Multifunctional Janus fluorescence film sensor designed with Bi-MOF: High-efficiency H2S monitoring with antibacterial and moisture---permeable ability.

Multifunctional film sensors have stood out as promising tools in real-time health and environmental monitoring, owing to its advantages of portability, non-invasiveness and high integration ability. In wearable devices, multifunctionality design was primarily motivated by practical application demands. Here, we presented a double-layer Janus fluorescence film for highly effective H2S sensing, antibacterial and moisture-permeable ability through sequential electrospinning. The H2S-sensing layer with hydrophilicity was fabricated through in situ growth of Bismuth Metal-Organic Framework (Bi-MOF) on the electrospun polyacrylonitrile (PAN) fiber (Bi-MOF/P). The hydrophobic layer (TN/P) was further constructed by using a PAN matrix incorporated with photosensitive antimicrobial molecule (TN), which was combined with the H2S-sensing layer, forming the Janus film with asymmetric wettability. The bright blue fluorescence of Bi-MOF film could be selectively "turn-off'' in the presence of H2S gas, achieving visual and sensitive H2S recognition with a detection limit as low as 23.3 ppb. The photosensitive molecules in TN/P could generate reactive oxygen species (ROS) under illumination and the Bi3+ released from Bi-MOF, which resulted in the excellent bactericidal efficacy (>82.8%) of the Janus film. When the Janus film was combined into the wearable mask, it enabled real-time H2S monitoring while offering efficient bacterial inactivation and barrier. Meanwhile, unidirectional water transport capabilities could quickly transfer moisture from the hydrophobic layer to the hydrophilic layer and significantly improve personal comfort. This work successfully integrated multiple functionalities into a convenient flexible film, showcasing great potential for advanced smart wearable sensors.