A–D–A Molecular Design Strategy Enabling Ultrasensitive NIR Vapor Sensing

Thin-film fluorescent chemosensors, characterized by their tunable design, high selectivity, and exceptional sensitivity, hold significant promise for gas detection applications. However, the simultaneous realization of the 3S attributes (sensitivity, selectivity, and stability) remains a formidable challenge, particularly in the underexplored field of near-infrared (NIR) gas detection. In this work, we employ an acceptor–donor–acceptor (A–D–A) molecular design strategy to drive the development of an organic semiconductor fluorescent material with a progressive red shift in the emission wavelength. As a result, we synthesized C8-IDTT-IC, a NIR fluorescent thin film with a peak emission at 790 nm. In contrast to conventional visible fluorescent materials, this NIR material demonstrates excellent resistance to background light interference and optical damage, particularly in the detection of biogenic amines. Systematic evaluations reveal that the material achieves remarkable selectivity, with a detection limit as low as 116 ppb, a rapid response time of less than 30 s, and an optical damage rate of only 3% over 1800 s. The practical utility of this material is further exemplified by its integration into a hand-held detector, enabling real-time monitoring of spoilage in beef and fish samples, showcasing its potential for real-world applications.