以修飾冠醚分子之矽奈米線場效應電晶體為基礎之鉀離子偵測器

Abstract

本實驗利用矽奈米線場效應電晶體作為基礎，並應用冠醚與鉀離子之親和性，將冠醚修飾於電晶體表面，使其與鉀離子辨認所造成之場效應能被矽奈米線元件所偵測，達到選擇性檢測離子之目標。 因為冠醚與鉀離子在水溶液中之結合常數較低，在較高濃度的分析物濃度範圍中，水溶液中離子濃度對電晶體有額外的雜訊影響。為了去除此因離子濃度造成之影響，在前半部的實驗中，我們專注於矽奈米線場效應電晶體在環境離子濃度改變時之偵測機制，並將其應用在後半部之離子量測實驗中。為了比較具不同場效應之元件所讀取之訊號，我們證實了較合理的數據處理方式是將訊號由電導變化轉換為相對之表面電位變化，以避免計入個別元件的差異，而可以對量測訊號有正確的詮釋。 我們利用三甲基矽烷基（trimethylsilyl group）在矽奈米線表面之修飾，確定離子濃度所造成之額外電訊號的主要來源為離子濃度在偵測器表面所造成的等效電容變化，而非矽奈米線表面與溶液中離子之非專一性庫倫靜電作用。確認離子濃度影響之來源後，我們更進一步在矽奈米線表面以修飾來改變其表面性質，使其能夠耐受更大的離子濃度變化；在我們嘗試過的表面改質中，效果較佳的氨基表面在其表面溶液環境由磷酸緩衝溶液（PBS）置換為成份複雜之動物血漿時，偵測器只有微小的電位變化，說明了表面修飾在生物偵測中之應用性。 我們運用表面修飾控制離子訊號的方法，來進行以冠醚對離子之偵測，其結果顯示元件之表面改質降低了離子濃度變化之干擾，呈現了原本和離子訊號混雜的冠醚－鉀離子辨認訊號；使用同一元件對鈉離子之偵測訊號與鉀離子電訊號之明顯差異，說明了此偵測器明顯的離子選擇性。另外，我們亦使用改變水溶液環境酸鹼值的方法來消除離子訊號，在此環境下，不同離子之偵測極限與冠醚對該離子之結合常數顯示了強烈的關聯性。

We demonstrated that the fair signal processing procedure for comparing two signals collected from different devices is mapping the conductance signal to potential change, although this method was first published by Professor Zhou. We use trimethylsilane group modification to show that the primary source of signal induced by ion concentration is the equivalent capacitance result from ion concentration, but not non-specific ion coulomb interaction. After elucidating the source of ionic background interference, we further try to use various surface modifications for reducing ionic strength effect. The best performance surface modification we have tried shown little response when solution environment changes from 1X PBS to mouse plasma, which indicates the possibility of this method to be applied in bio-analysis. We applied the ionic strength control method in potassium detection, the results revealed that the significance of surface blocking group and the distinguishable selectivity between potassium and sodium. We also applied the oxide surface theory to device surface and adjusted the surface potential to its pHpzc, under this certain circumstances, ionic strength shown no effect, and crown ether based ion sensor show strong correlation between device signals and crown ether ion affinity.