Scanning Tunneling Microscopy for the Study of Heterogeneous Electron Transfer

电子转移反应的研究在溶液和 在电极表面是目前的一个领域， research. 然而，目前存在一些 实验限制阻碍了许多方面的研究 异质电子转移。 该项目的目标是 Widrig博士正在开发一种通用技术， 研究电极反应，这将克服许多 这些目前的局限性。 在她的实验方法中， 最近已经在实现中改进的技术， 扫描隧道显微镜将应用于 研究单个分子的氧化还原化学。 这将通过使用扫描的尖端来完成 隧道显微镜和平面电极基板作为 双恒电位仪的两个工作电极。 基板 电极将用有组织的单分子 含有可逆氧化还原试剂的层。 因为提示是 位于衬底表面上方的角度内， 适合于氧化和还原的电压 固定化的物种将被施加到尖端和基底上 电极，分别。 当固定化的分子 尖端所处的位置被连续氧化， 减少，产生的电流的大小将是 取决于异质电子的速率常数 转移到这个物种。 初步计算显示 氧化还原电对的可测量电流 其标准速率常数大于2 cm/s。 这项技术的成功实施将使 测量以前无法确定的速率常数， “快速”电极反应，并允许前所未有的 电极-反应物分离作用的评估， 取向和异质电子中的环境 转移 前期工作包括准备和 电活性单层的表征， 尖端绝缘程序的开发， 通过单个分子的异质电子转移。 %%% 研究规划赠款使以前没有 独立的联邦研究支持， 研究项目。 这个项目涉及到技术的使用 为了在扫描中精确放置电极 隧道显微镜，用于有组织电解的精密电解 单分子层 这将允许测量 电子转移速率以前无法测量。

The study of electron transfer reactions both in solution and at electrode surfaces is currently an area of vigorous research. At the present, however, there exist a number of experimental constraints that hinder the study of many aspects of heterogenous electron transfer. A goal of the project of Dr. Widrig is the development of a general technique for the examination of electrode reactions which will overcome many of these current limitations. In her experimental approach, the technology that recently has been refined in the realization of the scanning tunneling microscope will be applied to the investigation of the redox chemistry of individual molecules. This will be accomplished by using the tip of the scanning tunneling microscope and a planar electrode substrate as the two working electrodes of a bipotentiostat. The substrate electrode will be derivatized with an organized, monomolecular layer containing a reversible redox reagent. As the tip is positioned within Angstroms above the substrate surface, voltages suitable for oxidation and reduction of the immobilized species will be applied to the tip and substrate electrodes, respectively. As the immobilized molecule over which the tip is positioned is continually oxidized and reduced, the magnitude of the resulting current will be dependent on the rate constant for heterogeneous electron transfer to that species. Preliminary calculations indicate that measureable currents will be obtained for redox couples whose standard rate constants are greater than 2 cm/s. Successful implementation of this technique will permit the measurement of formerly indeterminable rate constants for "fast" electrode reactions and allow an unprecedented assessment of the roles of the electrode-reactant separation, orientation, and environment in heterogeneous electron transfer. Preliminary work includes the preparation and characterization of the electroactive monolayer, the development of tip insulation procedures, and modeling of heterogeneous electron transfer through individual molecules. %%% Research Planning Grants enable women who have not had prior independent Federal research support to develop a competitive research project. This project involves the use of technology for the precise placement of electrodes in the scanning tunneling microscope for precision electrolysis of an organized monomolecular layer. This will permit the measurement of the rates of electron transfer previously not measurable.