Cationic Density Research Articles

Polyelectrolyte complex nanofiltration membranes by surface deposition of polyethylenimine on polyanion supports

AbstractPolyethylenimine (PEI) is a water‐soluble polymer with higher density of cations and strong adsorbability. In the present work, loose nanofiltration membranes based on PEI were prepared by surface deposition of PEI on hydrolyzed polyacrylonitrile (PANH) supports through a surface crosslink method without using extra crosslinkers. The thinner selective layer (around 50 nm) of polyelectrolyte complex was formed through the crosslinks (ionic and co‐valent) between amine groups in PEI and carboxyl groups in PANH. The PEI/PAN membranes were characterized by SEM, ATR‐IR, and XPS. Nanofiltration of PEGs and salt solutions were performed to evaluate the membrane performance. Loose nanofiltration membranes, with molecular weight cut‐off from 500 to 950 Da, permeances form 7 to 16 L m−2 h−1 bar−1, were obtained by the simple surface crosslink method. The membrane performance can be facile tailored by controlling the deposition parameters, including deposition time and post‐treatments.

Evaluation of the Sorption Capacity of a Maleic Acid Copolymer Towards Gold(III) Ions and Production of Catalytically Active Gold Nanoparticles on Its Base

Two spectrophotometric approaches are suggested for the assessment of the concentration of gold(III) cations in an aqueous solution: direct recording of the optical density of gold cations and galvanic substitution of silver atoms in polymer-stabilized silver nanoparticles with gold cations. The sorption capacity of a maleic acid copolymer towards gold cations is estimated. A colloidal composite containing gold nanoparticles is obtained from the polymeric gold salt. The catalytic properties of the resulting polymer-stabilized nanogold are studied in the aerobic oxidation of glucose to gluconic acid.

IR-Spectroscopic Study of Complex Formation of Nitrogen Oxides (NO, N2O) with Cationic Forms of Zeolites and the Reactivity of Adsorbed Species in CO and CH4 Oxidation.

The formation of complexes and disproportionation of nitrogen oxides (NO, N2O) on cationic forms of LTA, FAU, and MOR zeolites was investigated by diffuse-reflectance IR spectroscopy. N2O is adsorbed on the samples under study in the molecular form and the frequencies of the first overtone of the stretching vibrations ν10–2 and the combination bands of the stretching vibrations with other vibrational modes for N2O complexes with cationic sites in zeolites (ν30–1 + ν10–1, ν10–1 + δ0–2) are more significantly influenced by the nature of the zeolite. The presence of several IR bands in the region of 2400–2600 cm−1 (the ν10–1 + δ0–2 transitions) for different zeolite types was explained by the availability of different localization sites for cations in these zeolites. The frequencies in this region also depend on the nature of the cation (its charge and radius). The data can be explained by the specific geometry of the N2O complex formed, presumably two-point adsorption of N2O on a cation and a neighboring oxygen atom of the framework. Adsorption of CO or CH4 on the samples with preliminarily adsorbed N2O at 20–180 °C does not result in any oxidation of these molecules. NO+ and N2O3 species formed by disproportionation of NO are capable of oxidizing CO and CH4 molecules to CO2, whereas NOx is reduced simultaneously to N2 or N2O. The peculiarities in the behavior of cationic forms of different zeolites with respect to adsorbed nitrogen oxides determined by different density and localization of cations have been established.

Alkyl-Aryl Cation Mixing in Chiral 2D Perovskites.

We report 2D hybrid perovskites comprising a blend of chiral arylammonium and achiral alkylammonium spacer cations (1:1 mole ratio). These new perovskites feature an unprecedented combination of chirality and alkyl-aryl functionality alongside noncovalent intermolecular interactions (e.g., CH···π interactions), determined by their crystal structures. The mixed-cation perovskites exhibit a circular dichroism that is markedly different from the purely chiral cation analogues, offering new avenues to tune the chiroptical properties of known chiral perovskites, instead of solely relying on otherwise complex chemical syntheses of new useable chiral cations. Further, the ability to dilute the density of chiral cations by mixing with achiral cations may offer a potential way to tailor the spin-based properties in 2D hybrid perovskites, such as Rashba-Dresselhaus spin splitting and chirality-induced spin selectivity and magnetization effects.

Incorporating silica-magnetite synthesized from natural resources into the cation exchange membranes

Inorganic material-incorporated cation exchange membranes (CEMs) with improved properties have drawn attention for reverse electrodialysis (RED). This paper deals with improving CEMs properties by incorporating silica–magnetite inorganic materials from natural resources. First, silica and magnetite were extracted from rice husk and iron sand, respectively. CEMs were prepared using the phase inversion method by incorporating various ratios. The results showed that both silica and magnetite were in micron size with yields of 76.6% and 59.2% wt., respectively. The CEMs containing magnetite materials showed higher ion exchange capacity (IEC) and ionic conductivity than PVC membranes. However, they had a greater swelling degree. The presence of silica reduced the swelling degree from 18.38% to 7.15% leading to membrane strengthening. A maximum IEC and conductivity of CEMs of 0.26 meq/g and 0.524 S/cm were obtained for the membrane prepared with a SiO2/Fe3O4 ratio of 0:4, respectively. However, considering all aspects, the addition of a SiO2/Fe3O4 ratio of 1:3 was the most significant for increasing the fixed cation density and conductivity by 27.49% and 2815%, respectively, compared to other ratios. Thus, this SiO2/Fe3O4 ratio (1:3) should be considered for practical implementation. Performance examination using RED confirmed that the PVC/SiO2/Fe3O4 can be used as CEM for power generating and had comparable performance to commercial membrane.

A Novel MoS2-MXene Composite Cathode for Aluminum-Ion Batteries

Metal dichalcogenide cathodes can be used to increase the capacities of rechargeable aluminum-ion batteries. However, the higher charge density of trivalent metal cations (Al3+) and the inherently strong polarization effect on the host lattice result in poor MoS2 cycling performance. Thus, we designed MoS2-MXene composites as a novel cathode to improve the performance of rechargeable aluminum-ion batteries. The results of this study show that Ti3C2Tx MXene can provide a conductive framework with exceptional mechanical integrity for MoS2. The electrochemical performance of MoS2 can be significantly improved by compounding with Ti3C2Tx MXene.

Antimicrobial Ionic Liquid‐Based Materials for Biomedical Applications

AbstractExcessive and unwarranted administration of antibiotics has invigorated the evolution of multidrug‐resistant microbes. There is, therefore, an urgent need for advanced active compounds. Ionic liquids with short‐lived ion‐pair structures are highly tunable and have diverse applications. Apart from their unique physicochemical features, the newly discovered biological activities of ionic liquids have fascinated biochemists, microbiologists, and medical scientists. In particular, their antimicrobial properties have opened new vistas in overcoming the current challenges associated with combating antibiotic‐resistant pathogens. Discussions regarding ionic liquid derivatives in monomeric and polymeric forms with antimicrobial activities are presented here. The antimicrobial mechanism of ionic liquids and parameters that affect their antimicrobial activities, such as chain length, cation/anion type, cation density, and polymerization, are considered. The potential applications of ionic liquids in the biomedical arena, including regenerative medicine, biosensing, and drug/biomolecule delivery, are presented to stimulate the scientific community to further improve the antimicrobial efficacy of ionic liquids.

Biological In Vitro Evaluation of PIL Graft Conjugates: Cytotoxicity Characteristics.

In vitro cytotoxicity of polymer-carriers, which in the side chains contain the cholinum ionic liquid units with chloride (Cl) or pharmaceutical anions dedicated for antituberculosis therapy, i.e., p-aminosalicylate (PAS) and clavulanate (CLV), was investigated. The carriers and drug conjugates were examined, in the concentration range of 3.125–100 μg/mL, against human bronchial epithelial cells (BEAS-2B) and adenocarcinomic human alveolar basal epithelial cells (A549) as an experimental model cancer cell line possibly coexisting in tuberculosis. The cytotoxicity was evaluated by MTT test and confluency index, as well as by the cytometric analyses, including Annexin-V FITC apoptosis assay. The polymer systems showed supporting activity towards the normal cells and no tumor progress, especially at the highest concentration (100 μg/mL). The analysis of cell death did not show meaningful changes in the case of the BEAS-2B, whereas in the A549 cell line, the cytostatic activity was observed, especially for the drug-free carriers, causing death in up to 80% of cells. This can be regulated by the polymer structure, including the content of cationic units, side-chain length and density, as well as the type and content of pharmaceutical anions. The results of MTT tests, confluency, as well as cytometric analyses, distinguished the polymer systems with Cl/PAS/CLV containing 26% of grafting degree and 43% of ionic units or 46% of grafting degree and 18% of ionic units as the optimal systems.

Pyrolyzed Ca-impregnated lignite for aqueous phosphate removal: Batch and column studies

Lignite is an abundant carbon material with a variable surface structure and low cation density The introduction of metal (hydr)oxide phases has improved the anionic binding potential of lignite. In this study, activated lignite (A−L), Ca2+−modified lignite (Ca−L), and Ca2+−modified activated lignite (Ca−A−L) were synthesized to remove aqueous phosphate. Lignite was first activated (KOH: lignite, mass ratio, 3:1) at 750 ºC to prepare A−L, improving its surface area by ~984-fold. Ca−L (27 wt% Ca) showed a large phosphate uptake (227.3 mg/g) (adsorbent dose 50 mg, 25 mL of 10–1500 ppm phosphate, 24 h, 25 °C, initial pH 6), due to the large amounts of micro-sized CaCO3, Ca(OH)2, and CaO particles in Ca−L. These particles actively precipitate phosphate/hydrophosphate as CaHPO4/Ca3(PO4)2. The breakthrough capacity of a 2.0 g Ca−L bed column (bed height 2.5 cm, diameter 1 cm) was 58.2 mg/g (flow rate 1.5 mL/min, 25 ºC, initial [PO43-] = 46.6 mg/L, particle size, 125–150 µm), ~4 fold lower than the maximum Langmuir sorption capacity. An interference study indicated that Ca−L is highly selective for phosphate. Spent Ca−L may improve soil fertility as it retains more phosphate species for later slow-release to the soil. Unit weight of phosphate can be removed by Ca−L more inexpensively than Norit ROW and Darco KB (two commercial activated carbon carbons). Precipitated Ca2+ phosphates/hydrophosphates in exhausted Ca−L can be recovered using HCl and Ca−L recycled. Moreover, low-cost lignite is a promising carbon support for the future synthesis of different value-added products.

Controllable construction and theoretical simulation of silica aerogel/polymer composites with electrostatic interaction interfaces

In our previous work, aerogel/polymer composites with electrostatic interaction interface were successfully constructed. Interesting experimental phenomena in heat and stress transfer had also been found. On the basis of these works, we had been thinking about how to control the characteristics of electrostatic interaction phase interface, and how these phase interface characteristics affected the properties of materials. In this paper, the electrostatic interaction phase interface characteristics of the composite were regulated from the aspects of polymer chain movement, charge amount and charge distribution. The effects of phase interface characteristics on stress and heat transfer behavior of the composites were analyzed from the aspects of experimental test characterizations and molecular dynamics simulation. The results showed that the action region of electrostatic attraction phase interface can be controlled by the properties of polymer side chain and charged monomer. The density, heat transfer characteristics and stress transfer behavior of the composites were affected. α-Methyl was beneficial to the thermal stability of the composites, and the thermal conductivity was about 0.012 W m−1K−1. When the alkyl side chain was long, the molecular chain arrangement was irregular, the reorientation ability of the molecular chain was poor, and the molecular chain breaks in the compression stage. In the theoretical simulation, it can be found that more charged groups in a single charged part of the molecule led to the increase of cationic density in the organic phase, which made it easier to form effective chemical bonds in the crosslinking process, and the final crosslinking degree was improved.

Vapor deposition of CsPbBr3 thin films by evaporation of CsBr and PbBr2

Thin films of the inorganic halide perovskite, CsPbBr3, find applications in various optoelectronic devices, including solar cells, radiation detectors, light-emitting diodes, photodetectors, and lasers. Physical vapor deposition (PVD) by coevaporation of CsBr and PbBr2 onto a substrate is a scalable solventless approach to forming high purity large-grained polycrystalline films. Herein, we investigate the effects of deposition temperature, between 26 and 162 °C, and postdeposition annealing, between 250 and 350 °C, on the structure, texturing, and morphology of orthorhombic CsPbBr3 films formed by PVD. All films, regardless of the stable phase at the deposition temperature, transform to orthorhombic upon cooling to room temperature. The films deposited as orthorhombic or tetragonal CsPbBr3 below 130 °C were textured in the orthorhombic structure's ⟨202⟩ direction, while cubic CsPbBr3 films deposited above 130 °C were textured in the orthorhombic structure's ⟨121⟩ direction. This texturing favors the growth of high cation density planes of the stable phase at the deposition temperature. The orthorhombic ⟨202⟩ texturing also dominates after annealing as long as the films have ⟨202⟩ aligned grains before annealing.

Partial Order–Disorder Transformation of Interpenetrated Porous Coordination Polymers

Controlling interpenetration and flexibility behaviors is intriguing and fundamental for porous coordination polymers. We report exceptional interpenetration behaviors involving controllable partia...

Solvation, Speciation, and De-Solvation Penalties in Multivalent Battery Electrolytes

Although substantial effort has been applied to the development of new multivalent liquid electrolytes for next generation batteries, an improved understanding of how the solvation environment controls the properties of these electrolytes is needed. Most working electrolytes for Mg2+ and Ca2+ systems utilize low permittivity solvents, namely ethers, which enable the high charge density of the divalent cation to exert significant influence on the surrounding solvation environment. These effects lead to non-intuitive concentration-dependent speciation and significant ion correlations even when employing “weakly coordination” anions. In this presentation we describe the solvation environments of critical exemplar systems based on Ca2+, Mg2+, and Zn2+ working cations using complementary techniques, including dielectric relaxation spectroscopy and modeling. In select cases we connect these solvation details to electrochemical desolvation barriers through temperature-dependent impedance spectroscopy. Through these investigations we address critical questions regarding the magnitude and tunability of the dication desolvation penalty during metal deposition and/or cathode insertion.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Structure of cholinium glycinate biocompatible ionic liquid at graphite electrode interface.

We use constant potential molecular dynamics simulations to investigate the interfacial structure of the cholinium glycinate biocompatible ionic liquid (bio-IL) sandwiched between graphite electrodes with varying potential differences. Through number density profiles, we observe that the cation and anion densities oscillate up to ∼1.5 nm from the nearest electrode. The range of these oscillations does not change significantly with increasing electrode potential. However, the amplitudes of the cation (anion) density oscillations show a notable increase with increasing potential at the negative (positive) electrode. At higher potential differences, the bulkier N(CH3)3CH2 group of cholinium cations ([Ch]+) overcomes the steric barrier and comes closer to the negative electrode as compared to oxygen atom (O[Ch]+ ). We observe an increase in the interaction between O[Ch]+ and the positive electrode with a decrease in the distance between them on increasing the potential difference. We also observe hydrogen bonding between the hydroxyl group of [Ch]+ cations and oxygens of glycinate anions through the simulated tangential radial distribution function. Orientational order parameter analysis shows that the cation (anion) prefers to align parallel to the negative (positive) electrode at higher applied potential differences. Charge density profiles show a positive charge density peak near the positive electrode at all the potential differences because of the presence of partially positive charged hydrogen atoms of cations and anions. The differential capacitance (Cd) of the bio-IL shows two constant regimes, one for each electrode. The magnitude of these Cd values clearly suggests potential application of such bio-ILs as promising battery electrolytes.

Evidence of formation of an amorphous magnesium silicate (AMS) phase during alkali activation of (Na-Mg) aluminosilicate glasses

There is some ambiguity regarding the fate of Mg during the alkali activation of Mg-rich precursors within the broader field of alkali activated materials (AAMs). The present work addresses this issue by studying the reaction products in AAMs synthesized from (Na-Mg) aluminosilicate glasses. Here, instead of magnesium silicate hydrate (M-S-H) phase, Mg exclusively forms an amorphous magnesium silicate (AMS) phase. Compared to M-S-H, AMS is a more depolymerized phase, which has not previously been well documented. The formation of AMS seems to be driven by the high charge density of the Mg cation which effectively stabilizes the depolymerized silicate species. We also show that the lack of hydrotalcite-group phases is due to aluminum depletion by zeolite formation. This work highlights the need to consider the existence of the AMS phase in Mg-containing AAMs, especially in complex systems, where its identification may be difficult.

Characteristics of a Plasticized PVA-Based Polymer Electrolyte Membrane and H+ Conductor for an Electrical Double-Layer Capacitor: Structural, Morphological, and Ion Transport Properties.

Poly (vinyl alcohol) (PVA)-based solid polymer electrolytes doped with ammonium thiocyanate (NH4SCN) and glycerol were fabricated using a solution casting method. Lithium-based energy storage devices are not environmentally friendly materials, and they are toxic. Thus, proton-conducting materials were used in this work as they are harmless and are smaller than lithium. The interaction between PVA and the electrolyte elements was shown by FTIR analysis. The highest conductivity of 1.82 × 10−5 S cm−1 was obtained by the highest-conducting plasticized system (PSP_2) at room temperature. The mobility, diffusion coefficient, and number density of anions and cations were found to increase with increasing glycerol. FESEM was used to investigate the influence of glycerol on film morphology. TNM showed that the cations and anions were the main charge carriers. LSV showed that the electrochemical stability window of the PSP_2 system was 1.99 V. The PSP_2 system was applied in the preparation of an electrical double layer capacitor device. The shape of the cyclic voltammetry (CV) curve was nearly rectangular with no Faradaic peaks. From the galvanostatic charge-discharge analysis, the power density, energy density, and specific capacitance values were nearly constant beyond the first cycle at 318.73 W/Kg, 2.06 Wh/Kg, and 18.30 F g−1, respectively, for 450 cycles.

The effect of porewater ionic composition on arsenate adsorption to clay minerals

Adsorption of arsenate on clay minerals can control the partitioning and mobility of arsenic and subsequent contamination of groundwater. While the effect of ionic strength on arsenic adsorption to phyllosilicate minerals has been evaluated for various clay minerals, the specific ionic composition of the surrounding porewater can play a critical role in promoting adsorption (or desorption) of arsenate (HxAsO4x-4). We conducted a series of adsorption isotherms to evaluate the adsorption of arsenate to various phyllosilicates in the presence of monovalent (K+), divalent (Mg2+, Ca2+), and trivalent (La3+) cations while maintaining constant ionic strength and pH. Adsorption isotherms were combined with surface complexation modeling to examine retention processes of arsenate as a function of ionic composition in the surrounding solution. The higher charge density of greater valent cations results in stronger outer-sphere bridging complexes between negatively charged phyllosilicate mineral surfaces and negatively charged arsenate oxyanions. Higher valent cations thus enhance the propensity for arsenate adsorption on phyllosilicate minerals. We further deciphered surface complexation processes by conducting adsorption isotherms on various clay minerals including smectite, illite, and pyrophyllite to evaluate the role of interlayer, permanent charge, and terminal edge sites. We conclude that arsenate is most likely retained largely on the planar surface where structural negative charge emanates allowing cation bridging complexes to develop. Our findings illustrate that clay mineralogy of soils and sediments can combine with porewater ionic composition (and specifically the proportion of divalent cations) to describe arsenic transport, particularly in iron- or aluminum-oxide poor systems.

Effect of Ca2+, Mg2+, Ba2+ and Sr2+ cations on calcium carbonate scaling formation in oil-gas well: Based on density functional theory study and molecular dynamics simulation

The effect of different cations (Ca2+, Mg2+, Ba2+ and Sr2+) adsorption on carbonate type scaling formation was studied by using CASTEP and Forcite module based on density functional theory and molecular dynamics, respectively. By calculating the adsorption energy of cations adsorbed on four adsorption sites (top, hollow, short-range bridge and long-range bridge) of (2 × 1 × 1)CaCO3 (1 –1 0) surface, the most stable adsorption site was determined. On this basis, the banding mechanism of O atom and cation was studied by analyzing the state density of different cations adsorbed model. It has been shown that the Mg2+ cation adsorbed at top site of O atom on CaCO3(1 –1 0) surface was the most stable one according to the adsorption energy calculation results. Under the condition of multiple type of cations co-existence at the same ionic concentration, Mg2+ and Ba2+ would preferably combined with CO32– to form magnesium carbonate and barium carbonate scaling, causing the crystal growth process of calcium carbonate scaling inhibited. The converse is equally true that the existence of Sr2+ is more conducive to the calcium carbonate scaling crystal growth. The radial distribution function analysis indicated that the bonding strength between Mg2+ and O atom on CaCO3 (1 –1 0) surface is the largest, weakening followed Ba2+, Ca2+ and Sr2+ successively. Density of state study indicated that adsorption of Mg2+ cation on CaCO3 (1 –1 0) surface is mainly due to the interaction between 2p orbit of O atoms and 3s orbit of Mg2+ cation.

Nanoscale insight on the initial hydration mechanism of magnesium phosphate cement

The hydration rate, microstructure, mechanical properties and durability of Magnesium phosphate cement (MPC) prepared by different kinds of phosphates are quite different. These differences in macroscopic properties are essentially determined by microscopic chemical reactions. Therefore, in this paper, the adsorption mechanism of MgO interface to water and ions in the initial hydration process of MPC and the hydration structure of different ions were discussed at the molecular level. Herein, the structure and dynamics properties of water, NH4+, Na+, K+ and Cl− ions at MgO interface were analyzed by molecular dynamics method. The results show that the water molecules near the MgO interface can be connected to the matrix oxygen through hydrogen bonding and have a Coulomb interaction with the Mg on the interface. Therefore, the water molecules accumulate and stratify at the interface and the density distribution curve of water molecules forms a peak near the interface. This explains the stage of MgO adsorption of water molecules during the initial hydration of MPC. Besides, a large amount of ammonium ion, sodium ion and potassium ion are adsorbed on the MgO surface, and the cation density distribution curve also forms a peak near the interface. In addition, the radius of sodium ion is smaller and the Na-Os bond is stronger than that of NH4+ and K+ (Os represents the oxygen atom in MgO). Hence, the number of sodium ions adsorbed to the interface is the largest, the radial distribution function (RDF) of Na-Os forms a high-strength and sharp peak, The Os coordination number of Na+ is more than that of NH4+ and K+. This also explains the experimental phenomenon that sodium magnesium phosphate cement has a faster hydration rate and shorter setting time than ammonium magnesium phosphate cement and potassium magnesium phosphate cement. Due to the adsorption of the interface, the mean square displacement of cations has decreased to some extent compared with that in the corresponding pure solution models. This study provides a basic understanding of the initial hydration mechanism of MPC at the molecular level.

High-Throughput Automation of Endosomolytic Polymers for mRNA Delivery.

In recent years, there has been an increasing interest in designing delivery systems to enhance the efficacy of RNA-based therapeutics. Here, we have synthesized copolymers comprised of dimethylaminoethyl methacrylate (DMAEMA) or diethylaminoethyl methacrylate (DEAEMA) copolymerized with alkyl methacrylate monomers ranging from 2 to 12 carbons, and developed a high throughput workflow for rapid investigation of their applicability for mRNA delivery. The structure activity relationship revealed that the mRNA encapsulation efficiency is improved by increasing the cationic density and use of shorter alkyl side chains (2-6 carbons). Minimal cytotoxicity was observed when using DEAEMA-co-BMA (EB) polyplexes up to 18 h after dosing, independent of a poly(ethylene glycol) (PEG) first block. The lowest molecular weight polymer (EB10,250) performed best, exhibiting greater transfection than polyethyenimine (PEI) based upon the number of cells transfected and mean intensity. Conventional investigations into the performance of polymeric materials for mRNA delivery is quite tedious, consequently limiting the number of materials and formulation conditions that can be studied. The high throughput approach presented here can accelerate the screening of polymeric systems and paves the way for expanding this generalizable approach to assess various materials for mRNA delivery.