Type Of Cation Research Articles

Aggregation, retention and transport of γ-MnO2 nanoparticles in water-saturated porous media: Impact on the immobility of thallium

Nano-scale Mn oxides can act as effective stabilizers for Tl in soil and sediments. Nevertheless, the comprehensive analysis of the capacity of MnO2 to immobilize Tl in such porous media has not been systematically explored. Therefore, this study investigates the impact of γ-MnO2, a model functional nanomaterial for remediation, on the mobility of Tl in a water-saturated quartz sand-packed column. The mechanisms involved are further elucidated based on the adsorption and aggregation kinetics of γ-MnO2. The results indicate that higher ionic strength (IS) and the presence of ion Ca(II) promote the aggregation of γ-MnO2, resulting from the reduced electrostatic repulsion between particles. Conversely, an increase in pH inhibits aggregation due to enhanced interaction energy. γ-MnO2 significantly influences Tl retention and mobility, with a substantial fraction of γ-MnO2-bound Tl transported through the column. This might be attributed to the high affinity of γ-MnO2 for Tl through ion exchange reactions and precipitation at the surface of γ-MnO2. The mobility of Tl in the sand column is influenced by the γ-MnO2 colloids, exhibiting either inhibition or promotion depending on the pH, IS, and cation type of the solution. In solutions with higher IS and Ca(II), the mobility of Tl decreases as γ-MnO2 colloids tend to aggregate, strain, and block, facilitating colloidal Tl retention in porous media. Although higher pH reduces the mobility of individual Tl, it promotes the mobility of γ-MnO2 colloids, facilitating a substantial fraction of colloidal-form Tl. Consequently, the optimal conditions for stabilizing Tl by γ-MnO2 involve either high IS and low pH or the presence of competitive cations (e.g., Ca(II)). These findings provide new insights into Tl immobilization using MnO2- and Mn oxide-based functional materials, offering potential applications in the remediation of Tl contamination in soil and groundwater.

Computational Studies of Suitability of Triarylmethane-Coumarins as Sensitizer for Dye-Sensitized Solar Cells

Triarylmethanes are low cost synthetic dyes with intense absorption in the visible spectrum. This make it attractive to explore their suitability as sensitizer for dye sensitized solar cell. Using malachite green as a lead dye, we made intuitive structural modifications: incorporation of coumarin-3-carboxylic acid as acceptor/anchor, and substituting one or the two N, N-diethylaniline donors with N-propyl-1,6dimethyllutidine(s). The three resulting triarylmethane-coumarin structures were subjected to DFT calculations to investigate their suitability as sensitizers for DSSC applications. The calculation results showed that triarylmethane-coumarins with cationic type chromophores are unsuitable as DSSC sensitizer. The acceptor/anchor, coumarin-3-carboxylic acid, is basically excluded in the intramolecular charge transfer processes of the cationic dyes. Also, the LUMO levels of the cationic dyes are below the conduction band of TiO2, which is energetically uphill to electron injection into TiO2. Ultimately, the cationic triarylmethane-coumarin derivatives are unsuitable as sensitizer for DSSC. However, a charge-free triarylmethane-coumarin derivative shows promise as a sensitizer candidate for DSSC application.

Structure and self-diffusivity of mixed-cation electrolytes between neutral and charged graphene sheets.

Graphene-based applications, such as supercapacitors or capacitive deionization, take place in an aqueous environment, and they benefit from molecular-level insights into the behavior of aqueous electrolyte solutions in single-digit graphene nanopores with a size comparable to a few molecular diameters. Under single-digit graphene nanoconfinement (smallest dimension <2nm), water and ions behave drastically different than in the bulk. Most aqueous electrolytes in the graphene-based applications as well as in nature contain a mix of electrolytes. We study several prototypical aqueous mixed alkali-chloride electrolytes containing an equimolar fraction of Li/Na, Li/K, or Na/K cations confined between neutral and positively or negatively charged parallel graphene sheets. The strong hydration shell of small Li+ vs a larger Na+ or large K+ with weaker or weak hydration shells affects the interplay between the ions's propensity to hydrate or dehydrate under the graphene nanoconfinement and the strength of the ion-graphene interactions mediated by confinement-induced layered water. We perform molecular dynamics simulations of the confined mixed-cation electrolytes using the effectively polarizable force field for electrolyte-graphene systems and focused on a relation between the electrochemical adsorption and structural properties of the water molecules and ions and their diffusion behavior. The simulations show that the one-layer nanoslits have the biggest impact on the ions' adsorption and the water and ions' diffusion. The positively charged one-layer nanoslits only allow for Cl- adsorption and strengthen the intermolecular bonding, which along with the ultrathin confinement substantially reduces the water and Cl- diffusion. In contrast, the negatively charged one-layer nanoslits only allow for adsorption of weakly hydrated Na+ or K+ and substantially break up the non-covalent bond network, which leads to the enhancement of the water and Na+ or K+ diffusion up to or even above the bulk diffusion. In wider nanoslits, cations adsorb closer to the graphene surfaces than Cl-'s with preferential adsorption of a weakly hydrated cation over a strongly hydrated cation. The positive graphene charge has an intuitive effect on the adsorption of weakly hydrated Na+'s or K+'s and Cl-'s and a counterintuitive effect on the adsorption of strongly hydrated Li+'s. On the other hand, the negative surface charge has an intuitive effect on the adsorption of both types of cations and only mild intuitive or counterintuitive effects on the Cl- adsorption. The diffusion of water molecules and ions confined in the wider nanoslits is reduced with respect to the bulk diffusion, more for the positive graphene charge, which strengthened the intermolecular bonding, and less for the negative surface charge, which weakened the non-covalent bond network.

Effect of interlayer cations on the adsorption of ionic liquid on montmorillonite clays: comparative study

Industries are the most important resource of water pollution due as a result of toxic pollutants including surfactant or ionic liquids. It becomes urgent to propose low cost and environmentally friendly involving the use of local resources. Here,one of the main ionic liquids (BMImCl) were intercalated into three alkaline-earth, Mg2+, Ca2+, and Ba2+ exchanged montmorillonites. For all samples interlayer spacing after intercalation are similar about 13 Å as measured by X-ray diffraction. These findings are compared with previous results on similar montmorillonite exchanged with every type of alkali cations, i.e. Li+, Na+, K+, Rb+, and Cs+. The basal spacing of intercalated montmorillonite increased as the ionic potential (Z/R) is increased. The FTIR is another tool to confirm the differences between modified and unmodified montmorillonite samples. More specifically, the results showed that the formation of new bands of vibrations (1400–1500 cm-1) and (2850–2900 cm-1).Thermal measurements indicate that homoionic clay display two distinct regions. ‎(I) from room temperature to 160 0C corresponding to physical adsorption and removal of water of hydration, (II) dehydroxylation of the silicate structure in the temperature range of 160-700 0C.

Effects of cations on biofilms in gravity-driven membrane system: Filtration performance and mechanism investigation

The gravity-driven membrane (GDM) system is desirable for energy-efficient water treatment. However, little is known about the influence of cations on biofilm properties and GDM performance. In this study, typical cations (Ca2+ and Na+) were used to reveal the combined fouling behavior and mechanisms. Results showed that Ca2+ improved the stable flux and pollutant removal efficiency, while Na+ adversely affected the flux. Compared with GDM control, the concentration of pollutants was lower in Ca-GDM, as indicated by the low biomass, proteins, and polysaccharides. A heterogeneous and loose biofilm was observed in the Ca-GDM system, with roughness and porosity increasing by 43.06 % and 32.60 %, respectively. However, Na+ induced a homogeneous and dense biofilm, with porosity and roughness respectively reduced by 17.48 % and 22.04 %. The richness of bacterial communities increased in Ca-GDM systems, while it decreased in Na-GDM systems. High adenosine triphosphate (ATP) concentration in Ca-GDM system was consistent with the abundant bacteria and their high biological activity, which was helpful for the efficient removal of pollutants. The abundance of Apicomplexa, Platyhelminthes, Annelida and Nematoda increased after adding Ca2+, which was related to the formation of loose biofilms. Computational simulations indicated that the free volumes of the biofilms in Ca-GDM and Na-GDM were 13.7 and 13.2 nm3, respectively. The addition of cations changed intermolecular forces, Ca2+ induced bridging effects led to large and loose floc particles, while the significant dehydration of hydrated molecules in the Na-GDM caused obvious aggregation. Overall, microbiological characteristics and contaminant molecular interactions were the main reasons for differences in GDM systems.

POSTTRANSLATIONAL MODIFICATIONS OF THE SULFHYDRYL GROUP OF THE CYSTEINE RESIDUE OF GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE

This review considers the main types of oxidative posttranslational modi cations of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) targeting the sulfhydryl group of the catalytic cysteine residue Cys152. The highly reactive sulfhydryl group of Cys152 in the active centre of GAPDH undergoes oxidation and S-nitrosylation, leading to enzyme inactivation and destabilization. Upon reversible oxidation of the sulfhydryl group to form cysteine-sulfenic acid, the enzyme loses dehydrogenase activity, but gains the ability to catalyze the acyl-phosphatase reaction. Hydrolysis of the product of the dehydrogenase reaction, 1,3-diphosphoglycerate, under the action of the oxidized GAPDH leads to uncoupling of oxidation and phosphorylation at this stage of glycolysis. The action of nitric oxide results in S-nitrosylation of Cys152 GAPDH and the subsequent formation of cysteine-sulfenic acid due to hydrolysis of the S-NO-group. Data are presented on the relationship between S-nitrosylation of the catalytic Cys152 of GAPDH and its oxidation followed by S-glutathionylation of the enzyme at Cys152. The role of posttranslational modi cations of the sulfhydryl group of the catalytic cysteine residue in the regulation of enzyme activity, as well as the mechanisms ensuring the reversibility of such modi cations are discussed.

A cationic type long-lasting drag-reduction agent based on reduced interfacial water film thickness for enhanced injection in low-permeability reservoirs

In water injection development of low-permeability reservoirs, the elevated flow resistance between the rock surface and the injected water results in enhanced injection pressure. Reducing the thickness of interfacial water film to expand flow radius is a new thought to achieve a decrease in injection pressure. In this work, a hydroxyl-containing cationic surfactant tetradecyl methyl dihydroxy-ethyl ammonium bromide (HTTAB) was designed and synthesized. The introduction of hydroxyl groups enhances the binding to the negatively-charged rock surface. HTTAB can modify the strong hydrophilic rock surface to a hydrophobic state, with the water contact angle increasing from 20.2° to 110.3°. HTTAB shows excellent drag-reducing effect, maintaining a drag reduction rate of over 30 % even after 30 PV of flushing. Particle Image Velocimetry (PIV) experiments show that after HTTAB adsorption, the interfacial slip velocity and centerline velocity can increase by 1.67 times and 33.66 % respectively, and the flow radius expands significantly. In addition, the thickness of the interfacial water film is obtained using Atomic Force Microscope (AFM). The results show that the thickness of the interfacial water film is reduced significantly from 79.42 nm to 8.85 nm. This study provides important guidance for the design of drag-reducing agents and the understanding of interfacial drag-reduction behavior.

Cation-Induced Interfacial Hydrophobic Microenvironment Promotes the C-C Coupling in Electrochemical CO2 Reduction.

The electrochemical carbon dioxide reduction reaction (CO2RR) toward C2 products is a promising way for the clean energy economy. Modulating the structure of the electric double layer (EDL), especially the interfacial water and cation type, is a useful strategy to promote C-C coupling, but atomic understanding lags far behind the experimental observations. Herein, we investigate the combined effect of interfacial water and alkali metal cations on the C-C coupling at the Cu(100) electrode/electrolyte interface using ab initio molecular dynamics (AIMD) simulations with a constrained MD and slow-growth approach. We observe a linear correlation between the water-adsorbate stabilization effect, which manifests as hydrogen bonds, and the corresponding alleviation in the C-C coupling free energy. The role of a larger cation, compared to a smaller cation (e.g., K+ vs Li+), lies in its ability to approach the interface through desolvation and coordinates with the *CO+*CO moiety, partially substituting the hydrogen-bonding stabilizing effect of interfacial water. Although this only results in a marginal reduction of the energy barrier for C-C coupling, it creates a local hydrophobic environment with a scarcity of hydrogen bonds owing to its great ionic radius, impeding the hydrogen of surrounding interfacial water to approach the oxygen of the adsorbed *CO. This skillfully circumvents the further hydrogenation of *CO toward the C1 pathway, serving as the predominant factor through which a larger cation facilitates C-C coupling. This study unveils a comprehensive atomic mechanism of the cation-water-adsorbate interactions that can facilitate the further optimization of the electrolyte and EDL for efficient C-C coupling in CO2RR.

Variations in chloride ion sorption within Layered double hydroxides engineered with different cation types

Layered double hydroxides (LDHs) are new concrete additives that improve Cl- sorption capacity by varying their chemical composition. In this work, first-principles calculations were used to design the chemical compositions of LDHs with various cations. Accordingly, four cation types of LDHs (CaAl, MgAl, MgFe and ZnAl) were selected to be synthesized, their Cl- sorption kinetics were further measured. The objective was to establish a high-throughput screening approach to identifying the most promising cations for enhancing the sorption capacity of LDHs towards Cl-. Results revealed that the absolute value of Cl- binding energy increased as the interplanar spacing of different LDHs decreased from first-principles calculations. Particularly, CaAl exhibited the highest adsorption capacity for Cl- (3.25 mmol/g) from experiments, validating the simulation results that it has the highest absolute value of Cl- binding energy. MgFe-Cl-LDH has the smallest absolute value of Cl- binding energy with the lowest adsorption capacity for Cl- as well as the crystallinity. Moreover, multiple factors influencing the Cl- sorption ability of LDHs, such as chemical composition, crystallinity, microstructures and their synergistic effects, are discussed thoroughly based on the experimental results. This study established a connection between the simulation and experimental approaches in understanding the mechanism of Cl- adsorption.

Reexpansion of charged nanoparticle assemblies in concentrated electrolytes

Electrostatic forces in solutions are highly relevant to a variety of fields, ranging from electrochemical energy storage to biology. However, their manifestation in concentrated electrolytes is not fully understood, as exemplified by counterintuitive observations of colloidal stability and long-ranged repulsions in molten salts. Highly charged biomolecules, such as DNA, respond sensitively to ions in dilute solutions. Here, we use non-base-pairing DNA-coated nanoparticles (DNA-NP) to analyze electrostatic interactions in concentrated salt solutions. Despite their negative charge, these conjugates form colloidal crystals in solutions of sufficient divalent cation concentration. We utilize small-angle X-ray scattering (SAXS) to study such DNA-NP assemblies across the full accessible concentration ranges of aqueous CaCl2, MgCl2, and SrCl2 solutions. SAXS shows that the crystallinity and phases of the assembled structures vary with cation type. For all tested salts, the aggregates contract with added ions at low salinities and then begin expanding above a cation-dependent threshold salt concentration. Wide-angle X-ray scattering (WAXS) reveals enhanced positional correlations between ions in the solution at high salt concentrations. Complementary molecular dynamics simulations show that these ion-ion interactions reduce the favorability of dense ion configurations within the DNA brushes below that of the bulk solution. Measurements in solutions with lowered permittivity demonstrate a simultaneous increase in ion coupling and decrease in the concentration at which aggregate expansion begins, thus confirming the connection between these phenomena. Our work demonstrates that interactions between charged objects continue to evolve considerably into the high-concentration regime, where classical theories project electrostatics to be of negligible consequence.

The visible light photocatalytic performance of g-C3N4 is regulated by the Brønsted acid site on the mullite surface

Clay minerals are considered promising semiconductor carrier materials due to their unique physical and chemical properties. However, the exact mechanism by which clay minerals interact with semiconductor materials remains unknown. To this end, the present study was conducted to explore the formation of Brønsted acidic sites on the surface of mullite by modulating the cation types in mullite. It was hereby demonstrated for the first time that the presence of Brønsted acidic sites on the surface of clay minerals is conducive to the formation of N vacancies and dopant O in carbon nitride composites (CNM-30). The synergistic effect of N vacancy and doped O increases the specific surface area of CNM-30, enhances the electron-hole separation and transport efficiency, and ultimately makes CNM-30 produce more reactive oxygen species. CNM-30 possesses excellent degradation ability for gaseous phase pollutants (such as NO) and high concentration liquid phase pollutants (such as RhB and TC). Overall, this paper presents a new perspective on the design and development of semiconductor materials based on clay minerals.

Facilitated transport of toluene and naphthalene with humic acid in high- and low-permeability systems: Role of ionic strength and cationic type

The occurrence of colloids on pollutants transport in groundwater has attracted more attention. However, the research on the regulation mechanism of colloids on combined pollutants transport in heterogeneous aquifers is limited. In this study, a series of tank experiments were conducted to systematically investigate the effects of ionic strength, and cation type on humic acid (HA) facilitated transport of toluene (TOL), and naphthalene (NAP) in high- and low-permeability systems. The results showed that HA facilitated pollutants transport in low Na+ solution. In Ca2+ solution, the presence of HA hindered pollutants transport, and the inhibition increased with the increase of ionic strength. Both in Na+ solution and low Ca2+ solution, the influence of heterogeneous structure on pollutant transport played a dominant role, and TOL and NAP had a greater transport potential in the high permeability zone (HPZ) due to the preferential flow. Whereas, deposition of HA aggregates, and electrostatic attractive interaction had negative effects on transport than groundwater flow in high Ca2+ solution. Pollutants were prone to accumulate at the bottom of the HPZ, and the top of the low permeability zone (LPZ). These new findings provide insights into the mechanism of colloids influence on the pollutants transport in heterogenous aquifer.

Selective pore regulation of activated carbon using trace carbonate-assisted catalytic activation: Revealing the effect of cation catalysis on pore topology

Activated carbon is an important adsorbent for the adsorption removal of water or gas pollutants due to its low cost, high efficiency, and large-scale production potential; however, currently commercial activated carbon prepared through physical or chemical activation commonly shows a single microporous characteristic, making it difficult to match different kinds of pollutants. Here, we propose a convenient and cost-effective pore regulation strategy by introducing a trace carbonate catalysis process into the activation reaction, in which we find that the types of cations (Na, K, Ca) in carbonate have a significant impact on the pore topology of coal-based activated carbon, further revealing the role of cation induced catalytic gasification in pore regulation. Therein, K and Ca enhance the formation of micropores and meso-/macropores respectively, while Na promotes the pore development across the entire size range resulting in a hierarchically porous structure with high specific surface area. Kinetic analysis, density functional theory calculations, and three-dimensional pore fractal network characterization reveal that the pore development is collectively determined by the gasification reaction rate and depth. Evaluated as adsorbents, the obtained NaAC sample by Na catalysis demonstrates excellent adsorption capacities for both small-molecule toluene (467 mg g−1) and large-molecule tetracycline (374 mg g−1). This work for the first time elucidates the cation-induced gasification effect and provides a simple and cost-effective method for regulating the pore topology of activated carbon with only trace catalyst dosage.

Energy harvesting from water flow through porous reduced graphene oxide networks

AbstractUsing a syringe pump setup, the authors conducted water flow experiments through porous reduced graphene oxide (rGO). A variety of anions and cations were added to the water to study its effect on energy harvesting. More specifically, the authors performed tests to study effect of: (1) ion concentration in water, (2) type of anion used, (3) type of cation used, and (4) effect of flow rate. The test data indicates that water flow through rGO networks can directly induce drift of charge carriers in graphene and thus generate electricity. Graphene is ideally suited for this application, since it possesses high mobility charge carriers that are ready to be coupled to moving ions present in the flowing fluid. The proposed rGO material could enable harvesting of the ubiquitous, abundant, and renewable mechanical energy of moving water directly to electrical energy. Unlike traditional schemes, the graphene material directly converts the flow energy into electrical energy without the need for moving parts. Such graphene coatings could potentially replace conventional batteries (which are environmentally hazardous) in low‐power, low‐voltage, and long service‐life applications. Once scaled up, this concept offers a potentially transformative approach to energy harvesting, as opposed to incremental advances in current technologies.

Memristive properties and synaptic plasticity in substituted pyridinium iodobismuthates.

This study explores the impact of organic cations in bismuth iodide complexes on their memristive behavior in metal-insulator-metal (MIM) type thin-layer devices. The presence of electron-donating and electron withdrawing functional groups (-CN, -CH3, -NH2, and -N(CH3)2) on pyridinium cations induces morphological alterations in crystals, thus influencing the electronic or ionic conductivity of devices comprising sandwiched thin layers (thickness = 200 nm ± 50) between glass/ITO as bottom electrode (∼110 nm) and copper (∼80 nm) as the top electrode. It was found that the current-voltage (I-V) scans of the devices reveal characteristic pinched hysteresis loops, a distinct signature of memristors. The working voltage windows are significantly influenced by both the types of cation and the dimensionality of ionic fragments (0D or 1D) in the solid-state form. Additionally, the temperature alters the surface area of the I-V loops by affecting resistive switching mechanisms, corresponding log-log plots at three temperatures (-30 °C, room temperature and 150 °C) are fully studied. Given that a memristor can operate as a single synapse without the need for programming, aligning with the requirements of neuromorphic computing, the study investigates long-term depression, potentiation, and spike-time-dependent plasticity-a specific form of the Hebbian learning rule-to mimic biologically synaptic plasticity. Different polar pulses, such as triangle, sawtooth, and square waveforms were employed to generate Hebbian learning rules. The research demonstrates how the shape of the applied pulse series, achieved by overlapping pre- and post-pulses at different time scales, in association with the composition and dimensionality of ionic fragments, lead to changes in the synaptic weight percentages of the devices.

L-Cysteine oxalates with dimeric and trimeric cations

Single crystals of two new compounds, (l-CysH···l-Cys)(HC2O4) (I) and (l-CysH···l-Cys···l-CysH)(HC2O4)2·0.5H2O (II), were obtained. Crystal structures were solved and refined using single-crystal X-ray diffraction, and compared with the previously known orthorhombic and monoclinic modifications of the simple salt (l-CysH)(HC2O4). Compound (I) crystallizes in the triclinic crystal system (space group P1, Z=2) and contains (l-CysH···l-Cys) dimeric cations with very short O···O interatomic distance of 2.434(2) Å. Hydrogen oxalate anions form head-to-tail type chains with very short hydrogen bonds, characterized by O···O distances of 2.422(2) Å and 2.417(3) Å. The crystal lattice of (II) is monoclinic with the space group C2, Z=4. It contains a new type of cation, that has never been observed before for cysteine salts, i.e. trimeric (l-CysH···l-Cys···l-CysH) cation. Protonated l-cysteinium cations are connected to the zwitterionic l-cysteine moiety through the same oxygen atom of the carboxylate group via hydrogen bonds, with O···O distances of 2.6410(18) Å and 2.4888(19) Å. Similar to the structure (I), the hydrogen oxalate anions form head-to-tail type chains linked by short hydrogen bonds with O···O distances of 2.4369(17) Å and 2.4330(17) Å, respectively. The crystals were characterized by IR and Raman spectroscopy. The batches obtained on crystallization were also characterized by X-ray powder diffraction, in order to check the phase purity of all the sample.

INFLUENCE OF HIGH-MOLECULARS COMPOUNDS OF DIFFERENT NATURE ON THE EFFICIENCY OF PURIFICATION THE MOTHER LIQUOR OF MAGNESIUM SULFATE PRODUCTION FROM IMPURITIES Fe3+, Al3+ AND Cr3+ BY ELECTROFLOTATION

The effect of flocculants and surfactants of different nature on the process of purification of the MgSO4 mother liquor from Fe3+, Al3+ and Cr3+ impurities by electroflotation was investigated. The study is aimed at increasing the yield of magnesium sulfate by returning the purified mother liquor to the head of the process at the stage of acid decomposition of serpentinitomagnesite. In the experiments, model solutions with a concentration of MgSO4 – 100 g/l, the content ions of Fe3+ – 50 mg/l, Al3+ – 10 mg/l and Cr3+ – 10 mg/l were used. It was determined that all impurities during pH adjustment turn into slightly soluble compounds at values 6 – 7. For the MgSO4 purification process by electroflotation, the optimal current density was established, which is 0.4 A/l. The duration of the process of purification by electroflotation is 30 min. When studying the effect of surfactants of cationic, anionic, nonionic and amphoteric types on the MgSO4 purification process by electroflotation, it was found that the degree of extraction of Fe3+, Al3+ and Cr3+ impurities does not exceed 10-30%, the exception is the presence of an amphoteric surfactant, in which the degree of extraction of Fe3+ is 77 – 78%. It was found that the greatest efficiency of extraction of Fe3+, Al3+ and Cr3+ impurities from MgSO4 solution is achieved in the presence of anionic flocculant Praestol 2540. The degree of extraction for all components reaches 98-99% already at the tenth minute of the process. Thus, the purification of MgSO4 from Fe3+, Al3+ and Cr3+ impurities by electroflotation in the presence of anionic flocculant Praestol 2540 will allow the purified mother liquor to be returned to the beginning of the process at the stage of sulfuric acid decomposition of serpentinitomagnesite during the production of magnesium sulfate, which will increase the yield of the product.

Copper(II) coordination compounds based on bis-hydrazones of 2,6-diacetylpyridine: synthesis, structure, and cytotoxic activity.

By reacting a series of 2,6-diacetylpyridine bis-hydrazones containing pyrimidine (H2L1), benzimidazole (H2L2) and phthalazine (H2L3) heterocyclic fragments with copper(II) chloride and bromide, a variety of pentacoordinated complexes of the composition [Cu(H2L1)X]X, [Cu(HL2)X] and [Cu(HL3)X], where X = Cl-, Br-, are formed. The properties and structure of the compounds were studied by means of NMR, IR, UV-vis, ESR, and X-ray absorption spectroscopy, cyclic voltammetry and X-Ray single crystal diffraction methods. It was shown that complexes of the cationic type [Cu(H2L1)X]X have an asymmetric structure with a distorted square-pyramidal geometry of the coordination unit. The coordination polyhedron of metal chelates [Cu(HL2)X] and [Cu(HL3)X] is an almost ideal square pyramid. Investigations of the cytotoxic activity of the obtained compounds in vitro on human hepatocellular carcinoma (HepG2) and non-tumor human lung fibroblast (MRC-5) cell lines demonstrated that complexes show higher activity compared with the well-known anticancer agent cisplatin. In addition, metal chelates [Cu(H2L1)Cl]Cl, [Cu(HL2)Cl], [Cu(HL2)Br] and [Cu(HL3)Cl] were less toxic to non-tumor cells MRC-5. A study of the binding of complexes to bovine serum albumin (BSA) protein using fluorescence spectroscopy showed that copper complexes are strongly bound to BSA. To study the mechanism of interaction of the complexes with the DNA of cancer cells, molecular dynamics simulation of the compound [Cu(HL3)Cl] was carried out. It was shown that the complex enters into π-stacking interactions predominantly with adenine and thymine bases.

Ultra‐Broadband Organic THz Generators: Influence of Substituents on THz Phonon Vibrations in Phenolic Parallel‐Type Cation–Anion Assembly

AbstractOrganic terahertz (THz) crystals consist of polar molecules with various functional substituents, resulting in numerous molecular phonon vibrations in the THz frequency range. However, the effect of incorporating substituents into organic THz crystals on the resulting THz absorption is rather an unexplored area. In this work, by choosing an appropriate model system consisting of two benchmark organic nonlinear optical crystals, exhibiting an identical type of phenolic cation–anion assembly but different substituents, their ultra‐broadband THz wave generation characteristics are demonstrated and investigated. Compared to the unsubstituted crystals, the substituted crystals possess one more methoxy substituent on highly polar cationic chromophores. Their vibrational modes and THz absorption characteristics are investigated theoretically by periodic density functional theory and experimentally by ultra‐broadband THz spectroscopy up to 12 THz. In phenolic parallel‐type cation–anion assembled organic THz crystals, the existence of a methoxy substituent differently influences the molecular vibrations in low and high THz frequency ranges. In the lower THz frequency range, the unsubstituted crystals exhibit additional strong entire molecular vibrations, the so‐called cation‐on‐cation slipping vibrations, which do not exist in the substituted crystals. In contrast, the methoxy substituent leads to additional strong intramolecular vibrations in the higher THz frequency range.

Efficacy of Novel Quaternary Ammonium and Phosphonium Salts Differing in Cation Type and Alkyl Chain Length against Antibiotic-Resistant Staphylococcus aureus.

Antibacterial resistance poses a critical public health threat, challenging the prevention and treatment of bacterial infections. The search for innovative antibacterial agents has spurred significant interest in quaternary heteronium salts (QHSs), such as quaternary ammonium and phosphonium compounds as potential candidates. In this study, a library of 49 structurally related QHSs was synthesized, varying the cation type and alkyl chain length. Their antibacterial activities against Staphylococcus aureus, including antibiotic-resistant strains, were evaluated by determining minimum inhibitory/bactericidal concentrations (MIC/MBC) ≤ 64 µg/mL. Structure-activity relationship analyses highlighted alkyl-triphenylphosphonium and alkyl-methylimidazolium salts as the most effective against S. aureus CECT 976. The length of the alkyl side chain significantly influenced the antibacterial activity, with optimal chain lengths observed between C10 and C14. Dose-response relationships were assessed for selected QHSs, showing dose-dependent antibacterial activity following a non-linear pattern. Survival curves indicated effective eradication of S. aureus CECT 976 by QHSs at low concentrations, particularly compounds 1e, 3e, and 5e. Moreover, in vitro human cellular data indicated that compounds 2e, 4e, and 5e showed favourable safety profiles at concentrations ≤ 2 µg/mL. These findings highlight the potential of these QHSs as effective agents against susceptible and resistant bacterial strains, providing valuable insights for the rational design of bioactive QHSs.