烷基链长对紫精分子在Cu(100)电极表面吸附结构的影响

Effect of Alkyl Chain Length on the Structure of Viologen Adsorbed on a Cu(100) Electrode

用循环伏安法(CV)和原位扫描隧道显微镜(STM)研究了烷基取代的紫精分子在Cu(100)电极上的氧化还原行为及其吸附结构对电极电势的依赖性.对乙基紫精(DHV)和庚基紫精(DEV)在含有KCl电解质溶液中进行循环伏安曲线的测定,两者呈现出不同的氧化还原行为.从STM所得图像观察,二价庚基紫精在Cl-c(2×2)-Cu(100)电极上呈现出二维有序的点阵组装结构,而二价乙基紫精却未出现任何的吸附结构.降低电极电势至单电子转移反应发生时,形成的自由基庚基紫精在电极表面呈现出稳定的条带状组装结构,而自由基乙基紫精出现的条带组装结构比较密集且不能稳定存在.继续降低电极电势,庚基紫精的吸附结构会随之出现明显的变化,而乙基紫精不会有吸附结构改变的响应.

The redox behavior and the potential dependent adsorption structure of alkylated viologen on a Cu（100） electrode were investigated by cyclic voltammetry（CV） and in situ scanning tunneling microscopy（STM）.Heptyl viologen（1,1＇-diheptyl-4,4＇-bipyridinium dichloride）（DHV） and ethyl viologen（1,1＇-diethyl-4,4＇-bipyridinium dibromide）（DEV） showed different current waves during CV measurements in a KCl-containing electrolyte solution.The dicationic heptyl viologen molecules showed a highly ordered two dimension（2D） ＇dot-array＇ structure on the c（2×2）-Cl modified Cu（100） electrode surface in the STM images while the dicationic ethyl viologen molecules did not show any structures.With a decrease in the electrode potential,a one-electron reduction of the dication heptyl viologen resulted in the appearance of a stripe pattern that was formed by radical heptyl viologen as shown in the STM images.A more compact stripe pattern was visible in the radical ethyl viologen phase.The adsorption structure of heptyl viologen strongly depends on the electrode potential but the structure of the ethyl viologen adsorbed on the Cu（100） electrode was less response to the electrode potential.