Pure ZnO films and Au nanoparticles dispersed ZnO films were prepared by the sol-gel dip-coating technique. Thermal behavior and chemical composition of the dried ZnO precursor were investigated by thermogravimetry-differencial scanning calorimetry (TG-DSC) and Fourier transform infrared spectroscopy. The films were characterized by X-ray diffraction, scanning electronic microscopy and optical absorption measurements. Different aging times for the precursor solution at room temperature led to totally different crystalline structure of the ZnO films and the corresponding composite films. With longer aging time (24 h) at room temperature, highly oriented wurtzite structures were formed in ZnO. The crystallites were a-axis orientated instead of c-axis orientated. (C) 2003 Elsevier Science B.V. All rights reserved.