【作者】 徐彦辉；

【导师】 林祥钦；

【作者基本信息】 中国科学技术大学 ， 分析化学， 2008， 博士

【摘要】 本论文在详细综述了纳米材料的研究现状和最新进展的基础上，通过电化学方法制备了一系列新型的纳米材料，对纳米材料的表面性质和微观结构等方面进行了表征，进而以O₂、甲醇、H₂O₂、葡萄糖等物质为主要分析对象，探讨了所获得的新型纳米材料修饰电极在电催化氧化还原、电化学电容和生物传感器等方面的应用。主要内容包括：用电化学法共沉积法制备了Pt_0.9Pd_0.1二元合金，得到了电极表面均匀分散的、多孔的纳米合金层。该多孔合金层是由粒径约10．1 nm的Pt_0．9Pd_0．1合金的晶粒组成的，与相应的铂盘电极相比，表面积增大约790倍。合金中Pt与Pd的原子比例可通过电沉积溶液中两组分的浓度进行调控。研究表明，当合金中Pt与Pd的原子比例为9：1时，合金对ORR的电催化效果最好。同时，与单一的Pt纳米团簇相比，Pt_0．9Pd_0．1二元合金对MOR也具有优异的催化能力，起始氧化电位负移195 mV，氧化峰电流增大9倍。这说明，比例很小的Pd能够极大的增强Pt催化剂的催化效果，是一种有效的催化增强剂。进而，用电化学方法在温和氧化的MWCNTs的开口端实现了Pt纳米团簇的选择性沉积。该Pt纳米团簇的粒径范围为100～150 nm，是由粒径为10．8 nm的Pt晶粒组成的，这与其它文献报导的在碳管表面修饰的粒径很小的Pt纳米粒子有很大的区别。以ORR的催化反应为例，其催化效果可通过电沉积溶液的浓度与沉积圈数来进行调控。Pt纳米团簇修饰的MWCNTs对MOR显示出优异的催化效果。另外，我们发现，两根碳管端头可以由Pt纳米团簇“焊接”在一起，在溶液中经超声处理也不被破坏，因此可望成为在微观条件下焊接纳米碳管的新方法。同时，我们对Pt纳米团簇的形成与沉积的机理也进行了研究。这些研究结果说明，大尺寸的Pt纳米团簇有望用作燃料电池的高效催化剂材料。用电沉积的方法在电极表面的离子液体薄层内共沉积制备了PPy与MWCNTs纳米复合材料。用CV法研究了PPy／MWCNT复合材料的电容性质，用计时电流法研究了PPy／MWCNT的充放电性质。研究结果显示，PPy/MWCNT有很高的比电容（890 F／g），且材料性能稳定，循环寿命周期长。该制备方法可使ILS薄层内的碳管进行定向，新颖实用，可应用于其它复合材料的制备。用电化学方法，将离子液体薄层内的Cys共价键植在GCE表面，然后将Au纳米粒子组装到电极表面，再进一步吸附GOx，成功构筑了葡萄糖生物传感器，GOx／GNP／Cys／GCE。研究证明，该修饰电极显著加速了GOx的直接电化学的电子传递过程，GOx在该修饰电极在pH 7．0的PBS溶液中呈现出一对可逆的氧化还原峰，其异相电子转移速率常数为12．8 s^-1。以葡萄糖为分析对象，研究证明该电极可以对葡萄糖进行灵敏的电催化氧化检测，米氏常数Km值为12．0 mM。电极优异的生物传感性能与构建方法密切相关，共价键值的Cys层不仅为Au纳米粒子组装提供了一个很好的平台，同时也为GOx与电极间的快速电子传递提供了一个通道。最后，本论文研究了GCE表面电沉积的DNA层的电化学性质，发现其在空白的PBS（pH 7．0）中有一对可逆的氧化还原特征峰（E_m=-0．114 V）。初步研究表明，电沉积的DNA层对O₂和H₂O₂有优异的电催化效果。更多还原

【Abstract】 Based on the recent progress on the preparation and applications of nano-structured materials, several novel nano-structured materials were fabricated on the surface of glassy carbon electrode （GCE） using newly designed techniques involving electrochemical deposition processes. The surface morphology and composition of the prepared materials were well characterized using various techniques. Electrocatalytic activity and electrochemical sensing ability of these materials was examined for fuel cell applications and electrochemical sensors. The dissertation includes following five sections:A nano-thickness porous Pt_0.9Pd_0.1 alloy film with a greatly enhanced surface area were firstly synthesized at GCE using a facile cyclic voltammetry （CV）. It was found that the alloy film was in nanoporous structure and consisted of crystallites of 10.1 nm on average. The as-prepared electrode (Pt_0.9Pd_0.1/GCE) has an effective surface area as large as 790 times that of a corresponding bare Pt disk electrode, and has significantly higher stability and catalytic activity for both of the methanol electro-oxidation reaction （MOR） and the oxygen electro-reduction reaction （ORR） than the correspondingly nano-Pt modified GCE. We also found that the atomic ratio of the alloy can be tuned by altering the composition of the electrodeposition solution, and small amount of alloying Pd can significantly enhancing the catalytic activity of the Pt alloy, and 10% Pd is the optimal.Pt nano-clusters （nano-Pt） have been selectively attached to the open ends of mild-oxidated multi-wall carbon nanotubes （MWCNTs） by CV deposition at GCE. The excellent electrocatalytic activity of the as-prepared electrode was found for ORR and MOR. The electrocatalytic activity has been well tuned by varying the CV cycle number and the PtCl₆^2- concentration of the deposition solution. The optimal was found for the nano-Pt in average size of 100-150 nm, which consisted of nano-crystallite of an average size of 10.8 nm. The mechanism for the CV deposition is proposed. The nano-Pt deposition may be an alternative technique for wiring of nano-wires in nano-technology. The use of large sized nanoclusters （100-150 nm） as electrocatalyst may open a new opportunity for fuel cell applications.A novel composites of MWCNTs and polypyrrole （PPy） were synthesized by a method involving one-step electrochemical deposition from a thin-layer of ionic liquid solution （ILS） attached on the surface of GCE. The capacitance property of the prepared electrode were investigated by CV and chronopotentiometry. It shows that the PPy/MWCNT composites have a porous 3-D nanostructure, with high specific capacitance of 890 F/g （for the mass of PPy deposited） with high stability. The advantage of this approach was attributed to the oriented deposition of MWNT in the thin-layer ILS. This novel technique can be expected to have further applications in composite synthesis.A cysteamine （Cys） grafted GCE was firstly prepared in ILS. Gold nanoparticles （GNPs） of 20±5 nm diameter were self-assembled on the Cys grafted GCE and then glucose oxidase （GOx） was adsorbed on the top, giving a glucose biosensor GOx/GNPs/Cys/GCE. The immobilized GOx displays a pair nearly reversible redox peaks in pH 7 phosphate buffer solution （PBS） with a heterogeneous electron transfer rate constant （k_s） of 12.8 s^-1. The biosensor has excellent sensing ability to glucose with an apparent Michaelis-Menten constant of 12.0 mM of GOx. The advantage of the biosensor may be attributed to the grafted Cys layer that play important roles of electron transfer as a molecular nano-wire connecting and separating GNPs at a suitable distance for reducing the bulk effect of the block GCE.Finally, a DNA film was electrodeposited on GCE. The prepared electrode displays a novel pair of well defined and nearly reversible redox peaks at E_m of-0.114 V vs SCE in pH 7 PBS, and has excellent electrocatalytic activity toward ORR and redox reactions of H₂O₂.更多还原