季铵盐型Gemini表面活性剂在金表面的吸附行为

以邻苯二酚(CC)为电化学探针, 利用循环伏安、交流阻抗等方法研究了不同阳离子Gemini表面活性剂(C16H33(CH3)2N-C4H8-N(CH3)2C16H33 (C16-C4-C16)、C12H25(CH3)2N-C4H8-N(CH3)2C12H25 (C12-C4-C12)、C8H17(CH3)2N-C4H8-N(CH3)2C8H17 (C8-C4-C8))在金电极表面的吸附性能. 结果表明, CC在KNO3溶液中可产生两对峰; 当向溶液中加入阳离子Gemini表面活性剂时, 第一对峰降低, 第二对峰升高, 峰电位差变大; 碳链长的表面活性剂对CC的氧化还原峰的影响较大. 同样, 碳链长的表面活性剂使电极界面的阻抗增大较多, 使石英晶片的频率变化较大. 根据CC的第一个氧化峰的面积随表面活性剂吸附的变化, 估测了它们的吸附模式. 发现这三种表面活性剂在金电极表面的吸附基本符合Langmuir吸附模型.

The Adsorptive Behavior of Quaternary Ammonium Gemini Surfactants at Bare Gold Electrode

The adsorptive behavior of three cationic Gemini surfactants (C16H33(CH3)2N-C4H8-N(CH3)2C16H33 (C16-C4-C16), C12H25(CH3)2N-C4H8-N(CH3)2C12H25 (C12-C4-C12), C8H17(CH3)2N-C4H8-N(CH3)2C8H17 (C8-C4-C8)) at bare gold electrode has been studied with cyclic voltammetry, alternating current impedance spectra(ACIS), and quartz crystal microbalance (QCM). It is found that the electrochemical probe catechol (CC) can exhibit two pairs of redox peaks in the range of 0～0.8 V (vs SCE) in 0.3 mol•L-1 KNO3 solutions. When some cationic Gemini surfactants are introduced into the solutions, the first pair of peaks decreases, but the second pair of peaks increases. At the same time, the anodic peaks move in positive direction and the cathodic peaks shift in negative direction. For the three Gemini surfactants, their influence on the voltammetric behavior of CC follows such order as C8-C4-C8 ＜ C12-C4-C12 ＜ C16-C4-C16. ACIS shows that in the presence of Gemini surfactants, the impedance of the electrode interface grows. For those surfactants, the impedance rises with increasing alkyl-chain length. Similar result is obtained in QCM experiment. Namely, when the alkyl-chain is longer, the Gemini surfactant makes the frequency change more. The adsorption modes of those Gemini surfactants are estimated according to the change of the first anodic peak area of CC. It is found that their adsorption belongs to Langmuir adsorption.