Highly-stable Li⁺ ion-selective electrodes based on noble metal nanostructured layers as solid-contacts

Area of Science:

• Electrochemistry
• Materials Science
• Analytical Chemistry

Background:

• Development of stable and efficient Solid-Contact Ion-Selective Electrodes (SC-ISEs) is crucial for portable analytical devices.
• Lithium detection is vital for therapeutic drug monitoring in bipolar patients and environmental monitoring due to widespread lithium-ion battery use.
• Existing SC Li+ ISEs often rely on conductive polymers or carbon nanotubes, with limited options available.

Purpose of the Study:

• To develop highly stable, all-solid-state lithium ion-selective electrodes (Li+-ISEs) utilizing noble metal nanostructures as ion-to-electron transducers.
• To investigate the performance of gold nanocorals and platinum nanoflowers as transducer materials for SC-ISEs.
• To analyze the effects of substrate material, membrane thickness, and conditioning concentration on sensor performance.

Main Methods:

• Fabrication of SC-ISEs using electrodeposited gold nanocorals and platinum nanoflowers as ion-to-electron transducers.
• Morphological and electrochemical characterization using Scanning Electron Microscopy (SEM) and Current Reversal Chronopotentiometry (CRC).
• Evaluation of potentiometric response, Nernstian behavior, response time, potential drift, and selectivity.

Main Results:

• Noble metal nanostructures significantly increased SC capacitance and reduced SC resistance compared to flat metal contacts.
• The fabricated sensors exhibited Nernstian behavior (58.7±0.8 mV/decade) in the 10⁻⁵ to 0.1 M activity range with a short response time (∼15 s).
• Exceptional response stability was observed, even without applied potential, with high selectivity towards clinically relevant ions, including superior selectivity for Ca+2.

Conclusions:

• Noble metal nanostructures, particularly gold nanocorals and platinum nanoflowers, provide excellent ion-to-electron transduction for highly stable SC-ISEs.
• The developed SC-ISEs demonstrate superior performance characteristics, including Nernstian response, fast kinetics, and excellent stability and selectivity.
• This study presents a promising approach for simple, reproducible fabrication of high-quality, stable all-solid-state ISEs for various applications.