Ratiometric fluorescent capillary sensor for real-time dual-monitoring of pH and O2 fluctuation

The pH and O2 are the two important parameters to evaluate environmental conditions, healthcare, and industrial processes. Herein, we developed a ratiometric fluorescent capillary-based dual-functional sensor for simultaneous monitoring of pH and O2 fluctuations. The fluorescent sensor consists of a pH sensing unit and an O2 sensing unit on both ends of the capillary inner wall. The ratiometric fluorescent pH sensing unit includes pHsensitive probe HPTS and the reference dye Ce6, while the O2 sensing unit is composed of O2-sensitive probe RuDP and the reference dye C6. Under single-wavelength excitation at 430 nm, the ratiometric fluorescent dualfunctional sensor exhibits highly sensitive, selective and reproducible responses to both pH and O2. As for practical aqueous samples, the results about pH and O2 levels obtained by our sensor are considerable consistent with commercial devices. Meanwhile, the dynamic changes of pH and O2 levels during glucose catalysis by glucose oxidase can be detected in real-time and accurately. The dual-functional ratiometric fluorescent capillary transducer provides a significant potential platform for environmental monitoring and medical diagnosis.