Self-assembly fabrication of ZnO hierarchical micro/nanospheres for enhanced photocatalytic degradation of endocrine-disrupting chemicals

ZnO hierarchical micro/nanospheres were successfully synthesized via a facile and surfactant-free chemical solution route. The field emission scanning electron microscopy and transmission electron microscopy observations showed that the ZnO micro/nanospheres were assembled by large amounts of interleaving nanosheets with the thickness of about 17 nm. The X-ray diffraction, energy dispersion X-ray and Raman results revealed that the as-synthesized products were well-crystalline and possessing wurtzite hexagonal phase pure ZnO. Under UV irradiation, the ZnO micro/nanospheres showed an enhanced photocatalytic performance compared with the ZnO nanorods and commercial TiO₂ in the degradation of phenol. The photocatalytic enhancement of ZnO micro/nanospheres was attributed to their unique hierarchical porous surface structure and large surface area which can enhance the electron–hole separation and increased the yield of hydroxyl radical quantities as evidenced by the photoluminescence spectra. By using a certain of radical scavengers, hydroxyl radical was determined to play a pivotal role for the phenol degradation. Moreover, the as-synthesized ZnO micro/nanospheres could be easily recycled without any significant loss of the photocatalytic activity. Other endocrine-disrupting chemicals such as resorcinol, bisphenol A and methylparaben were also successfully photodegraded under identical conditions. These characteristics showed the practical applications of the ZnO micro/nanospheres in environmental remediation.