Dan Meng

Assembly of 3D flower-like NiO hierarchical architectures by 2D nanosheets: synthesis and their sensing properties to formaldehyde

Flower-like NiO hierarchical architectures were synthesized by a solvothermal process without using any other surfactant. Absolute ethanol and distilled water were adopted as solvent, and nickel nitrate hexahydrate was employed as the nickel source. The morphology and crystal structure were mainly investigated. Through annealing the as-obtained products, flower-like NiO hierarchical architectures with a cubic structure were synthesized, which were assembled by a number of thin nanosheets with a thickness of about 30 nm. The formaldehyde gas sensing measurements showed that well-defined NiO flower-like structures with large surface area exhibited higher responses compared with microsheets/nanosheets at a relatively lower operating temperature of 200 °C. Moreover, a reversible and fast response to formaldehyde gas at various gas concentrations, good selectivity and stability were obtained. The results indicated that the flower-like NiO hierarchical architectures are promising materials for gas sensors.

Size and morphology-controlled synthesis of Ni3C nanoparticles in a TEG solution and their magnetic properties

Nickel carbide nanoparticles (Ni3C NPs) were synthesized by a polyol solution refluxing route at a temperature of 300 °C for 20 min using triphenylphosphine oxide (TPPO) as the surfactant. Size and morphologies of the Ni3C NPs were controlled by adjusting the concentration of Ni(NO3)2 and TPPO. The products consisted of Ni and Ni3C could be kinetically controlled by a reaction temperature of 250–290 °C and time less than 20 min and the proportion of the Ni component was lower with longer reaction times and higher temperatures due to carbon atom insertion via a carbonaceous film that formed on the surface of the growing particles. The formation process of the Ni3C NPs was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) characterization. The saturation magnetizations of products decreased with decreasing ratio of Ni:Ni3C, which inferred that Ni3C was non-magnetic and the magnetism arose from trace Ni in the products.

CTAB-assisted hydrothermal synthesis of WO 3 hierarchical porous structures and investigation of their sensing properties

WO3 hierarchical porous structures were successfully synthesized via cetyltrimethylammonium bromide- (CTAB-) assisted hydrothermal method. The structure and morphology were investigated using scanning electron microscope, X-ray diffractometer, transmission electron microscopy, X-ray photoelectron spectra, Brunauer-Emmett-Teller nitrogen adsorption-desorption, and thermogravimetry and differential thermal analysis. The result demonstrated that WO3 hierarchical porous structures with an orthorhombic structure were constructed by a number of nanoparticles about 50-100 nm in diameters. The H2 gas sensing measurements showed that well-defined WO3 hierarchical porous structures with a large specific surface area exhibited the higher sensitivity compared with products without CTAB at all operating temperatures. Moreover, the reversible and fast response to H2 gas and good selectivity were obtained. The results indicated that the WO3 hierarchical porous structures are promising materials for gas sensors.

Solvothermal synthesis of mesoporous TiO2 microspheres with tailored pore size and specific surface area

Mesoporous TiO2 microspheres with high specific surface area were synthesized by a template-free solvothermal method with the aid of urea. The phase structure, morphology, pore and optical properties were characterized by XRD, SEM, N2 adsorption–desorption and UV–Vis diffuse reflectance spectra. By controlling the urea concentration, size, specific surface area, pore size and optical property of the mesoporous TiO2 microspheres can be tuned.