氧化銅奈米複合材料的製備以及在非酵素型葡萄糖感測器上之應用

Abstract

本論文主要著重於利用簡易的方式製備氧化銅複材應用在葡萄糖感測器之電極。參照文獻利用水熱法(Hydrothermal method) 製備氧化銅氧化石墨烯複材，其電極表現靈敏度高達3576 (μA/mM cm2)，線性範圍0.01-6 mM，最低偵測極限為10 M，已可媲美現今學術界之標準。為了再進一步提升靈敏度及降低偵測極限以廣泛應用於非侵入式感測器中測量唾液、尿液中葡萄糖含量，本研究首次利用脫層蒙脫土(exMMT)、多層奈米碳管(CNT)與氧化銅奈米粒子之複合材料，結合脫層蒙脫土的催化金屬離子氧化之特性與多層奈米碳管之高導電性，以改善氧化銅之表面形貌與導電性並應用於葡萄糖感測電極。接著利用XRD、TEM、XPS鑑定表 面型態，並利用循環伏安法、安培法和交流阻抗來分析電化學特’性。 首先利用 Cu(NO3)2 與Cu(OAc)2 製備氧化銅，XRD 鑑定CuO 屬於單斜晶系；TEM 觀察Cu(NO3)2 與Cu(OAc)2 製備之氧化銅大小各別約10 nm、5 nm，Cu(OAc)2製備之CuO 電性表現較差，主要因為顆粒小團聚較密集，葡萄糖氧化後電子不易傳遞到電極表面，但加入exMMT 後，exMMT 能有效分散CuO，而且尺寸較小、比表面積較大的Cu(OAc)2 製備之CuO 電性表現較好，因此以Cu(OAc)2 製備之CuO 作為本研究主要的CuO。根據本實驗室先前之研究得知，exMMT 中的Mg 離子具有催化金屬離子氧化之特性，並且在本研究的XPS 結果中看到，CuO/exMMT複材中exMMT 會釋出Mg 離子後氧化Cu 離子，並造成複材中出現孔洞。同樣以Cu(OAc)2 利用水熱法製備CuO/CNT 複合材料，以XRD 確認CuO 為單斜晶系，CuO 顆粒尺寸約5 nm，在適當的CNT 比例下，CNT 能夠有效分散CuO並提升複材之導電性，在CuO/CNT 系統中表現最好為CuO/CNT(3.1wt%)電極。 接著在表現最好的 CuO/exMMT (0.4wt%)系統中添加不同比例之CNT，並且改變CNT 加入之時機，以增加複合材料電極的效能。最後在含有葡萄糖之鹼性溶液中、電壓0.55 V 下進行電性分析，可得到三系統中表現最好之複材電極為：CuO/exMMT(0.4wt%)、CuO/CNT(3.1wt%)、CuO/exMMT(0.4wt%)/CNT(2.1wt%)，電極靈敏度分別為3582、3468、3654 (μA/mM cm2)。表現最好之三種電極經由尿液樣品測試後，結果表示上述三種電極在尿液樣品中皆可偵測葡萄糖； 干擾物測試後發現製備之CuO 、CuO/GO 、CuO/exMMT(0.4wt%)、CuO/CNT(3.1wt%)、CuO/exMMT(0.4wt%)/CNT(2.1wt%)電極對葡萄糖具有高度選擇性，血液與尿液中常見之干擾物質像是維他命c、尿酸、多巴胺等不會影響偵測；雖然在相同濃度的葡萄糖與干擾物中所偵測的電流值差不多，但干擾物在血液或尿液中濃度非常低(約1 比20 倍的葡萄糖)，因此我們仍可分辨葡萄糖的存在。本研究利用簡單、有效的方法製備上述氧化銅複材電極，希望未來能產業化，大量應用在非酵素型葡萄糖感測器上。

In this study, a simple strategy to prepare copper oxide/montmorillonite nanocomposite used for nonenzyme glucose detector was developed. By following the method published in the literature, we successfully prepared the CuO/GO/GCE electrode by using hydrothermal method. At the applied potential of 0.55V, the CuO/GO/GCE electrode presented a high sensitivity of 3576 (μA/mM cm2), linear range of 0.01-6 mM, detection limit of 10 M. In this research, the CuO nanoparticle was blended with exfoliate montmorillonite (exMMT) which could enhance the oxidation of metal ions and muti-walled carbon nanotube (CNT) which could improve the conductivity of CuO, and applied in non-invasive detection of glucose in saliva and urine. The surface morphology of as-prepared nanocomposites was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements including cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy (EIS) were employed to estimate their sensibility. First, CuO in monoclinic phase were prepared by Cu(NO3)3 and Cu(OAc)2 with diameter of 10 nm and 5 nm respectively which were characterized by XRD and TEM. Because of the aggregation of CuO in nature, glucose cannot diffuse into the porous surface of electrode to obtain the desirable electrochemical performance. When employing the appropriate concentration of exMMT, CuO can be effectively disaggregated. Therefore, CuO/exMMT prepared by Cu(OAc)2 was used for further studies in this research. According to the past research in our laboratory, Mg ion of exMMT could accelerate the oxidation of metal ion, and the XPS result also showed the exMMT would release the Mg ions to oxidase Cu ions in the CuO/exMMT composite, which may lead to the 3D porous structure. CuO/CNT were also fabricated by hydrothermal process. The CuO of CuO/CNT was in monoclinic phase with the particle size about 5 nm. Under the appropriate concentration of CNT, CuO can be disaggregated by CNT and improved composite’s conductivity. The result showed CuO/CNT (3.1wt%) composite had the best performance in the CuO/CNT system. Next, because the CuO/exMMT (0.4wt%) system had the highest sensitivity, we further incorporated different amount of CNT with the control of addition time to enhance the performance of composite electrodes. The results indicated that CuO/exMMT (0.4wt%), CuO/CNT (3.1wt%) and CuO/exMMT(0.4wt%)/CNT (2.1wt%) have the excellent performance in the glucose detection with sensitivity of 3582、3468、3654 (μA/mM cm2) at the applied potential of 0.55V. Moreover, these three electrodes can be used to determine the glucose concentration in urine. The interfering test showed the good selectivity of CuO, CuO/GO, CuO/exMMT(0.4wt%), CuO/CNT(3.1wt%), and CuO/exMMT(0.4wt%)/CNT(2.1wt%) electrodes toward glucose blending with common interfering species, such as ascorbic acid, uric acid, dopamine etc. Althought the sensitivity of these electrodes for the interfering species are almost the same as glucose, the concentration of interfering species in blood or urine is very low and will not interfere with the detection of glucose. Therefore, this research has demonstrated a simple and effective method to fabricate CuO nanocomposite electrodes for nonenzymatic detection of glucose.