Synthesis and structural characterization of tungsten trioxide nanoplatelet-containing thin films prepared by Aqueous Chemical Growth

We report the synthesis of WO3 thin films predominantly made up of nanoplatelets, on transparent plain glass microscope slides, by the low-temperature, soft chemistry method of Aqueous Chemical Growth (ACG). During the heterogeneous growth, by ACG, of WO3 thin films onto these plain glass substrates, nanoplatelet and nanorod-like structures of WO3 were also precipitated out of the Peroxotungstic acid precursor solutions and collected as slurries which were annealed at 500 °C to give ultra-fine powders of WO3. Scanning Electron Microscopy of the thin films and powders showed that nanoplatelets formed had thicknesses generally less than 300 nm and lengths and diameters in the 1–2 μm range. The thin films formed were less than 5 μm thick. Transmission Electron Microscopy (TEM) on one of the thin films confirmed the formation of nanoplatelets as well as nanorod-like structures, while High Resolution TEM alongside X-ray Diffraction and Raman spectroscopy suggested that the WO3 thin film grown on a plain glass microscope slide was monoclinic in crystal structure. While Energy Dispersive X-ray Spectroscopy, Fourier Transform-Infrared Spectroscopy, and Attenuated Total Reflection were used to establish the purity and bond structure of WO3 within the thin film, Selected Area Electron Diffraction gave further evidence of crystallinity within the nanostructures prepared. The potential use of the WO3 nanoplatelet-containing thin films for hydrogen sensing at 300 °C was demonstrated. - Highlights: ► WO3 thin films grown on glass slides by Aqueous Chemical Growth, at 90–95 °C ► Formation of square-nanoplatelets in the thin films is confirmed. ► Raman spectroscopy confirms platelets to be monoclinic in crystal structure. ► Drop-coated thick films of WO3 nanoplatelets on glass, sensed H2 at 300 °C