Ion-Sensing Systems Based on Mesoporous Carbon: from Bulk Electrodes to Paper-Based Ion Sensors.

다국어 초록 (Multilingual Abstract)

Potentiometric sensors, comprising ion-selective electrodes (ISEs) and reference electrodes, are a large subgroup of electrochemical ion sensors. In view of affordable and portable analytical devices, all-solid-state ISEs and reference electrodes, in which a solid contact is used as an ion-to-electron transducer, are highly desirable. Compared with conventional ISEs, all-solid-state ISEs offer comparable electrochemical performance with the distinct advantages of simple maintenance and miniaturization.This dissertation focuses on the development of robust all-solid-state potentiometric ion-sensing systems. It starts with the investigation of colloid-imprinted mesoporous (CIM) carbon as a novel solid contact material. CIM carbon exhibits desirable properties as a solid contact material, including a low content of redox-active impurities and a high double layer capacitance. Therefore, sensors based on CIM carbon can be constructed with superior electrochemical performance, including excellent ionic response, reproducibility, signal stability, and resistance to common interfering agents. These outstanding characteristics make CIM carbon-based potentiometric sensors promising candidates for the next generation of commercial ion sensors.To develop low-cost and simple ion sensors for point-of-care applications, this dissertation also involves the development of disposable ion-sensing platforms based on paper. The use of ISEs can be significantly simplified by embedding a conventional potentiometric cell into paper. Paper-based Cl- and K+ sensors are fabricated with highly reproducible and linear responses towards different concentrations of analyte ions in aqueous and biological samples. To further simplify the use of these paper-based ion sensors, CIM carbon-based ISEs and reference electrodes can be integrated into the paper substrate, thus constructing all-solid-state paper-based ion-sensing platforms.Finally, the dissertation explores the possibility of constructing robust calibration-free ion sensors by covalently attaching a redox buffer to CIM carbon. Click chemistry and amide coupling reactions are evaluated for the attachment, and the cobalt-based redox buffer can be attached to CIM carbon. It is found that the open circuit potential of modified CIM carbon films can be affected by the oxidation states of the redox buffer, but a higher redox buffer loading is required to achieve high electrode-to-electrode reproducibility. Possible approaches to achieving such high redox buffer loading are discussed at the end of this dissertation.