Search

Electrocatalytic activities for the oxygen reduction reaction (ORR) of Au electrodes modified by as prepared and size selected (0.45–1.0, 0.22–0.45, and 0.1–0.22 µm) h-BN nanosheet (BNNS), which is an insulator, were examined in O2 saturated 0.5M H2SO4 solution. The overpotential was reduced by all the BNNS modifications, and the smaller the size, the smaller the overpotential for ORR, i.e., the larger the ORR activity, in this size range. The overpotential was reduced by as much as ∼330 mV compared to a bare Au electrode by modifying the Au surface by the BNNS of the smallest size range (0.1–0.22 µm). The overpotential at this electrode was only 80 mV more than that at the Pt electrode. Both the rotation disk electrode experiments with Koutecky–Levich analysis and rotating ring disk electrode measurements showed that more than 80% of oxygen is reduced to water via the four-electron process at this electrode. These results strongly suggest and theoretical density functional theory calculations support that the ORR active sites are located at the edges of BNNS islands adsorbed on Au(111). The decrease in size of BNNS islands results in an effective increase in the number of the catalytically active sites and, hence, in the increase in the catalytic activity of the BNNS/Au(111) system for ORR. [ABSTRACT FROM AUTHOR]

Herein, we present a dark-green crystalline tetranuclear Cu(II) Schiff base complex {C1 = [Cu4L4](ClO4)4(DMF)4(H2O)} using a N,N,O donor ligand (HL), namely 2-(((2-hydroxypropyl)imino)methyl)-6-methoxyphenol. Spectro-photometrical investigation on the β-lactamase-like activity of this coordinately saturated system revealed its catalytic inefficiency towards hydrolysis of nitrocefin as a model substrate. This complex has attracted significant interest as a promising photo-catalyst owing to its narrow band gap (2.40 eV) as predicted from DFT calculations and its higher responsivity towards UV light. Therefore, C1 is effectively involved in the photocatalytic reduction of perchlorate to Cl− in the presence of a hole scavenger (H2O–MeOH) under prolonged UV irradiation and itself becomes photo-cleaved to yield a new dark-brown colored chlorobridged dinuclear crystalline complex C2 {[CuL(H2O)2Cl3]H2O}. Furthermore, C2 was deployed as a functional β-lactamase model and was found to show a remarkable catalytic proficiency towards the hydrolysis of nitrocefin in 70 : 30 (V/V) MeOH–H2O medium. This pro-catalyst C2 has been speculated to generate an aqua bridged active catalyst that plays a crucial factor in hydrolysis. This phenomenon was again experimentally established by potentiometric pH titration where C2 displays only one pKa value (7.11) in the basic pH range, indicating the deprotonation of the bridged water molecule. Based on several other kinetic studies, it may be postulated that the hydrolysis of nitrocefin is initiated by the nucleophilic attack of a bridging hydroxide, followed by very fast protonation of the intermediate to furnish the hydrolyzed product. It is noteworthy that the rate of nitrocefin hydrolysis is greatly inhibited in the presence of external chloride concentration. To the best of our knowledge, this is the first report on the photochemical behavior of such a tetranuclear copper(II) Schiff base complex. Our current interest is focused on inventing a potent β-lactamase inhibitory therapeutic as well as elucidating its mechanism through comprehensive chemical analysis. [ABSTRACT FROM AUTHOR]

In this work, the study of the new ligand 3,3′-bis[N,N-bis(pyridine-2-ylmethyl)aminomethyl]-2,2′-dihydroxybiphenyl (L) is reported, where a central 2,2′-biphenol (BPH) fluorophore was functionalized at 3,3′-positions with two dipicolylamine (DPA) side arms as receptor units. Following the synthesis and full chemical–physical characterization, the acid–base and Zn2+-coordination abilities of L were investigated through a combination of potentiometric, UV-Vis, fluorescence, NMR, XRD and DFT measurements. The optical properties of the ligand turned out to be strongly dependent on the pH, being straightforwardly associated with the protonation state of the BPH moiety, whereas its peculiar design allowed to form stable mono and dinuclear Zn2+ complexes. In the latter species, the presence of two Zn2+ ions coordinatively unsaturated and placed at close distance to each other, prompted us to test their usefulness as metallo-receptors for two environmental pollutants of great relevance, ibuprofen and ketoprofen. Potentiometric and fluorescence investigations evidenced that these important non-steroidal anti-inflammatory drugs (NSAIDs) are effectively coordinated by the metallo-receptors and, of relevance, both the stability and the fluorescence properties of the resulting ternary adducts are markedly affected by the different chemical architectures of the two substrates. This study aims at highlighting the promising perspectives arising from the use of polyamino phenolic ligands as chemosensors for H+/Zn2+ and other additional anionic targets in their metal-complexed forms. [ABSTRACT FROM AUTHOR]

Over the recent years, the detection and determination of level of pollutant in environment have become indispensable. This allows for the adoption of various methods to evade the pollution caused by these toxicant entities. This has enhanced the interest of researchers to develop sustainable sensors to determine the trace level concentration of harmful target species. Although the list of these pollutants is undoubtedly too long, toxic metal ions, like Pb2+ ions beyond certain limit, can severely endanger the whole ecosystem. Therefore, the present study is dedicated toward the development of Pb2+ ion-selective electrode based on the membrane of zinc oxide/polyaniline nanocomposites. Nanocomposite assembly was synthesized using in-situ chemical oxidative polymerization method and characterized using spectroscopic techniques, such as energy‐dispersive spectroscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, etc. The proposed potentiometric sensor exhibits excellent selectivity toward Pb2+ ions with detection limit of 2.239 × 10−6 M, Nernstian slope of 23.31 ± 2.5 mV decade−1 and a wide linear concentration range of 1.0 × 10−5 M to 1.0 × 10−1 M. Moreover, the designed Pb2+ ion-selective electrode was successfully examined for its practical applicability in Pb2+−EDTA complexometric titration as well as potentiometric determination of concentration of Pb2+ ions in real-life samples. [ABSTRACT FROM AUTHOR]

Polymeric membrane ion-selective electrodes (ISEs) have been widely used in environmental monitoring. However, in complicated marine environments, marine biofouling usually becomes a sticky problem for these electrodes. Herein, for the first time, a novel maintenance-free antifouling potentiometric marine sensor based on a self-polishing coating (SPC) is proposed. The SPC is synthesized by using the seeded emulsion polymerization method based on the triisopropylsilyl methacrylate monomer as the regulator of the self-renewal rate. This coating can be simply modified onto the electrode surface by drop-casting. The silyl acrylate side groups of the obtained SPC on the sensor surface can be hydrolyzed in the marine alkaline medium. The shear movement of seawater driven by sea waves, wind, gravity, or vibration removes the leftover (fouled) brittle polymer backbone and thus the fouling marine microorganisms. As a proof-of-concept experiment, a polymeric membrane Ca2+-ISE is chosen as a model. Compared to the unmodified electrode, the SPC-coated Ca2+-ISE exhibits remarkable improved antifouling properties in terms of superior anti-adhesive abilities towards marine microorganisms, such as bacterial cells and algae and excellent long-term stability even in the presence of high levels of marine microorganisms. Since no additional manual maintenance is required for maintaining the antifouling abilities of the sensor, the proposed self-polishing sensor may lay an important foundation for construction of unattended long-term potentiometric monitoring systems in real marine environments. [ABSTRACT FROM AUTHOR]

Schematic diagram of the whole process for detecting sulfur-containing components in lithium-sulfur batteries, including graded leaching, efficient oxidation and precise quantitative detection. [Display omitted] • A highly effective approach for the graded leaching and precise quantitative detection techniques of sulfur-containing components within Li-S batteries has been successfully developed. The total detection rate of this method for sulfur-containing components in Li-S batteries exceeds 99 %. • Clarify that the presence of lithium polysulfide in the electrolyte after discharge is the main factor for restricting the full utilization of Li-S batteries' capacity, and propose targeted improvement measures. • This study offers a considerably refined and comprehensive methodology for the capacity fading and failure mechanisms assessment of high-energy-density Li-S batteries. Lithium-sulfur (Li-S) batteries are a strong contender for the new-generation battery system to meet the growing energy demand due to their significantly high energy density (2600 Wh/kg) and cost-effectiveness. However, the practical operating conditions yield an initial capacity of less than 80 % of the theoretical capacity, resulting in a limited lifespan and hindering broader application. What's worse, current mechanism, especially the evolution process of sulfides for the initial capacity degradation is not clear due to the practical difficulties of effective separation and detection of sulfur-containing components. Herein, we have developed an instrumental analysis method enabling graded leaching and quantitative determination of sulfur-containing components. This technology achieves a detection precision surpassing 99.11 %, addressing the inherent deficiency in calculating sulfur-containing components using the decrement method. Applying this method reveals that the presence of lithium polysulfides in the electrolyte (26.34 wt%) after discharging is the primary factor causing insufficient capacity utilization in Li-S batteries. This work not only demonstrates the unique behavior of Li-S batteries at high sulfur loading but also provides a systematic evaluation method to guide further research on high-energy-density batteries, and provides theoretical and technical support to promote the development of high-energy, long-life Li-S batteries. [ABSTRACT FROM AUTHOR]

Sulfate is a critical component of schwertmannite. However, the sulfate content of schwertmannite decreases with the increase in AMD-polluted river pH value, and its impact on the surface properties and Cr(VI) adsorption of schwertmannite remains unclear. To address this issue, different methods, including batch adsorption, N 2 physisorption, scanning electron microscopy (SEM), potentiometric titration, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) in combination with two-dimensional correlation spectroscopy (2D-COS) analysis, and surface complexation modeling (SCM) were employed. Our results showed that sulfate existed as both non-protonated bidentate-binuclear complexes and non-protonated outer-sphere complexes in schwertmannite. The surface morphology and particle size of schwertmannite were unaffected by the sulfate content. However, a decrease in sulfate content resulted in a drop in the negative charge on the surface of schwertmannite, which is conducive to particle aggregation. An increase in pH, on the other hand, raised the negative charge and encouraged the dispersion of the particles. And then, reducing the sulfate content of schwertmannite led to a decrease in acid-base buffer and Cr(VI) adsorption capacity of schwertmannite. The adsorption process of Cr(VI) by schwertmannite can be divided into two stages. In the first stage, Cr(VI) was adsorbed primarily through anion exchange reactions with the sulfate; however, the contribution of surface complexation gradually increased as the initial sulfate content decreased because of a reduced likelihood of anion exchange and an increase in the specific surface area of schwertmannite. Additionally, the behavior of sulfate and Cr(VI) in this stage could be predicted based on the initial sulfate content of schwertmannite. In the second stage, surface complexation with hydroxyl sites became the predominant mechanism of adsorption, which still exhibited great potential at higher Cr(VI) concentrations. Finally, the aforementioned hypothesis was used to establish a CD-MUSIC model, and the fitting results demonstrated that the density and Cr(VI) adsorption capacity of the sulfate site dropped as the sulfate content decreased, while the hydroxyl site was less impacted. The findings have provided insights into further understanding the properties of schwertmannite and its adsorption of Cr(VI). [ABSTRACT FROM AUTHOR]

Recently, fluorescent sensors have gained considerable attention due to their high sensitivity, low cost and noninvasiveness. Among the different materials that can be used for this purpose, carbon dots (CDs) represent valuable candidates for applications in sensing. These, indeed, are easily synthesized, show high quantum yield and are highly biocompatible. However, it was pointed out that the photoluminescence properties of these nanomaterials are strictly dependent on the synthetic and purification methods adopted. The presence of halloysite nanotubes (HNTs), a natural, low cost and biocompatible clay mineral, has been found to be efficient in obtaining small and highly monodispersed CDs without long and tedious purification techniques. Herein, we report the comparison of synthetic pathways for obtaining halloysite-N-doped CDs (HNTs-NCDs) that could be used in biological sensing. One was based on the synthesis of N-doped CDs by a bottom-up approach on HNTs' surface by a MW pyrolysis process; the other one was based on the post-modification of pristine N-doped CDs with halloysite derivatives. The evaluation of the best synthetic route was performed by different physico-chemical techniques. It was found that the bottom-up approach led to the formation of N-doped CDs with different functional groups onto the HNTs' surface. This evidence was also translated in the different fluorescence quantum yields and the existence of several functional groups in the obtained materials was investigated by potentiometric titrations. Furthermore, the ability of the synthesized nanomaterials as sensors for Fe3+ ions detection was assessed by spectroscopic measurements, and the cellular uptake was verified by confocal/fluorescence microscopies as well. [ABSTRACT FROM AUTHOR]

Copper(II), nickel(II) and zinc(II) complexes of various peptide fragments of tau protein were studied by potentiometric and spectroscopic techniques. All peptides contained one histidyl residue and represented the sequences of tau(91–97) (Ac-AQPHTEI-NH2), tau(385–390) (Ac-KTDHGA-NH2) and tau(404–409) (Ac-SPRHLS-NH2). Imidazole-N donors of histidine were the primary metal binding sites for all peptides and all metal ions, but in the case of copper(II) and nickel(II), the deprotonated amide groups were also involved in metal binding by increasing pH. The most stable complexes were formed with copper(II) ions, but the presence of prolyl residues resulted in significant changes in the thermodynamic stability and speciation of the systems. It was also demonstrated that nickel(II) and especially zinc(II) complexes have relatively low thermodynamic stability with these peptides. The copper(II)-catalyzed oxidation of the peptides was also studied. In the presence of H2O2, the fragmentation of peptides was detected in all cases. In the simultaneous presence of H2O2 and ascorbic acid, the fragmentation of the peptide is less preferred, and the formation of 2-oxo-histidine also occurs. [ABSTRACT FROM AUTHOR]

Polymeric membrane ion-selective electrodes (ISEs) have been widely used in environmental monitoring. However, in complicated marine environments, marine biofouling usually becomes a sticky problem for these electrodes. Herein, for the first time, a novel maintenance-free antifouling potentiometric marine sensor based on a self-polishing coating (SPC) is proposed. The SPC is synthesized by using the seeded emulsion polymerization method based on the triisopropylsilyl methacrylate monomer as the regulator of the self-renewal rate. This coating can be simply modified onto the electrode surface by drop-casting. The silyl acrylate side groups of the obtained SPC on the sensor surface can be hydrolyzed in the marine alkaline medium. The shear movement of seawater driven by sea waves, wind, gravity, or vibration removes the leftover (fouled) brittle polymer backbone and thus the fouling marine microorganisms. As a proof-of-concept experiment, a polymeric membrane Ca2+-ISE is chosen as a model. Compared to the unmodified electrode, the SPC-coated Ca2+-ISE exhibits remarkable improved antifouling properties in terms of superior anti-adhesive abilities towards marine microorganisms, such as bacterial cells and algae and excellent long-term stability even in the presence of high levels of marine microorganisms. Since no additional manual maintenance is required for maintaining the antifouling abilities of the sensor, the proposed self-polishing sensor may lay an important foundation for construction of unattended long-term potentiometric monitoring systems in real marine environments. [ABSTRACT FROM AUTHOR]

Intense pulsed light was investigated for partial photoreduction of AgCl in a poly(vinyl butyral) matrix to obtain a Ag/AgCl reference membrane. The membrane was deposited on both glassy carbon and inkjet‐printed silver electrodes giving all‐solid‐state reference electrodes. Regardless of the electrode material, a sufficient potential stability was obtained in a broad concentration range of various salt solutions. Long‐term potential stability was significantly improved with inkjet‐printed silver electrical contacts. The electroanalytical performance of inkjet‐printed electrodes was successfully demonstrated in potentiometric and amperometric systems. [ABSTRACT FROM AUTHOR]

This work demonstrates the use of jute stick extract as a reducing and stabilizing agent for the synthesis of spherical gold nanoparticles (AuNPs). In UV‐Vis spectroscopy, peak at 550 nm was used to confirm the formation of AuNPs. The spherical surface morphology of AuNPs was determined through SEM and TEM analysis. While XRD investigation revealed the crystallinity of the prepared AuNPs. To ensure the biocompatibility of synthesized AuNPs, a bacterial investigation was conducted with negative results towards bacterial strain. The, modified FTO with AuNPs were able to detect glucose in CV analysis and the constructed sensor displayed a wide linear range of 50 μM to 40 mM with a detection limit of 20 μM. Scan rate analysis was performed to determine the charge transfer coefficient (0.42) and Tafel slope (102 mV/decade). Furthermore, the interfacial surface mechanism is illustrated to understand the interaction of glucose with the electrode surface in an alkaline medium and the product formation through the dehydrogenation and hydrolysis process. The prepared sensor also showed good stability, reproducibility, and anti‐interference capabilities. In the case of real sample analysis, we used a blood serum sample. A low RSD value (<10 %) suggests the practical use of AuNPs/FTO in real‐life applications. [ABSTRACT FROM AUTHOR]

The current study presents a comprehensive investigation into the synthesis and characterization of a composite material, Fe/N-CX, designed for the removal of methylene blue dye from aqueous solutions. The synthesis process involves co-precipitating iron salts into a carbon dispersion, resulting in the creation of a carbon xerogel infused with magnetic iron particles. Melamine serves as the nitrogen source for the carbon xerogel, integrated into the polymer matrix via the sol–gel method. This amalgamation of carbon xerogel and magnetic iron particles renders the Fe/N-CX composite a highly promising adsorbent for dye removal. Various characterization techniques, including powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), potentiometric titration, and N2 sorption isotherms, extensively probe the structural, chemical, and surface properties of the Fe/N-CX composite. These methods offer critical insights into its potential adsorption capabilities. Assessment of Fe/N-CX as a methylene blue dye adsorbent reveals an optimal pH of 11, indicating its highest adsorption capacity under slightly alkaline conditions. The maximum adsorption capacity, determined by the Langmuir model, reaches Qmax = 698 mg g−1. Furthermore, the adsorption kinetics data align well with the pseudo-second-order model. The prepared Fe/N-CX exhibits typical ferromagnetic properties, facilitating easy separation from the solution and allowing for multiple cycles of reuse. [ABSTRACT FROM AUTHOR]

The sulfur–iodine (S–I) thermochemical cycle for hydrogen production can be widely applied. The solubility of I 2 in complex and non-ideal HI–H 2 O–I 2 (HI x) ternary systems is critical for the phase separation behaviour and Bunsen reactor design. A new apparatus was established to measure the I 2 solubility using potentiometric titration. Fifty-two experimental data points of the I 2 solubility in the HI–H 2 O system were obtained at temperatures ranging from 293 K to 353 K, and the molar fraction of HI ranged from 7.69% to 15.74%. A new solubility model of I 2 in the HI–H 2 O system was developed using the solid-liquid phase equilibrium theory and a local composition model suitable for electrolyte systems (ELECNRTL). The complex effect of I 2 and I− promoting the dissolution of I 2 in the HI x system was also verified, in which the short-range interaction was dominant over the long-range interaction. The parameters of the model were determined by using the experimental data obtained in this work, where the average relative deviation (ARD) of the model was 2.73%. The model was also simultaneously validated using available experimental data, with which the calculated results were in agreement. This model satisfies the application requirements of the engineering design. • A high precision I 2 solubility measurement system for HI x solution system is established. • The I 2 solubility in HI x system is measured in the range of T = 293–353 K and x HI = 7.69–15.74%. • A high accuracy solubility model is established. • The change of internal forces in the HI x system is analysed. [ABSTRACT FROM AUTHOR]

This article explores the advancements and future prospects of biosensors, which are devices used for monitoring healthcare, environmental safety, and food quality. It discusses the history and evolution of biosensors, emphasizing the need for sustainable and environmentally friendly options. The article also mentions the potential of additive manufacturing techniques and the integration of biosensors with IoT technology and machine learning. It provides valuable insights into the current state and future directions of biosensor technology. Additionally, the document includes references to scientific articles and books on related topics, such as achieving net-zero emissions in global food systems and wearable sensors for personalized predictions of clinical laboratory measurements. [Extracted from the article]

A new construction of a potentiometric sensor was introduced for the first time. It relies on the use of two membranes instead of one, as in the well-known coated-disc electrode. For this purpose, a new electrode body was constructed, including not one, but two glassy carbon discs covered with an ion-selective membrane. This solution allows for the sensor properties to be enhanced without using additional materials (layers or additives) on the membrane. The new construction is particularly useful for in situ measurements in environmental samples. Two ion-selective polymeric membranes were used, namely H+ and K+-selective membranes, to confirm the universality of the idea. The tests conducted included chronopotentiometric tests, electrochemical impedance spectroscopy, and potentiometric measurements. The electrical and analytical parameters of the sensors were evaluated and compared for all tested electrodes to evaluate the properties of the planar electrode versus previously known constructions. Research has shown that the application of two membranes instead of one allows for the resistance of an electrode to be lowered and for the electrical capacitance to be elevated. Improving the electrical properties of an electrode resulted in the enhancement of its analytical properties. The pH measurement range of the planar electrode is 2–11, which is much wider in contrast to that of the single-membrane electrode. The linear range of the K+-selective planar electrode is wider than that of the coated-disc electrode and equals 10−6 to 10−1 M. The response time turned out to be a few seconds shorter, and the potential drift was smaller due to the application of an additional membrane in the electrode construction. This research creates a new opportunity to design robust potentiometric sensors, as the presented construction is universal and can be used to obtain electrodes selective to various ions. [ABSTRACT FROM AUTHOR]

Two new surfactant sensors were developed by synthesizing Pt-doped acid-activated multi-walled carbon nanotubes (Pt@MWCNTs). Two different ionophores using Pt@MWCNTs, a new plasticizer, and (a) cationic surfactant 1,3-dihexadecyl-1H-benzo[d]imidazol-3-ium-DHBI (Pt@MWCNT-DHBI ionophore) and (b) anionic surfactant dodecylbenzenesulfonate-DBS (Pt@MWCNT-DBS ionophore) composites were successfully synthesized and characterized. Both surfactant sensors showed a response to anionic surfactants (dodecylsulfate (SDS) and DBS) and cationic surfactants (cetylpyridinium chloride (CPC) and hexadecyltrimethylammonium bromide (CTAB)). The Pt@MWCNT-DBS sensor showed lower sensitivity than expected with the sub-Nernstian response of ≈23 mV/decade of activity for CPC and CTAB and ≈33 mV/decade of activity for SDS and DBS. The Pt@MWCNT-DHBI surfactant sensor had superior response properties, including a Nernstian response to SDS (59.1 mV/decade) and a near-Nernstian response to DBS (57.5 mV/decade), with linear response regions for both anionic surfactants down to ≈2 × 10−6 M. The Pt@MWCNT-DHBI was also useful in critical micellar concentration (CMC) detection. Common anions showed very low interferences with the sensor. The sensor was successfully employed for the potentiometric titration of a technical grade cationic surfactant with good recoveries. The content of cationic surfactants was measured in six samples of complex commercial detergents. The Pt@MWCNT-DHBI surfactant sensor showed good agreement with the ISE surfactant sensor and classical two-phase titration and could be used as an analytical tool in quality control. [ABSTRACT FROM AUTHOR]

The understanding of the thermodynamic stability and speciation of metal complexes in solution requires access to their enthalpy and entropy of formation. In this work, we specifically focus our investigation on the complexation process of silver(I) ion in acetonitrile (AN) with substituted mono pyridines and cyclic monoamines. The aim of this study is to provide reliable thermodynamic data to obtain insights on metal complex formation, focusing on ligands donor properties and solvation effects. Carefully designed potentiometric and calorimetric experiments allowed to define the species present at different ligand/metal ratios and to obtain the complex formation constants and enthalpies. In general, the enthalpy terms associated with the complex formation are highly exothermic, while the entropy values are always unfavorable. The formation constants of AgLj species for the ligands investigated in AN are compared with those previously obtained in dimethyl sulfoxide (DMSO) and water. The trends in stability constants and enthalpy values are discussed in relation to the pKa data available in the different solvents. Higher pKa values correspond to greater ligand basicity and result in more stable and more enthalpy stabilized complexes. [ABSTRACT FROM AUTHOR]

Amine solvents remain popular in the industries for post combustion carbon dioxide (CO2) capture. Dissociation constant of basic amine solvents plays significant role to influence the CO2 absorption. It is thus important to study the dissociation of new amine solvents for assessing their viability for CO2 capture. In the present work, potentiometric titration method is employed to determine the dissociation constants of dibasic (e. g. Piperazine (PZ), 1‐methyl piperazine (1‐MPZ) and tribasic amines (1‐(2‐aminoethyl‐piperazine) (AEPZ) which could be promising for formulating blended solvent system towards enhancing the rate of CO2 absorption. The estimated dissociation constants for the PZ and 1‐MPZ while match well with reported results, the dissociation constants for AEPZ has been determined newly here within the temperature range 298—318 K. In addition, the structural geometric parameters and Natural Bond Order (NBO) calculations of the amine solvents are performed based on Density Functional Theory (DFT). The NBO calculations predict charge distribution on the nitrogen and other elements, and envisage its effect on the pKa values of the amines. Further, potential energy surface (PES) scanning calculations are performed for AEPZ to explain it's ring inversion which is responsible for obtaining a single pKa value in experimental studies. [ABSTRACT FROM AUTHOR]

The kinetic features of electrodeposition of wear- and corrosion-resistant composite electrochemical coating (CEC) of nickel–cobalt–alumina from a chloride colloidal electrolyte are studied. The application of potentiodynamic, chronopotentiometric and temperature–kinetic methods, as well as the use of the calculated temperature coefficient of reaction rate and the diffusion coefficients of nickel ions, enabled us to determine the mechanism of CEC electrodeposition. The analysis of the data on the kinetic features of CEC electrodeposition showed that the nature of the slow stage of the process is associated with the electrophoretic transfer of electroactive particles to the cathode and the stage of the overgrowth of dispersed particles adsorbed on the cathode surface with the electrodeposited metals, which proceed at comparable rates. [ABSTRACT FROM AUTHOR]

The use of an electrochemical approach for assessment of the oxidative stress severity is a promising direction for point-of-care testing development, which is especially important for critically ill patients. The aim of this study was to determine the influence of different types of blood collection tubes (with clot activator and separating gel, lithium heparin, sodium citrate and K2EDTA) and storage conditions (at 25, 4 and -23 °C up to 5 days) on the electrochemical analysis of the antioxidant status of blood plasma, assessed by measuring the open circuit potential of platinum electrode (OCP) and antioxidant capacity via cyclic voltammetry method (q). It was obtained that blood collection tubes with lithium heparin and clot activator are the most suitable for the electrochemical analysis of antioxidant status of blood plasma, since they do not affect the results of measurements. Furthermore, data obtained during storage blood plasma samples in different temperature conditions indicate that it is preferable to perform electrochemical analysis in fresh samples. [ABSTRACT FROM AUTHOR]

Silicotungstic acid potassium salts had the silicon heteroatom substituted by Co(III) or Co(II) cations and were evaluated as catalysts in oxidation reactions of terpenic alcohols with hydrogen peroxide. Borneol was the model molecule selected. All the catalyst salts were characterized by Fourier-transformed infrared, ultraviolet–visible and Raman spectroscopies, thermal analyses, powder X-rays diffraction and cyclic voltammetry analyses, energy dispersive X-ray spectroscopy and scam electronic microscopy (SEM) analyses, potentiometric titration. This set of techniques revealed that salts containing Co(II) or Co(III) as the heteroatom were successfully obtained. The activity of potassium dodecatungstocobaltate(III) (i.e., K5CoIIIW12O40) was compared to other tungsten heteropoly catalysts (i.e., H4SiW12O40, K4SiW12O40, K6CoIIW12O40, Co2SiW12O40) and the precursor CoCl2. Among the various heteropoly compound investigated, the K5CoIIIW12O40 salt was the most active and selective catalyst toward oxidation product (i.e., camphor). Conversion and selectivity higher than 90% were achieved, indicating the high efficiency of this catalyst. The effects of the main reaction parameters such as temperature, the stoichiometry of reactants, type and catalyst load, were investigated. Special attention was given to correlating the structural properties of catalysts with their activity. Based on experimental data, a reaction pathway was proposed. As far as we know, it is the first time that silicotungstic acid-derived salts having heteroatom Co(II) or Co(III) cations, were used as catalysts in oxidation reactions of terpene alcohols. The effect of the oxidation state and position of Co on the activity of silicotungstic acid was evaluated. The H4SiW12O40 had the Si(IV) heteroatom exchanged with Co(II) or Co(III). Their potassium salts were tested in borneol oxidation reactions with H2O2 being the K5CoIIIW12O40 the most active and selective catalyst. [ABSTRACT FROM AUTHOR]

In this research, a coated graphite polyvinyl chloride (PVC) membrane electrode was fabricated for the potentiometric determination of lithium based on 13-(3-nitrophenyl)-12H,14H-benzo[g]chromeno[2,3-b]chromene-7,12,14(13H)-trione (L) as the ionophore. The best Nernstian response was observed from the membrane composition of 31% PVC, 7% L, 2% NaTPB, and 60% dioctyl phthalate (DOP) as the plasticizer. The designed sensor showed a wide linearity over the concentration range of 1 x 10-8-1 x 10-3 M with a slope of 60.2 ± 0.3 mV decade-1, and the limit of detection (LOD) of 7.5 x 10-9 M. The selectivity of the designed sensor was investigated by the matched potential method and no serious interference was observed. The response time and life span of the electrode were 5 s and 16 weeks, respectively. The potential response of the electrode was independent of solution pH in the pH range of 3.0-12.0. The influence of the presence of organic solvents on the potential response of the electrode was also scrutinized, and the results showed that the designed sensor keeps its Nernstian behavior in solutions with 20% non-aqueous content. In the end, the electrode was successfully applied to determine lithium carbonate in tablet, urine, and serum samples with recovery% values of 96.0 to 106.33 and RSD% 1.99-4.45. [ABSTRACT FROM AUTHOR]

Multiple-step nucleation pathways have been observed during mineral formation in both inorganic and biomineral systems. These pathways can involve precursor aqueous species, amorphous intermediates, or metastable phases. Despite the widespread occurrence of these processes, elucidating the precise nucleation steps and the transformation mechanisms between each step remains a challenging task. Using a suite of potentiometric, microscopic, and spectroscopic tools, we studied the nucleation pathway of SrSO4 as a function of the physico-chemical solution parameters. Our observations reveal that below a threshold supersaturation, nucleation is driven by bound species, akin to the prenucleation cluster model, which directly leads to the formation of the stable phase celestine, SrSO4. At higher supersaturations, this situation is altered, with nucleation dominated by the consumption of free ions. Importantly, this change in nucleation mechanism is coupled to the formation of a hemihydrate metastable phase, SrSO4 · 1/2H2O, which eventually transforms into celestine, adhering to Ostwald's rule of stages. This transformation is a solution-mediated process, also occurring in the presence of a fluid film and is controlled by the physico-chemical parameters of the surrounding environment. It proceeds through the dissolution of the metastable phase and the de novo crystallization of the final phase. Overall, our results reveal that ion association taking place during the prenucleation stage dictates whether the nucleation pathway goes through an intermediate phase or not. This also underlines that although Ostwald's rule of stages is a common process, it is not a prerequisite for mineral formation—even in systems where it can occur. [ABSTRACT FROM AUTHOR]

The degradation of engine oil (EO) directly affects the functional properties and service life of the engine. Thus, there is an immense need for EOs that are suitable for robust and stringent operating conditions. The goal of this study was to develop a nano-induced EO that is sustainable, energy-efficient, and was tested in a diesel-engine forklift. The performance properties such as chemical degradation, wear metal content, and total acidity/base numbers were analyzed using an FTIR spectrometer, an inductively coupled plasma spectrometer, and potentiometric titration techniques, respectively. According to the findings, nano-fluids now have a significantly longer service life than conventional EO. [ABSTRACT FROM AUTHOR]

The new era of solid contact ion selective electrodes (SC-ISEs) miniaturized design has received an extensive amount of concern. Because it eliminated the requirement for ongoing internal solution composition optimization and created a two-phase system with stronger detection limitations. Herein, the determination of venlafaxine HCl is based on a comparison study between different ion- to electron transduction materials (such as; multiwalled carbon nanotubes (MWCNTs), polyaniline (PANi), and ferrocene) and illustrating their mechanisms in their applied sensors. Their different electrochemical features (such as bulk resistance (Rb**), double-layer capacitance (Cdl), geometric capacitance (Cg), and specific capacitance (Cp)) were evaluated and discussed by using the Electrochemical Impedance Spectroscopy (EIS), Chronopotentiometry (CP), and Cyclic Voltammetry (CV) experiments. The results indicated that each transducer's influence on the proposed sensor's electrochemical characteristics is determined by their unique chemical and physical properties. The electrochemical features vary for different solid contact materials used in transduction mechanisms. The results confirm that the MWCNT sensor revealed the best electrochemical behavior with the potentiometric response of a near-Nernestian slope of 56.1 ± 0.8 mV/decade with detection limits of 3.8 × 10−6 mol/L (r2 = 0.999) and a low potential drift (∆E/∆t) of 34.6 µV/s. Also, the selectivity study was performed in the presence of different interfering species either in single or complex matrices. This demonstrates excellent selectivity, stability, conductivity, and reliability as a VEN-TPB ion pair sensor for accurately measuring VEN in its various formulations. The proposed method was compared to HPLC reported technique and confirmed no significant difference between them. So, the proposed sensors fulfill their solutions' demand features for VEN appraisal. [ABSTRACT FROM AUTHOR]

Mobile phase pH is a critically important parameter in reversed-phase liquid chromatographic (RPLC) separations involving analytes that display acidic or basic properties in the pH range used for the mobile phase. The main problem in measuring mobile phase pH lies in the fact that RPLC mobile phases are typically aqueous–organic mixtures. In addition to experimental difficulties, the pH values refer to different aqueous–organic compositions that cannot be correctly compared. Given this situation, the unified pH (wabs pH, also termed as) based on the absolute chemical potential of the solvated proton has been proposed as a rigorous way of characterising mobile phase acidity that is fully inter-comparable between mobile phases of any composition. Here we report the wabs pH values of 78 reversed-phase liquid chromatography-mass spectrometry mobile phases that were carefully measured by potential differences in a symmetric cell with two glass electrode half-cells and almost ideal ionic liquid triethylamylammonium bis((trifluoromethyl)sulfonyl)imide [N2225][NTf2] salt bridge with multiple overlapping measurements. The system of altogether 300 Δ wabs pH values was anchored to the pH value of standard pH 7.00 aqueous buffer solution. The consistency standard deviation of the whole set of measurements was 0.09 pH units. In addition to the differential potentiometric reference method, simpler measurement methods that use double junction reference or double junction combined electrodes were tested and were found suitable for routine laboratories if high accuracy is not required. [ABSTRACT FROM AUTHOR]

Organic ammonium and phosphonium salts exert excellent antimicrobial effects by interacting lethally with bacterial membranes. Particularly, quaternary ammonium lipids have demonstrated efficiency both as gene vectors and antibacterial agents. Here, aiming at finding new antibacterial devices belonging to both classes, we prepared a water-soluble quaternary ammonium lipid (6) and a phosphonium salt (1) by designing a synthetic path where 1 would be an intermediate to achieve 6. All synthesized compounds were characterized by Fourier-transform infrared spectroscopy and Nuclear Magnetic Resonance. Additionally, potentiometric titrations of NH3+ groups 1 and 6 were performed to further confirm their structure by determining their experimental molecular weight. The antibacterial activities of 1 and 6 were assessed first against a selection of multi-drug-resistant clinical isolates of both Gram-positive and Gram-negative species, observing remarkable antibacterial activity of both compounds against Gram-positive isolates of Enterococcus and Staphylococcus genus. Further investigations on a wider variety of strains of these species confirmed the remarkable antibacterial effects of 1 and 6 (MICs = 4–16 and 4–64 µg/mL, respectively), while 24 h-time-killing experiments carried out with 1 on different S. aureus isolates evidenced a bacteriostatic behavior. Moreover, both compounds 1 and 6, at the lower MIC concentration, did not show significant cytotoxic effects when exposed to HepG2 human hepatic cell lines, paving the way for their potential clinical application. [ABSTRACT FROM AUTHOR]

In general, concepts such as chemical equilibria and classical analytical chemistry, as well as instrumental methods such as potentiometry and flow injection analysis (FIA), are taught separately in the curricula of chemistry-related degree programs. However, FIA provides an opportunity to connect all of these important topics. This article shows how simple experiments can be used to link the fundamentals of FIA and potentiometry to the fundamentals of chemical equilibria and teach them in a sustainable way. The experiments were designed for undergraduate environmental science students with basic knowledge of chemical equilibria and classical analytical chemistry and minimal knowledge of electrochemistry. However, they can also be integrated into various courses on instrumental analysis in chemistry-related degree programs. [ABSTRACT FROM AUTHOR]

The potential of several ion-sensitive electrodes responds to the incorporated cations and anions. This has led some authors to misinterpret the potential of metal salt membrane electrodes and of electrodes of the second kind. Neglecting the kinetics of potential establishment and interpreting the potentials solely based on thermodynamics produce completely irrelevant data and suggest that ion concentrations down to 10−45 mol L−1 are accessible by simple potentiometric measurements. The switching from cation to anion response mechanism cannot be derived from thermodynamic equations. It bears complete similarity to the switching of response in the case of foreign interfering ions. [ABSTRACT FROM AUTHOR]

Cisplatin is an anticancer drug that can be used to treat a variety of solid tumors, where clinical use may be affected by several factors, including dose-limiting side effects and the emergence of drug resistance. Micellar-forming polymeric conjugates are a type of polymeric nanocarrier that can preferentially accumulate in tumors, thereby increasing therapeutic efficacy. In the current study, carboxylated PiPOx was synthesized first using a click reaction of 2-isopropenyl 2-oxazoline (iPOx) with thioglycolic acid (TGA) or methyl thioglycolate, followed by methyl triflate-initiated cationic ring opening polymerization (CROP). Next, different strategies were employed to prepare carboxylated PiPOx-mPEG copolymers: (a) CROP was initiated by iPOx-modified mPEG-thiol, (b) TGA-modified PiPOx were end-capped with mPEG-NH2, or (c) TGA-modified iPOx and iPOx-modified mPEG-thiol were randomly copolymerized. 1H-NMR, FT-IR, SEC, and potentiometric titration methods were used to characterize the synthesized polymers. Cisplatin-polymer conjugation was performed at three ratios of drug-to-polymer carboxyl groups (0.25, 0.5, and 1), and the conjugated cisplatin content was determined using UV–vis spectroscopy at 705 nm with O-phenylenediamine reagent. The cisplatin loading efficiencies (%) were 59.3, 26.7, and 91.0 for the respective copolymers at the chosen cisplatin/carboxyl 1:1 mol ratio. Cisplatin-conjugated PiPOx(TGA)-b-mPEG and mPEG-g-PiPOx(TGA) had mean hydrodynamic sizes of 113.3 and 178.8 nm, respectively. TEM imaging confirmed the formation of discrete and spherical particles of the cisplatin-conjugated copolymer. The MTT cytotoxicity assay demonstrated higher cytotoxicity of PiPOx(TGA)-b-mPEG compared to PiPOx(TGA)-g-mPEG polymers in both sensitive and resistant ovarian cancer cells. The IC50 values were approximately 113 µg/ml for PiPOx(TGA)-b-mPEG and 232 µg/ml for PiPOx(TGA)-g-mPEG in resistant tumor cells, confirming the potential application of cisplatin-conjugated copolymers in cancer chemotherapy. [ABSTRACT FROM AUTHOR]

Skin cancer and other skin-related inflammatory pathologies are rising due to heightened exposure to environmental pollutants and carcinogens. In this context, natural products and repurposed compounds hold promise as novel therapeutic and preventive agents. Strengthening the skin's antioxidant defense mechanisms is pivotal in neutralizing reactive oxygen species (ROS) and mitigating oxidative stress. Sunset Yellow (SY) exhibits immunomodulatory characteristics, evidenced by its capacity to partially inhibit the secretion of proinflammatory cytokines, regulate immune cell populations, and modulate the activation of lymphocytes. This study aimed to investigate the antioxidant and anti-genotoxic properties of SY using in-silico, in vitro, and physiochemical test systems, and to further explore its potential role in 7,12-dimethylbenz(a) anthracene (DMBA)/ 12-o-tetradecanoylphorbol-13-acetate (TPA)-induced two-stage skin carcinogenesis. In vitro experiments showed that pre-treatment of SY significantly enhanced the cell viability of HaCaT cells when exposed to tertiary-Butyl Hydrogen Peroxide (tBHP). This increase was accompanied by reduced ROS levels, restoration of mitochondrial membrane potential, and notable reduction in DNA damage in (SY + tBHP) treated cells. Mechanistic investigations using DPPH chemical antioxidant activity test and potentiometric titrations confirmed SY's antioxidant properties, with a standard reduction potential ( E o ) of 0.211 V. Remarkably, evaluating the effect of topical application of SY in DMBA/TPA-induced two-step skin carcinogenesis model revealed dose-dependent decreases in tumor latency, incidence, yield, and burden over 21-weeks. Furthermore, computational analysis and experimental validations identified GSK3β, KEAP1 and EGFR as putative molecular targets of SY. Collectively, our findings reveal that SY enhances cellular antioxidant defenses, exhibits anti-genotoxic effects, and functions as a promising chemopreventive agent. [ABSTRACT FROM AUTHOR]

The syntheses of two macrocycles containing original imidazothiadiazole heterocycles are presented. The protonation constants of the ligands have been determined by potentiometry and photophysical measurements. The photophysical properties of the corresponding Tb3+ complexes have been analyzed and the sensitization of the Tb3+ by the heterocyclic moiety demonstrated with modest quantum yields. The corresponding Gd3+ complexes are monohydrated and display higher relaxivities than GdDOTA, which could be explained by the larger size of these complexes. The different substitutions on the heterocycle do not affect strongly the protonation constants of the ligand, the quantum yield, water exchange rate or relaxation properties of the system. [ABSTRACT FROM AUTHOR]

[Display omitted] Manipulating metal valence states and porosity in the metal–organic framework (MOF) by alloying has been a unique tool for creating high-valent metal sites and pore environments in a structure that are inaccessible by other methods, favorable for accelerating the catalytic activity towards sensing applications. Herein, we report Fe3+-driven formation of catalytic active Ni3+ species in the amine-crafted benzene-dicarboxylate (BDC-NH 2)-based MOF as a high-performance electrocatalyst for glucose sensing. This work took the benefit of different bonding stability between BDC-NH 2 ligand, and Fe3+ and Ni2+ metal precursor ions in the heterometallic Ni x Fe (1- x) -BDC-NH 2 MOF. The FeCl 3 that interacts weakly with ligand, oxidizes the Ni2+ precursor to Ni3+-based MOF owing to its Lewis acidic behavior and was subsequently removed from the structure supported by Ni atoms, during solvothermal synthesis. This enables to create mesopores within a highly stable Ni-MOF structure with optimal feed composition of Ni 0.7 Fe 0.3 -BDC-NH 2. The Ni3+-based Ni 0.7 Fe 0.3 -BDC-NH 2 demonstrates superior catalytic properties towards glucose sensing with a high sensitivity of 13,435 µA mM−1 cm−2 compared to the parent Ni2+-based Ni-BDC-NH 2 (10897 μA mM−1 cm−2), along with low detection limit (0.9 μM), short response time (≤5 s), excellent selectivity, and higher stability. This presented approach for fabricating high-valent nickel species, with a controlled quantity of Fe3+ integrated into the structure allowing pore engineering of MOFs, opens new avenues for designing high-performing MOF catalysts with porous framework for sensing applications. [ABSTRACT FROM AUTHOR]

Electrodeposited amorphous hydrated iridium oxide (IrOx) is a promising material for pH sensing due to its high sensitivity and the ease of fabrication. However, durability and variability continue to restrict the sensor's effectiveness. Variation in probe films can be seen in both performance and fabrication, but it has been found that performance variation can be controlled with potentiostatic conditioning (PC). To make proper use of this technique, the morphological and chemical changes affecting the conditioning process must be understood. Here, a thorough study of this material, after undergoing PC in a pH-sensing-relevant potential regime, was conducted by voltammetry, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Fitting of XPS data was performed, guided by raw trends in survey scans, core orbitals, and valence spectra, both XPS and UPS. The findings indicate that the PC process can repeatably control and conform performance and surface bonding to desired calibrations and distributions, respectively; PC was able to reduce sensitivity and offset ranges to as low as ±0.7 mV/pH and ±0.008 V, respectively, and repeat bonding distributions over ~2 months of sample preparation. Both Ir/O atomic ratios (shifting from 4:1 to over 4.5:1) and fitted components assigned hydroxide or oxide states based on the literature (low-voltage spectra being almost entirely with suggested hydroxide components, and high-voltage spectra almost entirely with suggested oxide components) trend across the polarization range. Self-consistent valence, core orbital, and survey quantitative trends point to a likely mechanism of ligand conversion from hydroxide to oxide, suggesting that the conditioning process enforces specific state mixtures that include both theoretical Ir(III) and Ir(IV) species, and raising the conditioning potential alters the surface species from an assumed mixture of Ir species to more oxidized Ir species. [ABSTRACT FROM AUTHOR]

To explore novel terpenoid repellents, 22 candidate terpenoid derivatives were synthesized and tested for their electroantennogram (EAG) responses and repellent activities against Aedes albopictus. The results from the EAG experiments revealed that 5-(2-hydroxypropan-2-yl)-2-methylcyclohex-2-en-1-yl formate (compound 1) induced distinct EAG responses in female Aedes albopictus. At concentrations of 0.1, 1, 10, 100, and 1000 mg/L, the EAG response values for compound 1 were 179.59, 183.99, 190.38, 193.80, and 196.66 mV, demonstrating comparable or superior effectiveness to DEET. Repellent activity analysis indicated significant repellent activity for compound 1, closest to the positive control DEET. The in silico assessment of the ADMET profile of compound 1 indicates that it successfully passed the ADMET evaluation. Molecular docking studies exhibited favourable binding of compound 1 to the active site of the odorant binding protein (OBP) of Aedes albopictus, involving hydrophobic forces and hydrogen bond interactions with residues in the OBP pocket. The QSAR model highlighted the influential role of hydrogen-bonding receptors, positively charged surface area of weighted atoms, polarity parameters of molecules, and maximum nuclear-nuclear repulsion force of carbon-carbon bonds on the relative EAG response values of the tested compounds. This study holds substantial significance for the advancement of new terpenoid repellents. [ABSTRACT FROM AUTHOR]

Developing electrochemical sensors for ascorbic acid, uric acid and glucose detection provides advantages of rapid, precise and economical monitoring of disease condition, and they have the potential to transform healthcare by enabling point-of-care diagnostic and personalised treatment. Facile and cost-effective potentiometric sensors have been developed in this work for selective and sensitive detection of ascorbic acid, uric acid and glucose, based on molecularly imprinted polymer (MIP). The imprinted polymeric matrix of para-aminobenzoic (pPABA) was developed on the surface of electrochemically reduced graphene oxide modified paraffin impregnated graphite rod electrode (rGO/PIGE). The monomeric para-aminobenzoic acid (PABA) was electropolymerised with template, viz., ascorbic acid, uric acid and glucose individually. The molecularly imprinted electrode surface was created by removing the trapped template molecule. The surface analysis of the modified electrodes was carried out by cyclic voltammetry (CV), scanning electron microscopy (SEM), attenuated total reflection spectroscopy (ATR), Raman spectroscopy and contact angle measurements. Parameters controlling the performance of the MIP (p-PABA), viz., pH of the supporting electrolyte and number of polymerisation cycle, were optimised. Under optimised conditions, the potentiometric responses of MIPs were linearly related to concentrations of ascorbic acid, uric acid and glucose in the range of 3.4 × 10−7 M–2.5 × 10−5 M, 3.3 × 10−7 M–1.3 × 10−5 M, and 3.5 × 10−7 M–2.9 × 10−5 M with a correlation coefficient, R2 of 0.99, 0.99 and 0.98 respectively. All three sensors showed high selectivity even in the presence of high concentration of similar interfering compounds. A limit of detection (LOD) for ascorbic acid, uric acid and glucose was found to be 1.1 × 10−8 M, 2.8 × 10−8 M and 1.3 × 10−8 M respectively. In addition, the developed sensors exhibited long-term stability and good reproducibility. [ABSTRACT FROM AUTHOR]

The chemical speciation of binary and ternary VO2+-picolinic acid (HPic) complexes with the amino acids: Leucine (Leu, HL), Isoleucine (Ile, HL), Valine (Val, HL), Tryptophan (Thr, HL), Glutamine (Gln, HL), Lysine (Lys, HL), Arginine (Arg, HL) and Tyrosine (Tyr, H2L) were obtained. This study was performed by potentiometric titrations at 25 °C using 1.0 mol·dm−3 NaCl as the ionic medium. The experimental data were analyzed with the least squares program LETAGROP, and the respective distribution diagrams were obtained with the HYSS program. The relative stability parameters Δlog10K, log10X and %R.S were determined. [ABSTRACT FROM AUTHOR]

The reaction of the vanadyl ion (VO2+) with imidazole-4-carboxylic acid (Im4COOH), imidazole-2-carboxylic acid (Im2COOH) and methylimidazole-2-carboxylic acid (MeIm2COOH), respectively, in the presence of small bioligands (bL) [oxalate (Ox), lactate (Lact), citrate (Cit) and phosphate (Phos)] and high-molecular-weight (HMW) human serum proteins [albumin (HSA) and transferrin (hTf)] were studied in aqueous solution using potentiometric acid–base titrations. The species distribution diagrams for the high-molecular-mass (HMM) proteins with oxidovanadium(IV) under physiological pH were dominated by VO(HMM)2, VOL(HMM) for unsubstituted ligands (L− = Im4COO− and Im2COO−). However, for the N-substituted MeIm2COOH, the species distribution diagrams under physiological pH were dominated by VOL2, VO(HMM)2 and VO2L2(HMM). These species were further confirmed by LC-MS, MALDI-TOF-MS and EPR studies. The glucose-stimulated insulin secretion (GSIS) action of the complexes was investigated using INS-1E cells at a 1 µM concentration, which was established through cytotoxicity studies via the MTT assay. The neutral complexes, especially VO(MeIm2COO)2, showed promising results in the stimulation of insulin secretion than the cationic [VO(MeIm2CH2OH)2]2+ complex and the vanadium salt. Oxidovanadium(IV) complexes reduced insulin stimulation significantly under normoglycaemic levels but showed positive effects on insulin secretion under hyperglycaemic conditions (33.3 mM glucose media). The islets exposed to oxidovanadium(IV) complexes under hyperglycaemic conditions displayed a significant increase in the stimulatory index with 1.19, 1.75, 1.53, 1.85, 2.20 and 1.29 observed for the positive control (sulfonylurea:gliclazide), VOSO4, VO(Im4COO)2, VO(Im2COO)2, VO(MeIm2COO)2 and VO(MeIm2CH2OH)22+, respectively. This observation showed a potential further effect of vanadium complexes towards type 2 diabetes and has been demonstrated for the first time in this study. [ABSTRACT FROM AUTHOR]

The adsorption of divalent ions on metal oxides is controlled by the pH of a solution. It is commonly assumed that this is a reversible process for pH changes. However, there are reports that the sorption of ions on oxides may not be reversible. To verify this, we used potentiometric titration, ion-selective electrodes (ISEs), and electrokinetic measurements to examine the reversibility of the adsorption of hydrogen ions and three metal ions (Ca2+, Cu2+, and Fe2+) on TiO2. The ferrous ion was used as a reference because its adsorption is entirely irreversible. The surface charge determined by potentiometric titration and the adsorption edges measured using ISE indicate that the adsorption of copper ions is reversible with changes in pH. In the case of calcium ions, the results suggest a certain degree of irreversibility. There are apparent differences in the electrokinetic potential data obtained during titration with base and acid, which suggests that the adsorption is irreversible. We have explained this contradiction by considering the complex and dynamic nature of electrophoretic mobility. In our opinion, potentiometric titration may be the simplest and most reliable method for assessing the reversibility of multivalent ion adsorption. [ABSTRACT FROM AUTHOR]

Drug plant raw materials represent an important source of biologically active substances (BASs), which are used in pharmaceutical, cosmetic, food, and other industries. This paper presents the results of studying colloidal properties of crushed sophora Japanese fruits (hereinafter referred to as sophora) in order to improve the extraction of BASs. To achieve the goal, the following tasks have been set: the study of the ζ potential of sophora particles at different times of contact between the particles and an extractant and the pH values of the medium; determining the isoelectric point (IEP) of the sophora particles by electrophoresis; finding the point of zero charge (PZC) of sophora particles using potentiometric titration; and studying the influence of medium pH, sophora particle size, temperature, the presence of surfactants and ions, and the nature of an extractant on sophora swelling. The points of zero charge ) of the aqueous dispersions of sophora and extracted flavonoids are 5.8 and 5.2, respectively, thus being close to the values . The swelling of sophora particles is limited and accompanied by the gradual fracture of the plant cells. Adsorption equilibrium is achieved within 30 min. In an alkaline region and in the presence of alcohol, the swelling of the sophora particles decreases, while it increases at elevated temperature and in the presence of NaI ions. [ABSTRACT FROM AUTHOR]

In this article, we present the synthesis and characterization of new acyclic pyridine-containing polyaminocarboxylate ligands H4aPyta and H6aPyha, which differ in structural rigidity and the number of chelating groups. Their abilities to form complexes with Cu2+, Ga3+, Y3+, and Bi3+ cations, as well as the stability of the complexes, were evaluated by potentiometric titration method, radiolabeling with the corresponding radionuclides, in vitro studies, mass spectrometry, and HPLC. The structures of the resulting complexes were determined using NMR spectroscopy and DFT calculations. The results obtained made it possible to evaluate the influence of the structural features of the complexes on their stability. The developed chelators H4aPyta and H6aPyha were proved to be promising for further research in the field of radiopharmaceuticals. [ABSTRACT FROM AUTHOR]

This study has introduced a pioneering methodology by employing biochars as a basic carbocatalyst in the context of multicomponent reactions. Biochars were produced from different manures and organic wastes using the pyrolysis-carbonization process under limited oxygen conditions. The prepared biochars were well characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) analysis, and powder X-ray diffraction (XRD). The chemical characteristics and potentiometric titration analysis provide compelling evidence of the intriguing basicity properties exhibited by the prepared biochars. The pH values, ash content, and potentiometric titration results confirmed the exceptional basicity characteristics of cow manure biochar formed at 600 oC (CB600), establishing it as the most basic carbocatalyst in this study. Encouraged by these initial results, the activity of the biochars as basic carbocatalysts was evaluated in multicomponent synthesis of 4H-benzo[h]chromene and pyranopyrazoles and 600 °C exhibited the most pronounced catalytic performance owing to its superior total basicity. By these findings, it can be asserted that this work introduces the groundbreaking application of biochars as potent basic carbocatalysts for the multicomponent synthesis of structurally diverse heterocycles. Unveiling the vital basic role of biochars will definitely open up new opportunities in organic chemistry and provide salient features for environmentally-friendly chemistry, including easy retrieval, non-toxicity, and widespread accessibility. Highlights: Biochars were introduced as potent basic carbocatalysts for multicomponent synthesis of heterocycles. Quantitatively assess basicity of the prepared biochars was performed using potentiometric titration. The activity of the biochars as basic carbocatalysts was evaluated in multicomponent synthesis of chromenes and pyranopyrazoles. [ABSTRACT FROM AUTHOR]

Total alkalinity (AT) and dissolved inorganic carbon (CT) in the oceans are important properties with respect to understanding the ocean carbon cycle and its link to global change (ocean carbon sinks and sources, ocean acidification) and ultimately finding carbon-based solutions or mitigation procedures (marine carbon removal). We present a database of more than 44 400 AT and CT observations along with basic ancillary data (spatiotemporal location, depth, temperature and salinity) from various ocean regions obtained, mainly in the framework of French projects, since 1993. This includes both surface and water column data acquired in the open ocean, coastal zones and in the Mediterranean Sea and either from time series or dedicated one-off cruises. Most AT and CT data in this synthesis were measured from discrete samples using the same closed-cell potentiometric titration calibrated with Certified Reference Material, with an overall accuracy of ±4 µ mol kg -1 for both AT and CT. The data are provided in two separate datasets – for the Global Ocean and the Mediterranean Sea (10.17882/95414, Metzl et al., 2023), respectively – that offer a direct use for regional or global purposes, e.g., AT –salinity relationships, long-term CT estimates, and constraint and validation of diagnostic CT and AT reconstructed fields or ocean carbon and coupled climate–carbon models simulations as well as data derived from Biogeochemical-Argo (BGC-Argo) floats. When associated with other properties, these data can also be used to calculate pH, the fugacity of CO 2 (f CO 2) and other carbon system properties to derive ocean acidification rates or air–sea CO 2 fluxes. [ABSTRACT FROM AUTHOR]

The pKa values of propanolamine hydrochloride (PAMH) and poly(allylamine hydrochloride) (PAAMH) in concentrated solutions were determined by both Fourier transform infrared spectroscopy (FT-IR) titration and classical potentiometric (POT) titration and compared. Starting with the respective fully protonated forms PAMH and PAAMH and increasing the pH value by sodium hydroxide addition in situ attenuated total reflection FT-IR (ATR FT-IR) spectra on PAMH and PAAMH solutions show the variation of diagnostic infrared (IR) bands. From the decrease of the most intense δ(NH3+) band the dissociation process of the NH3+ groups could be followed. Thereby, from the respective normalized band area A the dissociation degree αIR of the ammonium groups could be determined. Plotting pH versus αIR and fitting this curve by a modified Henderson–Hasselbalch function pH = pKa + B log (αIR/1 – αIR) the parameters pKa and cooperativity factor B were obtained. pKa values from FT-IR titration were qualitatively in line with respective pKa values from POT titration. Quantitative systematic pKa deviations between polyelectrolyte (PEL) and respective monoelectrolyte and the tentative effects of PEL molecular weight, ambient ionic strength, and titration concept (FT-IR and POT) are discussed based on classical models of weak PEL. Graphical abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

The present work describes the complexation of the anti-inflammatory sialorphin derivative Pal-Lys-Lys-Gln-His-Asn-Pro-Arg (palmitic acid-lysine-lysine-glutamine-histidine-asparagine-proline-arginine) with Cu(II) ions in an aqueous solution, at a temperature of 25.0 ± 0.1 °C, over the whole pH range. The complexing properties were characterized by potentiometric and UV-Vis spectrophotometric methods. The potentiometric method was used to calculate the logarithms of the overall stability constants (log β) and the values of the stepwise dissociation constants (pKa) of the studied complexes. The percentage of each species formed in an aqueous solution was estimated from the species distribution curve as a function of pH. The absorbance (A) and molar absorption coefficient (ε) values for the Cu(II)-sialorphin derivative system were determined with UV-Vis spectroscopy. Our studies indicate that the sialorphin derivative forms stable complexes with Cu(II) ions, which may lead to future biological and therapeutic applications. [ABSTRACT FROM AUTHOR]

A wearable bioelectronic ion sensing device has been proposed based on the mixed electronic-ionic conductors of tungsten bronzes. The sensor features no requirement of organic ion selective membranes (ISM) for the ion recognition. This ISM-free characteristic offers the possibility for the next generation of solid ion sensor for biological applications. [Display omitted] Noninvasive and continuous monitoring of electrolytes in biofluids based on wearable biotechnology provides extensive health-related physiological information. The state-of-the-art wearable bioelectronic ion sensors depend on the organic ionophore-based solid-contact structure of potentiometric ion-selective electrodes. This structure contains two functional sensing layers, i.e., a solid contact (ion-to-electron signal transduction) and an ionophore-containing ion-selective membrane (ISM, ion recognition). However, the potential drift, biotoxicity, and expensive organic ionophores complicate practical wearable applications. These challenges intrinsically originate from the ISM. Herein, an ISM-free wearable ion sensor based on mixed electronic-ionic conductors of tungsten bronzes is reported. These materials can serve as a bifunctional sensing layer for simultaneous ion-to-electron transduction through the redox reaction of W6+/5+ and ion recognition through crystal ion exchange. The K- and Na-adjusted WO 3 disclosed Nernstian responses toward NH 4 + and H+, respectively. The selectivity is comparable to or even better than organic ionophores, such as ammonia ionophore of nonactin. Further, the on-body monitoring of sweat ammonia and pH was realized using an integrated ISM-free flexible sensor. Therefore, this work offers an ISM-free concept and emphasizes the importance of developing next-generation ISM-free wearable bioelectronic ion sensors. [ABSTRACT FROM AUTHOR]

The method of scanning contact potentiometry (SCP) was investigated in factory conditions, and the functional capabilities of the electrical nondestructive testing (NDT) method to detect structural heterogeneities and technological defects were demonstrated directly in the process of reactor equipment production. [ABSTRACT FROM AUTHOR]

Modern potentiometric sensors based on polymeric membrane ion‐selective electrodes (ISEs) have achieved new breakthroughs in sensitivity, selectivity, and stability and have extended applications in environmental surveillance, medical diagnostics, and industrial analysis. Moreover, nonclassical potentiometry shows promise for many applications and opens up new opportunities for potentiometric biosensing. Here, we aim to provide a concept to summarize advances over the past decade in the development of potentiometric biosensors with polymeric membrane ISEs. This Concept article articulates sensing mechanisms based on non‐equilibrium measurement techniques. In particular, we emphasize new trends in potentiometric biosensing based on attractive dynamic approaches. Representative examples are selected to illustrate key applications under zero‐current conditions and stimulus‐controlled modes. More importantly, fruitful information obtained from non‐equilibrium measurements with dynamic responses can be useful for artificial intelligence (AI). The combination of ISEs with advanced AI techniques for effective data processing is also discussed. We hope that this Concept will illustrate the great possibilities offered by non‐equilibrium measurement techniques and AI in potentiometric biosensing and encourage further innovations in this exciting field. [ABSTRACT FROM AUTHOR]