可撓式基材上金奈米結構之製備與其在生物感測及超級電容之應用

Abstract

在本論文中，我們在可撓式基材上製備並研究金奈米結構的成長與其在生物感測及超級電容的應用。論文架構及內容分成三大部。 首先，在可撓式塑膠基材(聚對苯二甲酸乙二酯)以電化學電鍍沉積金奈米結構，其結構包含奈米尖錐結構、奈米珊瑚結構、奈米片狀結構及奈米線結構。藉由調控電化學電鍍參數，探討金奈米結構的成長並討論其成長機制。上述所合成的金奈米結構中，以金奈米線結構具有最好的克真實表面積值(26100 cm2/g)，這是由於一維奈米金線結構具有很高的長寬比。進一步，將上述所合成的金奈米材料當作電極，分別應用於生物感測及超級電容。 在生物感測應用中，將所合成的金奈米材料作為感測電極，以電化學阻抗分析法偵測人類凝血酶的濃度作為生物感測應用的實驗。檢測凝血酶的方法是利用凝血酶結合適體與凝血酶具有很好的鍵結親和力，可以大幅增加感測電極的選擇性和靈敏性。因此，先將凝血酶適體利用硫金鍵的結合修飾於所合成的各種金奈米材料上。然後，利用電化學阻抗分析法檢測所修飾的各種金奈米材料電極於低濃度範圍(1 - 50 pM)的凝血酶其阻抗值的變化。其中，以金奈米線結構具有最好的凝血酶感測表現(1130 pM-1 cm-2)。由於金奈米線結構具有最大的真實表面積，因此在生物感測上具有好的感測靈敏性、選擇性和穩定性。 在超級電容應用中，是利用電化學沉積合成二氧化錳與金奈米線的複合材料作為超級電容電極。此奈米複合材料的組成結構是一薄層二氧化錳(厚度: 5  80 nm)包覆於金奈米線結構上(長度: 10 - 20 μm, 直徑: 20 - 100 nm)。在電化學電容表現中，此電極具有高的克電容值(1130 F/g)、高的克能量密度(15 Wh/kg) 、高的克功率密度(20 kW/kg)以及好的穩定性 (充放電5000圈依然維持90%電容值)。最後，將此電極作固態電容元件並呈現出優異的電容表現。

In this thesis, we studied fabrication of Au nanostructures on flexible substrate and its applications in biosensor and supercapacitor. A facile fabrication of high density Au nanostructures including nanothorns (NTs), nanocorals (NCs), nanoslices (NSs), and nanowires (NWs) which were electrochemically grown on flexible plastic substrates of polyethylene terephthalate (PET). By adjusting the electroplating conditions, we proposed a growth mechanism of Au nanostructures. Among them, the specific real surface area (RSA) of the Au NWs is the highest one (26100 cm2/g). This is due to the high aspect ratio of the one-dimensional NW structure. Further, as-fabricated Au nanostructures on flexible substrate were employed and used as electrode in biosensor and supercapacitor applications. For biosensor application, a thrombin-binding aptamer was immobilized on the surfaces of the Au nanostructures to form highly sensitive electrochemical impedance spectroscopic (EIS) as biosensors for thrombin recognition. The binding of thrombin to the aptamer was monitored by EIS in the presence of [Fe(CN)6]3-/4-(aq). The protein (1 – 50 pM) was detected linearly by the Au nanostructures. Among them, the Au NWs exhibited excellent thrombin detection performances (1130  pM-1 cm-2). The biosensor provided high sensitivity, selectivity, and stability due to its high surface area. For supercapacitor application, electrodes composed of ultrathin MnO2 (thickness 5 - 80 nm) spines on Au NW stems (length 10 - 20 μm, diameter 20 - 100 nm) were electrochemically grown on flexible PET substrates. The electrodes demonstrated high specific capacitance, high specific energy value, high specific power value, and long-term stability. In Na2SO4(aq) (1 M), the maximum specific capacitance was determined to be 1130 F/g by cyclic voltammetry (CV, scan rate 2 mV/s) using a three-electrode system. From a galvanostatic (GV) charge/discharge test using a two-electrode system, a maximum capacitance 225 F/g (current density 1 A/g) was measured. Even at a high charge/discharge rate 50 A/g, the specific capacitance remained at an extremely high value 165 F/g. The flexible electrodes also exhibited a maximum specific energy 15 Wh/kg and a specific power 20 kW/kg at 50 A/g. After five thousand cycles at 10 A/g, 90% of the original capacitance was retained. A highly flexible solid-state device was also fabricated to reveal its supercapacitance performance.