Highly uniform 3D sisal-like, dandelion-like and rose-like architectures of cobalt hydroxide carbonate with orthorhombic or monoclinic phase were synthesized through a facile selected-control hydrothermal process at 100, 140 and 180 degrees C, respectively. In addition, cobalt spinel Co3O4 superstructures with broom-like, dandelion-like and rose-like morphologies were obtained by thermal conversion of the corresponding precursor of 3D architectures based on the thermal analysis results, and TEM images show that all Co3O4 superstructures were assembled by nanoparticles. The optical absorption properties of the Co3O4 Superstructures were investigated and the results indicate that the superstructures are semiconducting with transitions corresponding to 775 and 530 nm in the UV-vis spectroscopy. (c) 2005 Elsevier B.V. All rights reserved.