Research Article Effect of Electrochemical Treatment on Electrical Conductivity of Conical Carbon Nanotubes S. M. Khantimerov, 1 P. N. Togulev, 1 E. F. Kukovitsky, 1 N. M. Lyadov, 1 and N. M. Suleimanov 1,2 1 Zavoisky Physical-Technical Institute, Te Russian Academy of Sciences, Sibirsky Trakt 10/7, Kazan 420029, Russia 2 Kazan State Power Engineering University, Krasnoselskaya 51, Kazan 420066, Russia Correspondence should be addressed to S. M. Khantimerov; khantim@mail.ru Received 30 June 2016; Revised 20 October 2016; Accepted 26 October 2016 Academic Editor: Valery Khabashesku Copyright © 2016 S. M. Khantimerov et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Interaction of conical carbon nanotubes (CNTs) with hydrogen during electrochemical treatment and its efect on their electronic properties was studied. Te temperature dependencies of electroconductivity of initial and electrochemically hydrogenated conical CNTs were investigated by using four-probe van der Pauw method. Te studies revealed that the electrochemical hydrogen absorption leaded to a signifcant reduction in the electroconductivity of conical carbon nanotubes. We assume that these changes can be associated with a decrease in the concentration of charge carriers as a result of hydrogen localization on the carbon -orbitals, the transition from sp 2 to sp 3 hybridization of conical CNTs band structure, and, therefore, a metal-semiconductor-insulator transition. 1. Introduction Carbon nanotubes (CNTs) attract considerable attentions due to their unique structural, electrical, and mechanical properties that make them suitable for various applications such as supercapacitors, catalyst supports, energy storage devices, and additives [1–5]. Te investigations of carbon nanotubes’ interaction with hydrogen are also of great interest [6–8]. A recent study [9] showed that graphene can react with atomic hydrogen, which, being localized on the carbon -orbitals, leads to a transition from sp 2 to sp 3 hybridi- zation of the graphite band structure and, hence, to a con- ductivity change. Considering the possible usage of carbon nanostructured materials and carbon based composites as lightweight microwave absorbers in the felds of commu- nication, microwave devices, and electromagnetic pollution defense [10–14], the investigations on variation of the electri- cal and magnetic properties of carbon nanotubes are in the focus of interest. In the present study conical carbon nanotubes were used as a testing material. Conical CNTs have a unique feature: the majority of their internal and external edges are open and this is favorable for hydrogen intercalation into their interplanar spaces. Previously, it was shown [15] that electrochemical hydrogen sorption leads to the structural changes occurring during hydrogenation in the conical walls of the CNTs. Such changes were associated with the hydrogen intercalation into the interplanar spaces of conical CNTs and its addition to the -bonds of graphite layers. We assumed that localization of hydrogen on the carbon -bonds should lead to electroconductivity reduction. A similar decrease in the electrical conductivity of carbon nanotubes by increasing the concentration of adsorbed hydrogen atoms was also theoretically described elsewhere [16]. Te purpose of this work was to investigate temperature dependencies of electroconductivity of initial and electro- chemically treated conical carbon nanotubes and to reveal hydrogen efect on the electronic properties of such struc- tures. 2. Materials and Methods Conical carbon nanotubes were grown by pyrolysis of granu- lar polyethylene as described elsewhere [17]. Te morphology Hindawi Publishing Corporation Journal of Nanotechnology Volume 2016, Article ID 8034985, 5 pages http://dx.doi.org/10.1155/2016/8034985