Carbon nanotubes (CNTs) have attracted the attention of numerous scientists because of their potential use as nanoelectrodes for bioelectrochemical applications due to their excellent electrical conductivity, mechanical robustness and biocompatibility. Amorphous carbon (a-C) exhibits a wide potential window, a low background current, and ultra-flat surface that also make it suitable for nanoelectrode fabrication. In this study we report the synthesis of a hybrid carbon structure, a-C coated multi-walled carbon nanotubes (MWNTs), by combining floating catalyst chemical vapor deposition and bubbler-assisted chemical vapor deposition. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman mapping were performed to study the hybrid material and the morphology of the a-C layer (Figure 1). Standard redox Fe(CN)₆^3-/4- cyclic voltammetry measurements of individual MWNT and a-C coated MWNT were performed to elucidate the effect of a-C coating on the electrochemical properties (Figure 2). The a-C coated MWNT with an approximate diameter of 70 nm and length of 3 µm exhibited a sixfold increase in the redox current signal when compared to individual MWNT of equivalent dimensions. These findings indicate the potential of a-C coating for enhancing the sensitivity of nanoelectrode sensors.

Figure 1. SEM images of (a) MWNTs (b) a-C coated MWNTs, TEM images of (c) MWNTs (d) a-C coated MWNTs

Figure 2. Cyclic voltammograms of individual MWNT and a-C coated MWNT in 0.5 molL^-1 Fe(CN)₆^3-/4- and 1 molL^-1 KCl solution at 50 mVs^-1

Akira Osaki

The Pennsylvania State University

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