Precipitation of various shapes of nanosized zinc oxide from zinc chloride solutions by neutralization with MgO and Ca(OH)₂ as non-transparent basic agents

Abstract

Various shapes of nanostructured wurtzite-type ZnO including nanorods, needle-like nanorods and spherical nanoparticles were synthesized by a simple aqueous controlled-precipitation process. The precipitation process of ZnO was accomplished via the reaction between ZnCl₂ solution and Ca(OH)₂ and MgO suspensions at 85 °C for 1 h. With MgO, layered zinc hydroxychloride was precipitated as a precursor which was converted to zinc oxide by adjusting the pH value or calcination at 520 °C for 4 h. Using Ca(OH)₂, ZnO was precipitated directly. One of the scopes of this study is to investigate the effect of solid particles of a non-transparent alkaline agent on the growth mechanism of the ZnO crystal. Nano spherical particles were produced by the addition of the zinc chloride solution into the basic suspension while, nanorods were obtained when the alkaline suspension was dropped into the zinc-containing solution. It can be concluded from the results that solid particles of a basic suspension can prevent the incorporation of the growth units into the crystal lattice of the ZnO nuclei when a zinc containing solution is dropped into a basic suspension.