Ion-Selective Electrodes with Solid Contact Based on Composite Materials: A Review

Potentiometric sensors are the largest and most commonly used group of electrochemical sensors. Among them, ion-selective electrodes hold a prominent place. Since the end of the last century, their re-development has been observed, which is a consequence of the introduction of solid contact constructions, i.e., electrodes without an internal electrolyte solution. Research carried out in the field of potentiometric sensors primarily focuses on developing new variants of solid contact in order to obtain devices with better analytical parameters, and at the same time cheaper and easier to use, which has been made possible thanks to the achievements of material engineering. This paper presents an overview of new materials used as a solid contact in ion-selective electrodes over the past several years. These are primarily composite and hybrid materials that are a combination of carbon nanomaterials and polymers, as well as those obtained from carbon and polymer nanomaterials in combination with others, such as metal nanoparticles, metal oxides, ionic liquids and many others. Composite materials often have better mechanical, thermal, electrical, optical and chemical properties than the original components. With regard to their use in the construction of ion-selective electrodes, it is particularly important to increase the capacitance and surface area of the material, which makes them more effective in the process of charge transfer between the polymer membrane and the substrate material. This allows to obtain sensors with better analytical and operational parameters. Brief characteristics of electrodes with solid contact, their advantages and disadvantages, as well as research methods used to assess their parameters and analytical usefulness were presented. The work was divided into chapters according to the type of composite material, while the data in the table were arranged according to the type of ion. Selected basic analytical parameters of the obtained electrodes have been collected and summarized in order to better illustrate and compare the achievements that have been described till now in this field of analytical chemistry, which is potentiometry. This comprehensive review is a compendium of knowledge in the research area of functional composite materials and state-of-the-art SC-ISE construction technologies.

Conductive Polymer Nanoparticles as Solid Contact in Ion-Selective Electrodes Sensitive to Potassium Ions

A preparation method of nanocomposites based on poly (3-octylthiophene-2,5-diyl) (POT) and carbon black (CB) as the transducer of an all-solid potassium ion selective electrode is proposed. POT is used as the dispersant of CB, and the obtained nanocomposites have unique characteristics, including high conductivity, high capacitance and high stability. The potassium ion selective electrode based on POT and CB was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronopotentiometry. The results showed that the detection limit of potassium ions was 10−6.2 M, and the slope was 57.6 ± 0.8 mV/façade. The water layer test and anti-interference test show that the electrode has high hydrophobicity, the static contact angle reaches 139.7° and is not easily affected by light, O2 and CO2.

Kilo-scale synthesis and purification of 4,4′-[di-t-butyldibenzo]-18-crown-6 and its catalytic reduction to 4,4′-[di-t-butyldicyclohexano]-18-crown-6

This article reports the large scale synthesis, scale up chromatographic purification and Rh catalyzed hydrogenation of DTBDB18C6. Confirmation of molecular structure was done by SCXRD and complete hydrogenation was achieved with the use of K+ ions.

Novel Hybrid Nanoparticles: Synthesis, Functionalization, Characterization, and Their Application in the Uptake of Scandium (III)Ions from Aqueous Media

The aim of this study was to prepare novel supramolecular hybrid nanoparticles (HNPs) that can selectively separate and recover scandium metal ions, Sc(III), from an aqueous phase based on molecular recognition technology (MRT). Moreover, this approach is fully compatible with green chemistry principles. In this work, natural amorphous silica (SiO₂) nanoparticles were prepared by a precipitation method from Iraqi rice husk (RH) followed by surface modification with 3-amino-propyl triethoxysilane (APTES) as coupling agent and Kryptofix 2.2.2 (K2.2.2) as polycyclic ligand. To evaluate the potential of the hybrid nanoparticles, the prepared HNPs were used for the solid-liquid extraction of scandium, Sc(III), ions from model solutions due to the fact that K2.2.2 are polycyclic molecules. These polycyclic molecules are able to encapsulate cations according to the corresponding cavity size with the ionic radius of metal by providing a higher protection due their cage-like structures. Moreover, the authors set the objectives to design a high-technology process using these HNPs and to develop a Sc recovery method from the aqueous model solution prior to employing it in industrial applications, e.g., for Sc recovery from red mud leachate. The concentrations of Sc model solutions were investigated using the UV-Vis spectrophotometer technique. Different characterization techniques were used including scanning electron microscope (SEM), atomic force microscopy (AFM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), X-ray fluorescence (XRF), and Fourier transform infrared (FTIR). The extraction efficiency of Sc varied from 81.3% to 96.7%. Moreover, the complexed Sc ions were efficiently recovered by HCl with 0.1 mol/L concentration. The stripping ratios of Sc obtained ranged from 93.1% to 97.8%.

Amperometric Ion Sensing Approaches at Liquid/Liquid Interfaces for Inorganic, Organic and Biological Ions

Electrochemistry at the interface between two immiscible electrolyte solutions (ITIES) has become an invaluable tool for the selective and sensitive detection of cationic and anionic species, including charged drug molecules and proteins. In addition, neutral molecules can also be detected at the ITIES via enzymatic reactions. This chapter highlights recent developments towards creating a wide spectrum of sensing platforms involving ion transfer across the ITIES. As well as outlining the basic principles needed for performing these sensing applications, the development of ITIES-based detection strategies for inorganic, organic, and biological ions is discussed.