Synthesis and characteristics of ZnGa₂O₄ hollow nanostructures via carbon@Ga(OH)CO₃@Zn(OH)₂ by a hydrothermal method

ZnGa₂O₄ hollow nanostructures were synthesized by a two step hydrothermal and calcination process using carbon spheres as a template. We observed that the carbon@Ga(OH)CO₃ core-shell nanostructures were covered by a uniform shell of Zn(OH)₂ nanoparticles when prepared using 2.5 mmol of ZnAc, and ZnGa₂O₄ hollow nanostructures with diameters of approximately 200 nm and shell thicknesses of around 15 nm could then be obtained. After calcination at 900 °C for 1 h, the amorphous core-shell-shell nanostructures yielded highly crystalline ZnGa₂O₄ hollow nanostructures. The shell possesses a single-crystal structure and a lattice spacing of around 0.253 nm which corresponds to the d spacing of (311) crystal planes of cubic ZnGa₂O₄. The composition and surface electron state of the ZnGa₂O₄ hollow nanostructures prepared at 900 °C were confirmed by X-ray photoelectron spectroscopy. UV and blue emissions of the ZnGa₂O₄ hollow nanostructures were found to result from self-activation centers of the octahedral Ga-O groups in the spinel structures and symmetry distortion of the octahedral sites by oxygen vacancies, respectively.