Preparation of Hollow ZnO Microspheres Using Poly(methyl methacrylate) as a Template with Supercritical CO2-Ethanol Solution

Hollow ZnO microspheres were prepared using poly(methyl methacrylate) (PMMA) as a template with the assistance of supercritical CO2-ethanol solution. A precursor solution of zinc nitrate (Zn(NO3)2·6H2O) was dissolved in supercritical CO2/ethanol mixtures and was impregnated on the surface of the PMMA template. After the removal of the PMMA template by calcination in air, hollow ZnO microspheres were obtained. The products were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), nitrogen adsorption−desorption experiments, and scanning electronic microscopy (SEM). Furthermore, the effects of experimental conditions, such as the concentration of precursor, calcination temperature, impregnation media, and operating temperature during the depressurization process, on the particle morphology were investigated.