Synthesis of Nanostructured Tungsten Oxide Thin Films: A Simple, Controllable, Inexpensive, Aqueous Sol−Gel Method

Among the available metal oxide nanostructures, tungsten oxide has remained, at times, troublesome to fabricate, with many synthetic methods often requiring exotic equipment and or reagents. In this work, we present a systematic investigation demonstrating a new method for the deposition of anhydrous and hydrated nanostructured tungsten oxide thin films via spin coating. The attributes of these materials include the following: high surface area, controllable deposition, and compatibility with existing semiconductor fabrication infrastructure making this method a suitable candidate for application in the manufacture of gas sensors and dye sensitized solar cells. We will show that it is possible to form micrometer thick highly crystalline nanostructured thin films and, using Raman, SEM, XRD, XPS, and TEM analysis, will prove that these nanostructures can be rendered into anhydrous or partially or fully hydrated tungsten oxides. We further demonstrate the application of these materials in the fabrication of an inexpensive NO 2 gas sensor, capable of sensing sub-ppm levels of NO 2 concentrations at a modest operating temperature of 175 °C.