Time dependent spectral change upon potential step perturbation for Au nanoparticles immobilized on an organic monolayer-modified ITO electrode
Time dependent spectral change upon potential step perturbation for Au nanoparticles immobilized on an organic monolayer-modified ITO electrode
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DOI：
10.1016/j.colsurfa.2006.03.003
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发表时间：
2006-09
期刊：
影响因子：
--
通讯作者：
A. Toyota;T. Sagara
中科院分区：
文献类型：
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作者：
A. Toyota;T. Sagara
研究了固定在ITO电极上的金纳米粒子在电极电位变化时的光谱随时间的变化。在ITO电极上，将直径为11 nm的Au纳米颗粒固定在含胺或硫醇端基的烷基硅氧烷单层上。除了先前阐明的粒子在高于8赫兹的正弦波电势调制下的充放电过程外，本工作还发现在电势阶跃之后可见光吸收的非常缓慢的松弛。响应于电势阶跃的吸光度的瞬变是1s内的快分量和半衰期为30-150s量级的慢单指数分量的总和。慢组分的半衰期和两组分的幅值比取决于入射光波长和电势阶跃的方向。这些结果表明，Au纳米颗粒在电位变化后的吸收光谱具有时间依赖性。在吸附电解质阴离子的存在下，特别是在正电势下，慢弛豫在总光谱变化中的相对幅度增大，但快组分的影响较小。讨论了这些结果的含义，并提出了在吸附阴离子存在的情况下，金纳米颗粒表面存在缓慢表面过程的可能性。
Time dependent spectral change of Au nanoparticles immobilized on an ITO electrode upon the change of electrode potential was investigated. Au nanoparticles of a diameter of 11nm were immobilized on a monolayer of alkylsiloxane with an amine or thiol end group on an ITO electrode. In addition to the previously clarified charging–discharging process of the particles in response to the sine-wave potential modulation at frequencies higher than 8Hz, very slow relaxation of visible light absorption after a potential step was found in the present work. The transient of absorbance in response to the potential step was a sum of a fast component within 1s and a slow single exponential component with a half-life of the order of 30–150s. The half-life of the slow component and the magnitude ratio of the two components depended on the incident light wavelength and the direction of the potential step. These results suggested that the absorption spectrum of the Au nanoparticles after the potential change is time dependent. The relative magnitude of the slow relaxation in the total spectral change was enhanced in the presence of adsorptive electrolyte anions such as Cl−and Br−, especially at positive potentials, at the expense of the fast component. Implications of these results were discussed, and the possibility of the presence of a slow surface process on the Au nanoparticle surface in the presence of adsorptive anions was invoked.