Synthesis of sealed sponge ZnO nanospheres through a novel NH3-evaporation method

Sealed sponge ZnO nanospheres are prepared through a novel NH3-evaporation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and N2 physisorption analysis show that the samples obtained are ZnO nanospheres with hexagonal wurtzite structure. The particle size is in the range 80-130 nm and the pores inside are estimated to be in the range 2-35 nm. During the preparation process, the carboxyls derived from the polyacrylamide hydrolyzation tend to attach to the particle surface and bring about the interaction between particles by hydrogen bonding. Results show that the polyacrylamide and alcohol are crucial to the formation of the sealed sponge ZnO, by forming a diffusion layer around the particle. The formation mechanism is considered to be controlled by the diffusion of Zn2+ through the diffusion layer, and the mass transmission between the initial particles