Apple pectin-mediated green synthesis of hollow double-caged peanut-like ZnO hierarchical superstructures and photocatalytic applications

Hollow ZnO superstructures have potential technological applications. With this motivation, a simple approach is developed to prepare hollow double-caged peanut-like ZnO hierarchical superstructures with the assistance of apple pectin. The biotemplate-assisted approach concurs with "green" chemistry as it is simple and environmentally friendly. The products are characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results reveal that the pectin-directed hydrothermal process is essential to obtain the final products. The morphologies and dimensions of the ZnO structures could be easily tuned by varying the molar ratios of the pectin to zinc ion, the amount of ammonia, the reaction time and the temperature. A possible formation mechanism for the hollow superstructures is described. In addition, the optical properties of the ZnO superstructures were investigated in some detail. The as-prepared samples showed high photocatalytic activity towards methyl orange (MO) under ultraviolet (UV) irradiation.