Rate Of Anion Exchange Research Articles

Synergistic ligand mediated anion exchange of CsPbI3 quantum dots for high performance white LED and anti‐counterfeiting

AbstractAnion exchange is an effective strategy to regulate the composition and optoelectronic properties of perovskite quantum dots (PQDs). Though promising, it is more desirable to synthesize PQDs to avoid the decrease of photoluminescence quantum yield (PLQY). Herein, we developed a ligand mediated anion exchange approach, in which the phase transition from CsPbBr3 QDs to CsPbI3 QDs was observed with the introduction of N‐Acetyl‐l‐cysteine (NAC) and 1,3‐dimethylimidazolium iodide (DMII) aqueous solution in CsPbBr3 QDs solution. NAC is expected to create more halogen vacancies in CsPbBr3 QDs, which provides sufficient adsorption sites for I− ions, resulting in accelerating the anion exchange rate in the process of DMII incorporation. Benefiting from the synergistic ligand mediated anion exchange, high PLQY of 97% and remarkable stability of CsPbI3 QDs are obtained. Furthermore, a white light‐emitting diode (WLED) with a lumen efficiency (LE) of 116.82 lm/W is constructed, showing remarkable stability under continuous operation.image

Linearly Manipulating Color Emission via Anion Exchange Technology for High Performance Amplified Spontaneous Emission of Perovskites.

The most attractive advantages of all-inorganic cesium lead halide perovskites are their optical gain over broad spectral ranges through the visible spectrum, so are well suited to use in tunable lasers or broadband amplifiers. Most reported anion exchange reactions face a challenge to achieve the desired halogen-variable perovskites due to rapid and uncontrollable reactions and difficulty to synthesize directly. In this study, a simple vapor/solid anion exchange strategy is demonstrated for controlling the reaction process and realizing a wide range tuning of band gap and amplified spontaneous emission (ASE) wavelength, which exhibits a temperature-dependent anion exchange rate. By optimizing the reaction temperature at 90°C, the ASE wavelength can be linearly manipulated by just controlling the reaction time. A clear quantitative relationship between ASE peak position and reaction time is achieved. Compares with the CsPbClBr2 film obtained via the liquid phase anion exchange method, the fabricated perovskite films obtained by vapor/solid anion exchange technology exhibit superior film quality and enhanced ASE performance. This work may have applications in the future using facile and controllable techniques to develop high-quality full-color visible lasers.

A study on the reversible anion-exchange rate in perovskite CsPbX3 nanocrystals

The anion-exchange among halogen ions is an effective technique for tuning the chemical composition and emission color of all-inorganic halide perovskite CsPbX3 (X = Cl, Br, and I) nanocrystals by tailoring their bandgaps. This work is focused on the rate of the reversible anion-exchange through finely tuning the luminescence color of perovskite nanocrystals (NCs) in any region between red and green. The luminescence color of the perovskite CsPb(I1-xBrx)3 (0 ≤ x ≤ 1) has been finely tuned through tailoring its bandgap with the anion-exchange between CsPbI3 and 4-bromo-butyric acid (BBA) instead of introducing of bromide salts as starting materials. The BBA could serve as triple functions to afford Br− ions source, short chain ligand with carboxyl group for surface passivation, and weak acid. A systematic study has been carried out to elucidate the effect of experimental parameters, on the color rangeability of the NCs and the anion-exchange rate between CsPbI3 and BBAThe trace of water added into the system can hinder the spontaneous transformation from red CsPbI3 to CsPbBr3 with aging time. It is particularly valuable to realize the reversible processes from green to yellow and finally to red successively by increasing the concentration of the isolated I− ions from various inorganic iodides.

Reconstruction and intercalating anion exchange of ZnAl-layered double hydroxide

Layered double hydroxides (LDHs) have recently attracted considerable attention as a promising multi-functional material due to their controllable properties depending on the type and composition ratio of metal cations and interlayer anions. Despite active research on controlling the composition to improve the properties of LDHs, anion intercalation techniques capable of obtaining the desired morphologies of LDHs have rarely been investigated. Herein, we report the anion exchange of ZnAl-LDHs grown on a silicon substrate using a post-treatment-based reconstruction process. Structural and chemical investigations verified that the calcined ZnAl-LDH was reconstructed by a NaCl solution during the anion exchange process. The anion exchange rate and the reconstructed fraction of the ZnAl-LDH increased as the NaCl concentration increased from 0.15 M to 0.60 M, though they decreased when the NaCl concentration exceeded 0.90 M. Therefore, the anion composition and morphology of the ZnAl-LDHs could be modulated by controlling the NaCl concentration during the reconstruction process. These results provide important information about the probability of controlling the structure and composition of LDHs intercalated with desired anions for a wide variety of device applications, such as memory, sensor, and energy storage.

Improved performance of wrinkled CoNi-LDHs via in situ immobilization onto cotton gauze for solid phase extraction of non-steroidal anti-inflammatory drugs

Solid phase microextraction (SPME) based on advanced composites as stationary phase is an effective technical means to preconcentrate trace analytes from environment samples. Here, a wrinkled cobalt nickel-layered double hydroxide arrays was successfully fabricated via in situ growing on polydopamine-coated cotton gauze (CoNi-LDH@PDC). Thanks to the wrinkled morphology of CoNi-LDH, the anion exchange rate and adsorption capacity of the fabricated composite were remarkably improved. The morphology of the fabricated CoNi-LDH@PDC composite was characterized by scanning electron microscopy, and the interaction between the adsorbent and analytes were analyzed by Fourier transform infrared spectroscopy. Then, a piece of 2 × 3 cm modified cotton gauze was packed into a pipette tip for simultaneous extraction and concentration three kinds of non-steroidal anti-inflammatory drugs (NSAIDs) including ketoprofen, fenbufen and ibuprofen, following analysis through high-performance liquid chromatography. Potential factors affecting the SPME process were studied in detail. Under the optimized conditions, the developed method exhibited excellent performance as the detection limits of 0.075, 0.18 and 0.17 μg L−1, besides the linear range of 0.20–3000, 0.50–200 and 0.50–3000 μg L−1 for ketoprofen, fenbufen and ibuprofen, respectively. The recoveries for spiking 5, 20 and 100 μg L−1 NSAIDs in tap water and drinking water samples were 77.3–92.4% and 82.6–95.6%, respectively. Moreover, the proposed SPME column was stable enough for 30 days experiments of extraction and desorption without obvious loss of extraction efficiency.

The Influence of Redox-Active Linkers on the Stability and Physical Properties of a Highly Electroactive Porphyrin Nanoprism.

Redox-active metal-organic nanocages are of interest for many applications, but the development of cages with extensive redox activity is often hindered by their limited stability and solubility across multiple charge states. This report reveals that these properties can be tuned for cages with redox-active walls by incorporating additional redox activity into the linkers. In particular, new +12 charged triangular nanoprisms 1a,b were formed from three electroactive tetrakis(3-pyridyl)porphyrin walls linked by six [(TMEDA)Pt]2+ (for 1a) or [(2,2'-bipy)Pt]2+ (for 1b) vertices, the latter of which are also electroactive. Thus, 1b exhibits extensive redox activity, consisting of two porphyrin-centered (x3) and two 2,2'-bipy-centered (x6) reductions that provide reversible access to +12, +9, +3, 0, and -6 charge states, whereas 1a undergoes only two, porphyrin-centered (x3) reversible reductions. Comparisons of 1a and 1b (and monomeric control compounds) by cyclic voltammetry and UV-vis-NIR spectroelectrochemistry show that the redox-activity of the linkers in 1b lowers the second reduction potential of the porphyrins by 100 mV and improves the stability and solubility of this structure under highly reducing conditions (e.g., -2.25 V vs Fc+/0 in MeCN). These findings reveal new principles for controlling the properties of highly electroactive molecular nanostructures. Anion exchange rates (≫103 s-1) were also probed, showing that the narrow apertures (≤3 Å van der Waals width) of 1a,b do not impede the loss/gain of PF6- anions during redox processes.

Impact of acute inflammation on Band 3 protein anion exchange capability in human erythrocytes

Objective: The impact of acute inflammation, revealed by C-reactive protein (CRP) plasma levels, has been studied on the erythrocytes anion exchanger Band 3 protein.Methods: Anion exchange capability through Band 3 protein, lipid peroxidation, -SH membrane groups and intracellular GSH levels have been measured on erythrocytes from patients with CRP >8 mg/L.Results: Under acute inflammation, a significant increase in anion exchange capability, increased lipid peroxidation, decreased–SH groups and GSH content were observed. Serum CRP levels recovery (after one week) was associated to –SH groups and GSH recovery, but not to anion exchange capability restoration. After 2 months, a total recovery of all parameters was observed.Conclusion: Band 3 protein anion exchange capability is affected by acute inflammation; the accelerated rate of anion exchange may be mainly due to lipid peroxidation, rather than to –SH groups oxidation; erythrocytes renewal could be needed to have a total recover of their function.

Structure and dynamics of the molten alkali-chloride salts from an X-ray, simulation, and rate theory perspective.

Molten salts are of great interest as alternative solvents, electrolytes, and heat transfer fluids in many emerging technologies. The macroscopic properties of molten salts are ultimately controlled by their structure and ion dynamics at the microscopic level and it is therefore vital to develop an understanding of these at the atomistic scale. Herein, we present high-energy X-ray scattering experiments combined with classical and ab initio molecular dynamics simulations to elucidate structural and dynamical correlations across the family of alkali-chlorides. Computed structure functions and transport properties are in reasonably good agreement with experiments providing confidence in our analysis of microscopic properties based on simulations. For these systems, we also survey different rate theory models of anion exchange dynamics in order to gain a more sophisticated understanding of the short-time correlations that are likely to influence transport properties such as conductivity. The anion exchange process occurs on the picoseconds time scale at 1100 K and the rate increases in the order KCl < NaCl < LiCl, which is in stark contrast to the ion pair dissociation trend in aqueous solutions. Consistent with the trend we observe for conductivity, the cationic size/mass, as well as other factors specific to each type of rate theory, appear to play important roles in the anion exchange rate trend.

Green solvent assisted synthesis of cesium bismuth halide perovskite nanocrystals and the influences of slow and fast anion exchange rates.

Replacing lead in halide perovskites to address the concerns of their toxicity and stability has driven a recent surge in research toward alternative lead-free perovskite materials. Lead-free all inorganic cesium bismuth halide (Cs3Bi2X9) perovskite nanocrystals have attracted attention in recent years due to the air-stability and non-toxic nature of bismuth. Herein, we demonstrate a facile sonication-assisted approach for the preparation of all-inorganic cesium bismuth iodide (Cs3Bi2I9) perovskite nanocrystals (NCs) using propylene carbonate as a green, alternative solvent. The photoluminescence (PL) spectra of the Cs3Bi2X9 NCs have a peak emission that can be tuned from 410 to 550 nm by controlling the composition of the NCs through an anion exchange reaction using tetraalkylammonium halides as a source of halide ions. The rate of this anion exchange reaction is demonstrated to have a significant influence on the dimensions of the NCs obtained from the parent Cs3Bi2I9 NCs. The PL emission of these nanocrystals is predominately due to exciton recombination processes. The NCs also exhibit air-stability for at least 150 days.

Multivalent Crown Ether Receptors Enable Allosteric Regulation of Anion Exchange in an Fe4L6 Tetrahedron

AbstractWe report a strategy for regulating the rate of internally bound anion exchange within an Fe4L6 metal–organic tetrahedron through external coordination of tripodal tris(alkylammonium) cations. The cage features three flexible 18‐crown‐6 receptors at each of its FeII vertices, facilitating strong tritopic interactions with tris(ammonium) cations to “cap” the vertices of the tetrahedron. This capping mechanism restricts the flexibility of the cage framework, thereby reducing the rate of anion exchange within its central cavity by 20‐fold. Thus, we demonstrate the first use of an externally bound multivalent effector to allosterically control internal guest binding in a molecular cage.

Multivalent Crown Ether Receptors Enable Allosteric Regulation of Anion Exchange in an Fe4 L6 Tetrahedron.

We report a strategy for regulating the rate of internally bound anion exchange within an Fe4 L6 metal-organic tetrahedron through external coordination of tripodal tris(alkylammonium) cations. The cage features three flexible 18-crown-6 receptors at each of its FeII vertices, facilitating strong tritopic interactions with tris(ammonium) cations to "cap" the vertices of the tetrahedron. This capping mechanism restricts the flexibility of the cage framework, thereby reducing the rate of anion exchange within its central cavity by 20-fold. Thus, we demonstrate the first use of an externally bound multivalent effector to allosterically control internal guest binding in a molecular cage.

Free Energy Landscape of Sodium Solvation into Graphite

Na is known to deliver very low energy capacity for sodium intercalation compared to Lithium. In this study, we use quantum mechanics based metadynamics simulations to obtain the free energy landscape for sodium ion intercalation from Dimethyl sulfoxide (DMSO) solvent into graphite. We find that the lowest free energy minima from the metadynamics are associated with sodium solvated by 3 or 4 DMSO. The free energy minima of these states are activated by a free energy of solvation computed to be 0.17 eV, which in turn are the most thermodynamically stable. We observe weak interactions of sodium with graphite sheets during the unbiased and biased molecular dynamics simulations. Our simulations results indicate that solvent plays an important role in stabilizing the sodium intercalation into graphite through shielding of the sodium while modulating the interaction of the solvent with the graphite sheets. In order to facilitate this intercalation, we propose solvents with negatively charged groups and aromatic cores (e.g., cyclic ethers) that could allow a greater rate of anion exchange to increase Na+ mobility.

Solid-State Anion Exchange Reactions for Color Tuning of CsPbX3 Perovskite Nanocrystals

Herein, we report on a room-temperature anion exchange reaction of highly emitting, all-inorganic CsPbBr3 nanocrystals (NCs) taking place entirely in the solid state. A fast exchange from Br to I and Br to mixed Br/Cl without exertion of additional energy is observed within minutes to hours, taking place by immobilization of the perovskite NCs on pure potassium halide salts (KCl, KBr, and KI). Via adjustment of the halide ratios of the embedding salt matrix, the bright fluorescence of the CsPbX3 (X = Cl, Br, or I) NCs can be tuned over a wide spectral range (400–700 nm) while maintaining the initial photoluminescence quantum yields of ∼80% and narrow full widths at half-maximum. We found that combinations of different initial CsPbX3 NCs and KX matrices result in different final halogen contents of the NCs. This is explained with a host-lattice limiting exchange mechanism. The anion exchange rate can be accelerated by pressing the soft, NC-loaded salts under pressure of 2.2 GPa. Because of the “cold flow” ...

Facile Conversion of Hydroxy Double Salts to Metal-Organic Frameworks Using Metal Oxide Particles and Atomic Layer Deposition Thin-Film Templates.

Rapid room-temperature synthesis of metal-organic frameworks (MOFs) is highly desired for industrial implementation and commercialization. Here we find that a (Zn,Cu) hydroxy double salt (HDS) intermediate formed in situ from ZnO particles or thin films enables rapid growth (<1 min) of HKUST-1 (Cu3(BTC)2) at room temperature. The space-time-yield reaches >3 × 10(4) kg·m(-3)·d(-1), at least 1 order of magnitude greater than any prior report. The high anion exchange rate of (Zn,Cu) hydroxy nitrate HDS drives the ultrafast MOF formation. Similarly, we obtained Cu-BDC, ZIF-8, and IRMOF-3 structures from HDSs, demonstrating synthetic generality. Using ZnO thin films deposited via atomic layer deposition, MOF patterns are obtained on pre-patterned surfaces, and dense HKUST-1 coatings are grown onto various form factors, including polymer spheres, silicon wafers, and fibers. Breakthrough tests show that the MOF-functionalized fibers have high adsorption capacity for toxic gases. This rapid synthesis route is also promising for new MOF-based composite materials and applications.

Kinetics and mechanism of exogenous anion exchange in FeFbpA–NTA: significance of periplasmic anion lability and anion binding activity of ferric binding protein A

The bacterial transferrin ferric binding protein A (FbpA) requires an exogenous anion to facilitate iron sequestration, and subsequently to shuttle the metal across the periplasm to the cytoplasmic membrane. In the diverse conditions of the periplasm, numerous anions are known to be present. Prior in vitro experiments have demonstrated the ability of multiple anions to fulfill the synergistic iron-binding requirement, and the identity of the bound anion has been shown to modulate important physicochemical properties of iron-bound FbpA (FeFbpA). Here we address the kinetics and mechanism of anion exchange for the FeFbpA-nitrilotriacetate (NTA) assembly with several biologically relevant anions (citrate, oxalate, phosphate, and pyrophosphate), with nonphysiologic NTA serving as a representative synergistic anion/chelator. The kinetic data are consistent with an anion-exchange process that occurs in multiple steps, dependent on the identity of both the entering anion and the leaving anion. The exchange mechanism may proceed either as a direct substitution or through an intermediate FeFbpA-X* assembly based on anion (X) identity. Our kinetic results further develop an understanding of exogenous anion lability in the periplasm, as well as address the final step of the iron-free FbpA (apo-FbpA)/Fe(3+) sequestration mechanism. Our results highlight the kinetic significance of the FbpA anion binding site, demonstrating a correlation between apo-FbpA/anion affinity and the FeFbpA rate of anion exchange, further supporting the requirement of an exogenous anion to complete tight sequestration of iron by FbpA, and developing a mechanism for anion exchange within FeFbpA that is dependent on the identity of both the entering anion and the leaving anion.

Derangement of Erythrocytic AE1 in Beta-Thalassemia by Caspase 3: Pathogenic Mechanisms and Implications in Red Blood Cell Senescence

Considering its complex molecular pathophysiology, beta-thalassemia could be a good in vivo model to study some aspects related to erythrocyte functions with potential therapeutic implications not only within the frame of this particular hemoglobinopathy but also with respect to conditions in which the cellular milieu, altered by a deranged anion exchanger, could display a significant pathogenetic role (i.e., erythrocyte senescence, complications of red cell storage, renal tubular acidosis and some abnormal protein thesaurismosis). This work evaluates the anionic influx across band 3 protein in normal and beta-thalassemic red blood cells (RBCs) and ghosts. Since redox-mediated injury is an important pathway in the destruction of beta-thalassemic RBCs, we studied the anion transport and the activity of caspase 3 in the absence and presence of t-butylhydroperoxide in order to evaluate the effect of an increase of cellular oxidative stress. Interestingly, beta-thalassemic erythrocytes show a faster rate of anion exchange than normal RBCs and absence of any modulation mechanism of anion influx. These findings led us to formulate a hypothesis about the metabolic characteristics of beta-thalassemic erythrocytes, outlining that one of the main targets of caspase 3 in RBCs is the cytoplasmic domain of band 3 protein.

The Proton Complex of a Diaza-macropentacycle: Structure, Slow Formation, and Chirality Induction by Ion Pairing with the Optically Active 1,1′-Binaphthyl-2,2′-diyl Phosphate Anion

The protonation of a sterically crowded [N2S6] macropentacycle (1) with 1 equiv of CF3SO3H in CDCl3 is slow and gives the singly (oo(+) [1 x H](+)) and doubly (o(+)o(+) [1 x 2H](2+)) protonated forms as kinetic products, the i(+)o form of [1 x H](+) being the thermodynamic product. i(+)o [1 x H](+) is C3 helically chiral in the solid state and in solution. The barrier to racemization (DeltaG(double dagger)) of the [1 x H](+) propeller is >71 kJ mol(-1). The ammonium proton is encapsulated in the tetrahedral coordination sphere provided by the endo (i) nitrogen bridgehead atom and the three proximal thioether sulfurs, which makes [1 x H](+) a proton complex. Use of the optically active acid (R)-(-)- or (S)-(+)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (BNPH) in chloroform allowed us to induce a significant diastereomeric excess (24% de), which produced a detectable ICD. The de was decreased in acetone-d6 (10%), suggesting that the sense of chirality of [1 x H](+) is controlled by ion-pair interactions. Detailed NMR studies allowed us to locate the chiral anion on the endo side of [1 x H](+), in the cavity lined by endo t-Bu groups, and to establish that the rate of anion exchange in [1 x H][(S,R)-(+/-)-BNP] was higher than the rate of propeller inversion of [1 x H](+).

Intestinal water absorption, anion exchange, proton transport and epithelial metabolic rate in marine teleost fish

Intestinal water absorption, anion exchange, proton transport and epithelial metabolic rate in marine teleost fish

Anion Exchange by Mixed-bed Ion Exchange at Ultralow Concentrations

The effects of the cation-to-anion resin ratio and the amount of resin on anion exchange performance was experimentally studied with mixed-bed columns. Three different amounts of resin and five different cation-to-anion resin ratios were selected, and 10-4 M NaCl solution was used. The experiments were performed in continuous packed bed ion exchange column with commercially available exchange resins. The performance was evaluated with the breakthrough curves obtained. The results showed that the shape of chloride breakthrough curves and the level of leakage depended on the amount of anion exchange resin based on the resin ratio. In addition, the selectivity coefficient for chloride-hydroxide exchange and the diffusion coefficient influenced the steepness and the pattern of breakthrough curves. It was expected that cation exchange rate could be higher than anion exchange rate depending on resin capacities. However, anion exchange rate was higher due to other parameters that influence ion exchange rate, i.e. the shape of breakthrough curve. They were selectivity coefficients, mass-transfer coefficients and diffusion coefficients of ions.

PAT-1 (Slc26a6) is the predominant apical membrane Cl−/HCO3− exchanger in the upper villous epithelium of the murine duodenum

Basal HCO(3)(-) secretion across the duodenum has been shown in several species to principally involve the activity of apical membrane Cl(-)/HCO(3)(-) exchanger(s). To investigate the identity of relevant anion exchanger(s), experiments were performed using wild-type (WT) mice and mice with gene-targeted deletion of the following Cl(-)/HCO(3)(-) exchangers localized to the apical membrane of murine duodenal villi: Slc26a3 [down-regulated in adenoma (DRA)], Slc26a6 [putative anion transporter 1 (PAT-1)], and Slc4a9 [anion exchanger 4 (AE4)]. RT-PCR of the isolated villous epithelium demonstrated PAT-1, DRA, and AE4 mRNA expression. Using the pH-sensitive dye BCECF, anion exchange rates were measured across the apical membrane of epithelial cells in the upper villus of the intact duodenal mucosa. Under basal conditions, Cl(-)/HCO(3)(-) exchange activity was reduced by 65-80% in the PAT-1(-) duodenum, 30-40% in the DRA(-) duodenum, and <5% in the AE4(-) duodenum compared with the WT duodenum. SO(4)(2-)/HCO(3)(-) exchange was eliminated in the PAT-1(-) duodenum but was not affected in the DRA(-) and AE4(-) duodenum relative to the WT duodenum. Intracellular pH (pH(i)) was reduced in the PAT-1(-) villous epithelium but increased to WT levels in the absence of CO(2)/HCO(3)(-) or during methazolamide treatment. Further experiments under physiological conditions indicated active pH(i) compensation in the PAT-1(-) villous epithelium by combined activities of Na(+)/H(+) exchanger 1 and Cl(-)-dependent transport processes at the basolateral membrane. We conclude that 1) PAT-1 is the major contributor to basal Cl(-)/HCO(3)(-) and SO(4)(2-)/HCO(3)(-) exchange across the apical membrane and 2) PAT-1 plays a role in pH(i) regulation in the upper villous epithelium of the murine duodenum.