Calibration-Free Ion Sensing

本项目由化学学部化学测量与成像项目资助。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上的应用。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，其方法类似于温度计用于测量温度。特别是，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测量。不幸的是，传统的离子传感器必须经常重新校准，这需要持续的试剂供应和自动化或训练有素的人员。这使即时护理应用变得复杂，并提高了成本。这项工作消除了重新校准的需要。更广泛的影响还体现在将高中生纳入研究活动和推广活动中，这些活动在社区图书馆的动手活动中引入了传感器。聚合物和纳米多孔碳材料在良好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一种独特的方法。在这个项目中开发的材料表现出与之前报道的具有氧化活性基团的聚合物和碳不同的特点：它们表现出与批次无关的电化学电位，具有高重复性和良好的长期化学稳定性。这些特性源于两个设计原则：(i)氧化还原缓冲聚合物和纳米多孔碳以等量的氧化还原形式结合了不同的氧化还原偶联，定义了由能斯特方程给出的电势。（ii）氧化活性基团是特别选择的，在氧化和还原形式的环境条件下都是稳定的。利用这些新材料的电位传感器的响应机制进行了深入的研究，其中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.