Ultra-sensitive optical waveguide sensor with D–π–A chromophore for fluoride ion detection

We present a polymer optical waveguide sensor for fluoride ion (F − ) detection utilizing D–π–A dipolar molecules functionalized with tert-butyl dimethyl siloxane (TBS) groups. The sensing mechanism relies on F − -induced cleavage of Si O bonds through a desilylation reaction, which triggers a corresponding fluorescence quenching at 607 nm. By employing a 532 nm excitation laser and exploiting evanescent field interactions at waveguide interfaces, we developed an optical sensing platform that enables both qualitative identification and quantitative measurement of trace F − concentrations through real-time fluorescence monitoring. The sensor demonstrates exceptional performance with an ultra-low detection limit of 2.25 ppb and rapid response characteristics (≈3 s). The device architecture permits configuration into multiple parallel detection channels, making it particularly promising for high-efficiency environmental monitoring and biomedical applications requiring simultaneous multi-sample analysis. Furthermore, the sensor exhibits excellent anti-interference capability and specific detection performance, demonstrating reliable detection characteristics both in the presence of other interfering substances and in practical sample applications. The combination of superior sensitivity, rapid response, and scalable design positions this platform as a significant advancement in optical chemical sensing technology