Facilitating ZnO nanostructure growths by making seeds for self-catalytic reactions

Long and straight single-crystalline ZnO nanowires were successfully synthesized on ZnCl2-coated Zn foils in oxygen environment by using simple thermal annealing processes. With relatively low reaction temperatures (410 and 700 °C), nanowires whose lengths and diameters are up to ∼50 μm and 10–100 nm were obtained. We found that ZnO seeds created from ZnCl2 played an important role in facilitating the ZnO nanowire growth via self-catalytic reactions. Systematic studies by altering critical synthesis factors that determine shape, length, diameter, and density of the nanowires were performed in order to unveil the growth mechanisms. We also compared the nanowires synthesized from Zn foils with tetrapod ZnO nanostructures synthesized from Zn powders at various temperatures. - Graphical abstract: (Left panel) ZnO seeds from ZnCl2 after thermal annealing at 500 °C for 5 min, (right panel) dense ZnO nanowires grown from Zn foils with ZnCl2 coating after thermal annealing at 700 °C for 60 min. Highlights: ► ZnCl2 facilitated ZnO nanowire growth by creating ZnO seeds. ► ZnO nanowires were synthesized via self-catalytic reactions. ► Long and straight single-crystalline ZnO nanowires were synthesized. ► Key parameters in thermal annealing processes were identified.