Hydrothermal synthesis of one-dimensional tungsten oxide nanostructures using cobalt ammonium sulfate as a structure-directing agent

Hydrothermal synthesis of one-dimensional tungsten oxide nanostructures was performed using cobalt ammonium sulfate as a structure-directing agent, and the effect of the concentration of cobalt ammonium sulfate on the characteristics of the tungsten oxide nanostructures was investigated. XRD measurements showed that hexagonal tungsten oxide (h-WO₃) structures were obtained at a higher concentration of cobalt ammonium sulfate (0.2 M), while cubic tungsten oxide (c-WO₃) structures were obtained at a lower concentration of cobalt ammonium sulfate (0.01M). Mixed structures of h-WO₃ and c-WO₃ were observed at an intermediate concentration of cobalt ammonium sulfate. Morphological studies revealed that h-WO3 appeared as nanowires with a diameter of about 40 nm and an average length of 1 μm. c-WO₃ was shaped in pillar-like nanorods with a diameter of about 30 nm. A red-shift in the UV/Vis absorption peak was observed with different phases of tungsten oxide nanostructures.