Controlled formation of ZnO hexagonal prisms using ethanolamines and water

Formation of crystalline hexagonal ZnO prisms from a sol–gel method is presented. The method requires zinc acetate, water, and diethanolamine to create a zinc hydroxide/zinc hydroxide acetate gel, which in the presence of water and upon heating forms hexagonal prisms. Ethanolamines were found to be critical for gel and prism formation, while other bases such NaOH and triethylamine produce nanoparticles. Scanning electron microscope images showed hexagonal prisms with uniform size (approx. 0.5 × 2 µm) and very distinct edges. Transmission electron microscope and electron diffraction images showed that the prisms were highly crystalline with rough surfaces. Transmission electron microscope also showed a change from randomly oriented particles in the gel to ordered crystals after heating. Using an X-ray diffraction high-temperature chamber to characterize the gel, it was determined that it formed ZnO at 100 °C. Along with heating, acetate and water were found to be necessary for prism formation. In a potential application, the prisms efficiently acted as a photocatalyst in the degradation of organic dye.