This study consists of three parts; 1-synthesize of molybdenum oxide nanosheets, 2-decolorization of blue colloidal solution by PdCl 2 solution and 3-study of gasochromic and photochromic properties of decolorized colloidal solutions. In the first part of thesis, blue colloidal solutions of molybdenum oxide were prepared using a simple electrochemical anodizing of molybdenum foils in an electrolyte composed of 0.02 M HCl. Structure, chemical and optical properties of the colloidal nanoparticles were characterized by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FE-SEM), Furrier Transform Infrera-Red (FTIR) spectroscopy, X-Ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy. XRD revealed that the as-prepared nanoparticles are amorphous. TEM images showed the presence of nanosheets of irregular shapes in the colloidal solutions. XPS spectra of Mo3d confirmed coexistence of Mo 5+ and Mo 6+ oxidation states. The optical absorption spectra of the initial blue colloidal nanosheets displayed a large absorption peak at 600-1100 nm wavelength range. Each spectrum could be de-convoluted into four distinct absorption peaks centered at 1.2, 1.4, 1.6 and 1.9 eV. At the second part, we observed for the first time that by addition PdCl 2 solution into the initial blue color colloids they became colorless. The do-colorization time was depended on Pd:Mo molar ratio and vary from few minutes to several days. Comparision of XRD of as-prepared and Pd-MoO 3 samples after annealing at 500 °C showed that a preferential growth along (0k0) peaks which gives rise to change in aspect ratio of crystalline particles. TEM revealed a significant increase in the average size of nanoparticles. XPS revealed reduction of Mo 5+ concentration in Pd-MoO 3 sample that the decolorization can be linked to reduce in Mo 5+ oxidation state. In the last section, we examined the gasochromic and photochromic properties of decolorized samples. For gasochromic investigations, the decolorized solutions were exposed to bubbling diluted hydrogen (10%H 2 /90%Ar) gas. The samples display a strong coloration from traarent to blue. Moreover, for photochromic investigations traarent samples were exposed to UV pulsed laser irradiation. A considerable coloration was observed upon laser irradiation. Based on the fact that NIR absorption peaks of gasochromic and photochromic coloration are almost similar to that of initial blue samples, some physical descriptions based on small polaron theory and inter-band transition were given.