. QCM crystal sensors for long-chain fatty acid and the cholesterol ester were also built up by using the AT-cut quartz crystal with fullerene C60-cyptand-22 coating. The QCM crystal sensors detected the long-chain fatty acid and the cholesterol ester concentration in a non-ionic surfactant emulsion solution. The hydrolysis of cholesterol ester was carried out with catalysts of free and fullerene C60-immobilized cholesterol esterase, respectively. The detection limit of cholesterol with the QCM crystal sensors was estimated to be 62 μM in good comparison with the clinical spectroscopic method. The clinical spectroscopic method is a tri-enzyme reactions system with very expensive cost but the QCM cholesterol sensors with fullerene-immobilized cholesterol esterase was a mono-enzyme system with low cost substantially for the quantitative measurement of cholesterol.