Molybdenum oxide nanostructures as colorogenic material have been widely used in optical sensors, electrochemical, electrochemical, thermochromic, catalytic and plasmonic applications. The penetration of hydrogen atoms into the molybdenum oxide lattice in the gasochromic process causes to create oxygen vacancy and free charge carriers and so the plasmonic absorption bands in the NIR region. In addition, heat treatment in a reducing flame atmosphere is another method of creating oxygen deficiency and plasmonic properties in this material. As a result of these phenomena, the milky (white) color of molybdenum oxide changes. In recent years, the production of metal oxides with colorogenic properties using simple, inexpensive and fast manufacturing methods, has been considered. electrooxidation and solid feed flame methods are efficient synthesis methods for the preparation of molybdenum oxide structures in the form of colloids and thin layers. In this research, in the first part, the colloidal nanoparticles of molybdenum oxide are synthesized by using the anodizing method. Due to reduction properties of MoOx colloidial solution, gold salt ions can be reduced into gold metal nanoparticles by MoOx particles. Au-MoO3 colloidal solution shows a gasochromic hydrogen gas sensing. Plasmonic peaks of gold nanoparticles in the visible region (~ 550 nm) as well as plasmonic peak of molybdenum oxide nanoparticles in the visible to near infrared region (~ 780 nm) red shifted by increasing the hydrogen gas concentration (0-3%). The shift of gold plasmonic peak related to variation in sourounding refractive index (MoOx) and the plasmonic peak shift of Moox related to incresing the carriedr density through hydrogen exposure. The cummulative absoption curves of Au:MoOx solution verse H2 gas concentration show a linear relationship .In the second part, a layers of molybdenum oxide are deposited on the glass substrate using the solid fed flame method. In this section, we investigate the role of substrate temperature during the deposition process on morphology and crystal structure. As the substrate temperature increases during the flame vapor deposition (25-400 ℃), the crystal structure improves as the crystalite phase changes from monoclinic to orthorombic. In addition the morphology of flame deposited nanoparticles changes from spherical nanoparticles to thick micro-plate. To activate the gasochromic properties of MoO3 films, a thin layer of pd catalyst sputtered. After hydrogen exposure a plasmonic absorption band was appaired in Vis-NIR. The XRD and Raman analysis confirm the variation in the crystalit structure of molybdenium oxid after hydrogenation. By making a simple device, the sensing properties of the films are eva‎luated through the parameters of sensitivity to different gas concentrations, stability and selectivity at optimal operating temperature. In the third section, using the simple and fast flame method, the molybdenum oxide layers were deposited at room temperature on the quartz glass substrates. The MoO3 layers are reduced when placed at different distances and times within the torch flame. The flame reduction process leads to appear of a plasmonic absorption peak in the infrared region. We investigated the role of plasmonic peaks for the thermal shield windows application.

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پرويز كاملي

محمد مهدوي، حميده شاكري پور، فاطمه داور