Template-free synthesis of CdS hollow nanospheres based on an ionic liquid assisted hydrothermal process and their application in photocatalysis

Polycrystalline CdS hollow nanospheres with diameter of about 130 nm have been successfully synthesized in high yield by an ionic liquid (IL) assisted template-free hydrothermal method for the first time. Both the molar ratios of Cd/S precursor in the solution and the reaction temperature play important roles in the formation of the CdS hollow nanospheres. The concentrations of capping agent hexamethylenetetramine (HMT) and polyvinylpyrrolidone (PVP) are also crucial for the morphology and size of the final product. IL was found to be a key component in the formation of CdS hollow structures, because solid spheres were obtained in the absence of IL. A subsequent growth mechanism of hollow interior by localized Ostwald ripening process has been further discussed. Such hollow structures show high photocatalytic ability in the photodegradation of methylene blue.