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

M. E. SALETA; H. E. TROIANI; S. RIBEIRO GUEVARA; G. RUANO; R. D. SÁNCHEZ; M. MALTA; R. M. TORRESI

JOURNAL OF APPLIED PHYSICS

AMER INST PHYSICS

Año: 2011 vol. 109 p. 93914 - 93923

0021-8979

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, while the metallic elements have been quantified by the instrumental neutron activation analysis technique. The static and dynamic magnetic properties were studied by collecting data of magnetization as a function of magnetic field and temperature and by electron paramagnetic resonance. At difference of the majority reports in the literature, we do not observe magnetic dimers in vanadium oxide nanotubes. Also, we observed that the incorporation of metallic ions (Co2+, S = 3/2 and Ni2+, S = 1) decreases notably the amount of V4+ ions in the system, from 14−16% (nondoped case) to 2%−4%, with respect to the total vanadium atoms (fact corroborated by XPS experiments) anyway preserving the tubular nanostructure. The method to decrease the amount of V4+ in the nanotubes improves considerably their potential technological applications as Li-ion batteries cathodes.