A novel all-solid-state ammonium electrode with polyaniline and copolymer of aniline/2,5-dimethoxyaniline as transducers

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.

Unlocking All-Solid Ion Selective Electrodes: Prospects in Crop Detection

This paper reviews the development of all-solid-state ion-selective electrodes (ASSISEs) for agricultural crop detection. Both nutrient ions and heavy metal ions inside and outside the plant have a significant influence on crop growth. This review begins with the detection principle of ASSISEs. The second section introduces the key characteristics of ASSISE and demonstrates its feasibility in crop detection based on previous research. The third section considers the development of ASSISEs in the detection of corps internally and externally (e.g., crop nutrition, heavy metal pollution, soil salinization, N enrichment, and sensor miniaturization, etc.) and discusses the interference of the test environment. The suggestions and conclusions discussed in this paper may provide the foundation for additional research into ion detection for crops.

Effects of colloids on ammonia nitrogen release under different ion conditions in natural sediments of Lake Taihu, China

Colloids act as vectors for accelerating contaminant movement in natural porous media such as lake sediments. Releasing characteristics of colloids and colloid-adsorbed ammonia nitrogen from lake sediments with the presence of monovalent and divalent cations were studied by an indoor anaerobic flooding incubation experiment. Results show that release of colloids was influenced by valence state and strength of the cation. In the presence of Na⁺ and Ca²⁺, the concentrations of the colloids in the overlying water were 11-163 mg/L and 13-88 mg/L during the entire incubation process and their values increased by 12.7%-122.3% and 1.5%-29.1%, respectively, compared to the control group, which indicated that the promoting effect of monovalent cations on release of colloids was more obvious than that of divalent cations. However, the total mass of colloids release reduced with the increasing ionic strength. Colloid-adsorbed ammonia nitrogen in the overlying water reached 0.15-1.72 mg/L and 0.15-1.12 mg/L with the presence of Na⁺ and Ca²⁺ and was higher 61.7%-161.7% and 21.3%-80.9%, respectively, than in the control group, indicating a consequent effect of ion conditions on the release of ammonium nitrogen from sediments. A significant positive correlation between colloids and ammonia nitrogen concentration further shows that colloidal activity determinately resulted in the increase or decrease in the ammonia nitrogen concentration in the overlying water, which could adsorb ammonia nitrogen and act as vehicles to carry ammonia nitrogen together into the aqueous medium or sink into the sediment. The release of ammonia nitrogen is possibly enhanced by colloidal behavior and varies with spatiotemporal ionic conditions in natural sediments. These findings are essential for improving the understanding of the geological fate of environmental colloids and associated nutritive salts, which provide scientific basis and technical support for the control of endogenous pollution and the comprehensive treatment of water bodies in Lake Taihu.

Succinyl-κ-carrageenan Silver Nanotriangles Composite for Ammonium Localized Surface Plasmon Resonance Sensor

This research investigates the physicochemical properties of biopolymer succinyl-κ-carrageenan as a potential sensing material for NH4+ Localized Surface Plasmon Resonance (LSPR) sensor. Succinyl-κ-carrageenan was synthesised by reacting κ-carrageenan with succinic anhydride. FESEM analysis shows succinyl-κ-carrageenan has an even and featureless topology compared to its pristine form. Succinyl-κ-carrageenan was composited with silver nanoparticles (AgNP) as LSPR sensing material. AFM analysis shows that AgNP-Succinyl-κ-carrageenan was rougher than AgNP-Succinyl-κ-carrageenan, indicating an increase in density of electronegative atom from oxygen compared to pristine κ-carrageenan. The sensitivity of AgNP-Succinyl-κ-carrageenan LSPR is higher than AgNP-κ-carrageenan LSPR. The reported LOD and LOQ of AgNP-Succinyl-κ-carrageenan LSPR are 0.5964 and 2.7192 ppm, respectively. Thus, AgNP-Succinyl-κ-carrageenan LSPR has a higher performance than AgNP-κ-carrageenan LSPR, broader detection range than the conventional method and high selectivity toward NH4+. Interaction mechanism studies show the adsorption of NH4+ on κ-carrageenan and succinyl-κ-carrageenan were through multilayer and chemisorption process that follows Freundlich and pseudo-second-order kinetic model.

Fabrication of an All-Solid-State Ammonium Paper Electrode Using a Graphite-Polyvinyl Butyral Transducer Layer

A planar solid-state ammonium-selective electrode, employing a composite mediator layer of graphite particles embedded in a polyvinyl butyral matrix on top of an inkjet-printed silver electrode, is presented in this paper. The effect of graphite powder mass fraction on the magnitude of the potentiometric response of the sensor was systematically verified using a batch-mode and a flow injection measurement setup. Under steady-state conditions, the paper electrode provided a Nernstian response of 57.30 mV/pNH4 over the concentration range of 10−5 M to 10−1 M with a detection limit of 4.8 × 10−6 M, while the analytical performance of the array in flow mode showed a narrower linear range (10−4 M to 10−1 M; 60.91 mV/pNH4 slope) with a LOD value of 5.6 × 10−5 M. The experimental results indicate that the prepared electrode exhibited high stability and fast response to different molar concentrations of ammonium chloride solutions. The pH-response of the paper NH4-ISE was also investigated, and the sensor remained stable in the pH range of 2.5–8.5. The potentiometric sensor presented here is simple, lightweight and inexpensive, with a potential application for in-situ analysis of environmental water samples.

Solid-Contact Ion-Selective Electrodes: Response Mechanisms, Transducer Materials and Wearable Sensors

Wearable sensors based on solid-contact ion-selective electrodes (SC-ISEs) are currently attracting intensive attention in monitoring human health conditions through real-time and non-invasive analysis of ions in biological fluids. SC-ISEs have gone through a revolution with improvements in potential stability and reproducibility. The introduction of new transducing materials, the understanding of theoretical potentiometric responses, and wearable applications greatly facilitate SC-ISEs. We review recent advances in SC-ISEs including the response mechanism (redox capacitance and electric-double-layer capacitance mechanisms) and crucial solid transducer materials (conducting polymers, carbon and other nanomaterials) and applications in wearable sensors. At the end of the review we illustrate the existing challenges and prospects for future SC-ISEs. We expect this review to provide readers with a general picture of SC-ISEs and appeal to further establishing protocols for evaluating SC-ISEs and accelerating commercial wearable sensors for clinical diagnosis and family practice.

Monitor application of multi-electrochemical sensor in extracting bromine from seawater

In this paper, a set of online measurement devices of multi-electrochemical sensor was investigated. Combined with industrial distributed control system, it was first applied in extracting bromine from seawater to realize the real-time adjustment of production process parameters. In the process of extracting bromine from seawater, the pH value of acidified raw brine, the addition amount of Cl₂ in the oxidation stage and the addition amount of SO₂ in the absorption stage are key parameters to control the whole production process. The multi-electrochemical sensor realized a rapid and high-throughput detection of the above parameters by integrating an all-solid-stage bromide ion selective electrode (Br-ISE), Eh electrode and pH electrode. The Br-ISE and the pH electrode were self-developed electrodes and the Pt electrode was Eh electrode. The pH electrode was used to control the addition amount of H₂SO₄ during the acidification of the brine. The Eh electrode was used to control the addition amount of Cl₂ during the oxidation stage and the addition amount of SO₂ during the absorption stage. The Br-ISE was used to monitor the Br^- concentration change in the raw brine. Results showed the optimum range of Eh in the oxidation stage and absorption stage of brine were 950-1000 mV and 580-610 mV, respectively. The application of multi-electrochemical sensor in industrial bromine production can realize real-time control of material addition and save the cost of production.

Doped PANI Coated Nano-Ag Electrode for Rapid In-Situ Detection of Bromide in Seawater

In this paper, we successfully fabricated a novel bromide ion selective electrode (Br-ISE), which was coated by bromine ion doped polyaniline as sensitive film. Using Ag wire as the substrate, a uniform and dense nano-silver layer was electroplated to enhance the specific surface area of the electrode. Subsequently, a polyaniline (PANI) film was coated onto the electrode by cyclic voltammetry in a 0.3 M aniline and 1 M HCl solution and was in-situ doped by 0.1 M KBr solution. The morphology and performance of the electrode were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and other electrochemical analysis methods, respectively. The prepared Br-ISE exhibited a wide linear dynamic range between 1.0 × 10−1 and 1.0 × 10−7 M with a near-Nernst slope of 57.33 mV/decade. In addition, the electrode possessed extremely fast response time (<1 s) and low impedance (300 Ω), high sensitivity, and good selectivity. The electrode potential drifted within 2 mV in 8 h. The lifespan was larger than three months.

A novel chemical sensor with multiple all-solid-state electrodes and its application in freshwater environmental monitoring

Freshwater quality detection is important for pollution control. Three important components of water quality are pH, ammonia and dissolved H₂S and there is an urgent need for a high-precision sensor for simultaneous and continuous measurement. In this study, all-solid-state electrodes of Eh, pH, NH₄ ⁺ and S^2- were manufactured and mounted to a wireless chemical sensor with multiple parameters. Calibration indicated that the pH electrode had a Nernst response with slope of 53.174 mV; the NH₄ ⁺ electrode had a detection limit of 10^-5 mol/L (Nernst response slope of 53.56 mV between 10^-1 to 10^-4 mol/L). Ag/Ag₂S has a detection limit of 10^-7 mol/L (Nernst response slope of 28.439 mV). The sensor was cylindrical and small with low power consumption and low storage demand to achieve continuous in-situ monitoring for long periods. The sensor was tested for 10 days in streams at Trawsgoed Dairy farm in Aberystwyth, UK. At the intensively farmed Trawsgoed, the concentration of NH₄ ⁺ in the stream rose sharply after the application of slurry to adjacent fields. Further, the stream was overhung with extensive vegetation and exhibited changes in pH, which correlated with photosynthetic activity. Measurements of S^2- were stable throughout the week. Our data demonstrate the applicability of our multiple electrode sensor.

The influence of Na+ and Ca2+ on the migration of colloids or/and ammonia nitrogen in an unsaturated zone medium

This experiment was conducted with an indoor sand-column device, the migration of colloids with the presence of Na⁺ and Ca²⁺ and the migration of ammonia nitrogen with the presence of Na⁺, Ca²⁺ or/and colloids was studied. The results showed that the migration of colloids was influenced by the ion valence state, different ions with different valence could block the migration of colloids. In addition, the blocking effect of bivalent ions was more obvious than that of monovalent ions. In the presence of Na⁺ and Ca²⁺, the R_d value of the ammonia-nitrogen migration process were 1.01 and 1.41, respectively, which indicated that bivalent ions have a greater blocking effect on ammonia-nitrogen migration than monovalent ions. Colloids could also block the ammonia-nitrogen migration, and R_d value in the ammonia-nitrogen migration process was 1.17. Moreover, the presence of Na⁺/colloids and Ca²⁺/colloids could enhance the blocking effect on the ammonia-nitrogen migration, and resulting the R_d values at 1.20 and 1.52, respectively. The cohesion of colloids caused by the compaction of its electric double layer with those ions added maybe the key causes of those blocking.