Department of Chemistry, University of Warwick, Coventry, CV4 7AL, United Kingdom.
ACS Nano. 2011 Dec 27;5(12):10017-25. doi: 10.1021/nn203823f. Epub 2011 Nov 28.
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, k(0), 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 (k(0) > 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.
纳米线（NWs）和原生单壁碳纳米管（SWNTs）可以很容易地用作伏安分析的定义明确的纳米级电极（NSEs）。这里，通过模板辅助的电沉积在超长流排列的 SWNTs 上，展示了亚毫米长的 Au、Pt 和 Pd NWs 的简单无光刻制造，高度小于 100nm。单独的 Au NWs 和 SWNTs 都被用作电子转移（ET）动力学定量的 NSE，使用循环伏安法（CV），结合基于微毛细管的电化学方法。一个内径在 30-70μm 范围内的小毛细管，填充有包含氧化还原活性介质（FcTMA(+)（三甲基铵甲基铁）、Fe(CN)(6)(4-)或肼）的溶液，位于 NSE 上方，使得溶液弯月面完成电化学池。使用忠实再现实验几何形状的 3D 有限元模型，对实验 CV 进行分析，并使用 Butler-Volmer 动力学推导非均相 ET 的速率。对于 70nm 高的 Au NW，可以解析高达约 1cm s(-1)的固有速率常数 k(0)。使用相同的实验配置也可以访问单个 SWNTs 的电化学。对于 FcTMA(+/2+)电解，模拟的 ET 动力学参数产生非常快的 ET 动力学（k(0) > 2 ± 1cm s(-1)）。实验伏安法和理想化模型之间存在一些偏差，这表明双层效应可能会影响纳米尺度上的 ET。
