Biomimetic Gradient Porous Core-Shell Fibers with Enhanced Gas Sensing for CO-Temperature Dual-Mode Early Fire...

Early fire detection systems that are highly sensitive are essential for reducing the impact of fire disasters. However, their development still faces significant challenges due to the lack of capability for simultaneous monitoring of both temperature and gas. Herein, we propose a facile coaxial wet-spinning strategy to fabricate a dual-parameter fiber sensor capable of simultaneously detecting carbon monoxide (CO) and temperature for early combustion warning. The resulting core-sheath structured fiber consists of a CO sensing sheath made of SnO₂/In₂O₃ heterojunction/aramid nanofiber (ANF)/silver nanowire composite with biomimetic gradient pores, an ANF isolation layer, and a temperature sensing core composed of MXene. The gradient porous sheath constructed by gradient-induced phase separation technology exhibits gradually decreasing pore sizes from outer (> 10 μm) to inner (< 3 μm) regions. This structure demonstrates a significant enhancement in the fiber sensor's sensitivity to CO, achieving a 15% higher response compared to non-gradient porous structures (ΔR/R₀ = 0.95%/ppm; detection limit of 10 ppm), with the response time reduced to 19.28 s, surpassing the response speed of most fire-warning fibers. Additionally, this fiber sensor can rapidly monitor abnormal temperature increases, enabling flame alarm functionality within 3 s. It also achieves precise real-time temperature detection within the range of 50-300 °C, exhibiting high sensitivity (20.6 μV K^-1) and a strong linear correlation (R² = 0.99). This work highlights the significant potential of gradient pore in enhancing CO sensing and offers a novel perspective for the design of ultrafast early fire-warning fiber sensors.