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

提出的研究旨在利用氧化还原端端单分子膜来电化学激活、驱动和调节固液界面的物理化学过程，从而有可能促进宏观到纳米级电化学技术的发展。由二茂铁、二二甲苯、电子供体或电子受体组成的有机硫酸酯自组装单层（sam）被化学吸附到金表面，用作电活性分子界面。这些氧化还原活性SAMs的电荷转移引起的变化将被用于微机械驱动和二维集成的形成，包括固体支持的脂质膜、溶致液晶纳米材料薄膜和纳米颗粒阵列。前一项研究的目标是确定如何通过电化学触发小的（埃级）构象变化并利用其进行更大规模的机械工作，而后一项研究的目标是证明如何使用氧化还原刺激产生的界面离子对或电荷转移复合物来创建表面吸附的组件。我们特别试图确定氧化还原部分的空间拥挤，单层主链中重复单元的数量，单层中的（超）分子组织，分子间范德华相互作用以及离子对或电荷转移相互作用的强度在研究过程中所起的作用。电荷存储在二元二茂铁衍生物具有不重叠的氧化还原电位，以及双二茂铁端端SAMs，其氧化还原稳定性远远优于通常的二茂铁端端SAMs，将被研究用于开发电化学稳健的多态分子开关。最后，将探讨局部表面等离子激元激发对表面拴系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和实现纳米结构的区域特异性化学功能化。预期的结果是氧化还原和光介导过程的发展，用于操纵固液界面上的分子事件，并可用于设计功能氧化还原响应系统，如机电致动器，电子存储器或光电器件。

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.