Ion-pair Research Articles

Minimal Coarse-Grained Models of Polar Solvent for Electrolytes: Stockmayer Versus Dumbbell.

This study explores the potential of the dumbbell solvent as a minimal model for understanding electrolyte solutions in polar solvents. Our investigation involves a comparative analysis of the dumbbell model and the Stockmayer model, focusing on ion solvation and ion-ion correlations. We examine electrolytes containing symmetric monovalent salts dissolved in polar solvents while varying the ion density and solvent polarity. Both models predict an augmented solvent coordination number around ions as the solvent polarity increases, with the dumbbell solvent displaying a more pronounced effect. Notably, radial distribution functions (RDFs) between solvent and ions yield differing trends; Stockmayer models exhibit a nonmonotonic relationship due to strong dipole-dipole interactions at higher polarity, while RDFs for ions and dumbbell solvents consistently rise. In response to increased solvent polarity, Stockmayer solvents within the ion's solvation shell undergo continuous dipole orientation shifts, whereas the dumbbell solvent predominantly adopts pointing-away dipole orientations, diminishing pointing-to orientations. This underscores the significance of the interplay between the solvent molecular orientation and dipole rotation. Both models qualitatively predict ion pairing and clustering behaviors across varying solvent dipole strengths and salt concentrations. The Stockmayer solvent generally provides stronger electrostatic screening than the dumbbell solvent due to its neglect of the coupling between molecular orientation and dipole rotation. What's more, at a high dipole moment regime, ion-ion correlations in Stockmayer solvent can become stronger with increasing dipole moment due to stronger solvent-solvent correlations. This study underscores the effectiveness of the dumbbell solvent model in systematically elucidating the fundamental principles governing electrolytes and offers potential applications in the rational design of electrolyte systems.

Insight into the solvation and dynamic behaviors of lithium salt in water-in-bisalt electrolytes

Through a combination of molecular dynamics simulations and experimental approaches, the solvation structure and diffusion behavior of Li+ was investigated in water-in-bisalt electrolytes formed by introducing a second lithium salt (LiBF4, LiNO3, LiOAc) into the LiTFSI aqueous electrolyte. The calculation and experimental results indicate that nanostructures of water-in-bisalt electrolytes include “water-rich” and “anion-rich” domains. When LiBF4 is added, Li+ is mostly located in the water-rich domain, effectively increasing the diffusion coefficient of Li+. This electrolyte exhibits a higher conductivity and a much lower price compared to mono-LiTFSI electrolytes, On the contrary, with the addition of LiOAc, OAc− will strongly coordinate with Li+ to change the solvation structure of solvent separated ion pairs (Li+(H2O)4) to aggregates, which results in the decrease of Li+ diffusion coefficient. These fundamental insights highlight the correlation of microstructural and dynamic heterogeneities of water-in-bisalt electrolytes, which are expected to trigger rational design of solvation and dynamic behaviors of advanced aqueous electrolytes.

Multitype Electronic Interactions in Precursor Solutions of Molecular Doped P3HT Polymer.

Spin-casting of molecularly doped polymer solution mixtures is one of the commonly used methods to obtain conductive organic semiconductor films. In spin-casted films, electronic interaction between the dopant and polymer is one of the crucial factors that dictates the doping efficiency. Here, we investigate excitonic couplings using ultrafast two-dimensional electronic spectroscopy to examine the different types of electronic interactions in ion pairs of the prototype F4TCNQ-doped P3HT polymer system in a precursor solution mixture for spin-casting. Off-diagonal peaks in the 2D spectra clearly establish the excitonic coupling between P3HT+ and F4TCNQ- ions in solution. The observed excitonic coupling is the direct manifestation of a Coulombic interaction between the ion pair. The excited-state lifetime of F4TCNQ- in ion pairs shows biexponential decay at 30 and 200 fs, which hints toward the presence of a heterogeneous population with different interaction strengths. To examine the nature of these different types of interactions in solution mixtures, we study the system using molecular dynamics simulations on a fully solvated model employing the generalized Amber force field. We retrieve three dominant interaction modes of F4TCNQ anions with P3HT: side chain, π-stack, and slipped stack. To quantify these interactions, we complement our studies with electronic structure calculations, which reveal the excitonic coupling strengths of ∼ 75 cm-1 for side chain, ∼ 150 cm-1 for π-π-stack, and ∼69 cm-1 for slipped stack. These various interaction modes provide information about the key geometries of the seed structures in precursor solution mixtures, which may determine the final structures in spin-casted films. The insights gained from our study may guide new strategies to control and ultimately tune Coulomb interactions in polymer-dopant solutions.

Structures and bonding characteristics of KCl(H2O)n clusters with n = 1-10 based on density functional theory.

Aqueous inorganic salt solutions play a prominent role in both physiological and chemical experiments, and significant attention has been directed toward understanding the mechanisms underlying salt dissolution. In our effort to elucidate the hydration process of potassium chloride, we employed a comprehensive genetic algorithm to explore the structures of KCl(H2O)n (n = 1-10). A series of stable structures were identified by high-level abinitio optimization and single-point energy calculations with a zero-point energy correction. An analysis of the probability distribution of KCl(H2O)1-10 revealed that clusters with high probability at low temperatures exhibit reduced probabilities at higher temperatures, while others become more prevalent. When n = 1-9, the contact ion pair configurations or partially dissociated structures dominate in the system, and the probability distribution plot shows that the proportion of the solvent-separated ion pair (SSIP) structures of KCl(H2O)n is very small, while the SSIP configuration in KCl(H2O)10 becomes a stable structure with increasing temperature. The results from natural bond orbital analysis reveal a stronger interaction between chloride ions and water molecules. These findings provide valuable insights for a more comprehensive understanding of the intricacies of potassium chloride dissolution in water.

Speciation and Organic Phase Structure in Nitric Acid Extraction with Trioctylamine.

Understanding chemical speciation and intermolecular interactions in multicomponent liquids is essential to understanding their phase and chemical equilibria, which underpin chemical separation processes, including solvent extraction. Here we report on the extraction of nitric acid from its aqueous solutions into organic solutions of trioctylamine (TOA) in toluene, investigated with spectroscopic, X-ray scattering, and computational tools to understand molecular speciation in the organic phase and its relationship with the nanoscale structure of the organic phase. Trends in acid and water extraction clearly show two and three regimes, respectively, indicating different stoichiometric relationships, but speciation of HNO3, water, and amine in these regimes is not apparent. 1H NMR of the organic phase shows that there are at least two distinct acidic protons in the organic phase while ATR-FTIR results show that the organic phase with excess acid extraction is a mixture of trioctylammonium-nitrate ion pairs (TOAH·NO3), and undissociated HNO3 molecules. Comparison with DFT-computed IR spectra show that the chain-like configurations of TOAH·NO3·HNO3·H2O are favored over TOAH·NO3·H2O·HNO3, i.e., direct interaction between the nitrate and HNO3 molecules is more favored compared to a water-mediated interaction. SAXS of the organic phases were modeled as sums of Ornstein-Zernike (O-Z) scattering and a prepeak feature in the higher Q region that corresponds to extractant packing. The extraction of undissociated HNO3 by the ion pairs leads to an increased X-ray scattering contrast in the organic phase without any significant change in the correlation length. These results show that the organic phase nanostructure is more sensitive to the concentration of TOAH·NO3 and is relatively unaffected by excess acid extraction. These findings will enable a molecular understanding of the mechanisms behind metal extraction from acidic media with basic extractants.

Anion Competition at Positively Charged Surfactant Monolayers.

Interactions of anions with hydrophobic surfaces of proteins and water-soluble polymers depend on the ability of the ions to shed their hydration shells. At positively charged surfactant monolayers, the interactions of anions are less well understood. Due to the interplay of electrostatic surface forces, hydration effects, and ion-ion interactions in the electrostatic double layer, a comprehensive microscopic picture remains elusive. Herein, we study the interactions of chloride, bromide, and a mixture of these two anions at the aqueous interface of dihexadecyldimethylammonium (DHDA+) and dioctadecyldimethylammonium (DODA+) cationic monolayers. Using molecular dynamics simulations and three surface-sensitive X-ray scattering techniques, we demonstrate that bromide interacts preferentially over chloride with both monolayers. The structure of the two monolayers and their interfacial electron density profiles obtained from the simulations quantitatively reproduce the experimental data. We observe that chloride and bromide form contact ion pairs with the quaternary ammonium groups on both monolayers. However, ion pairing with bromide leads to a greater reduction in the number of water molecules hydrating the anion, resulting in more energetically stable ion pairs. This leads to long-range (>3 nm) lateral correlations between bromide ions on the structured DODA+ monolayer. These observations indicate that ion hydration is the dominant factor determining the interfacial electrolyte structure.

β particles enhance the modulating lattice distortion of Mn-doped BiFeO3 and photo-responsive catalyzing of As(III) and Sb(III)

In this work, metal Mn was doped into BiFeO3(BFO) to modulate the lattice, and a high-energy β electron beam was used to irradiate the Mn-BiFeO3(BFMO) to produce lattice distortions, resulting in reducing the photogenerated carrier complexation rate of the material and improving the photocatalytic activity for arsenic and antimony. The physical properties of the BFMO with lattice distortion also produced some changes, with the Bi: O ratio on the surface decreasing from 1.0: 3.0–1.0: 1.6 and the band gap decreasing from 1.5 eV to 1.3 eV. In addition, the experiment results show that the structure of Bi-Mn-Fe-O can efficiently enhance the photocatalytic oxidation of As(III) and Sb(III) at different initial pH values, and the elimination rates of As(III) and Sb(III) can reach 100% and 79.9%, respectively. Characterization by PL, Mott-Schottky, transient photocurrent response, and DFT calculations demonstrated that BFMO-450 (irradiated at a dose of 450 KGy) has excellent charge mobility, which is conducive to the separation and transfer of photogenerated carriers. The XPS results showed that the BFMO-450 surface has optimal Mn4+/Mn2+ and Fe2+/Fe3+ ion pairs, and the formation of the Fe-Mn structure is favorable for the generation of superoxide radicals (·O2−, whereas the most prominent radicals in the photocatalytic process are the ·O2−, which was proved by the electron paramagnetic resonance (EPR) and bursting experiments. This study provides a novel approach to modifying BFMO composites and demonstrates that materials possessing lattice distortion have advantages in treating heavy metal-contaminated water.

Structural and Electronic Insights into 1-Ethyl-3-Methylimidazolium Bis(fluorosulfonyl)imide Ion Pair Conformers: Ab Initio DFT Study.

An understanding of the nature of molecular interactions among the ion pairs of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide [EMI[FSI]] can offer a starting point and significant insight into the more dynamic and multiple interactions within the bulk liquid state. In this context, close inspection of ion pair conformers can offer insight into the effects in bulk [EMI][FSI] liquid. The current work, therefore, gives a detailed analysis of the [EMI][FSI] ion pair conformers through analysis of the interaction energies, stabilization energies, and natural orbital of the ion pair conformers. The structures of the cations, anions, and cation-anion ion pairs of the conformers are optimized systematically by the ωB97X-D method with the DGDZVP basis sets, considering both the empirical dispersion corrections and the presence of a polar solvent, and the most stable geometries are obtained. The [FSI]- anions, unlike [TFSI]- anions, exist at the top position with respect to imidazolium rings. The presence of out-of-plane interactions between the [EMI]+ and [FSI]- ions is in good agreement with the stronger interactions of the [FSI]- anions with alkyl group hydrogens. The presence of out-of-plane conformers could also be related to the interaction of the anion with the π clouds of the [EMI]+ ring. In the [EMI]+ cation, the aromatic ring is π-acidic due to the presence of a positive charge in the N1-C1-N2 ring, which leads to the presence of [FSI]- anion donor [EMI]+ π-acceptor type interactions. The [EMI]+ cation and [FSI]- anions tend to form multiple σ* and π* interactions but reduce the strength of the individual contributions from a potential (linear) maximum. For the ion pair [EMI][FSI], the absolute value of the interaction energies is lower than the normal hydrogen bond energy (50 kJ/mol), which indicates that there is a very weak electrostatic interaction between the [EMI]+ cations and [FSI]- anions. The weaker attraction between the [EMI]+ and [FSI]- ions is suggested to contribute to the larger diffusion coefficients of the ions.

Ion Pairing Enables Targeted Prodrug Activation via Red Light Photocatalysis: A Proof-of-Concept Study with Anticancer Gold Complexes.

Photocatalysis has found increasing applications in biological systems, for example, in localized prodrug activation; however, high-energy light is usually required without giving sufficient efficiency and target selectivity. In this work, we report that ion pairing between photocatalysts and prodrugs can significantly improve the photoactivation efficiency and enable tumor-targeted activation by red light. This is exemplified by a gold-based prodrug (1d) functionalized with a morpholine moiety. Such a modification causes 1d to hydrolyze in aqueous solution, forming a cationic species that tightly interacts with anionic photosensitizers including Eosin Y (EY) and Rose Bengal (RB), along with a significant bathochromic shift of absorption tailing to the far-red region. As a result, a high photoactivation efficiency of 1d by EY or RB under low-energy light was found, leading to an effective release of active gold species in living cells, as monitored by a gold-specific biosensor (GolS-mCherry). Importantly, the morpholine moiety, with pKa ∼6.9, in 1d brings in a highly pH-sensitive and preferential ionic interaction under a slightly acidic condition over the normal physiological pH, enabling tumor-targeted prodrug activation by red light irradiation in vitro and in vivo. Since a similar absorption change was found in other morpholine/amine-containing clinic drugs, photocages, and precursors of reactive labeling intermediates, it is believed that the ion-pairing strategy could be extended for targeted activation of different prodrugs and for mapping of an acidic microenvironment by low-energy light.

Upconversion luminescence and temperature sensing performance of Zn2+-doped Ba2GdAlO5: Yb3+, Er3+ phosphors

Although upconversion luminescence (UCL) materials have attracted considerable attention in biomedical, lighting, anti-counterfeiting, and solar cells due to their excellent fluorescence properties, reports of the dibarium gadolinium aluminum oxide (Ba2GdAlO5) are scarce. Herein, we synthesized the single-phase Ba2GdAlO5 material with non-stoichiometric Ba2Gd1.06Al0.94O5 (denoted as BGAO, hereafter). The X-ray Rietveld refinement reveals that the substitution of Gd for Al accounts for the non-stoichiometry. Notably, the UCL properties of BGAO are realized by doping with Yb3+ and Er3+ ion pair, and it can be further enhanced significantly by co-doping with appropriate Zn2+ ions. The SEM images show that the particle size increases as the concentration of Zn2+ ions increases. The X-ray Rietveld refinement results of the Zn-doped BGAO: 0.1 Yb3+, 0.03Er3+ phosphor indicate the substitution of Zn2+ for Ba2+ and Al3+ ions simultaneously. Grain growth and lattice distortion account for the improvement of UCL properties after Zn2+ ions doping. In addition, the temperature sensing performance of the Zn2+-doped sample has been researched based on the fluorescence intensity ratio (FIR) technique, and the maximum absolute and relative sensitivities (SA-max and SR-max) are obtained to be 4.8 × 10−3 K−1 at 498 K and 1.1% K−1 at 298 K, respectively. This work provides a candidate with high UCL intensity for potential applications in optical temperature sensors.

Ion pair induced supramolecular assembly for development of novel pyridine 2, 6 diamide spacer acyl hydrazone-based derivatives for selective sensing of ZnCl2 and AlCl3

The work reports the development of a novel pyridine 2, 6 diamide spacer acyl hydrazone-based dual sensor H2L via two intermediates 1 and 2. The sensor as well as intermediates have been spectroscopically characterized. The structure of intermediate 1 is validated by its single crystal data analysis. As H2L bears both amide and acyl hydrazone moiety which have selective detection ability of anion and cation respectively, after rigorous characterization, the sensors are exposed to check their dual binding behavior. The results of several spectroscopic studies disclose the fact that H2L can optically and fluorometrically detect Al (III) and Zn (II) among several competitive cations and Cl− among competitive anions in semi-aqueous and aqueous medium respectively. Interestingly in a 9:1 DMSO-water medium, the probe can act as an ion pair sensor and in this medium, the probe can simultaneously detect Zn (II)/Cl- and Al (III)/Cl- forming H2L-ZnCl2, H2L-AlCl3 adduct. The 1:1 probe-analyte ion-pair binding is confirmed by NMR and mass spectral study. The Density Functional Theory (DFT) study optimizes the structures of the probe-analyte complexes. Impressively the probe has the potential to detect and quantify the Al (III) from market-available drug samples.

Modeling the alkylation of amines with alkyl bromides: explaining the low selectivity due to multiple alkylation.

Nucleophilic substitution reactions of aliphatic amines with alkyl halides represent a simple and direct mechanism for obtaining higher-order aliphatic amines. However, it is well known that these reactions suffer from low selectivity due to multiple alkylations, which is attributed to the higher reactivity of the newly formed amine. In order to provide a detailed explanation for this kind of system, we have investigated the reactivity of primary and secondary amines with 1-bromopropane and 2-bromopropane. The free energy profile in acetonitrile solution was obtained and a detailed microkinetic analysis was needed to analyze this complex reaction system. We have found that the product of the first alkylation is an ion pair corresponding to the protonated secondary amine and the bromide ion, which can transfer the proton to the reactant primary amine. Then, the newly formed secondary amine can also react, leading to a second alkylation to produce a tertiary protonated amine. Our modeling points out that both the proton transfer equilibria and the similar reactivity of the primary and secondary amines produce reduced selectivity. The proton transfer equilibria also contribute to slowing down the kinetics of the first alkylation. The exploration of the mechanism was done by geometry optimization using the CPCM/X3LYP/ma-def2-SVP method, followed by harmonic frequency calculation at this same level of theory. A composite approach was used to obtain the free energy profile, using the more accurate ωB97X-D3/ma-def2-TZVPP level of theory for electronic energy and the SMD model for the solvation free energy. These calculations were performed with the ORCA 4 program. The detailed microkinetic analysis was done using the Kintecus program.

Microfabrication and electrochemical behaviors of single microcrystal of copper-doped sodium chloride solid solution

Understanding the single-particle level of electrochemical processes taking place at the electrode/electrolyte interface is crucial for the rational development of high-performance and sustainable electrochemical microdevices. Based on scanning electrochemical cell microscope (SECCM) technology, copper-doped sodium chloride solid solution microcrystal was prepared in-situ and assembled into microdevices. In the process of synthesizing copper-doped sodium chloride solid solution, the redox behavior of Cu(II)-Cl system in the microelectrochemical cell was studied. The CV curve showed that the microdroplet contact between the microtubule and substrate was supersaturated, confirming the thin layer electrochemical response characteristics. By constructing the microcrystal between 2.5 µm spaced gold electrode pairs, the "solid" redox behavior of a single copper-doped sodium chloride microcrystal in the absence of electrolyte was studied. It is found that there is a well-resolved transformation between Cu(0), Cu(I) and Cu(II) in the microcrystal. It should be noted that the adsorbed water provides H+as a pair of ions, which plays an important role in the whole system. With the continuous progress of potential scanning, the solid-state CV curves of microcrystals gradually show semiconductor characteristics. This work presented herein is expected to promote the production of practical materials by SECCM and the practical application of on-site construction of electrochemical microsystem into all solid-state microdevices.

The impact of synergistic action of methacrylic acid/zinc oxide/carbon nanotubes on metal Friction and wear

The continuous operation of essential refining equipment, internal mixers, leads to wear on their end faces, resulting in an increased gap between the mixer chamber and the end face. This, in turn, causes material leakage, reducing mixing efficiency and adversely impacting rubber performance. Therefore, investigating metal wear on the mixer's end face during the mixing process is essential. Scholars have introduced dynamic covalent bonds into rubber molecular chains, bestowing self-repairing capabilities upon the materials. This innovation has significant implications for extending rubber lifespan and lowering production costs. It involves adding methacrylic acid (MAA) and excess zinc oxide (ZnO) to construct an ionic crosslinking network, limiting covalent crosslinking of rubber molecules and enabling in-situ polymerization of MAA/ZnO, resulting in self-repairing properties. However, it is crucial to consider corrosive wear induced by MAA's strong acidity on metals. This study combines MAA, ZnO, and multi-walled carbon nanotubes (MWCNTs) through mechanical mixing to create a composite material called zinc methacrylate (ZDMA)/MWCNTs/rubber. The research investigates the in-situ synthesis mechanism of MAA and ZnO and the synergistic mechanism of ZDMA and MWCNTs. The study analyzes the impact of MWCNTs additive amount on the frictional wear of the internal mixer's metal end face. During the mixing process, ZDMA is grafted and polymerized onto rubber's macromolecular chains, forming ionic pairs with strong electrostatic interactions, creating a primarily reversible supramolecular network dominated by ion crosslinking. This ion crosslinking network, along with the three-dimensional mesh structure of MWCNTs, establishes a stable spatial structure within the rubber matrix. The study reveals that increasing the MWCNTs content to 3 phr reduces the aggregation of SiO2 particles and ZDMA granules within the rubber matrix, resulting in reduced friction coefficients, roughness, and wear rates of the metal. However, exceeding 3 phr of MAA content leads to excessive MWCNT aggregation within the rubber matrix, increasing wear rates, roughness, and friction coefficients due to hindrance of rubber macromolecular chain crosslinking and reduced SiO2 particle dispersion within the rubber matrix. These findings provide valuable insights into the dynamics of frictional wear in internal mixers.

Dominant Solvent-Separated Ion Pairs in Electrolytes Enable Superhigh Conductivity for Fast-Charging and Low-Temperature Lithium Ion Batteries.

The low ionic conductivities of aprotic electrolytes hinder the development of extreme fast charging technologies and applications at low temperatures for lithium-ion batteries (LIBs). Herein, we present an electrolyte with LiFSI in acetone (DMK). In DMK electrolytes, the solvation number is three, and solvent-separated ion pairs (SSIPs) are the dominant structure, which is largely different from other linear aprotic electrolytes where salts primarily exist as contact ion pairs (CIPs). With incompact solvation structures due to the weak solvation ability of DMK with Li+, the ionic conductivity reaches 45 mS/cm at room temperature. The percentage of SSIPs increases as temperatures decrease in DMK electrolytes, which is totally different from the carbonate-based electrolytes but greatly beneficial to low-temperature ionic conductivity. With the appropriate addition of VC and FEC, DMK-based electrolytes still exhibit a superhigh ionic conductivity. Even at -40 °C, the ionic conductivity is greater than 10 mS/cm. With DMK-based electrolytes, LIBs with thick LiFePO4 electrodes can be cycled at high rates and at low temperatures.

Hybrid anionic block copolymerization: From organocatalysis‐streamlined crossover to internally microphase‐separated aggregates

AbstractPolyolefin‐b‐poly(ethylene oxide) (PEO) represents the most widely investigated amphiphilic block copolymers. So far, one‐pot continuous synthesis of such hybrid block copolymers has only been fulfilled by anionic polymerization through sequential addition of vinyl monomers and ethylene oxide (EO). It still remains challenging to achieve altogether high block efficiency, high polymerization efficiency, and high molar mass for PEO. Here, we report a one‐pot hybrid block copolymerization approach to polyisoprene/polystyrene(PI/PS)‐b‐PEO, in which PI/PS are formed by sBuLi‐initiated anionic vinyl‐addition polymerization, then in situ employed as macroinitiators for the anionic ring‐opening polymerization (ROP) of EO aided by an organic Lewis pair. The cooperative (dual‐ion‐complexing) catalytic effect of organobase and triethylborane is proven, for the first time, effective for lithium alkoxide initiator system, allowing to achieve at room temperature high ROP activity (complete EO conversion and PEO of 3–64 kg/mol reached in 1–6 h), narrow molar mass distribution, controlled block lengths and composition. Density functional theory calculation shows that phosphazene bases are particularly effective, compared with N‐heterocyclic bases, for complexing with Li+ and enhancing the nucleophilicity of oxyanion. The rate of ROP is also affected by Li+‐induced aggregation of the chain‐end ion pairs, which though can be offset by adequate catalyst loadings. The versatility of this approach is further demonstrated in the one‐pot synthesis of tri‐/tetrablock ter‐/quaterpolymers constituted by PI, PS, PEO, and poly(propylene oxide). Of great interest, PS‐b‐PI‐b‐PEO triblock terpolymer with a specific composition is found to form internally microphase‐separated micellar aggregates when dispersed in water.

Modulating fluorescent sensing of the pyrene-based ion pair receptor by docking on graphene quantum dots

We successfully synthesized squaramide-based ion pair receptor 3, possessing a cation binding domain linked to the receptor scaffold so as act as an electron-withdrawing group and enhance anion binding. This compound was able to efficiently and cooperatively bind anions in the presence of sodium cations. Using reference compounds 1 and 2, we demonstrated that the presence of a carbonyl group on the aromatic ring significantly enhances the efficiency of anion binding. The incorporation of this group in the structure of receptor 3, combined with other strongly electron-withdrawing groups located on another aryl subunit, enabled the receptor to bind salts even in the presence of water. Furthermore, the capacity for modular synthesis of diarylsquaramides allowed to obtain sensor 4, which features a pyrene moiety directly attached to the anion-binding domain, selectively sensing dihydrogen phosphate anions. Besides the signaling feature, the presence of pyrene rings facilitated the docking of sensor 4 onto the surface of graphene quantum dots, resulting in a conjugate with improved fluorescent properties.

Quantifying carboxymethyl lysine and carboxyethyl lysine in human plasma: clinical insights into aging research using liquid chromatography-tandem mass spectrometry

ObjectiveThe objective of this study was to establish a methodology for determining carboxymethyl lysine (CML) and carboxyethyl lysine (CEL) concentrations in human plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The test results were also used for clinical aging research.MethodsHuman plasma samples were incubated with aqueous perfluorovaleric acid (NFPA), succeeded by precipitation utilizing trichloroacetic acid, hydrolysis facilitated by hydrochloric acid, nitrogen drying, and ultimate re-dissolution utilizing NFPA, followed by filtration. Cotinine-D3 was added as an internal standard. The separation was performed on an Agela Venusil ASB C18 column (50 mm × 4.6 mm, 5 μm) with a 5 mmol/L NFPA and acetonitrile/water of 60:40 (v/v) containing 0.15% formic acid. The multiple reaction monitoring mode was used for detecting CML, CEL, and cotinine-D3, with ion pairs m/z 205.2 > 84.1 (for quantitative) and m/z 205.2 > m/z 130.0 for CML, m/z 219.1 > 84.1 (for quantitative) and m/z 219.1 > m/z 130.1 for CEL, and m/z 180.1 > 80.1 for cotinine-D3, respectively.ResultsThe separation of CML and CEL was accomplished within a total analysis time of 6 minutes. The retention times of CML, CEL, and cotinine-D3 were 3.43 minutes, 3.46 minutes, and 4.50 minutes, respectively. The assay exhibited linearity in the concentration range of 0.025–1.500 μmol/L, with a lower limit of quantification of 0.025 μmol/L for both compounds. The relative standard deviations of intra-day and inter-day were both below 9%, and the relative errors were both within the range of ±4%. The average recoveries were 94.24% for CML and 97.89% for CEL.ConclusionThe results indicate that the developed methodology is fast, highly sensitive, highly specific, reproducible, and suitable for the rapid detection of CML and CEL in clinical human plasma samples. The outcomes of the clinical research project on aging underscored the important indicative significance of these two indicators for research on human aging.

Building Water Models Compatible with Charge Scaling Molecular Dynamics.

Charge scaling has proven to be an efficient way to account in a mean-field manner for electronic polarization by aqueous ions in force field molecular dynamics simulations. However, commonly used water models with dielectric constants over 50 are not consistent with this approach leading to "overscaling", i.e., generally too weak ion-ion interactions. Here, we build water models fully compatible with charge scaling, i.e., having the correct low-frequency dielectric constant of about 45. To this end, we employ advanced optimization and machine learning schemes in order to explore the vast parameter space of four-site water models efficiently. As an a priori unwarranted positive result, we find a sizable range of force field parameters that satisfy the above dielectric constant constraint providing at the same time accuracy with respect to experimental data comparable with the best existing four-site water models such as TIP4P/2005, TIP4P-FB, or OPC. The present results thus open the way to the development of a consistent charge scaling force field for modeling ions in aqueous solutions.

Double-Model Decay Strategy Integrating Persistent Photogenic Radicaloids with Dynamic Circularly Polarized Doublet Radiance and Triplet Afterglow.

Organic phosphors integrating circularly polarized persistent luminescence (CPPL) across the visible range are widespread for applications in optical information encryption, bioimaging, and 3D display, but the pursuit of color-tunable CPPL in single-component organics remains a formidable task. Herein, via in situ photoimplanting radical ion pairing into axial chiral crystals, we present and elucidate an unprecedented double-module decay strategy to achieve a colorful CPPL through a combination of stable triplet emission from neutral diphosphine and doublet radiance from photogenic radicals in an exclusive crystalline framework. Owing to the photoactivation-dependent doublet radiance component and an inherent triplet phosphorescence in the asymmetric environment, the CPL vision can be regulated by altering the photoactivation and observation time window, allowing colorful glow tuning from blue and orange to delayed green emission. Mechanism studies clearly reveal that this asymmetric electron migration environment and hybrid n-π* and π-π* instincts are responsible for the afterglow and radical radiance at ambient conditions. Moreover, we demonstrate the applications of colorful CPPL for displays and encryption via manipulation of both excitation and observation times.