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 pH-sensitive 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 dual-functional 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.