利用旋轉塗佈法製備還原氧化石墨烯適體生物感測器應用於心臟Troponin-I檢測之研究

Abstract

本論文以開發心臟病量測晶片為背景，利用旋轉塗佈法（Spin-coating method）在量測晶片上製作還原氧化石墨烯(Reduced graphene oxide)薄膜，以其用來當作感測區材料。臨床上對於急性冠心症(acute coronary syndrome, ACS)的診斷為症狀評估、心電圖的缺氧變化以及心肌酶濃度升高，而心肌生物標記(Cardiac biomarker)的濃度在心肌受損初期即會微量提升，因此只要提早偵測到生物標記的濃度變化，將可及時對病患做緊急治療。本論文所屬計畫致力於開發一生物感測晶片，期望能使用二維材料-石墨烯(Graphene)來當作感測區，以達到使用方便、檢測快速、效能穩定、價格便宜的效果，因此將著重於製備石墨烯薄膜的方法以及其均勻性的控制，以能夠成為商品及量產為目標。利用石墨烯作為感測區的方式已有許多文獻提出，然而多以化學氣相沉積法(chemical vapor deposition, CVD)來製備，再藉由濕式轉印方式將石墨烯轉移至感測晶片上，此轉印的過程中，通常會造成石墨烯機械應力的拉扯以及損毀，因此本論文使用石墨烯氧化物以及旋轉塗佈法來製備石墨烯氧化物薄膜，以達到更為均勻之石墨烯薄膜。在本論文中，首先將石墨烯氧化物分散於甲醇與水的混和分散液中，利用食人魚洗劑(Piranha solution)以及半胱胺(cysteamine)對基材二氧化矽(SiO2)以及金電極(Au)進行親疏水改質，藉由親疏水性的改變，石墨烯氧化物薄膜的覆蓋率可從36%提升至100%。再使用旋轉塗佈法將石墨烯氧化物旋塗在改質過後的晶片表面，並藉由白光干涉儀(Optics-Type surface analyser)可得知當轉速為每分鐘2000、3000、4000以及5000轉時，石墨烯氧化物厚度為14.4 nm、10.2 nm、7.2 nm以及6.6 nm，經由與Washo’s與Meyerhofer’s模型比較膜厚與轉速之間的關係，可得膜厚與轉速成-0.905次方關係。最後將石墨烯氧化物薄膜泡入抗壞血酸(L-Ascorbic acid)水溶液中進行還原，並利用拉曼光譜儀(Raman spectrometer)中D band 與G band的比例變化來證實還原氧化石墨烯的氧化程度，其中ID/IG還原前為0.93還原後為1.05，其中以每分鐘5000轉時重複旋塗3次擁有最好的電阻穩定性，此時平均電阻值為0.25 Ω，誤差除以平均值為4.3%。

Based on the development of a heart disease detection chip, this dissertation proposed to adopt the spin-coating method to form a reduced graphene oxide thin film as the sensing material on the detection chip. The clinical diagnosis of acute coronary syndrome, ACS, is based on symptom assessment, signs of oxygen deprivation on the electrocardiogram (ECG), and increase in the myocardial enzyme concentration. Because the concentration of cardiac biomarkers is increased in the early stage of myocardial damage, the early detection and subsequent emergency treatment of patients is possible. This dissertation is a part of a larger project that is targeted at developing a biosensor chip using a two dimensional material, graphene, as the detector region in order to realize a final product that is convenient, rapid, stable, and cost-effective. Therefore, this study is emphasized on the graphene thin film preparation method as well as the uniformity control with the goal of developing and mass producing for an actual product. While several studies have already proposed to employ the graphene as the sensor region material, most teams used the method of chemical vapor deposition (CVD) followed by subsequent transferring via wet-printing to the sensor region of the chip. However, during the transfer process, defects may occur resulting from the mechanical residual stress in the graphene's structure. Thus, this study employed the spin-coating method to prepare a graphene oxide (GO) thin film that was highly uniform. Briefly, GO was first dispersed in a solution containing water and methanol. On the side, a piranha solution and cysteamine solution were used to modify the SiO2 and Au electrode surface for the hydrophilicity. By increasing the hydrophilicity of the substrate, the coverage of the GO thin film increased from 36% to 100%. Then the spin-coating method was used to cover the GO onto the modified chips. As determined using the Optics-Type surface analyser, the thickness of the GO film was 14.4 nm, 10.2 nm, 7.2 nm, and 6.6 nm at spin rate of 2000 rpm, 3000 rpm, 4000rpm, and 5000rpm, respectively. After adopting Washo's and Meyerhofer's models to establish a relationship between film thickness and spin rate, a -0.905 power relationship was established. Lastly, the GO film was soaked in an L-Ascorbic acid solution for the reduction process. The reduction level was determined by Raman spectroscopy through calculating the change in the ratio of the D band and the G band. Wherein, ID/IG was 0.93 before reduction and 1.05 after reduction. The highest resistance stability was achieved by coating at 5000 rpm for three times. The resultant mean resistance value was 0.25Ω and the standard deviation/mean value was 4.3%.