Characteristically shaped ZnO particles produced by periodic precipitation in organic gel media

Wurtzite-type ZnO particles were directly prepared in agar gel containing zinc sulfate by diffusion of hydroxyl ions (OH−). A banded structure consisting of characteristically shaped particles, such as star-like, ellipsoidal, and round grains, was obtained through periodic precipitation along the direction of the OH− diffusion. The individual particles were composed of nanoscale ZnO crystallites elongated in the c-axis. The star-like and ellipsoidal ZnO aggregates were produced through a dissolution-precipitation process from previously precipitated thin plates of ZnSO4·3Zn(OH)2. The gel media provided a diffusion field of the precursors resulting in the formation of various kinds of characteristic shapes consisting of nanoscale ZnO particles.