Van Der Waals Interactions Research Articles

Interaction of charged magnetic nanoparticles with surfaces

The behavior of magnetic nanoparticles covering the surface with positive charges (MN), suspended in a continuous medium, was simulated by Brownian dynamics. Then, we studied the behavior of the MN in an aqueous-like suspension and their adsorption on a negatively charged surface, mimicking a mica surface. After several microseconds, particles are deposited onto the charged surface. Experimental results of ordered magnetic nanoparticles in surfaces are compared with the present simulation results of MN in two dimensions. We also demonstrate the effect of charged MN on the hexagonal structure when electrical repulsions dominate against magnetic dipole-dipole and van der Waals attractions. On one hand, the adsorption of MN on the surface depends on the electrostatic attraction force with the surface, while the surface organization of MN results from balancing electrostatic repulsion forces and magnetic attraction forces among particles. In magnetic nanoparticles simulated with a non-charged surface or weakly charged surface, dipole-dipole interactions dominate the particle-particle interactions, and the interactions between particles and a mica-like surface are conducted by van der Waals forces.

Investigation of the interaction mechanism and enzyme activity of trypsin with cerium oxide nanoparticles

In this study, the interaction mechanism and native conformational variation of trypsin (Try) affected by CeO2 nanoparticles (NPs) were systematically studied via various spectroscopic methods. The results of fluorescence spectroscopy revealed that CeO2 NPs markedly quenched the endogenous fluorescence of Try via the mechanism of static quenching. The main forces that contributed to the binding of Try and CeO2 NPs were van der Waals forces, hydrogen bonds, and electrostatic forces, as observed by the binding constants and significant thermodynamic characteristics of the two substances. The incorporation of CeO2 NPs lead to a slight change in the structure of Try, as shown by synchronized fluorescence spectroscopy, three-dimensional fluorescence spectroscopy and circular dichroism (CD) spectroscopy. Moreover, the enzyme activity of Try decreased with the addition of CeO2 NPs. This study is highly important for fully evaluating the use of CeO2 NPs in biomedical sciences and is helpful for clarifying the mechanism between Try and CeO2 NPs at the molecular level.

Study of interfacial competitive distribution and synergistic permeation in nanofiltration separation of Salvia divinorum acids from the aqueous extract

The contact between solution and membrane during nanofiltration separation produces the interfacial layer fluid, and the competitive distribution laws of solutes in the interfacial layer are difficult to be analyzed, giving rise to diversified separation results that are challenging to explain using traditional nanofiltration separation theory. Four Salvia divinorum phenolic acid components—sodium salvinorin, protocatechuic aldehyde, rosmarinic acid, and salvianolic acid B—which have gradient relative molecular masses and dissociation constants, were selected as the objects of study. The nanofiltration separation parameters, such as membrane flux and permeation rate of the Salvia divinorum phenolic acids and their variability with the monomer solution under the complex solution environment were systematically analyzed. Based on the correlation between the concentration of the interfacial layer and the initial concentration, membrane flux and mass transfer coefficient in the theory of concentration polarization, the concentration of the interfacial layer of the nanofiltration membrane was calculated. This was combined with the state of association characterized by the distribution of particle sizes in the solution, the research model based on the ‘Associative State-Interfacial Competition-Separation Behavior’ was constructed, and the competitive and synergistic membrane separation regulations of the constituents of salvia phenolic acids were clarified. In acidic solutions, van der Waals forces dominate the interfacial competition, and of the four phenolic acids, salvinorin acid B diffused most easily to the membrane surface, showing that the component with the larger relative molecular mass inhibited the penetration of the smaller component; In alkaline solution, Coulomb force and Van der Waals force together dominate the interfacial competition, and the more acidic sodium salvinorin, etc., would preferentially react with hydroxide. At the same time, combined with the feature that the more molecular states in the particle size distribution of the solution are more likely to form aggregates, it was proven that the dissociation of protocatechuic acid aldehyde was inhibited, and its molecular state was more complete. It was shown that the more acidic sodium salvinorin and others facilitated the less acidic protocatechuic aldehyde to pass through the membrane.

Three-dimensional linker-promoted hierarchical porous metal–organic framework for natural gas purification

The purification of methane from natural gas is extremely important for industrial applications. In this study, hierarchical porous material LIFM-Z1 with microporous cages and mesoporous hexagonal one-dimensional channels was successfully synthesized and evaluated. The results show that LIFM-Z1 can effectively separate CH4 from the mixed gas containing CH4, C2H6, C3H8 and n-C4H10. Single-component adsorption experiments revealed the selective adsorption ability of LIFM-Z1 for C2H6, C3H8, and n-C4H10, enabling a clear distinction between these components and CH4. This selectivity was further verified by dynamic breakthrough experiments. Theoretical analysis shows that the interaction between LIFM-Z1 and gas molecules mainly depends on the synergistic effect of C–H⋯O hydrogen bond and C–H⋯C van der Waals force. The results highlight the potential of utilizing 3D linkers to enhance the inner wall interaction with CH4 and its related gases in MOF construction. These characteristics of LIFM-Z1 not only successfully demonstrate the potential of separation and purification of natural gas with high efficiency, but also show its broad application prospects in the actual natural gas processing.

Substituent Effect in Salicylaldehyde 2-Furoic Acid Hydrazones: Theoretical and Experimental Insights into DNA/BSA Affinity Modulation, Antimicrobial and Antioxidant Activity

The biological properties of five aroylhydrazones derived from salicylaldehyde and its 5-substituted derivatives with 2-furoic acid hydrazide were thoroughly investigated. NMR analysis confirmed the predominant existence of the aroylhydrazones in the keto-amine form in aqueous solution. Geometries of these compounds were optimized using density functional theory (DFT) calculations with the B3LYP hybrid functional, while ADMET analysis predicted their pharmacokinetic and toxicological properties. Substituent effects on the interactions between the salicyl aroylhydrazones and BSA and DNA were elucidated through experimental and molecular docking studies, revealing the bromo-substituted hydrazone as the most potent binder to both biomolecular targets. Experimental results aligned well with theoretical predictions, indicating that salicyl hydrazones predominantly act as DNA groove binders. Thermodynamic analysis suggested that the hydrazones predominantly interact with BSA through hydrogen bonding and van der Waals forces. Moreover, antioxidant potential assessment using DPPH, ABTS, FRAP, and metal chelating assays demonstrated the potent antioxidant power of nitro and hydroxy-substituted derivatives. Additionally, the antimicrobial properties of hydrazone against Gram-positive and Gram-negative bacteria, as well as fungi, were thoroughly explored, highlighting the nitro derivative as the most prominent candidate with broad-spectrum antimicrobial potential.

Exploring the binding characteristics between lorlatinib and human alpha-1-acid glycoprotein: Multispectral and molecular modeling techniques

Approval in 2019 was granted for the highly selective, targeted agent lorlatinib, which primary target is ROS1 and ALK. The purpose of this work was to examine the binding mechanism between lorlatinib (LOR) and HAG employing multispectral and molecular modeling techniques. Fluorescence data demonstrated that LOR quenched HAG fluorescence as a static quenching, interecalated into the hydrophobic cavity of HAG with a moderate affinity. Thermodynamic and competitive experiments pointed out that LOR bound with HAG primarily through hydrogen bonding, hydrophobic, and van der Waals forces. Circular dichroism, three-dimensional and synchronous fluorescence spectroscopic studies noted that the secondary structure of HAG and microenvironments around tyrosine (Tyr) and tryptophan (Trp) residues were altered due to binding with LOR. The contribution of each energy involved in binding process of LOR and HAG has been analyzed by molecular simulation techniques. Besides, the environmental conditions with metal ions have also been studied. The present study is expected to provide a theoretical basis for further studying the metabolism of LOR in vivo, which may help to gain a deeper understanding of the general pharmacological activity of the drug.

Polyphenol co-pigments enhanced the antioxidant capacity and color stability of blue honeysuckle juice during storage

The study aimed to assess the impact of incorporating five co-pigments (gallic acid, quercetin, rutin, catechin, and epigallocatechin gallate (EGCG)) on the color stability of blue honeysuckle juice (BHJ). Additionally, it sought to determine the influence of varying proportions of anthocyanins in an accelerated test (light at 40 °C for 24 d). Results indicated that the addition of polyphenol co-pigments effectively mitigated the thermal degradation of anthocyanins, enhancing color saturation and antioxidant capacity of BHJ. Notably, quercetin, rutin, catechin, and EGCG exhibited superior efficacy compared to gallic acid. FTIR analysis revealed non-covalent complex formation between co-pigments and anthocyanins, including hydrogen bonds and van der Waals forces, thereby shielding them from degradation. HPLC-ESI-QTOF-MS2 identified 15 anthocyanins and 39 non-anthocyanin polyphenols. Addition of co-pigments effectively curbed anthocyanin degradation, thus stabilizing juice system. Consequently, judicious incorporation of co-pigments holds promise as a technology for enhancing the color quality and stability of BHJ during processing.

Exploring Nano‐Protein Corona Dynamics: Tracing the Hard‐to‐Soft Corona Transition with Trypsin and Graphene Oxide in a Silver Nanocomposite Model

AbstractIn this work, the adsorption of Trypsin on synthesized Silver (Ag), Graphene Oxide: Silver (GO: Ag) nanocomposite (2:1), and Graphene Oxide (GO) nanoparticles (NPs) and, their effect on the conformation of Trypsin was studied by various spectroscopic and microscopic techniques to understand the transition of nano Protein Corona (PC) from “hard” to “soft.” The results showed that the adsorption of Trypsin on synthesized NPs followed the Freundlich adsorption isotherm and pseudo‐second‐order kinetics. The conformational changes that occurred in Trypsin upon interaction with synthesized NPs were investigated by using Circular Dichroism (CD), Fluorescence, and Fourier Transform Infrared (FTIR) spectroscopy. The morphological investigation of nano PC using High‐Resolution Transmission Electron Microscopy (HR‐TEM) and Atomic Force Microscopy (AFM) indicated the formation of hard, semi‐soft, and soft nano PC in the presence of Ag, GO: Ag, and GO NPs, respectively. The negative value of the thermodynamic parameters ΔG, ΔH, and ΔS in all three cases suggests the reaction to be exothermic and spontaneous. The van der Waals interaction and hydrogen bonding are the major forces responsible for binding Trypsin on the surface of Ag, GO: Ag, and GO. The catalytic efficiency of trypsin in the absence and presence of NPs was examined by performing the protein assay showing the highest catalytic activity of pure Trypsin compared with trypsin‐NPs constructs. Our findings provide useful information for the applications of GO‐based nanocomposites for various biological applications.

Theoretical exploration and experimental investigation of acidic deep eutectic solvents as green solvents to separate carbazole from model crude anthracene oil

Carbazole is a highly value-added compound derived from crude anthracene. Deep eutectic solvents (DESs) have been extensively used as promising green solvents for the separation of target compounds from mixture. In this work, 135 acidic DESs, formed by combining 9 quaternary ammonium salts with 15 common acids, were screened based on the conductor-like screening model for real solvents (COSMO-RS) model. The four top-ranked DESs, including tetraethylammonium chloride (TEAC)/2 acetic acid (AA), TEAC/2 propionic acid (PA), tetrapropylammonium chloride (TPAC)/2AA, and TPAC/2PA were identified as suitable extractants for carbazole separation based on their performance index (PI). Among them, TEAC/2AA had the best separation performance for carbazole due to its highest PI value (1448.19). Liquid–liquid extraction experiments were performed, and the results were in good accordance with those predicted by COSMO-RS calculations. Therefore, TEAC/2AA was determined as the most promising DES for the carbazole separation. The extraction conditions of TEAC/2AA were optimized. The extraction efficiency (EE) and selectivity (SE) of carbazole were 97.67 % and 66.64 %, respectively, under the optimal extraction conditions (25 ℃, 5 min of extraction time, DES-oil mass ratio of 1:5, initial carbazole concentration of 5000 ppm). Additionally, the deionized water was employed to regenerate the DES and recovery of carbazole. The recycling performance of promising DES was also investigated. Finally, quantum chemical calculations and Fourier Transform Infrared spectroscopy (FT-IR) analysis were conducted to explore the separation mechanism. The results indicated that the separation of carbazole by DESs were predominantly dominated by hydrogen bonds and van der Waals interaction. This work provided a valuable reference for the selection and design of DES extractants to separate other high value-added components from mixture.

Molecular dynamics study of shale oil adsorption and diffusion behavior in reservoir nanopores: Impact of hydrocarbon composition and surface type

Understanding shale oil adsorption in reservoir nanopores is essential for efficient extraction. This study used MD simulations to analyze the adsorption and diffusion of two- and multi-component hydrocarbons (Aromatics, Alkanes, Resin) on various shale surfaces (Calcite, Montmorillonite, Quartzite, Organic) at 353 K and 25 MPa. Hydrocarbons formed a bilayer adsorption structure comprising a high-concentration adsorption layer (L1, 0.35–0.90 g/cm3) and a low concentration weak adsorption layer (L2), with adsorption density ranked as Resin > Aromatics > Alkanes. Reservoir surfaces were classified as ionic (e.g., calcite, montmorillonite) and non-ionic (e.g., quartz, graphite), and polar hydrocarbons exhibited higher adsorption densities and energies on ionic surfaces due to combined electrostatic and van der Waals interactions, while non-ionic surfaces showed smaller adsorption differences. For multicomponent hydrocarbons, adsorption layer densities followed the order: graphite > MMT-SiO > quartz > calcite > MMT-Na, with competitive adsorption observed. The polar component exhibited a greater adsorption advantage on the calcite, MMT-SiO side and graphite surfaces due to electrostatic interactions and π-π interactions, and a lesser advantage on the MMT-Na side and quartz surfaces. Hydrocarbon diffusivity was influenced by molecular mass and polarity and ordered as Alkanes > Aromatics ≫ Resin. Polar molecules had a weaker diffusion than nonpolar molecules at similar molecular masses. Among the multicomponent hydrocarbons, the self-diffusion coefficient (Self-D) of Resin increased, while that of lighter components decreased compared to two-component systems. These findings offer strategies for improving shale oil recovery by tailoring injection fluids to reservoir types, anionic surfactants or chelating agents may be used to reduce electrostatic interactions in carbonate and clay reservoirs, while nonionic surfactants may be more effective in quartz reservoirs.

Identification of potential inhibitors against Corynebacterium diphtheriae MtrA response regulator protein; an in-silico drug discovery approach

Corynebacterium diphtheriae is a multi-drug resistant bacteria responsible for the life-threatening respiratory illness, diphtheria which can lead to severe Nervous system disorders, mainly infecting the lungs, heart, and kidneys if left untreated. In the current study, Corynebacterium diphtheriae MtrA response regulator protein was targeted, which regulates a two-component system of bacterial pathogenesis, and initiates DNA replication and cell division. In the current study a computational approach have been described for drug development against C. diphtheriae infections by inhibiting MtrA protein by small molecules acting as potential inhibitors against it. Molecular docking analysis of the equilibrated MtrA protein revealed compound-0.2970, compound-0.3029, and compound-0.3016 from Asinex Library as the promising inhibitors based on their lowest binding energies (−9.8 kJ/mol, −9.2 kJ/mol, and −8.9 kJ/mol), highest gold scores (40.53, 47.41, and 48.41), drug-likeness and pharmacokinetic properties. The MD simulation studies of the identified top-ranked inhibitors at 100 ns elucidated the system stability and fluctuations in the binding pocket of MtrA protein. Molecular Dynamics Simulations of the top three docked complexes further revealed that the standard binding pocket was retained ensuring the system stability. The rearrangements of H-bonds, van der Waals, pi-pi, and solid hydrophobic interactions were also observed. The binding free energy calculations (MM/PBSA and MM/GBSA) suggested a fundamental binding capability of the ligand to the target receptor MtrA. Therefore, the current study has provided excellent candidates acting as potent inhibitors for developing therapeutic drugs against C. diphtheriae infections. However, in vivo and in vitro animal experiments and accurate clinical trials are needed to validate the potential inhibitory effect of these compounds.

In vitro and in silico DNA interaction studies of a series of 3-carboxamide-4-quinolone derivatives prepared from an one-pot stepwise synthesis (OPSS) method

The 3-carboxamide-4-quinolone framework is highly regarded in the fields of Medicinal and Bioorganic Chemistry mainly due to its widespread bioactive properties. This versatile scaffold allows for the development of compounds with various pharmacological effects. In this sense, the present work explores a novel one-pot stepwise (OPPS) method for synthesizing fifteen 3-carboxamide-4-quinolone derivatives, some of which exhibit antitumor profiles in previous works. These compounds were synthesized using the OPPS methodology with yields ranging from 35 % to 88 %, streamlining the synthetic process and reducing solvent usage. Furthermore, interaction studies with calf-thymus DNA were done by UV–Vis absorption and steady-state fluorescence measurements combined with molecular docking calculations. Compounds 10a-b, 10d-g, 10k, and 10n were selected for the CT-DNA interaction assays, from which it was possible to demonstrate their DNA-binding property through peripheral secondary interactions. Molecular docking results suggested van der Waals and hydrogen bonds as the main binding forces responsible for the interactive profile between the nucleobases and the 3-carboxamide-4-quinolone derivatives. All these results unveiled promising insights into their role as DNA replication inhibitors, highlighting their potential in developing antiproliferative drugs.

Ammonium ion removal from contaminated water using Cikancra natural zeolite

Abstract Water quality in water bodies is deteriorating due to human activities such as industries, agriculture, and households. These activities have been reported to increase the levels of nitrogen species in water bodies, including ammonium (NH4 +). Various processes have been used to reduce NH4 + concentration in water, including adsorption and ion exchange using zeolite which is renowned as an excellent adsorbent and ion exchange material. In this study, we assessed the ability of Cikancra natural zeolite to reduce the NH4 + concentration in water. Heat pre-treatment was carried out on the zeolite to reveal its effect on the NH4 + removal rate. Furthermore, several factors such as contact time, grain size, and initial NH4 + concentration were evaluated to determine the optimum absorption condition. The experimental results reveal that heat-pretreated natural zeolite can reduce the NH4 + concentration by up to 84% after 60 minutes of contact time. Furthermore, the absorption capacity of the zeolite is reaching 2.37 mg/g at an initial NH4 + concentration of 50 mg/L. The evaluation using Freundlich and Langmuir isotherm models indicates that the process occurs physically due to Van Der Waals interaction between the adsorbate and the adsorbent.

Trifluoroacetyl peroxynitrate (CF3C(O)O2NO2, FPAN) degradation in wet atmosphere

Trifluoroacetyl peroxynitrate (FPAN) is the fluorinated analogue of PAN, proposed as a degradation intermediate of fluorinated compounds like CFC (chlorofluorocarbons) and their replacements. FPAN presents a longer atmospheric lifetime in comparison with the hydrogenated PAN. On the other hand, participation of water in atmospheric processes have received significant attention due to its potential impact on the stability of pollutants and chemical reactions. For example, the interaction between PAN and water by van der Waals interactions can lead to an increase in the degradation rate of PAN. The present work expands the knowledge about the stability of fluorinated peroxynitrates in wet atmosphere.The interaction between FPAN and water was studied from mixtures containing FPAN/H2O and FPAN/H2O/NO2 and monitored by infrared spectroscopy. The analysis of spectra reveals formation of CF3C(O)OH in both systems. Ab initio calculations were performed to explore the interactions at molecular level.Finally, a reaction mechanism is proposed considering the experimental evidence and theoretical calculations results. Rate coefficients for the formation of CF3C(O)OH were estimated using a kinetic software.

A Comprehensive Review on Co-Crystals: Transforming Drug Delivery with Enhanced Solubility and Bioavailability

Poor solubility and bioavailability of various drug compounds are the biggest challenges faced by researchers and industrialists, hindering their therapeutic efficacy. Researchers have developed a versatile approach to enhance the solubility and bioavailability of the drug i.e., co-crystallization. Pharmaceutical co-crystals are solid, crystalline materials consisting of API and co-formers that have supramolecular chemistry with one another. Co-crystallization helps in enhancing a drug’s physico-chemical properties, such as bioavailability, solubility and dissolution, preserving its therapeutic effect. The API and co-former in co-crystals are bound to each other via hydrogen bonding, π-stacking, and Van der Waals forces. Several methods to prepare co-crystals, such as solvent evaporation method, grinding method, cooling crystallization method, etc, and various research reports, including all the methods of preparation are discussed in this review article. Conventional marketed products and patents on co-crystals are also included. Data has been gathered, and relevant literature reports have been examined utilizing a variety of search engines, including Google Scholar, ScienceDirect, Pubmed, and Google patents. After reviewing the literature, the researchers found that the cocrystallization method is one the simplest method to enhance drug bioavailability and solubility. Moreover, it enhances the pharmacokinetics parameters, pharmacodynamics properties, and melting point of the drug. In this review article, the researchers have compiled the recent literature reports on enhanced drug solubility via co-crystallization method. The researchers concluded that this review article can help other researchers by providing them with recent literature on this article and can compare the various methods of enhancing drug solubility and bioavailability. It also consists of compiled data of patents and marketed formulations prepared by the co-crystallization technique. Thus, co-crystallization could be established as a versatile approach for enhancing drug solubility and bioavailability.

Eutectic molten salt assisted fabrication of microporous biochar for greenhouse gases adsorption

The utilization of eutectic molten salt technology has emerged as a prominent area of investigation aimed at fabricating a novel carbon material sorbent based on biomass wastes. The adsorption mechanism on CO2 adsorption remains inadequately elucidated as well. Herein, the biochar fabrication process involving eutectic molten salt method at intermediate-low temperature of 550 °C was successfully achieved and investigated in detail. The impacts of molten salt composition, monomer salt’s anion and cation, and pyrolysis parameters were firstly studied on the resulting microporous biochar of 1.8 nm pore diameter and 975 m2/g surface area. The optimized conditions are 550 °C, 15 °C min−1 ramp rate, 120 min holding time, Na+ cation, NO3– anion, and ternary salt KCl/NaNO3/Na2SO4 of 32.5/30.4/37.1. The efficient adsorbent exhibited abundant micropores and a substantial specific surface area, leading to enhanced CO2 adsorption quantity of 3.75 mmol/g (the calculated capacity is up to 4.54 mmol/g) at pressure state of 1.6 MPa. Investigation into key factors, adsorption kinetics, and adsorption isotherm revealed that CO2 capture by optimal adsorbent predominantly stemmed from micropore filling, van der Waals forces, hydrogen bonds, and Lewis acid-base interactions. This research contributes novel insights into the utilization of biochar adsorbents for CO2 capture in the realm of industry.

Unveiling the dynamic behavior of water molecules and subsequent kaolinite microstructure change during wetting: A large-scale molecular dynamics investigation

Direct experimental observation of water molecule trajectories and the corresponding evolution of kaolinite microstructure during wetting presents significant challenges. To overcome these limitations, this study utilizes a computational model replicating a large-scale flocculated kaolinite microstructure. Molecular dynamics (MD) simulations were employed to investigate the dynamic reconfiguration of the kaolinite network as water ingress progresses. Driven by van der Waals interactions and electrostatic forces, water molecules exhibit diffusive transport and preferential adsorption onto kaolinite particle surfaces. The orientation of water molecules constantly changes during the adsorption process on the gibbsite surface. Due to the difference in properties between gibbsite face and silica face, the dynamic behavior of water molecules flowing in the gibbsite-gibbsite pores, silica-silica pores and gibbsite-silica pores is also different. Driven by physicochemical interactions at the water-clay interface, kaolinite particles undergo rearrangement in their spatial disposition and orientation. This phenomenon induces a transition in the kaolinite packing structure from a flocculated to a dispersed state, ultimately leading to a reduction in the overall volume at macroscale. These observations illuminate the dynamic microstructural evolution of kaolinite particles and establish a foundation for future investigations into the impact of environmental variables on the volumetric contraction of collapsible soils.

Molecular recognition of an odorant by the murine trace amine-associated receptor TAAR7f

There are two main families of G protein-coupled receptors that detect odours in humans, the odorant receptors (ORs) and the trace amine-associated receptors (TAARs). Their amino acid sequences are distinct, with the TAARs being most similar to the aminergic receptors such as those activated by adrenaline, serotonin, dopamine and histamine. To elucidate the structural determinants of ligand recognition by TAARs, we have determined the cryo-EM structure of a murine receptor, mTAAR7f, coupled to the heterotrimeric G protein Gs and bound to the odorant N,N-dimethylcyclohexylamine (DMCHA) to an overall resolution of 2.9 Å. DMCHA is bound in a hydrophobic orthosteric binding site primarily through van der Waals interactions and a strong charge-charge interaction between the tertiary amine of the ligand and an aspartic acid residue. This site is distinct and non-overlapping with the binding site for the odorant propionate in the odorant receptor OR51E2. The structure, in combination with mutagenesis data and molecular dynamics simulations suggests that the activation of the receptor follows a similar pathway to that of the β-adrenoceptors, with the significant difference that DMCHA interacts directly with one of the main activation microswitch residues, Trp6.48.

Statistical physics of azo reactive dye adsorption by metal hydroxide sludge for water remediation

We performed a theoretical investigation of azo reactive red (RR-120) on metal hydroxide sludge (MHS) using five advanced statistical physics models to interpret thermodynamic equilibrium data for potential water remediation applications. Each model incorporates multiple physicochemical parameters to comprehensively describe the microscopic process through empirical data fitting. The thermodynamic functions (entropy, internal energy and Gibbs free energy) were analyzed using the grand canonical formalism. Our analysis indicated that the single-energy monolayer model represents the most realistic scenario. The adhesion of RR-120 onto MHS was endothermic with an adsorption energy below 40.0 kJ/mol suggesting that Van der Waals interactions and hydrogen bonding are the predominant driving forces. The stereographic analysis demonstrated that as the density of receptor sites (Nm) incremented, there was a corresponding decline in the number of anchored entities per site (n). Moreover, thermodynamic assessment revealed that the disorder increased before half-saturation and decreased after half-saturation while negativity of Gibbs free energy indicated a spontaneous process of RR-120 adsorption in all tested temperatures. The exceptional adsorption capabilities of MHS will open up new avenues in wastewater treatment, soil remediation and air purification.

Investigating the Structure of Defects in Heterometallic Zeolitic Imidazolate Frameworks ZIF-8(Zn/Cd) and Its Interaction with CO2 Using First-Principle Calculations

Inducing defect in metal-organic frameworks (MOFs) is one of the strategies to modify the structure and properties of this functional material. Defect may occur in a pristine MOF due to missing organic linkers, metal centres and/or other structural behaviours. In this study, the structure of defects in multicomponent MOFs especially heterometallic MOFs of zeolitic imidazolate framework (ZIF-8(Zn/Cd)) was examined to unveil the possible preference defect formation due to missing 2-methylimidazolate (MeIm) and metal centres of Cd2+ and Zn2+. Assuming defect formation due to the reaction between ZIF-8(Zn/Cd) and water, MeIm linker removal is energetically lower than removing metal centres of either Cd2+ or Zn2+. But, the MeIm linker is easier to be removed when it is connected to Cd2+ (Cd-MeIm-Cd) than when it is connected to Zn2+ (Zn-MeIm-Zn). Defect in ZIF-8(Zn/Cd) affects the band gap energy to give slightly lower value than it in pristine ZIF-8(Zn/Cd). Non-covalent interaction (NCI) and interaction region indicator (IRI) analyses were also performed to indicate possible intermolecular forces such as van der Waals and attractive forces present in non-defective and defective ZIF-8(Zn/Cd). The presence of defects in mixed-metal ZIF-8(Zn/Cd) was also tested for its potential use on CO2 adsorption. The interaction energy of CO2 inside defective ZIF-8(Zn/Cd) indicates an exothermic behaviour where CO2 molecule has a preference to be adsorbed inside the framework. This is especially when the capping agents at the defective ZIF-8(Zn/Cd) sites are removed to give open metal sites. This study provides insight how defects in multicomponent MOFs might presence affecting the structural and properties changes. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).