Controllable template-free hydrothermal synthesis of 3D porous CeO2 hollow nanospheres and their optical performances

The almost monodisperse three dimensional (3D) porous CeO2 hollow nanospheres with a diameter of about 200-500 nm and rough surface have been synthesized by a facile template-free hydrothermal route. It was found that each hollow spherical nanostructure is composed of numerous nubbly nano-particles with several decade nanometers in diameter as the building blocks, which are randomly assembled with lower density to form a 3D porous structure. Many characterization means have been employed to study the CeO2 hollow nanospheres, including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman, and ultraviolet-visible spectrum. The 3D CeO2 hollow nanospheres own a cubic fluorite structure and many Ce3+ ions and oxygen vacancies exist in their surface. The morphology structure of samples, size of building blocks, and the oxygen vacancies may be the reason for the red-shifted in band gap of the 3D CeO2 hollow nanospheres.