Integrating Self-Assembled Alkylthiol-Modified Metal–Organic Framework Nanoparticles with U-Shaped Tapered Optical Fiber for Volatile Organic Compound Sensing

Self-assembled nanoparticles (NPs) demonstrate significant promise in various fields, such as display, substance detection, and sensing applications. Their structural tunability, high specific surface area, and pronounced interfacial effects make them suitable for fabricating high-performance sensors. However, the fabrication, performance optimization, and system integration of self-assembly remain challenging. To address these challenges, this study synthesized and employed alkylthiol-group-modified hydrophobic zeolitic imidazolate framework-8 (ZIF-8) NPs, which were combined with a gas–liquid interfacial self-assembly strategy to prepare freestanding ZIF-8 self-assembled films. To demonstrate its function, we integrated this film with a U-shaped tapered optical fiber (U-TOF) for evanescent field coupling, creating a novel all-fiber volatile organic compound (VOC) sensing platform. This novel fabrication process circumvents the repetitive growth steps of the existing in situ methods by leveraging the low-loss cross-substrate transfer of gas–liquid self-assembled films. U-TOF sensor fabrication was achieved in under 10 s by utilizing the Langmuir–Blodgett method. Fabricated by this rapid and facile method, the U-TOF sensor ultimately achieved highly sensitive detection of trace ethanol, offering new insights into the efficient preparation of gas-sensitive optical fiber sensors.