beta-Ga2O3 3D microstructures were prepared by ethylenediamine (En)-mediated solvothermal technique at low temperature (200 degrees C). These microstructures were characterized by X-ray diffraction, scanning electron microscopy and field emission scanning electron microscopy. The optical absorbance and photoluminescence spectroscopic studies of these microstructures indicated that the optical property of the microstructures were synthesis parameter dependent. The volume ratio of En to water played a crucial role in the conversion of initial alpha-Gao(OH) nanowires into beta-Ga2O3 nanoflakes and finally to 3D microstructures. Photoluminescence spectra of the samples revealed gallium-oxygen vacancy-related defects in these nano- and microstructures. A plausible growth mechanism for the variation of morphology with synthesis parameter is discussed. (C) 2008 Elsevier B.V. All rights reserved.