Hydrothermal fabrication of uniform hexagonal NiO nanosheets: Structure, growth and response

• The synthesized NiO sample presents perfect regular hexagonal nanosheet which was much less reported.
• The concentration of ammonia solution and the additive of EG were controlled in the synthesis processing.
• It was the first to illustrate the growth mechanism for this hexagonal structure by the crystal structure theory.
• The hexagonal NiO nanosheets were promising sensing materials for alcohol among various gases.

Uniform hexagonal NiO nanosheets were perfectly prepared by a controlled hydrothermal method followed by calcination. The as-prepared products were characterized by X-ray powder diffraction (XRD), which illustrated the precursor Ni(OH)2 and the final product NiO. The morphologies of NiO were characterized in detail by field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM). The SAED pattern is detected from a sampling area covering a collection of constituent nanoparticles. Based on the experimental results and the crystal structure theory, the chemical reaction processes and the growth mechanism for hexagonal structure were proposed. In addition, the gas-sensing performances of uniform hexagonal NiO were investigated toward 50 ppm of several reductive gases including ethanol, CO, H2S, CH4 and NH3 at different working temperatures.

(a) The FE-SEM image shows the as-synthesized NiO product presents uniform hexagonal nanosheets, and (b) the HRTEM image gives a special feature of a perfect hexagonal nanosheet. Figure optionsDownload as PowerPoint slide