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Functionalizing Carbon Substrates with a Covalently Attached Cobalt Redox Buffer for Calibration-Free Solid-Contact
Minog Kim1, Xin I N Dong1, Brian D Spindler1
1Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Analytical Chemistry
|May 2, 2024
Summary
This study introduces a novel solid contact for ion-selective electrodes using functionalized colloid-imprinted mesoporous carbon. This advancement minimizes calibration needs and enhances long-term stability for potentiometric sensing applications.
Area of Science:
- Electrochemistry
- Materials Science
- Analytical Chemistry
Background:
- Ion-selective electrodes (ISEs) traditionally require frequent calibration and can suffer from long-term instability.
- Solid contacts in ISEs are crucial for stable potentiometric measurements but often present challenges in achieving reliable interfacial potentials.
- Developing robust solid contacts with minimal calibration requirements is essential for advancing electrochemical sensing technologies.
Purpose of the Study:
- To develop and evaluate a novel solid contact material for ion-selective electrodes (ISEs) based on functionalized colloid-imprinted mesoporous (CIM) carbon.
- To investigate the performance of CIM carbon functionalized with a cobalt redox buffer as a solid contact for potassium (K+) sensors.
- To assess the impact of different ion-selective membrane (ISM) matrices on the stability and reproducibility of the developed solid-contact ISEs (SC-ISEs).
Main Methods:
- Covalent functionalization of CIM carbon with a terpyridine ligand via diazonium chemistry.
- Formation of a bis(terpyridine) cobalt complex on the CIM carbon surface, followed by partial oxidation to create a redox buffer.
- Fabrication of SC-ISEs using the functionalized CIM carbon as a solid contact, valinomycin as the ionophore, and either plasticized PVC or silicone as the ISM matrix.
- Characterization of the solid contact's redox capacitance and evaluation of SC-ISE performance, including potential stability and emf drift.
Main Results:
- The developed CIM carbon solid contact exhibited a redox capacitance of 3.26 F/g, facilitating a well-defined interfacial potential.
- SC-ISEs with plasticized PVC ISMs showed excellent potential stability (standard deviation of E° as low as 0.3 mV) and low emf drift (20 μV/h over 100 h).
- SC-ISEs with silicone ISMs demonstrated good performance but with slightly higher potential variation and emf drift compared to PVC-based sensors, highlighting the influence of the polymeric matrix.
Conclusions:
- Functionalized CIM carbon with a cobalt redox buffer serves as an effective solid contact for SC-ISEs, offering improved stability and reduced calibration needs.
- The choice of polymeric matrix for the ISM significantly impacts the long-term stability and reproducibility of SC-ISEs.
- This approach provides a promising pathway for developing next-generation potentiometric sensors with enhanced performance characteristics.
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