Synthesis and characterization of nano ZnO rods via microwave assisted chemical precipitation method

A microwave assisted chemical precipitation method has been employed for the synthesis of nano zinc oxide rods by reacting zinc nitrate and potassium hydroxide. The amount of potassium hydroxide was adjusted for three different pHs to achieve ZnO nano rods with varying aspect ratio. The mechanism of growth of nano rods is explained briefly. The average crystallite size of the as synthesized samples was analyzed by means of powder XRD pattern and estimated to vary from 25.6 nm to 43.1 nm. The existence of rods was confirmed using scanning electron microscopy (SEM). The samples were also analyzed using FT-IR. The optical properties of the samples were also studied by means of UV–visible spectra and Room Temperature Photo Luminescence studies. The band gap of the samples was determined from the DRS spectrum. A strong near band emission peaks due to surface defects are observed in the PL spectrum.

At the solution pH of 11 and 9, tetrapod-like and flower-like ZnO nano rods were formed along with separated rods respectively due to the formation of activated nuclei of different sizes.Figure optionsDownload as PowerPoint slideHighlights
► Increase in alkalinity of the precursor solution results in longer rods.
► Beyond a saturation limit, the excess of added OH− ions inhibited the growth of rods.
► Keeping all parameters the same, the alkalinity can only modify the aspect ratio of the rods and not their morphology.