Polymer optical waveguide recoverable evanescent field nitroaromatics sensor based on D-π-A chromophore.

Nitroaromatics are a significant concern due to their high explosiveness and potential for water pollution. Optical waveguide sensing technology has been employed in the detection of nitroaromatics, leveraging its advantages of affordability, high sensitivity, reusability, and effective detection results. However, most current optical waveguide sensors operate on the principle of cumulative refractive index change, which necessitates extended detection times. Additionally, although many optical waveguide sensors are reusable, they often require complex and time-consuming post-processing steps for device recovery, and their detection performance significantly degrades after multiple uses, thus limiting their practical applications. In this work, we developed an evanescent field optical waveguide sensor for the detection of nitroaromatics in water, utilizing polymeric optical waveguide materials and D-π-A chromophore molecule. We integrated the sensing molecules into the hydrophobic fluorosilicone resin upper cladding material and employed the evanescent field principle to monitor changes in the optical properties of the surface sensing molecules following their interaction with nitroaromatics. This approach not only prevented contaminant penetration into the sensor, allowing for rapid device recovery, but also facilitated quick quantitative detection. Our sensor demonstrates a detection time of approximately 5 s, a recovery time of about 3 s, and achieves a detection limit of 0.11 ppm, with performance remaining largely intact after several detection cycles.