Guanzhou Qiu

Shape-controlled synthesis and properties of uniform spinel cobalt oxide nanocubes

Inorganic nanoparticles with controlled size and shape seem especially technologically important due to the strong correlation between these parameters and their magnetic, electrical, and catalytic properties. Herein we demonstrate that uniform spinel cobalt oxide (Co3O4) nanocubes can be successfully synthesized on a large scale via a facile hydrothermal synthetic route under mild conditions. The size and shape of final products can be readily tuned in a wide range by tuning process parameters such as hydrothermal time, reaction temperature, surfactant, concentration, and molar ratios of starting material.

Mechanochemical synthesis of cobalt oxide nanoparticles

Abstract Cobalt oxide (Co 3 O 4 ) nanoparticle was synthesized by thermal treatment of the precursor obtained via mechanochemical reaction of Co(NO 3 ) 2 ·6H 2 O with NH 4 HCO 3 . Calcination of the precursor at 300 °C resulted in the formation of Co 3 O 4 nanoparticles of 13 nm in crystal size. The precursor was examined by simultaneous differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The Co 3 O 4 nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Effect of calcination temperature on Co 3 O 4 crystal size was discussed. The activation energy ( E ) of Co 3 O 4 nanoparticle formation during thermal treatment was calculated to be 15.9 kJ/mol.

Cobalt hydroxide nanosheets and their thermal decomposition to cobalt oxide nanorings.

We demonstrate herein that single-crystalline beta-cobalt hydroxide (beta-Co(OH)(2)) nanosheets can be successfully synthesized in large quantities by a facile hydrothermal synthetic method with aqueous cobalt nitrate as the cobalt source and triethylamine as both an alkaline and a complexing reagent. This synthetic method has good prospects for the future large-scale production of single-crystalline beta-Co(OH)(2) nanosheets owing to its high yield, low cost, and simple reaction apparatus. Single-crystalline porous nanosheets and nanorings of cobalt oxide (Co(3)O(4)) were obtained by a thermal-decomposition method with single-crystalline beta-Co(OH)(2) nanosheets as the precursor. A probable mechanism of formation of beta-Co(OH)(2) nanosheets, porous Co(3)O(4) nanosheets, and Co(3)O(4) nanorings was proposed on the basis of the experimental results.

Synthesis of tin oxide nanoparticles by mechanochemical reaction

Abstract The synthesis of tin oxide (SnO 2 ) nanoparticles by mechanochemical reaction (SnCl 2 +Na 2 CO 3 ) with NaCl as diluent and subsequent thermal treatment was investigated using differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), infrared spectroscopy (IR) and transmission electron microscopy (TEM). Heat treatment of the as-milled powder at 600xa0°C in air and removal of NaCl through washing produced the SnO 2 nanocrystallites with an average crystal size of about 28 nm, varying with the thermal treatment temperature. The mechanism of nanocrystallites growth is discussed.

Rationally synthetic strategy: from nickel hydroxide nanosheets to nickel oxide nanorolls

We demonstrate here that single-crystal β-Ni(OH)2 nanosheets can be selectively synthesized in large quantities through a facile hydrothermal synthetic method using aqueous nickel nitrate as the nickel source and sodium hydroxide as alkaline reagent. This attempt is based on the treatment of aqueous nickel nitrate with high concentrations of sodium hydroxide solution under hydrothermal condition. Single-crystal NiO nanorolls can be obtained via a thermal decomposition method using single-crystal β-Ni(OH)2 nanosheets as the precursor. The influences of alkaline concentration and reaction temperature are carefully investigated in this paper. The morphologies and phase structures of the as-prepared products are investigated in detail by x-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The probable formation mechanism of the NiO nanorolls is proposed on the basis of the experimental results.

Shape-controlled synthesis and characterization of cobalt oxides hollow spheres and octahedra

We demonstrated that single-crystalline cobalt monoxide (CoO) hollow spheres and octahedra could be selectively synthesized via thermal decomposition of cobalt(II) acetylacetonate in 1-octadecene solvent in the presence of oleic acid and oleylamine. The morphologies and sizes of as-prepared CoO nanocrystals could be controlled by adjusting the reaction parameters. Cobalt oxide (Co(3)O(4)) hollow spheres and octahedra could also be selectively obtained via calcination method using corresponding CoO hollow spheres and octahedra as precursors. The morphology, size and structure of the final products were investigated in detail by XRD, SEM, TEM, HRTEM, DSC, TG, and XPS. The results revealed that the electrochemical performance of cobalt oxide hollow spheres is much better than that of cobalt oxide octahedra, which may be related to the degree of crystallinity, size, and morphology of cobalt oxides.

Hollow spherical rare-earth-doped yttrium oxysulfate: A novel structure for upconversion

AbstractA facile biomolecule-assisted hydrothermal route followed by calcination has been employed for the preparation of monoclinic yttrium oxysulfate hollow spheres doped with other rare-earth ions (Yb3+ and Eu3+ or Er3+). The formation of hollow spheres may involve Ostwald ripening. The resulting hybrid materials were used for upconversion applications. The host crystal structure allows the easy co-doping of two different rare-earth metal ions without significantly changing the host lattice. The luminescent properties were affected by the ratio and concentration of dopant rare-earth metal ions due to energy transfer and the symmetry of the crystal field. The type of luminescent center and the crystallinity of samples were also shown to have a significant influence on the optical properties of the as-prepared products.n

General synthetic strategy for high-yield and uniform rare-earth oxysulfate (RE2O2SO4, RE = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, Ho, and Yb) hollow spheres

A general and facile synthetic strategy for fabrication of a series of high-yield and uniform rare-earth oxysulfate hollow spheres is demonstrated as the first example via calcination corresponding rare-earth coordination compounds obtained using L-cysteine as a biomolecular template. Furthermore, the hollow spheres can also be successfully doped or formed in a double-shell form for property modification and technological applications.

Controllable fabrication and magnetic properties of double-shell cobalt oxides hollow particles

Double-shell cobalt monoxide (CoO) hollow particles were successfully synthesized by a facile and effective one-pot solution-based synthetic route. The inner architecture and outer structure of the double-shell CoO hollow particles could be readily created through controlling experimental parameters. A possible formation mechanism was proposed based on the experimental results. The current synthetic strategy has good prospects for the future production of other transition-metal oxides particles with hollow interior. Furthermore, double-shell cobalt oxide (Co3O4) hollow particles could also be obtained through calcinating corresponding CoO hollow particles. The magnetic measurements revealed double-shell CoO and Co3O4 hollow particles exhibit ferromagnetic and antiferromagnetic behaviour, respectively.

Nickel dichalcogenide hollow spheres: controllable fabrication, structural modification, and magnetic properties.

Magnetize your chemistry! A facile hydrothermal synthetic route was developed for the synthesis of uniform NiS2 hollow spheres, which could be transformed into NiSe2 and NiTe2 hollow spheres through a chemical conversion process. Furthermore, NiS and NiO hollow spheres could be selectively obtained by calcination of NiS2 hollow spheres at different temperatures.