Hierarchical ZnO hollow microspheres with strong violet emission and enhanced photoelectrochemical response

Abstract Hierarchical ZnO hollow microspheres were prepared via a carbon microspheres-templated approach, and their microstructures were analyzed by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The as-prepared ZnO products show well-defined hollow spherical morphology with a size of 2–4 µm. The thickness of ZnO shells is around 100 nm, and they are assembled by numerous nanoparticles of 30–50 nm. The optical properties of the ZnO hollow microspheres were studied, and they exhibit a narrowed band gap (2.96 eV) and a sharp violet emission at 434 nm. Moreover, the ZnO hollow microspheres show a stable and greatly enhanced photocurrent response to visible light, which can be attributed to the hierarchical structures and the narrowed band gap resulted from the carbothermic process.