Low temperature, rapid and controllable growth of highly crystalline ZnO nanostructures via a diluent hydrolytic process and its application to transparent super-wetting films

One-dimensional ZnO nanospike arrays were prepared on substrates via a low temperature rapid water bath growth method based on the diluent of a nearly saturated solution. Commercial ZnO powder, NaOH and water were the source chemical reagents, without other reacting additives during the whole experimental process. Detailed structural and spectral characterization reveals the high crystallinity of the as-grown ZnO nanostructures, despite the fast growth process. The microstructure and crystalline states can be tailored via the appropriate control of variables such as reaction time, growth temperature and the dilution ratio of the near-saturated solution. The ZnO nanospike arrays contribute to the formation of a transparent superhydrophobic film as a result of their gradient refractive index structure and the ultra-low solid-liquid contact area under wetting conditions. Besides, highly crystalline two-dimensional ZnO nanosheets and three-dimensional ZnO microflowers were also acquired via growth control. And the successful growth of ZnO on a curved surface extends its application to various engineering interfaces with different surface morphologies. What is more, the whole growth mechanism was explored through the analysis of products growing in solution and on substrates. This approach contains a series of advantages for the preparation of scaled ZnO nanostructures with high crystallization and uniformity, such as low cost, low temperature (lower than 80 degrees C), rapid reaction (shorter than 30 minutes) and ease of control, which endows this approach with potential for application in optoelectronic devices.