Carbon nanotubes (CNTs) have been used in multiple areas to create macro-, micro-, and nanoelectrodes. They are an ideal material for electrochemical studies due to their electrical conductivity, chemical inertness, and large aspect ratio. Vertically aligned CNTs (VA-CNTs) have been used to fabricate both nanoelectrode arrays (NEA) and ensembles (NEE). NEAs have controlled interspacing for the CNTs employed as the sensing area, which leads to radial diffusion to each electrode. In contrast, NEEs have the CNTs randomly distributed, leading to overlapping diffusion layers. Sensors for environmental pollutants and biological analytes use NEA/NEEs. This work uses spinnable/drawable CNTs to fabricate CNT nanoelectrode ensembles (CNT-NEE). The bulk material, made of alternating layers of the spinnable CNT films and a passivation layer of hydrogenated nitrile butadiene rubber (HNBR), is microtomed to expose the open ends of the CNTs. The sensing area of interest for these CNT-NEE are the open ends; their performance was characterized as a working electrode via cyclic voltammetry to probe the electrode performance in a redox active species. Scanning electrochemical cell microscopy (SECCM) was used to limit the exposed area of the electrode to approximately 200 nm to observe the steady-state current response. The CNT-NEE was employed to detect Pb<sup>2+</sup> ions in acetate buffer using square-wave anodic stripping voltammetry; a limit of detection of 0.57 ppb with a linear range of 10-35 ppb was achieved.

Characterization of carbon nanotube nanoelectrode ensembles

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