Crystalline Metal Oxide Nanoparticle Films for Renewable Energy Technologies

Hot-wire chemical vapor deposition (HWCVD) has been employed as a scalable method for the deposition of crystalline tungsten oxide nanorods and nanoparticles. Under optimal synthesis conditions, only crystalline WO$_{3}$ nanostructures with a smallest dimension of $\sim $ 10 - 50 nm are observed with extensive transmission electron microscopy (TEM) analyses. X-ray diffraction (XRD), Raman spectroscopy and electron diffraction confirm that the crystalline phases of the nanostructures may be tuned by varying the synthesis conditions such that a single phase is obtained. HWCVD has also been employed to produce crystalline molybdenum oxide nanoparticles at high density. TEM analyses show that the smallest dimension of these nanostructures is $\sim $ 5 -- 30 nm. XRD and Raman analyses reveal that the materials are highly crystalline and consist of Mo, MoO$_{2}$ and MoO$_{3}$ phases. It is also possible to fabricate large area porous films of either the tungsten or molybdenum oxide nanoparticles using a novel electrophoresis deposition technique. Furthermore, WO$_{3}$ nanoparticle films have led to profound advancement in state-of-the--art electrochromic technologies, and MoO$_{x}$ films are promising for new lithium-ion batteries.