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Nanostructured Polyaniline Based Composites-preparation, properties and applications
Nanostructured conducting polymer
第一部份為利用電化學合成方法，直接將聚苯胺奈米線成長在碳布表層，並同時植入葡萄糖氧化酶以製備成酵素電極，繼而應用於葡萄糖濃度的偵測。碳布被選擇作為電流的收集器，乃是考慮其具備高導電性、化學穩定性及其高孔洞三維結構可提供高表面積，可提供聚苯胺奈米線更多的成長空間；另由於直接成長的聚苯胺奈米線與碳布之間，有效降低介面瑕疵因素，因而可展現優異的偵測靈敏度。本研究所製備一維聚苯胺奈米線具備高表面積特性，有利於較高濃度葡萄糖氧化酶的植入，可將葡萄糖的偵測靈敏度提高至~2.5 mAmM-1cm-2程度，相關葡萄糖濃度的偵測範圍為0-8 mM，具備可應用於人體葡萄糖濃度的偵側能力。
至於超級電容器的應用，本論文主要探討聚苯胺奈米線/碳布與聚苯胺與奈米碳管，兩種奈米聚苯胺複合材料電極。本研究所製備出的聚苯胺奈米線/碳布電極，不僅具備高單位重量電容值之外，同時也具備相當高的單位面積電容值，顯示出極佳的電容效能。根據定電流充放電分析，其單位重量電容值高達1079Fg-1 ，相關比能量與比功率則分別為100.9Whkg-1和 12.1 Wkg-1，至於其單位面積電容值可高達1.8 Fcm-2程度。然而基於聚苯胺本身的電子傳導性較差(相較於金屬導體)，因此在可逆氧化還原轉變的過程中，通常會由於聚苯胺本身的內電阻效應而導致部份電子的損失，降低了電容的穩定性，致使面臨無法長時間重複循環使用的缺點。對於奈米碳管材料而言，由於具備良好的導電性和機械性質，因而奈米碳管和聚苯胺複合材料，可大幅改善電極的導電性。因此，聚苯胺與奈米碳管混合式複合材料所製備電極，不但可提升其功率密度，而且也因具備優良的械性質，有效降低因重複循環使用所造成電極結構上的破壞程度。|
Polyaniline is one of conducting polymers that has been widely studied for chemical, biosensor, supercapacitor and solar cell applications, owing to its unique reversible reduction/oxidation chemical behaviors enabling control over properties such as electrical conductivity and optical activity. In recent years, one-dimensional (1-D) polyaniline nanostructures, including nanowires, rods, and tubes have been studied with the expectation that such materials will possess the advantages of both low-dimensional systems and organic conductors. However its application is needed to be further investigated and clarified in reality. Therefore, the preparation, properties and applications of nanostructured polyaniline based composites including glucose sensor and supercapacitor were described in the present work. In the first part of this study, we provide a convenient route to directly grow polyaniline nanowires (PANI-NWs) onto the surface of carbon cloth (CC) by an electrochemical method followed by incorporation of glucose oxidase (GOx) to fabricate the amperometric enzyme electrodes. CC was specifically selected as the current collector due to its cost-effectiveness, high conductivity, reasonable chemical stability, and 3D structure with high porosity, hence high surface area support for PANI-NWs growth. The defect-free interfaces, along with the excellently sensitive organic nanostructured-surface, as evident from its significantly large effective surface area (24 times the geometric area) for redox-sensing, allows efficient entrapment/immobilization and sensing of biomolecules, via rapid electron-transfer at NWs-CC. The GOx-immobilized PANI-NWs/CC exhibited an excellent sensitivity, ~2.5 mAmM-1cm-2 to glucose, over detection range 0-8 mM, adequate for clinical monitoring of human glucose levels. This work clearly reveals a cost-effective simple system possessing enormous potentiality for biosensors, bioenergy and bioelectronics applications. In the supercapacitor applications, relatively high gravimetric capacitance of 1079Fg-1 at a specific energy of 100.9 Whkg-1, a specific power of 12.1 kWkg-1 and exceptionally high area-normalized capacitance of 1.8 Fcm-2 were achieved for the PANI-NWs/CC electrodes. The diffusion length of proton within the PANI-NWs was estimated to be about 180nm by electrochemical impedance analysis, which indicating the electrochemical performance of the electrode is not limited by the thickness of PANI-NWs. On the other hand, the electrodes of PANI/CNx NTs-CC composite by growing directly nitrogen- containing carbon nanotube (CNx NTs) onto a CC followed by coating PANI by in-situ polymerization process were performed in order to enhance the power density of PANI-based supercapacitor. Results showed the power density of PANI/CNx NT-CC is threefold higher than PANI-NWs /CC due to minimization of internal and contact resistance between CNx NTs and CC. Therefore, the use of PANI-NWs/CC and PANI/CNx NTs-CC nanocomposite electrodes as supercapacitor revealed credible attention in the commercial availability.
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