Superhydrophobic ZnAl double hydroxide nanostructures and ZnO films on Al and glass substrates

Superhydrophobic nanostructured ZnAI: layered double hydroxides (LDHs) and ZnO films have been fabricated on Al and glass substrates, respectively, by a simple and cost effective chemical bath deposition technique. Randomly oriented hexagonal patterned of ZnAI: LDHs thin nanoplates are clearly observed on Al-substrate in the scanning electron microscopic images. The average size of these hexagonal plates is similar to 4 mu m side and similar to 30 nm of thickness. While on the glass substrate, a oriented hexagonal patterned ZnO nanorods (height similar to 5 mu m and 1 mu m diameter) are observed and each rod is further decorated throughout the top few nanometers with several nanosteps. At the top of the nanorod, a perfectly hexagonal patterned ZnO surface with similar to 250 nm sides is observed. The tendency to form hexagonal morphological features is due to the hexagonal crystal structure of ZnO confirmed from X-ray diffraction patterns and transmission electron microscopy image. The ZnAI: LDHs and/or ZnO coated substrates have been passivated by using stearic acid (SA) molecules. Infrared spectra of passivated ZnAI: LDHs coated substrates confirm the presence of SA. X-ray diffraction pattern also corroborates the results of infrared spectrum. The contact angle of the as prepared samples is zero. The superhydrophobicity is achieved by observing contact angle of similar to 161 degrees with a hysteresis of similar to 4 degrees for Al-substrate. On the glass substrate, a higher contact angle of similar to 168 degrees with a lower hysteresis of similar to 3 degrees is observed. A lower surface roughness of similar to 4.93 mu m is measured on ZnAI: LDHs surface layer on the Al substrate as compare to a higher surface roughness of 6.87 mu m measured on ZnO layer on glass substrate. The superhydrophobicity of passivated nano structured films on two different substrates is observed due to high surface roughness and low surface energy. (C) 2016 Elsevier B.V. All rights reserved.