Lotus-root-like NiO nanosheets and flower-like NiO microspheres: synthesis and magnetic properties

Abstract

The synthesis of lotus-root-like NiO nanosheets and flower-like NiO microspheres was realized through a simple hydrothermal method and subsequent calcination. The diameter of the lotus-root-like NiO nanosheets is about 400 nm and the pore size is about 5$20 nm. The diameter of the flower-like NiO microspheres is about 2.5 mm, and are composed of staggered lotus-root-like nanosheets. During the synthetic procedure, aqueous ammonia was used as an alkaline complexing reagent, and PVP was used as the template. Interestingly, when the pH value of the precursor solution increased from 8.30 to 10.80, the NiO nanosheets gradually assembled into microspheres, indicating that aqueous ammonia plays a key role in controlling the final morphology. Based on the experimental observation and analysis, a possible mechanism is proposed to understand the formation of the NiO nanostructured materials. In addition, the resultant NiO nanostructures present anomalous magnetic properties and display a spin-glass state at low temperature.

Annealing-dependent structural and magnetic properties of nickel oxide (NiO) nanoparticles in a silica matrix

“…Although bulk NiO is antiferromagnetic, nanoparticles exhibit room-temperature coercivity, spin-glass behavior, superparamagnetism, memory effects, exchange bias effects and magnetic transitions at low temperature [17][18][19][20][21][22][23][24][25][26][27][28][29]. The novel magnetic properties of NiO nanoparticles compared to bulk material are mainly due to a complex interplay between finite size effects, surface effects and inter-particle interactions [4,6,16,22,24,27,28].…”

Controlled synthesis of mesoporous β-Ni(OH)2 and NiO nanospheres with enhanced electrochemical performance

“…Ni(OH) 2 can be conveniently synthesized in solutions of Ni(II) by a chemical precipitation method, while NiO can be conveniently prepared by thermal decomposition of Ni(OH) 2 . Up to now, Ni(OH) 2 and NiO with various structures and morphologies have been synthesized, such as nanoparticle, nanorod, nanowire, nanosheet and nano/microsphere, and their properties have also been investigated [10][11][12][13][14][15][16][17]. The results showed that the performances of Ni(OH) 2 and NiO in most of their applications largely depended on their crystal structure, morphology and surface area.…”

Monodisperse rutile microspheres with ultrasmall nanorods on surfaces: Synthesis, characterization, luminescence, and photocatalysis

“…Its advantages include a low growth temperature, low cost, and good potential for scale-up [14,15]. Numerous materials with complex morphologies, such as nanoflowers [16][17][18][19]4], nanotrees [20][21][22], hierarchical microspheres [23][24][25][26][27], and hierarchical tubes [28][29][30][31][32][33][34][35], have been synthesized by this approach. However, achieving various three-dimensional nanostructures still remains a challenge.…”