Laboratoire d'Electrochimie Moleculaire, Unite Mixte de Recherche Universite, CNRS No. 7591, Universite Paris Diderot, Paris 7, 15 rue Jean-Antoine de Baif, 75205 Paris Cedex 13, France.
ACS Nano. 2009 Oct 27;3(10):2927-40. doi: 10.1021/nn9009054.
We describe the development of a new type of high-resolution atomic force electrochemical microscopy (AFM-SECM), labeled Tarm (for tip-attached redox mediator)/AFM-SECM, where the redox mediator, a ferrocene (Fc), is tethered to the AFM-SECM probe via nanometer long, flexible polyethylene glycol (PEG) chains. It is demonstrated that the tip-attached ferrocene-labeled PEG chains effectively shuttle electrons between the tip and substrate, thus acting as molecular sensors probing the local electrochemical reactivity of a planar substrate. Moreover the Fc-PEGylated AFM-SECM probes can be used for tapping mode imaging, allowing simultaneous recording of electrochemical feedback current and of topography, with a vertical and a lateral resolution in the nanometer range. By imaging the naturally nanostructured surface of HOPG, we demonstrate that Tarm/AFM-SECM microscopy can be used to probe the reactivity of nanometer-sized active sites on surfaces. This new type of SECM microscopy, being, by design, free of the diffusional constraints of classical SECM, is expected to, in principle, enable functional imaging of redox nanosystems such as individual redox enzyme molecules.
我们描述了一种新型的高分辨率原子力电化学显微镜（AFM-SECM），标记为 Tarm（用于尖端附着的氧化还原介体）/AFM-SECM，其中氧化还原介体，即二茂铁（Fc），通过纳米长的柔性聚乙二醇（PEG）链连接到 AFM-SECM 探针上。结果表明，尖端附着的二茂铁标记的 PEG 链有效地在尖端和基底之间传递电子，从而充当分子传感器，探测基底的局部电化学反应性。此外，Fc-PEGylated AFM-SECM 探针可用于敲击模式成像，允许同时记录电化学反馈电流和形貌，具有纳米级的垂直和横向分辨率。通过对 HOPG 的自然纳米结构表面进行成像，我们证明了 Tarm/AFM-SECM 显微镜可用于探测表面纳米级活性位点的反应性。这种新型的 SECM 显微镜，由于设计上不受经典 SECM 的扩散限制，原则上有望实现氧化还原纳米系统的功能成像，例如单个氧化还原酶分子。
