Electrochemistry at Nanoscale Electrodes: Individual Single-Walled Carbon Nanotubes (SWNTs) and SWNT-Templated Metal Nanowires

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• 作者：Petr V. Dudin ; Michael E. Snowden ; Julie V. Macpherson ; Patrick R. Unwin
• 刊名：ACS Nano
• 出版年：2011
• 出版时间：December 27, 2011
• 年：2011
• 卷：5
• 期：12
• 页码：10017-10025
• 全文大小：1065K
• 年卷期：0
• ISSN：1936-086X

文摘

Individual nanowires (NWs) and native single-walled carbon nanotubes (SWNTs) can be readily used as well-defined nanoscale electrodes (NSEs) for voltammetric analysis. Here, the simple photolithography-free fabrication of submillimeter long Au, Pt, and Pd NWs, with sub-100 nm heights, by templated electrodeposition onto ultralong flow-aligned SWNTs is demonstrated. Both individual Au NWs and SWNTs are employed as NSEs for electron-transfer (ET) kinetic quantification, using cyclic voltammetry (CV), in conjunction with a microcapillary-based electrochemical method. A small capillary with internal diameter in the range 30–70 μm, filled with solution containing a redox-active mediator (FcTMA⁺ ((trimethylammonium)methylferrocene), Fe(CN)₆^4–, or hydrazine) is positioned above the NSE, so that the solution meniscus completes an electrochemical cell. A 3D finite-element model, faithfully reproducing the experimental geometry, is used to both analyze the experimental CVs and derive the rate of heterogeneous ET, using Butler–Volmer kinetics. For a 70 nm height Au NW, intrinsic rate constants, k⁰, up to ca. 1 cm s^–1 can be resolved. Using the same experimental configuration the electrochemistry of individual SWNTs can also be accessed. For FcTMA^+/2+ electrolysis the simulated ET kinetic parameters yield very fast ET kinetics (k⁰ > 2 ± 1 cm s^–1). Some deviation between the experimental voltammetry and the idealized model is noted, suggesting that double-layer effects may influence ET at the nanoscale.