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. (c) 2005 Elsevier B.V. All rights reserved.