Self-assembled ZnO nanostructures with various morphologies were prepared via a rapid and simple microwave-assisted technique. The spherical, raspberry-like and hollow spherical nanostructures were synthesized in the presence of triethanolamine (TEA) as a capping agent and in different adjusted pHs. The volumetric amount of TEA has affected the particle size and crystallite size of the obtained nanostructures significantly. The ZnO nanostructures were obtained due to self-assembly of Zn2+ ionic complexes, and the internal voids of the hollow spheres were formed by the Ostwald ripening mechanism. The obtained nanostructures were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. The optical properties of the synthesized materials were investigated by Raman spectroscopy. (C) 2008 Elsevier B.V. All rights reserved.