Simultaneous reduction and electrode patterning of TiO₂/GO films via femtosecond laser for UV-enhanced flexible CO gas sensors

Reliable and sensitive gas sensors are essential for ensuring industrial safety and environmental monitoring. In this study, a flexible carbon monoxide (CO) gas sensor based on titanium dioxide (TiO₂) and reduced graphene oxide (rGO) composite was developed for rapid and highly sensitive detection. The device was fabricated using one-step femtosecond laser (Fs-laser) processing, which simultaneously reduced a TiO₂/graphene oxide (GO) thin film and patterned electrodes directly on a flexible substrate. Optimized laser parameters, including a repetition rate of 100 kHz, a scanning speed of 50 mm/sec, and a fluence of 0.34 J/cm², enabled efficient film reduction and ensured reliable device performance. The sensor exhibited an initial response of 39.6% to CO gas at room temperature (25 °C), which was further enhanced to a maximum response of 43.8% under ultraviolet (UV) irradiation. Under 365 nm UV irradiation, the photocatalytic activity of TiO₂ induced a substantial reduction in overall resistance, significantly improving the sensing capability. These findings demonstrate the potential of TiO₂/rGO composite in UV-enhanced flexible CO gas sensors, and provide a promising strategy to improve sensitivity, selectivity, and stability in gas sensing applications.