Strong reduction of V4+ amount in vanadium oxide/hexadecylamine nanotubes by doping with Co2+ and Ni2+ ions: EPR and magnetic studies

Abstract: In this work we present a complete characterization and magnetic study of vanadium oxide/hexadecylamine nanotubes (VOx/Hexa NT's) doped with Co2+ and Ni2+ ions. The morphology of the NT's has been characterized by Transmission Electron Microscopy (TEM) while the metallic elements have been quantified by Instrumental Neutron Activation Analysis (INAA) technique. The static and dynamic magnetic properties were studied collecting data of magnetization as a function of magnetic field and temperature and by Electron Paramagnetic Resonance (EPR). We observed that the incorporation of metallic ions (Co2+, S=3/2 and Ni2+, S=1) decrease notably the amount of V4+ ions in the system, from 14-16% (non-doped case) to 2-4%, with respect to the total vanadium atoms into the tubular nanostructure, improving considerably their potential technological applications as Li-ion batteries cathodes.