The sol-gel dip-coating method is used for the preparation of MoO3 thin films. The 6 layered MoO3 films were prepared and annealed at various temperatures in the range of 200-350 degrees C. The band gap value for MoO3 films were calculated from optical absorption measurements and it is in the range of 3.55-3.73 eV. XRD spectrum reveals (0 2 0) is the major diffraction plane for the films prepared above 250 degrees C, which reveals the formation of MoO3 in alpha-orthorhombic phase. The films prepared at 200 degrees C and 250 degrees C exhibits amorphous nature. The FTIR spectrum confirms the presence of Mo-O-Mo and Mo=O bonds. Nanorods were observed in the SEM images in the case of MoO3 films prepared above 250 degrees C. The films prepared at 250 degrees C exhibit maximum anodic diffusion coefficient of 9.61x10(-11) cm(2)/s. The same film exhibits the change in optical transmission of 58.4% at 630nm with the optical density of 0.80. (C) 2010 Elsevier B.V. All rights reserved.