NiO Nanoparticle Synthesis Using a Triblock Copolymer: Enhanced Magnetization and High Specific Capacitance of Electrodes Prepared from the Powder

Abstract

Nickel oxide nanoparticles of diameter ∼21 nm were prepared by a sol–gel method using the triblock copolymer poly(ethylene glycol)- b -(propylene glycol)- b -(ethylene glycol). X-ray photoelectron spectroscopy analysis showed the presence of Ni 2+ and Ni 3+ ions in the material. The electrical conductivity of this material was due to small polaron hopping between Ni 2+ and Ni 3+ sites. The magnetization shown by these nanoparticles was much higher than that reported in the literature. This is ascribed to the presence of Ni 3+ ions with uncompensated spin moments. Spin-glass behavior was exhibited by the material at 10.7 K. The electrochemical characterization of electrodes comprising of these NiO nanoparticles using cyclic voltammetric measurements showed a specific capacitance value of 810 F/g, the highest reported for this material. These materials will thus form one of the useful multifunctional systems.

Large magnetodielectric effect and negative magnetoresistance in NiO nanoparticles at room temperature

“…The diffraction peaks have been identied to be those pertaining to NiO crystals. 10 Using Debye-Scherrer equation 42 viz.,…”

“…So, ferromagnetic-like behaviour in NiO nanoparticles was reported by various researchers. 10,20,[28][29][30] In this paper, it is shown that, NiO nanoparticles exhibit ferromagnetic like behaviour in contrast to antiferromagnetism at higher elds. This has been explained as arising due to the presence of uncompensated spins associated with Ni 3+ ions in the material.…”

“…Application of a magnetic eld may contribute to a change of permittivity by either of two possible mechanisms viz., either by movement of electric charges in a direction perpendicular to those of the applied electric and magnetic elds respectively 41 or a change of electrical conductivity of one of the phases present 40 as a function of applied magnetic eld. In this paper, we have explored the magnetic properties of NiO nanoparticles with small particle sizes than previously reported result 10 where these particles exhibit ferromagnetic like behaviour with antiferromagnetism at higher elds. The spin glass like state was found in this material with high magnetodielectric effect in the light of our results given below on their magnetic properties.…”

“…4,5 Nickel oxide (NiO) nanoparticles have been studied lately because of their very useful applications viz., as catalysts, gas sensors, electrochromic lms, dye-sensitized photo cathodes, electrode materials for fuel cells, batteries etc. [6][7][8][9][10][11][12][13] Various synthesis techniques of NiO nanoparticles have been attempted and reported in recent years by many researchers [14][15][16][17] to have variety of applications. The magnetic properties of transition metal oxides are getting attention due to their structural aspects.…”

“…18,19 Several investigations were done on NiO nanoparticles to study magnetism and magnetic interaction which have received great attention due to novel magnetic properties since Néel 20 and Brown 21 developed a magnetization relaxation theory for non-interconnecting single domain nanoparticles. 10,[22][23][24] NiO nanoparticles generally exhibit antiferromagnetism with a Néel temperature at 523 K which is involved in various applications. 20,25,26 The magnetic property is dependent on size and surface morphology of the nanoparticles.…”