The Role of H‐bond in Solubilizing Drugs by Ionic Liquids: A Molecular Dynamics and Density Functional Theory Study

Revealing the Two-Stage Charging Process in Sulfuric Acid Electrolyte by Molecular Dynamics Simulation

Two-dimensional MXene materials perform excellently in supercapacitor applications, but self-stacking and overlap limit their applications. Constructing a reasonable layered structure by combining MXene and graphene can effectively inhibit the restacking and overlap of MXene and improve the performance of supercapacitors. In this work, we studied the energy storage performance of a conventional MXene electrode and MXene/graphene composite electrode in sulfuric acid aqueous electrolyte by molecular dynamics (MD) simulation and analyzed their energy storage mechanisms. The simulation results reveal that the MXene/graphene composite electrode showed faster charge-discharge speed and larger capacity and had more obvious advantages as a cathode. The charging process of the composite cathode can be divided into two stages. In the first stage, SO42- and H3O+ enter the electrode as a whole in a nearly 1:2 ratio, and a unique three-layer structure is formed in the graphene area, while a large number of HSO4- leaves the electrode. In the second stage, SO42- with a part of H3O+ (ratio of 2:2 to 2:3) leave the electrode, and the three-layer structure is gradually destroyed. The cooperation of these two stages leads to a particular "concave" in the total energy change of the composite cathode. The introduction of graphene has brought about changes in ion distribution, migration mechanism, and energy change, making the MXene/graphene cathode show significant advantages in energy storage. This work is of great significance for understanding the microscopic energy storage mechanism of MXene/graphene-based electrodes.

A novel theoretical strategy for predicting dissolution kinetics and mechanisms of pharmaceuticals in complex biorelevant media

The influence mechanism of biorelevant media on the dissolution of active pharmaceutical ingredients (APIs) is the key to their formulation design. The dissolution kinetics of naproxen (NAP) and indomethacin (IND) in biorelevant media was systematically investigated. The dissolution mechanism was analyzed by chemical potential gradient model to explore the influence of surfactant type, pH and ionic strength. Hexadecyl trimethyl ammonium bromide (CTAB) is superior to sodium dodecyl sulfate (SDS) in promoting the dissolution of NAP and IND by increasing the solubility and accelerating the surface reaction processes. The electrostatic repulsion between SDS and NAP and IND with the same negative charge facilitates the diffusion of API, while the mutual attraction between CTAB and NAP and IND is not conducive to diffusion. High pH was favorable for the dissolution of acidic NAP and IND, as the simultaneous increase in solubility, surface reaction constant, and diffusion constant. High ionic strength was beneficial for the surface reaction of NAP and IND, but hindered their diffusion. It was shown that the modeling results were in conformity with the in vitro experimental data. These results are expected to provide theoretical supports for the design of biorelevant media and pharmaceutical formulations in the pharmaceutical development.

Binding Study of Antibacterial Drug Ciprofloxacin with Imidazolium-Based Ionic Liquids Having Different Halide Anions: A Spectroscopic and Density Functional Theory Analysis

Herein, we have shown the interaction of an antibiotic drug ciprofloxacin (CIP) with three surface-active ionic liquids (ILs), having the same cation and different anions, namely, 1-decyl-3-methylimidazoliumtetrafluoroborate [C10mim][BF4], 1-decyl-3-methylimidazolium bromide [C10mim][Br], and 1-decyl-3-methylimidazolium chloride [C10mim][Cl]. This study has been performed by exploiting various spectroscopic techniques such as steady-state fluorescence, time-resolved fluorescence, and UV-visible spectroscopy. The fluorescence emission study of CIP with ILs was performed at various concentrations of all the three ILs. The emission spectra of CIP decreased in the presence of ILs, suggesting complex formation between CIP-IL. The effect of different concentrations of ILs on the emission spectra of CIP was exploited in terms of quenching and binding parameters. Further, fluorescence emission study was validated by the time-resolved fluorescence technique by measuring the average lifetime (τavg) of CIP in the presence of all the three ILs. The τavg value of the drug changed with the addition of ILs, which suggests complex formation between the drug and ILs. This complex formation was also confirmed by UV-visible spectroscopy results of CIP with all the three ILs. Further, for evaluating the thermodynamic parameters of the CIP-IL interactions, isothermal titration calorimetry (ITC) was performed. The ITC experiment yielded the thermodynamic parameters, ΔH (change in the enthalpy of association), ΔG (Gibbs free energy change), ΔS (entropy change), and binding constant (Ka). The binding parameters driven by ITC revealed that CIP-IL interactions are spontaneous in nature and enthalpy-driven, involving hydrophobic forces. Further, the classical density functional theory (DFT) calculations were performed, which provided deep insight for CIP-IL complex formation.

Evaluating ionic liquids for its potential as eco-friendly solvents for naproxen removal from water sources using COSMO-RS: Computational and experimental validation

An emerging contaminant of concern in aqueous streams is naproxen. Due to its poor solubility, non-biodegradability, and pharmaceutically active nature, the separation is challenging. Conventional solvents employed for naproxen are toxic and harmful. Ionic liquids (ILs) have attracted great attention as greener solubilizing and separating agent for various pharmaceuticals. ILs have found extensive usage as solvents in nanotechnological processes involving enzymatic reactions and whole cells. The employment of ILs can enhance the effectiveness and productivity of such bioprocesses. To avoid cumbersome experimental screening, in this study, conductor like screening model for real solvents (COSMO-RS) was used to screen ILs. Thirty anions and eight cations from various families were chosen. Activity coefficient at infinite dilution, capacity, selectivity, performance index, molecular interactions using σ-profiles and interaction energies were used to make predictions about solubility. According to the findings, quaternary ammonium cations, highly electronegative, and food-grade anions will form excellent ionic liquid combinations for solubilizing naproxen and hence will be better separating agents. This research will contribute easy designing of ionic liquid-based separation technologies for naproxen. In different separation technologies, ionic liquids can be employed as extractants, carriers, adsorbents, and absorbents.

Molecular Modelling of Ionic Liquids: Situations When Charge Scaling Seems Insufficient

Charge scaling as an effective solution to the experiment-computation disagreement in molecular modelling of ionic liquids (ILs) could bring the computational results close to the experimental reference for various thermodynamic properties. According to the large-scale benchmark calculations of mass density, solvation, and water-ILs transfer-free energies in our series of papers, the charge-scaling factor of 0.8 serves as a near-optimal option generally applicable to most ILs, although a system-dependent parameter adjustment could be attempted for further improved performance. However, there are situations in which such a charge-scaling treatment would fail. Namely, charge scaling cannot really affect the simulation outcome, or minimally perturbs the results that are still far from the experimental value. In such situations, the vdW radius as an additional adjustable parameter is commonly tuned to minimize the experiment-calculation deviation. In the current work, considering two ILs from the quinuclidinium family, we investigate the impacts of this vdW-scaling treatment on the mass density and the solvation/partition thermodynamics in a fashion similar to our previous charge-scaling works, i.e., scanning the vdW-scaling factor and computing physical properties under these parameter sets. It is observed that the mass density exhibits a linear response to the vdW-scaling factor with slopes close to -1.8 g/mL. By further investigating a set of physiochemically relevant temperatures between 288 K and 348 K, we confirm the robustness of the vdW-scaling treatment in the estimation of bulk properties. The best vdW-scaling parameter for mass density would worsen the computation of solvation/partition thermodynamics, and a marginal decrease in the vdW-scaling factor is considered as an intermediate option balancing the reproductions of bulk properties and solvation thermodynamics. These observations could be understood in a way similar to the charge-scaling situation. i.e., overfitting some properties (e.g., mass density) would degrade the accuracy of the other properties (e.g., solvation free energies). Following this principle, the general guideline for applying this vdW-tuning protocol is by using values between the density-derived choice and the solvation/partition-derived solution. The charge and current vdW scaling treatments cover commonly encountered ILs, completing the protocol for accurate modelling of ILs with fixed-charge force fields.