Controllable Synthesis of ZnO with Various Morphologies by Hydrothermal Method

ZnO microstructures with various morphologies have been controllably synthesized by hydrothermal route using different precipitant and zinc source in liquid solution. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the ZnO₂, Zn(OH)₂ and ZnO structures to understand the role of precipitant and precursors in the growth of various morphologies. The nucleation and growth process can regulate by changing the precipitant. When H₂O₂ was used as precipitant, ZnO particles with a rather uniform particle size of ∼500 nm and a rather rough surface was obtained. While, ZnO synthesized in this polyvinyl pyrrolidone (PVP) solution has the same granular morphology with particle size of 300–1000 nm. In contrast, ZnO sunflower and polyhedron aggregates composed of several smaller polyhedron were formed, when ammonium hydroxide and NH4HCO3 was applied, respectively. Meanwhile, precursors play an important role in the determination of the morphology of ZnO. Sunflower and dumbbell like ZnO composed of nanosheets were obtained, when different centrifugal component of Zn(OH)₂ suspension was applied as zinc source. In contrast, sunflower and dumbbell like ZnO composed of nanorods and ZnO rods were obtained, when different centrifugal components of ZnO₂ suspension were used as zinc sources. The growth mechanism of ZnO nanostructures fabricated by the hydrothermal process using different zinc sources was tentatively investigated.