One-step hydrothermal synthesis of ZnO microflowers and their composition-/hollow nanorod-dependent wettability and photocatalytic property

Diverse hollow and solid microflowers of wurtzite ZnO were prepared by one-step hydrothermal method without secondary heat treatment. N2H4 acts as the suppressing and structure-directing agents simultaneously. The solid and hollow ZnO flowers are constructed by nanorods/nanoneedles (with different tips), and hollow nanoprisms/nanorods respectively. The diameter of hollow ZnO flowers (S4) can reach 34 μm. HRTEM demonstrates that ZnO nanocrystals exhibit single-crystalline feature, which is stacked by the ABAB··· mode. The Zn/O atom ratio of S1 or S6 is very close to ZnO stoichiometric ratio. The composition, reflectance and PL of ZnO can be tuned by changing reagent concentrations. The hollow S4 and S5 exhibit the largest BET surface areas (22.6 m2/g (S4) and 46.652 m2/g (S5)) and the best photocatalytic performance, and decompose about 79% of MO (S4), 80% of RhB (S4) and 82% of MB (S5) within 90, 80 and 50 min respectively. The photoactivity of S5 for MB is equal to that of commercial TiO2-P25 within 50 min. The water contact angle of S7 is 135.4° and exhibits high hydrophobic surface, while hollow S3, S4 and S5 show relatively high surface hydrophilic nature. The composition of ZnO influences its wettability, while the novel hollow nanostructure mainly contributes to the enhanced hydrophilic and photocatalytic properties of ZnO simultaneously. In addition, the effect mechanism of N2H4 was proposed.