Beyond Nonactin: Potentiometric Ammonium Ion Sensing Based on Ion-selective Membrane-free Prussian Blue Analogue Transducers

Abstract

The determination of ammonium ions (NH4 +) is of significance to environmental, agriculture, and human health. Potentiometric NH4 + sensors based on solid-contact ion selective electrodes (SC-ISEs) feature point-of-care testing and miniaturization. However, the state-of-the-art SC-ISEs of NH4 + during the past 20 years strongly rely on the organic ammonium ionophore-based ion selective membrane (ISM), typically by nonactin for the NH4 + recognition. Herein, we report a Prussian blue analogue of copper­(II)-hexacyanoferrate (CuHCF) for an ISM-free potentiometric NH4 + sensor without using the ionophores. CuHCF works as a bifunctional transducer that could realize the ion-to-electron transduction and NH4 + recognition. CuHCF exhibits competitive analytical performances regarding traditional nonactin-based SC-ISEs of NH4 +, particularly for the selectivity toward K+. The cost and preparation process have been remarkably reduced. The theoretical calculation combined with electrochemical tests further demonstrate that relatively easier intercalation of NH4 + into the lattices of CuHCF determines its selectivity. This work provides a concept of the ISM-free potentiometric NH4 + sensor beyond the nonactin ionophore through a CuHCF bifunctional transducer.

Organic Eutectic Salts‐Assisted Direct Lithium Regeneration for Extremely Low State of Health Ni‐Rich Cathodes

“…The structural optimization was completed with energy and force convergence set at 1.0 × 10 −5 eV and 0.02 eV Å −1 , respectively. [ 43,44 ] Through calculations, the adsorption energy of lithium by NCM with vacancies is −3.25 eV, while that by NCM without vacancies is −1.52 eV. This reveals that the adsorption energy of the NCM material can be significantly reduced after the generation of vacancies, which is favorable for the enrichment of lithium during the lithium replenishment process.…”

Anti-fouling TiO2-Coated Polymeric Membrane Ion-Selective Electrodes with Photocatalytic Self-Cleaning Properties

“…Currently, polymeric membrane ion-selective electrodes (ISEs) have played an important role in environment monitoring due to their advantages of simplicity, low cost, and high reliability. − In many cases of practical relevance, however, when these electrodes are applied to complex environmental samples ( e.g. , seawater and sewage) for long-term monitoring, electrode fouling usually occurs.…”

Development of Mixed Matrix Membranes with Penetrating Subnanochannels for Efficient Molecule/Ion Separation

“…Porous separation membrane materials, including metal organic frameworks (MOFs), [15] covalent organic frameworks (COFs), [16] Prussian blue (PB) [17] and its analogs (PBAs), [18] porous organic cages (POCs), [19] porous aromatic frameworks have been developed with varying framework structures (Figure 1a). [20] The advent of nanoporous materials, which leverage their inherent pore size to selectively separate ions or molecules differing in size, has led to their widespread adoption in membrane separation applications [21] .…”