Novel Dye Based pH sensor to Supplement Commercial pH Glass Probe

  The glass probe pH sensor is the most broadly used sensor in many aspects.  The main drawback, nevertheless, lies in its fragility and its restricted use in pH 3 ~ 9 due to “acid error” and “sodium error."  We report a new pH detector that can be used in very strong acidic environment (pH<3). This detector is based on redox-active dyes that were anchored onto conducting transducer substrates. Anchoring includes simple adsorption and entrapment in ionomer/carbon nanoparticle composite. While both attachments reveal similar response, the latter possess better reproducibility. We utilize the voltammetric response of redox-active dyes towards hydrogen ions, which exhibit stable, reversible and sensitive current signal upon changing pH. The ionomer, Nafion® has received growing interest and remains a focus in primarily electrochemistry based research because of its high ionic conductivity. Its unique properties make it useful in applications including high temperature coating, super-acid catalyst, proton transportation, water purification, and fuel cells. We have incorporated various carbon powders into Nafion® polymer network by simple mixing. Nanopowders display high sensitivity to the acidity change, because the proposed pH sensing is based on voltametric (redox) measurement rather than Nernstian response. The proposed method can be used in strong acidic media while commercial potential pH glass probe fails to respond. For practical application, we therefore systematically compared the dyes and finalized the optimal entrapment and follow-up pH sensing. This work was supported by NASA-TSGC-NIP, SACP-UARP, UHD-ORC, Brown Foundation, and Welch Grant (BJ-0027).