Amorphous SiO2-based all-inorganic self-supporting nanofiber membrane: a flexible and breathable sensing platform for NO2 detection

Flexible, breathable, and sensitive sensors have significant applications in gas detection, healthcare, body motion tracking, and more. However, most current flexible sensors are frequently built with polymer substrates with restricted flexibility, poor gas permeability, and poor temperature tolerance, thus limiting their multifunctional applications in wearable electronics. Herein, an easy, universal, and effective two-spinneret electrospinning approach is developed to construct an all-inorganic self-supporting multifunctional nanofiber membrane with high flexibility and gas permeability, consisting of an amorphous SiO2 nanofiber (NF) substrate layer and interwoven PdO–SnO2–SiO2 NF sensing component. The highly flexible and structurally stable amorphous SiO2 NFs are embedded randomly within the PdO–SnO2 NF sensing layer as a skeleton, effectively preventing the cracking and detachment of the sensing layer. Gas-sensing results demonstrate flexible room-temperature sensing towards ppb-level NO2 with excellent sensitivity, selectivity, and cycling stability over 3200 cycles. Additionally, SiO2 NFs endow the flexible sensor with a unique high-temperature sensing ability to selectively monitor NO2 in a fire scenario. Real-time monitoring of breath-related health signals also shows multifunctional applications with high sensing performance. The results provide an important advance towards the universal construction of flexible and breathable multifunctional membranes for high-performance flexible and wearable sensing applications.