Calibration-Free Ion Sensing

该项目由化学部的化学测量和成像计划资助。明尼苏达大学双城分校的Philippe Buhlmann教授正在开发氧化还原缓冲聚合物和氧化还原缓冲纳米多孔碳，以展示它们在传感器中的应用。这种方法延长了传感器的使用寿命，并且不需要校准。化学传感器用于测量水、食品、工业液体和生物样品中化学物质的浓度，其方式与温度计用于测量温度类似。特别地，具有高选择性的电化学传感器每年用于数十亿次离子浓度的测量。不幸的是，传统的离子传感器必须频繁地重新校准，这需要不断供应试剂以及自动化或训练有素的人员。这使即时护理应用复杂化并提高了成本。这项工作消除了重新校准的需要。更广泛的影响也体现在将高中生纳入研究活动和推广活动中，在社区图书馆的实践活动中引入传感器。聚合物和纳米多孔碳材料在明确的电化学电位下具有氧化还原缓冲能力，为制备免校准传感器提供了独特的方法。该项目中开发的材料具有与先前报道的具有氧化还原活性基团的聚合物和碳相区别的特征：它们具有高重现性和良好的长期化学稳定性的批次独立的电化学电势。这些性质由两个设计原理产生：（i）氧化还原缓冲聚合物和纳米多孔碳以相等的量结合不同氧化还原对的氧化和还原形式，从而限定由能斯特方程给出的电势。(ii)氧化还原活性基团被特别选择为在环境条件下以氧化和还原形式都是稳定的。深入研究了使用这些新材料的电位传感器的响应机理，包括氧化还原缓冲聚合物中电子和离子电导率的定量以及界面电子和离子转移动力学。

This project is funded by the Chemical Measurement and Imaging Program of the Division of Chemistry. Professor Philippe Buhlmann of the University of Minnesota - Twin Cities is developing redox buffer polymers and redox buffer nanoporous carbons to demonstrate their application for sensors. This approach extends the sensor lifetime and requires no calibration. Chemical sensors are used to measure the concentration of chemical species in water, food, industrial liquids, and biological samples in a similar way as a thermometer is used to measure temperature. In particular, electrochemical sensors with high selectivities are used for billions of measurements of ion concentrations annually. Unfortunately, conventional ion sensors must be recalibrated frequently, which requires a constant supply of reagents and either automation or trained personnel. This complicates point-of-care applications and raises cost. This work eliminates the need for recalibration. Broader impacts are also evidenced through the inclusion of high school students in the research activities and outreach activities that introduce sensors in hands-on-activies in community libraries. Polymers and nanoporous carbon materials with a redox buffer capacity at a well-defined electrochemical potential offer a unique way to prepare calibration-free sensors. The materials developed in this project exhibit features distinguishing them from previously reported polymers and carbons with redox-active groups: they exhibit batch-independent electrochemical potentials with a high reproducibility and good long-term chemical stabilities. These properties result from two design principles: (i) the redox buffer polymers and nanoporous carbons incorporate both the oxidized and reduced form of a distinct redox couple in equal quantitities, defining the potential as given by the Nernst equation. (ii) the redox-active groups are specifically selected to be stable under ambient conditions both in the oxidized and reduced form. The response mechanism of potentiometric sensors using these new materials is thoroughly investigated, which includes the quantification of electron and ion conductivities in the redox buffer polymers as well as the interfacial electron and ion transfer kinetics.