Impact of stirring time and the corresponding growth mechanism in the solvothermal synthesis of WO₃ nanostructures

WO₃ nanostructures with different morphologies and dimensions were fabricated via solvothermal synthesis by adjusting the stirring time of the precursor solution. Ethanol-based solutions of the WCl₆ precursor with various colors (dark green, yellow, white, blue, and blue-black) were prepared, and this triggered a significant change in the growth behavior during the evolution of WO₃ nanostructures. Controlling the initial state of the precursors in solution enabled sequential nucleation and growth which resulted in the production of zero-to-three-dimensional nanostructures including nanoparticles, a mixture of nanosheets and nanoparticles, jointed-nanosheets, and three-dimensionally clustered jointed-nanosheets. The crystallographic characteristics (preferred orientation along the (002) plane) and the concentration of surface oxygen vacancies were also controllable, suggesting the formation of nanostructures with tuneable surface reactivity. Differing NO₂ sensing performances were observed because of the variation in configurations of the WO₃ nanostructures.