Electroactive Self-Assembled Monolayers: Putting Surface-Confined Redox Reactions to Work

这项拟议的研究旨在利用氧化还原端基的单分子膜在固-液界面上电化学激活、驱动和调制物理化学过程，从而潜在地促进宏观到纳米级电化学技术的发展。以二茂铁、双二茂铁、电子给体或电子受体基团官能化的有机硫代化合物自组装单分子膜(SAM)化学吸附到金表面作为电活性分子界面。这些氧化还原活性自组装膜中的电荷转移诱导的变化将被用于微机械驱动和二维系综的形成，包括固体支撑的脂膜、溶致液晶纳米材料膜和纳米颗粒阵列。前者的研究重点是确定如何通过电化学触发和利用微小的(埃尺度)构象变化来执行更大规模的机械工作，而后者的目的是展示如何利用氧化还原刺激产生的界面离子对或电荷转移络合物来创建表面吸附的组件。我们特别寻求确定氧化还原部分的空间拥挤、单层主干中重复单元的数量、单层中的(超)分子组织、分子间van der Waals相互作用以及离子对或电荷转移相互作用的强度对所研究过程的影响。由两个氧化还原电位互不重叠的二茂铁衍生物组成的二元自组装膜，以及氧化还原稳定性远优于普通二茂铁端基自组装膜的电荷储存，将被研究用于开发电化学性能良好的多态分子开关。最后，将探讨局域表面等离子体激发对表面束缚分子的法拉第电化学和化学不稳定性的影响，以促进表面受限的电化学反应，使纳米结构的区域特定的化学功能化成为可能。预期的成果是开发氧化还原和光介导的过程，用于操纵固-液界面上的分子事件，并可用于设计功能性氧化还原响应系统，如机电执行器、电子存储器或电光设备。

The proposed research is aimed at harnessing redox-terminated monomolecular films to electrochemically activate, drive, and modulate physicochemical processes at solid-liquid interfaces in ways that can potentially facilitate the development of macro- to nano-scale electrochemical technologies. Self-assembled monolayers (SAMs) of organothiolates, functionalized with ferrocene, biferrocenylene, electron donor or electron acceptor moieties, chemisorbed to gold surfaces are used as electroactive molecular interfaces. Charge-transfer-induced changes in these redox-active SAMs will be exploited for micromechanical actuation and the formation of two-dimensional ensembles, including solid-supported lipid membranes, films of lyotropic liquid crystal nanomaterials, and nanoparticle arrays. The objective of the former research thrust is to establish how small (angstrom-scale) conformational changes can be electrochemically triggered and harnessed to perform much larger-scale mechanical work, while that of the latter is to demonstrate how the interfacial ion pairs or charge transfer complexes generated by a redox stimulus can be used to create surface-adsorbed assemblies. We specifically seek to establish the roles played by the steric crowding of the redox moieties, number of repeat units in the monolayer backbone, (supra-)molecular organization in the monolayer, intermolecular van der Waals interactions, and the strength of the ion pair or charge transfer interactions on the processes investigated. Charge storage in binary SAMs comprising two ferrocene derivatives with nonoverlapping redox potentials, as well as biferrocenylene-terminated SAMs, whose redox stability is far superior to that of the usual ferrocene-terminated counterparts, will be investigated for the development of electrochemically robust multistate molecular switches. Finally, the effect of localized surface plasmon excitation on the Faradaic electrochemistry and chemical lability of surface-tethered molecules will be explored with the aim of facilitating surface-confined electrochemical reactions and enabling the regiospecific chemical functionalization of nanostructures. The expected outcomes are the development of redox- and light-mediated processes for manipulating molecular events at solid-liquid interfaces and that can be used to engineer functional redox-responsive systems such as electromechanical actuators, electronic memories or electrooptical devices.