Electroreflectance study of potential dependent phase changes of dodecyl sulfate adlayer on a Au(1 1 1) Electrode
Electroreflectance study of potential dependent phase changes of dodecyl sulfate adlayer on a Au(1 1 1) Electrode
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Au(1 1 1) 电极上十二烷基硫酸盐吸附层电势相关相变的电反射研究
DOI：
10.1016/j.electacta.2014.10.109
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发表时间：
2015
影响因子：
6.6
通讯作者：
Kenji Izumi
中科院分区：
文献类型：
--
作者：
Takamasa Sagara;Kenji Izumi
电反射 (ER) 方法（电位调制紫外可见反射光谱）用于跟踪 Au(1 1 1) 电极表面上十二烷基硫酸盐 (DS−) 吸附层的电位依赖性相变。在浓度低于 cmc 的含有 Na-DS (SDS) 的水溶液中，尽管表面活性剂是无色的，但仍可以清晰地观察到迄今为止众所周知的两步非法拉第相变作为 ER 信号。在ER光谱结构的基础上，信号的来源是Au的电反射率，它依赖于Au表面的表面自由电子密度的变化。二次谐波频率 ER 信号帮助我们了解非线性程度以及响应于电位调制的反射率变化的动力学。 ER 测量结果使我们发现，-0.18 V (Ag/AgCl/sat-KC1) 下的吸附半胶束形成-解吸过程比 +0.50 V 下叉指双层和半胶束相之间的相变过程更快。从叉指双层到半胶束相的相变响应于电位阶跃而表现出成核生长型性质，并且出现了这种相变比反向变化慢。
Electroreflectance (ER) methods (potential-modulated UV-visible reflectance spectroscopy) were used to track the potential dependent phase changes of ann-dodecyl sulfate (DS−) adlayer on a Au(1 1 1) electrode surface. In the aqueous solution containing Na-DS (SDS) at a concentration lower than cmc, two step non-faradaic phase changes, which have been well known so far, were clearly observed as ER signals, although the surfactant is colorless. On the ER spectral structure basis, the origin of the signal was the electroreflectance from Au, which relies on the change of surface free electron density on the Au surface. The second harmonic frequency ER signal helped us gain perspective on the extent of non-linearity and kinetics of the reflectance change in response to the potential modulation. Results of the ER measurements enabled us to find that adsorptive hemi-micelle formation-desorption at -0.18 V (Ag/AgCl/sat-KC1) is faster process than the phase change process between interdigitated bilayer and the hemi-micellar phase at +0.50 V. The phase change from the interdigitated bilayer to the hemi-micellar phase exhibited a nucleation-growth type nature in response to a potential step, and this phase change appeared slower than the reverse change.