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 ZnSO 4 ·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.