Nanoscale Electrochemical Imaging of Aligned Semiconducting and Metallic Single-Walled Carbon Nanotube Bundles

Carbon nanotubes have been studied in the variety of research fields from electronic devices to energy harvesting applications [1]. In general, their unique properties come from their ideal one-dimensional structure and tremendous metallic or semiconducting behavior depending upon their chirality. For energy application, it is an important issue to develop a good separation technique for the metallic and semiconducting single-walled carbon nanotubes (SWNTs) in large volume and to understand their electrochemical activities of both types of nanotubes. Recent progress for separation between metallic and semiconducting of has been developed. For example, a gel-based separation technique reported by Tanaka and co-workers [2]. Also, Unwin’s group has revealed the electrochemical activities for each type of the individual SWNT by scanning electrochemical cell microscopy [3]. In this study, we have at first created aligned SWNT bundles by dielectrophoresis [4] using by the commercially available suspension created by a gel separation technique. The aligned nanotube samples were prepared from either semiconducting or metallic nanotube suspension. Then, scanning electrochemical cell microscopy with a single-barrel nanopipette [5] was applied to each sample for the detection of the existence of the other property of the nanotube, referring to the difference in electrochemical activities between semiconducting and metallic nanotubes [3]. [1] M. F. L. De Volder et al., Science 339, 535, (2013). [2] T. Tanaka et al., Nano Lett. 9, 1497 (2009). [3] A. G. Guel et al., Nano Lett., 14, 220 (2014). [4] R. Krupke et al., Science 301, 344 (2003). [5] Y. Takahashi et al. Nat. Comm. 5:6450 (2014).