High-Performance Flexible Gas Sensors Based on W–VO 2 /1D-Carbon Composites for Real-Time Ammonia Detection in Breath and Environmental Monitoring

Flexible resistive-type ammonia (NH₃) sensors offer great potential for IoT, healthcare, and environmental monitoring applications due to their cost-effectiveness and precise film morphology fit. However, the limited response and stability of existing gas sensors limit their practicality. Herein, we propose a high-response flexible resistive-type NH₃ sensor array based on tungsten-doped vanadium dioxide with 2 at % tungsten (W_0.02-V_0.98O₂) integrated with graphene nanoribbons (GNRs) (W_0.02-V_0.98O₂: GNRs_0.4), which has been developed by a mask-assisted drop-casting method. The fabricated sensor exhibits excellent response performance (response rate of 136.1%), fast recovery time (45 s), and excellent flexibility and stability to 20 ppm of NH₃ at room temperature (about 25 °C) because the chemical integration enhanced the active sites for adsorption and improved the charge transfer pathways. Furthermore, the sensitivity of the integrated sensor array can be conveniently tuned by adjusting the internal resistance and the smoothness of the sensing film to meet specific application requirements. The sensing device possesses the ability to detect NH₃ exposure through the respiratory process, at human physiological temperature, indoor environment, and in open air, making the device one of the stable sensors for practical applications in diverse environments reported to date based on inorganic metal oxides.