Spray deposited superhydrophobic ZnO coatings via seed assisted growth

Superhydrophobic zinc oxide (ZnO) coatings were synthesized by a simple and cost-effective spray pyrolysis technique (SPT) via seed assisted growth onto the glass substrates at 723 K from an aqueous zinc acetate precursor solution. Initially, the ZnO seeds were synthesized from an aqueous 0.4 M zinc acetate solution onto the glass substrates at 723 K. For the seed assisted growth of ZnO, the solution concentrations (0.1 M to 0.4 M) were used and its effect on structural, morphological, optical and wettability properties of ZnO thin films was investigated. The synthesized films were found to be polycrystalline, with preferential growth along c-axis. Scanning electron microscopy (SEM) images show the uniform distribution of spherical grains of about 60-80 nm grain size. After seed assisted growth, film surface becomes very rough. The films were specular and transmittance of thin films decreases as the concentration of the precursor solution increases. The optical absorption spectrum shows a sharp absorption band-edge at 381 nm, corresponding to optical gap energy (Eg) of 3.25 eV. All samples are superhydrophobic in nature. The Zn4 sample shows the superhydrophobicity with highest value of the contact angle (CA) i.e. 165°. Such a superhydrophobic coatings can be useful in the anti-snow, anti-fog and self cleaning surfaces.