Improving the dielectric properties of ethylene-glycol alkanethiol self-assembled monolayers.
Improving the dielectric properties of ethylene-glycol alkanethiol self-assembled monolayers.
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DOI：
10.1021/la403983b
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发表时间：
2014-02-11
期刊：
影响因子：
--
通讯作者：
Wälti C
中科院分区：
文献类型：
--
作者：
Zaccari I;Catchpole BG;Laurenson SX;Davies AG;Wälti C
自组装单分子层（SAM）可以在固体和流体之间的界面处形成，并且通常用于改变固体的表面性质。最广泛使用的SAM系统之一是利用硫醇-金化学，其与基于烷烃链的分子一起提供SAM形成的可靠方式以改变电极的表面性质。寡聚乙二醇（OEG）封端的烷醇单分子膜显示出优异的抗氧化性能，并已被广泛用于生物传感器电极的涂层，以最大限度地减少非特异性结合。在这里，我们报告的COOH封端的OEG单分子膜的介电性能的调查，并展示了一种策略，以改善介电性能显着混合OEG SAM与小浓度的11-mercaptodendecanol（MUD）。采用交流阻抗谱、水接触角、椭圆偏振仪和X射线光电子能谱等测试手段对膜的组成和性能进行了表征。提出了一个等效电路模型来解释的EIS数据，并确定单分子层的电导率。我们发现，对于增加MUD浓度高达约5%的SAM的电阻率稳步增加，这与阻抗的相位的相当大的减少一起，证明单层的介电性能显着改善。这样的单分子膜将发现广泛的应用，这严重依赖于良好的介电性能，如电容生物传感器。
Self-assembled monolayers (SAMs) can be formed at the interface between solids and fluids, and are often used to modify the surface properties of the solid. One of the most widely employed SAM systems is exploiting thiol-gold chemistry, which, together with alkane-chain-based molecules, provides a reliable way of SAM formation to modify the surface properties of electrodes. Oligo ethylene-glycol (OEG) terminated alkanethiol monolayers have shown excellent antifouling properties and have been used extensively for the coating of biosensor electrodes to minimize nonspecific binding. Here, we report the investigation of the dielectric properties of COOH-capped OEG monolayers and demonstrate a strategy to improve the dielectric properties significantly by mixing the OEG SAM with small concentrations of 11-mercaptoundecanol (MUD). The monolayer properties and composition were characterized by means of impedance spectroscopy, water contact angle, ellipsometry and X-ray photoelectron spectroscopy. An equivalent circuit model is proposed to interpret the EIS data and to determine the conductivity of the monolayer. We find that for increasing MUD concentrations up to about 5% the resistivity of the SAM steadily increases, which together with a considerable decrease of the phase of the impedance, demonstrates significantly improved dielectric properties of the monolayer. Such monolayers will find widespread use in applications which depend critically on good dielectric properties such as capacitive biosensor.
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