Synthesis of light green sheets like WO₃ nanostructures for room temperature humidity sensing applications

Semiconducting metal oxide-based gas sensors are an appealing option for numerous applications, including as air quality monitoring and for the detection of hazardous gases in the environment. We report a fabrication of highly stable tungsten oxide (WO₃) based humidity sensor using a simple hydrothermal method. The morphological analysis reveals the formation of sheets like nanostructures of average size ~ 1.35 μm and thickness ~ 160 nm and the structural analysis reveals the monoclinic crystal structure of WO₃. The 3.53 eV bandgap of WO₃ nanostructures, determined by optical analysis using the Tauc equation, significantly enhances charge transfer properties. The Fourier transform-infrared spectroscopy (FTIR) spectra of all bands associated with the formation of WO₃. Energy Dispersive X-ray Spectroscopy(EDS) identified tungsten and oxygen components. In Raman analysis the bands at 711.08 cm^− 1 and 801.41 cm^− 1 correspond to the monoclinic phase of WO₃ (W-O-W stretching mode). The sensor shows higher response, ~ 112.5, for the relative humidity of ~ 90% in addition to fast response and recovery time of 33 and 9 s, respectively. The enhanced humidity response from the fabricated sensor is due to the high surface area of the nanostructures which enables the adsorption of large amount of water molecules through the physisorption process. Overall, the designed WO₃-based chemi-resistive sensors provides its strong humidity sensing capability at an ambient condition.