Nanocomposites and nanomaterials
Transport properties of surface modified single-walled carbon nanotubes
Shpylka D.O.1, Ovsiienko I.V.1, Len T.A.1, Matzui L.Yu.1, Prylutskyy Yu.I.2 Tsaregradskaya T.L.1, Mirzoiev I.G.3
Taras Shevchenko National University of Kyiv, Department of Physics1 and Biophysics2, 01601, Volodymyrska st. 64/13, Kyiv, Ukraine
3B. Verkin Institute for Low Temperature Physics and Engineering of NAS of Ukraine, 61103, Nauky Ave. 47, Kharkiv, Ukraine
E-mail: denys8600@ukr.net
In the work the results of complex investigations of electrical and magnetic conductivity of bulk specimens of as prepared and surface modified single-walled carbon nanotubes (SWCNTs) are presented. As prepared SWCNTs have been produced by acetylene decomposition method with use nickel as catalysts. These SWCNTs have been modified on surface by cobalt-containing complexes according to several schemes with different sequence of main stages, such as cutting of tubes along defects, removal of metal catalyst and particles of disordered carbon, forming of complicated cobalt-containing complexes at SWCNTs surface. For investigation of electrical and magnetic resistivity, the bulk specimens from as prepared and modified SWCNTs powders have been made by cold compacting without binder. The resistance has been measured in the temperature interval from 4.2 K to 293 K and in the magnetic fields up to 2.5 T.
Figure 1 presents the temperature (a) and magnetic field (b) dependences of resistivity  for bulk specimens of as prepared and modified SWCNTs.
a)	b)	It is found that for as prepared SWCNTs, the main mechanism of conductivity is 3D hopping with the variable hopping length. Surface modification of SWCNTs with cobalt -containing complexes leads to the creation on the surface of SWCNT small localized negative	
Figure 1. Dependences of resistivity (T)(a) and magnetoresistance /(B)(b) for bulk specimens of as prepared (1) and modified (2) SWCNTs. Inset: dependence /(B2) for as prepared SWCNTs, T = 77 K		
charge. For modified SWCNTs the bulk specimens’ conductivity is described in the terms of power temperature law, that is typical for individual SWCNTs.