Effect of Solution pH and ZnCl₂ on Zinc Oxide Nanostructures Grown on Zn Foil

Department of Mining, Metallurgical and Materials Engineering, University of the Philippines, 1101 Diliman, Quezon City, Philippines

^a Corresponding author: copelicano@upd.edu.ph
^b mdlbalela@gmail.com.

Abstract

Zinc oxide (ZnO) nanostructures were formed by wet oxidation of zinc (Zn) foil in water at 90°C for 4 h. The effect of pH and ZnCl₂ concentration on the morphology and structure of the resulting ZnO nanostructures on the surface of Zn foil were investigated. Clusters of ZnO nanosheets were visibly grown on top of hexagonal flat-topped nanorods in the presence of 0.05 M ZnCl₂. Addition of higher ZnCl₂ concentration resulted to layered plate-like structures of simonkolleite compound (Zn₅(OH)₈Cl₂.H₂O). The formation of this compound is favored at high concentrations of Zn₂₊ and Cl⁻ ions. In addition, flower-like structures of hexagonal nanorods, coarse nanorods and nanotubes were obtained at increasing pH values from 6.3 to 10. The increased concentration of OH⁻ ions possibly hindered further deposition of hydrolyzed Zn(II) ions and the subsequent dissolution and redeposition of the existing ZnO nanostructures directed the formation of coarse nanorods and nanotubes.