碳原子线修饰电极对肾上腺素及尿酸的电催化作用

【作者】 刘佳梅；

【导师】 薛宽宏；

【作者基本信息】 南京师范大学 ， 物理化学， 2006， 硕士

【摘要】 本文报告碳原子线（carbon atom wires，简写为CAWs）修饰电极对肾上腺素和尿酸的电催化作用。肾上腺素和尿酸是人体内的生理活性物质，研究它们的电化学反应对深入研究生命科学和医药科学具有十分重要的意义。 利用循环伏安法、紫外可见吸收光谱法和强制对流法研究了肾上腺素在碳原子线修饰电极上的电化学行为和反应机理。与裸玻碳电极相比，硝酸处理的碳原子线修饰玻碳电极在含有1mmol／L肾上腺素的0.5mol／L H₂SO₄水溶液中的循环伏安曲线上的氧化峰电位E_pa负移87mV，还原峰电位E_pc正移139mV，氧化峰电流i_pa和还原峰电流i_pa分别增加5.6倍和16.4倍。由强制对流法测得，在0.5mol／L H₂SO₄水溶液中、硝酸处理过的碳原子线修饰电极上，肾上腺素氧化成肾上腺素醌的异相电子传递标准速率常数k⁰相对于裸电极增大16倍，这些结果表明碳原子线对于肾上腺素的电极过程具有非常高的电催化活性。通过循环伏安法结合紫外可见吸收光谱研究了肾上腺素的电极过程的反应机理。结果表明，肾上腺素的氧化还原过程比较复杂，在反应过程中除了电极上的多步电子转移外，还伴随有化学反应，并且在一些反应步骤中有H⁺的参与，因此，肾上腺素的循环伏安曲线上的电化学响应与扫描速率及介质的pH值密切相关。碳原子线修饰电极上的肾上腺素的循环伏安实验还表明，其氧化还原峰电流与其浓度在1×10^-4～1×10^-2mol／L范围内成线性关系，因此碳原子线修饰电极可用于肾上腺素的电分析，检测限为2×10⁶mol／L。 本文利用差分脉冲伏安法研究了尿酸在不同电解质溶液中的电化学行为，显示碳原子线修饰电极对尿酸的电化学过程具有很好的催化作用。此外，本文还研究了pH在碳原子线修饰电极对尿酸电催化作用过程中的影响，结果表明，在pH=4～9的范围内，氧化峰电位E_pa与pH成线性关系，其线性方程的斜率表明，在该电极反应过程中有相同数目的质子和电子参与电极反应。由实验还测得，碳原子线修饰电极的氧化峰电流与扫描速率的平方根成正比，说明该电极反应受扩散控制。更多还原

【Abstract】 An investigation was carried out on electrocatalysis of the CAW （carbon atom wire） modified electrode to the electrochemical redox of adrenaline and uric acid, active physiological substances inside the human body, due to their important part played in life and medical sciences.Cyclic voltammetry combined with UV-vis spectrometry, and the forced convection method were applied in the investigation. As to the electrochemical response of redox of adrenaline/adrenalinequinone couple in 0.50 mol/L H₂SO₄, at a nitric acid treated CAW modified electrode, the anodic and cathodic peak potentials E_pa and E_pc shifted by 87 mV negatively and 139 mV in the positive direction, the anodic and cathodic peak current i_pa and i_pc increased by 5.6 and 16.4 times respectively, and standard heterogeneous rate constant k° increased by 16 times compared to the corresponding bare electrode, indicating the extraordinary activity of CAWs in electrocatalysis for the process. The redox process of adrenaline investigated by cyclic voltammetry combined with UV-vis spectrometry, is rather complicated, involving electron transfers coupled with chemical reactions, and strongly affected by the scan rate and the pH value in medium due to H⁺ involvement in some steps. It was also found that the anodic peak current on CVs of adrenaline in solutions with different concentrations at the CAW modified electrode had an excellent linear relation with the concentration of adrenaline within the range of 1.0×10^-4 - 1.0×10^-2 mol/L, with the detection limit of 2.0×10^-6 mol/L, implying the potential application of the modified electrode in determination of adrenaline.The electrochemical behavior of uric acid at the CAW modified electrode in different electrolytes was investigated by differential pulse voltammetry, showing high electrocatalytic activity of the modified electrode in the redox of uric acid. The slop in the linear relationship of anodic peak potentials and pH values, in the range of pH = 4-9, obtained from CVs of uric acid in solutions with different pH values at the CAW modified electrode, suggested that the electrode reaction involved the same numbers of proton and electron. The linear dependence of anodic peak currents on the square root of scan rates showed the redox of uric acid as a diffusion controlled process.更多还原