Xiaoguang San

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.

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.

Facile preparation of size-controlled TiO2 nanoparticles by hot-filament metal oxide deposition method and their gas sensing properties to NO2

Titanium dioxide (TiO2) nanoparticles were prepared by resistive heating Ti filament under an oxygen atmosphere. The obtained nanoparticles were confirmed to be a tetragonal crystal TiO2 and the particle size increased with increasing the oxygen pressure. The NO2 gas sensing properties of the TiO2 nanoparticles were investigated. All the sensors made of TiO2 nanoparticles with different particle sizes exhibited the maximum sensitivities to 1 ppm NO2 at a relative low operating temperature of 150°C. Comparing with the large particle size of TiO2 nanoparticles, the ones with the smallest particle size exhibited the highest sensitivity and the best response and recovery characteristic to various NO2 gas concentrations.