W₁₈O₄₉ Nanofibers Functionalized with Graphene as a Selective Sensing of NO₂ Gas at Room Temperature

Recent trends in two-dimensional (2D) graphene have demonstrated significant potential for gas-sensing applications with significantly enhanced sensitivity even at room temperature. Herein, this study presents fabrication of distinctive gas sensor based on one-dimensional (1D) W₁₈O₄₉ nanofibers decorated 2D graphene, specifically coated on copper (Cu)-based interdigitated electrodes formed by DC sputtering, which can selectively detect NO₂ gas at room temperature. The sensor device fabricated using W₁₈O₄₉/Gr1.5% (i.e., W₁₈O₄₉ nanofibers hybrid nanocomposite with 1.5 wt % graphene) displays excellent overall sensing performance at 27 °C (room temperature) with high response (∼150-160 times) to NO₂ gas. The W₁₈O₄₉/Gr1.5%-based sensor device reflects the highly selective detection toward NO₂ gas among various gases with quick response time of 3 s and speedy recovery in 6 s. The limit of detection of ∼0.3 ppm with excellent reproducibility and stability for 3 months in all weather conditions (tested in humidity conditions 20-97%) are superior features of the device under test. However, W₁₈O₄₉/Gr3% displayed higher selectivity for NO₂ but resulted with comparatively reduced sensitivity than W₁₈O₄₉/Gr1.5% sensor. The enhanced sensing performance could be attributed to the graphene content to decorate the nanofibers on it, oxygen vacancies/defects, and the contacts between the sensing material and Cu. This favorable synthesis and properties of self-assembled hybrid composite materials provide a potential utilization for detecting NO₂ gas in environmental safety inspection.