Van Der Waals Interactions Research Articles

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).

ANN based optimization of nano-beam oscillations with intermolecular forces and geometric nonlinearity

In this study, we investigate the effect of Van der Waals and Casimir forces on the mathematical model of nano-electromechanical systems (NEMS) such as nano-beam actuators that contain cantilever and double cantilever beams. The singular nonlinear boundary value problem governing the beam-type actuators, including geometric nonlinearity is solved by using an intelligent strength of feedforward artificial neural networks (ANNs) and hybridization of optimization algorithms such as arithmetic optimization algorithm (AOA) and active set algorithm (ASA). The proposed ANN-AOA-AS algorithm is employed to quantify the effect of changes in applied voltage, dispersion forces, geometric nonlinearity parameters, and initial axial strain on the deflection of the beam. Furthermore, to validate the results obtained by the proposed algorithm, statistical analyses are conducted to compare the approximate solutions with state-of-the-art methodologies available in the latest literature. In addition, performance indicators are defined such as mean square error (MSE), Nash–Sutcliffe efficiency (NSE), mean absolute deviations (MAD), root mean square error (RMSE), and Error in Nash–Sutcliffe efficiency (ENSE) to study the accuracy and efficiency of the solutions. The results show that these indicators’ mean percentage values lie around 10−4 to 10−6 which reflects the perfect modeling of the approximate solutions.

Reorientation of interfacial water molecules during melting of brain sphingomyelin is associated with the phase transition of its C24:1 sphingomyelin lipids

Melting of brain sphingomyelin (bSM) manifests as a broad feature in the DSC curve that encompasses the temperature range of 25 – 45 °C, with two distinguished maxima originating from the phase transitions of two the most abundant components: C24:1 (Tm,1) and C18:0 (Tm,2). While C24:1/C18:0 sphingomyelin transforms from the gel/ripple phase to the fluid/fluid phase, the dynamics of water molecules in the interfacial layer remain completely unknown. Therefore, we carried out a calorimetric (DSC), spectroscopic (temperature-dependent UV-Vis and fluorescence) and MD simulation study of bSM in the absence/presence of Laurdan® (bSM ± L) suspended in Britton-Robinson buffer with three different pH values, 4 (BRB4), 7 (BRB7) and 9 (BRB9), and of comparable ionic strength (I = 100 mM). According to DSC, T̅m, 1 (≈ 34.5 °C/≈ 32.1 °C) and T̅m, 2 (≈ 38.0 °C/≈ 37.2 °C) of bSM suspended in BRB4, BRB7, and BRB9 in the absence/presence of Laurdan® are found to be practically pH-independent. Turbidity-based data (UV-Vis) detected both qualitative and quantitative differences in the response of bSM suspended in BRB4/BRB7/BRB9 (T̅m: ∼ 35 °C/32.0 ± 0.2 °C/36.4 ± 0.4), suggesting an intricate interplay of weakening of van der Waals forces between their hydrocarbon chains and of increased hydration in the polar headgroups region during melting. The temperature-dependent response of Laurdan® reported a discontinuous, pH-dependent change in the reorientation of interfacial water molecules that coincides with the melting of C24:1 lipids (on average, T̅m (LTC/HTC): ≈ 31.8 °C/30.6 °C/30.5 °C). MD simulations elucidated the impact of Laurdan® on a change in the physicochemical properties of bSM lipids and characterized the hydrogen bond network at the interface at 20 °C and 50 °C.

Synergistic effect of bonding heterogeneity and phonon localization in introducing excellent thermoelectric properties in layered heteroanionic NdZnSbO material

Layered rare-earth metal oxides, harnessing the dual properties of oxides and two-dimensional layered materials, exhibit remarkable thermal stability and quantum confinement effects. Therefore, this work adopts the first-principles calculation combined with the Boltzmann transport theory to predict the thermoelectric properties of NdZnSbO compound. The coexistence of weak interlayer van der Waals interactions, robust intralayer ionic bonding, and partial covalent bonding leads to remarkable bonding heterogeneity, which engenders pronounced phonon scattering and imposes constraints on thermal transport along the out-of-plane direction. The weakened chemical bonds induced by the antibonding states, together with the rattling-like behavior of the Zn atom, culminate in the profound anharmonicity in the layered NdZnSbO compound. The weakening bond and heavy element contribute to the softness of phonon modes, which significantly diminishes the phonon group velocity. The redistribution-dominated four-phonon scattering process spans a large optical gap, which effectively reduces the lattice thermal conductivity. The NdZnSbO compound exhibits direct semiconductor characteristic with a bandgap of 0.73 eV by adopting the Heyd-Scuseria-Ernzerhof (HSE06) functional in combination with spin–orbit coupling (SOC) effect. The multi-valley feature of NdZnSbO compound augur favorably for band degeneracy, thus amplifying the power factor. Consequently, an optimal figure-of-merit (ZT) of 3.40 at 900 K is achieved for the n-type NdZnSbO compound. The present study delves deeply insights into the origins for the low thermal conductivity of NdZnSbO compound and proposes an optimization scheme to enhance overall thermoelectric performance.

Constructing binuclear sites to modulate the charge distribution of MIL-101 for enhanced toluene adsorption performance: experimental and theoretical studies

Toluene is a class of volatile organic compounds (VOCs) in the air that harm environmental quality and human health. To enhance the adsorption performance of adsorbents for toluene, based on the principle that unsaturated metal sites in MOFs can be replaced, nanoscale M@MIL-101(M represents Mg, Ca, Sr) with binuclear sites was prepared by a one-step solvothermal method. The second metal was successfully introduced into the topology of MIL-101 by partially substituting Cr sites. The results of the dynamic adsorption experiments showed that 20%Sr@MIL-101 exhibited the highest toluene adsorption capacity, which was about 60% higher than that of the undoped MIL-101. Analysis using a monolayer and multilayer model based on statistical physics theory indicated that the Sr/Cr binuclear sites could enhance the interaction strength of the adsorption system, promoting the adsorption of more layers of toluene molecules on the surface of MIL-101. Characterization and simulation together confirmed that constructing Sr/Cr binuclear sites in MIL-101 can cause significant redistribution of charge within the pores, enhancing the van der Waals interactions, π-π stacking interactions, hydrogen bonding, and Lewis acid-base interactions between the pore interior and the adsorbate molecules. Additionally, density functional theory (DFT) revealed that the adsorption sites of toluene in MIL-101 were distributed in a trigonal prism arrangement and were symmetrically aligned with a 180° rotation of the MIL-101 triangular cage.

Self-assembled belt[12]pyridine nanotube for the adsorption and removal of anti-TB drugs from wastewater

Environmental safety is a major concern of today's world, and it has attracted the attention of the scientific research community. The environment gets contaminated due to various toxic drugs and pharmaceutical toxins coming from different sources. Therefore, removing these toxins is necessary for making the environment greener and safer. Nanomaterials are excellent candidates for adsorption and removal of harmful materials due to their unique properties. Herein we have studied self-assembled nanotube based on belt[12]pyridine (2-(12BPy)) as an adsorbent for the removal of antituberculosis drugs i.e. isoniazid (INZ) and pyrazinamide (PZA). The adsorption ability is studied by considering the adsorption energy (Eads), non-covalent interaction index analysis (NCI), quantum theory of atoms in molecules (QTAIM), energy decomposition analysis (EDA), charge transfer via natural bond orbital analysis (NBO) and electron localization function (ELF), and dipole moment. The results indicate strong adsorption of selected drugs with self-assembled nanotube without altering the electronic properties. Recovery time of the complexes is also calculated to understand the regeneration of the nanotube. Results also demonstrate that van der Waals forces are major contributor in the adsorption of drug molecules within the nanotube. Our results indicate that belt[12]pyridine (2-(12BPy)) nanotube can be used as an adsorbent for the removal of toxic drug molecules from the environment. This research will benefit the scientists working in the field of new sensors for biological components and materials.

CO2 adsorption on 3d transition metal-alloyed Pt clusters supported on pyridinic N-doped graphene

CO2 adsorption on Pt4 and on Pt2M2 (M = Co, Ni, and Cu) clusters supported on N-doped graphene (PNG) was analyzed using density functional theory. The Pt2M2 (M = Co, Ni) clusters supported on PNG had the maximum binding energy and charge transfer. Furthermore, the adsorption energy and charge transfer of CO2 were high for Pt2M2 (M = Co, Ni, and Cu) supported on PNG. In addition, bond elongation and bending angle were observed in the CO2 molecule after it was adsorbed on metal clusters supported on PNG. Non-covalent interaction contours revealed a repulsive interaction due to the steric effect between Pt2M2 (M = Co, Ni, and Cu) and PNG, whereas the Pt4/PNG composite showed a combination of repulsive and van der Waals interactions. This investigation proved that Pt2M2 (M = Co, Ni, and Cu) clusters supported on PNG are promising candidates for CO2 adsorption and activation.

Investigation of antitumor activity and albumin interaction of new sulfosalicylate-based complex by spectroscopic and computational approaches.

In the present study, the drug delivery by albumin protein and antiproliferetaive activity of new transition metal complex i.e., [Pd (phen)(SSA)] (where phen and SSA represent 1, 10 phenanthroline and sulfosalicylic acid, respectively) was investigated. DFT (density functional theory) calculations were conducted at B3LYP level with 6-311G(d,p)/aug-ccpVTZ-PP basis set for the purpose of geometry optimization, frontier molecular orbital (FMO) analysis, molecular electrostatic potential (MEP), and natural bond orbital (NBO) analysis. Experimental tests were conducted to preliminarily assess the lipophilicity and antitumor activity of the metal complex, resulting in promising findings. In-silico prediction was accomplished to assess its toxicity and bioavailability. To evaluate the binding of the newly formed complex with DNA (which results in halting the cell cycle) or serum albumin protein (drug transporter to the tissues), in-silico molecular modeling was employed. Experimental results (spectroscopic and non-spectroscopic) showed that the new compound interacts with each biomolecule via hydrogen bond and van der Waals interactions. Molecular docking demonstrated the binding of this complex to the DNA groove and site I of BSA occurs mainly through hydrogen bonds. Molecular dynamics simulation confirmed the interactions between [Pd (phen)(SSA)] with DNA or BSA through stable hydrogen bonds.

Synthesis, Crystal Structure, and Theoretical Screening of Solvatochromism and Light-Harvesting Performance of Hexamine V-Substituted Lindqvist-Based Photosensitizer for Photovoltaic Solar Cells.

In this paper, we employ density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches to predict the solvatochromism and light-harvesting properties of a newly synthesized hybrid hexamine (HMTA) vanadium-substituted Lindqvist-type (V 2 W 4 ) polyoxometalate (POM), (C7H15N4O)2(C6H13N4)2[V2W4O19]·6H2O, (HMTA-V 2 W 4 ) for application in dye-sensitized solar cells (DSSCs). Single crystal X-ray diffraction (XRD) and noncovalent interaction (NCI) analyses show a 3D-supramolecular packing stabilized by means of hydrogen bonds and van der Waals (vdW) and ionic interactions between highly nucleophilic cage-like HMTA surfactant, lattice water, and electrophilic V 2 W 4 polyanions. Experimental and theoretical UV/vis absorption spectra show large absorption in the visible region, which is strongly solvent polarity dependent. This solvatochromic behavior can be attributed to hydrogen bonding interactions between the V 2 W 4 polyanion and protic solvents. Furthermore, the energy level of semiconductor-like nature of HMTA-V 2 W 4 with high LUMO level matches well with the conduction band (CB) of TiO2, which is beneficial for the photovoltaic device performance. The photovoltaic empirical parameters are theoretically predicted to demonstrate a remarkably high open-circuit voltage (Voc) value (1.805 eV) and a photoelectric conversion efficiency (PCE) value up to 8.7% (FF = 0.88) along with superior light-harvesting efficiency (LHE) (0.7921), and therefore, the studied compound is expected to be a potential candidate as a photosensitizer dye for applications in DSSCs. The aim of this work was to broaden the range of applications of POMs, owing to their low-cost fabrication, leveraging and flourishing optoelectronic properties, and ever-improving efficiency and stability for use in future technology pointed to the development of clean and green renewable energy sources to solve the current energy crisis.

A dual growth mode unique for organic crystals relies on mesoscopic liquid precursors

Organic solvents host the synthesis of high-value crystals used as pharmaceuticals and optical devices, among other applications. A knowledge gap persists on how replacing the hydrogen bonds and polar attraction that dominate aqueous environments with the weaker van der Waals forces affects the growth mechanism, including its defining feature, whether crystals grow classically or nonclassically. Here we demonstrate a rare dual growth mode of etioporphyrin I crystals, enabled by liquid precursors that associate with crystal surfaces to generate stacks of layers, which then grow laterally by incorporating solute molecules. Our findings reveal the precursors as mesoscopic solute-rich clusters, a unique phase favored by weak bonds such as those between organic solutes. The lateral spreading of the precursor-initiated stacks of layers crucially relies on abundant solute supply directly from the solution, bypassing diffusion along the crystal surface; the direct incorporation pathway may, again, be unique to organic solvents. Clusters that evolve to amorphous particles do not seamlessly integrate into crystal lattices. Crystals growing fast and mostly nonclassically at high supersaturations are not excessively strained. Our findings demonstrate that the weak interactions typical of organic systems promote nonclassical growth modes by supporting liquid precursors and enabling the spreading of multilayer stacks.

Enhanced adsorption of lung cancer biomarkers using Biphenyl-Derived quantum dots

This study explores the interaction between biphenyl quantum dot (BP-B2B1) and lung cancer biomarkers (LCBs), specifically methanal, ethanal, and propanal. The investigation involves optimizing the structures of BP-B2B1 and its doped variants (with B, N, O, P, S, and Si) to assess their stability and electronic properties. Natural bond orbital (NBO) analysis reveals significant charge transfer from BP-B2B1 and its doped forms to the LCBs upon adsorption, indicating enhanced interaction. Optical properties are examined through shifts in absorption spectra and excited states, showing that doping affects the electronic structure and interaction with LCBs. Non-covalent interaction (NCI) analysis provides insights into the nature of the interactions, identifying predominant van der Waals forces between BP-B2B1 and the LCBs. The results demonstrate that dopants enhance the binding and electronic response of BP-B2B1 to LCBs, highlighting its potential for use in biosensing applications for lung cancer detection.

Interfacial heat transport properties of graphene/natural rubber composites studied based on molecular dynamics approach

The interface between graphene and natural rubber significantly impacts the thermal properties of graphene/natural rubber composites. This paper uses molecular dynamics to investigate interfacial heat transport. The study found that the thermal conductivity of the composites increases non-linearly with graphene content: a 136 % increase at 10.5 % graphene and only 12.23 % at 16.4 % graphene. As graphene content increases, graphene agglomerates within the natural rubber due to weak van der Waals forces. The interfacial thermal resistance of the composites increases with temperature, rising by 69.94 % from 200K to 450K. When pressure increases from 0.1 MPa to 2.5 MPa, the maximum change in interfacial thermal resistance is 24.39 %. The study also found that interfacial thermal resistance increases with the number of graphene layers. Thus, the interfacial thermal resistance between graphene and natural rubber is the main reason for the minor change in the thermal conductivity of the composites, with temperature having a greater impact.

Isoreticular Metal-Organic Frameworks with Aromatic Pores and Dimethylammonium Cations Enable Separation of Light Hydrocarbons and Xenon/Krypton.

The separation of C2-C3 hydrocarbons from methane in natural gas and xenon/krypton purification are crucial yet challenging industrial processes. Herein, we report two isoreticular metal-organic frameworks, ZJU-89 and ZJU-90, featuring aromatic pore environments and dimethylammonium cations, that synergistically enhance the separation of these industrially relevant gas mixtures. ZJU-90 exhibits an exceptional separation performance, achieving C3H8/CH4 and C2H6/CH4 ideal adsorbed solution theory (IAST) selectivities of 1065 and 48, respectively, at ambient conditions, outperforming most reported adsorbent materials. Remarkably, ZJU-90 enables the recovery of >99.95% purity methane from a C3H8/C2H6/CH4 mixture in a single adsorption step. The material also demonstrates the efficient separation of xenon from krypton, even at low concentrations. The superior performance stems from the aromatic rings decorating the pore walls and the free dimethylammonium cations in the channels, which provide an ideal chemical environment for the selective binding of C2H6, C3H8, and Xe through multiple C-H···π interactions and van der Waals forces, as elucidated by theoretical calculations. This work highlights the power of reticular chemistry in designing materials with synergistic pore environments for efficient separations.

Enhancing the inhibitory activities of polyphenols in passion fruit peel on α-Amylase and α-Glucosidase via β-Glucosidase-producing Lactobacillus fermentation

Passion fruit peel contained various phenolic compounds with α-glucosidase and α-amylase inhibitory activities in vitro. However, the bound state and glycosylated forms hindered their active expression. In this article, β-glucosidase-producing Lactobacilli were inoculated into fermented peels for targeted metabolism. The results showed that the release of bound polyphenols and the increase of free polyphenols were significantly correlated with β-glucosidase activity. The strain G1 with high enzyme activity degraded 48.20% of the bound polyphenols after 24 h. The ability of extracts to inhibit α-glucosidase and α-amylase activities was significantly enhanced and closely related to the content of free polyphenols (r = −0.96 and −0.88, P < 0.001). Computer-assisted screening identified 38 phenolic compounds as potential dual inhibitors of α-glucosidase and α-amylase. Among them, 22 α-glucosidase inhibitors and 24 α-amylase inhibitors were identified for the first time. Various inhibitors, including phenolic acids, flavones, and flavonols, increased in content after fermentation. The total content of 14 glycosylated polyphenols decreased to 28.38% at 48 h, which was opposite to the aglycone. Molecular docking indicated that glycosylated polyphenols bind to β-glucosidase through hydrogen bonds and van der Waals forces. Different glycosylations at the C-3 position of quercetin bound at same sites to β-glucosidase. This study contributes to the theory of enhancing the functional activity of natural products through targeted fermentation transformation.

Light exposure of tetra-cationic porphyrins containing peripheral Pd(II)-bipyridyl complexes and the induced effects on purified DNA molecule, fibroblast and melanoma cell lines.

Photodynamic therapy (PDT) combines a light source, oxygen, and a photosensitizer (PS) to generate reactive oxygen species (ROS) for treating diseases. In this study, we evaluated two meso-tetra-pyridyl porphyrins with [Pd(bpy)Cl]+, namely 3-PdTPyP and 4-PdTPyP, as PS for PDT application. DNA interaction was assessed by spectroscopic measurements (UV-Vis and fluorescence emission), viscosity analysis, and molecular docking simulations. The results indicate that Pd(II)-porphyrins do not intercalate into DNA, suggesting that the minor groove is the primary interaction site, mainly through van der Waals forces. These metalloporphyrins effectively induced nitrogenous bases oxidation, particularly in purines, after white light irradiation. The induced DNA lesions were able to inactivate plasmid DNA metabolism (DNA replication and transcription) in a bacterial model. 3-PdTPyP and 4-PdTPyP significantly decreased the viability of treated melanoma cell lines (A375 and B16-F10), demonstrating that melanoma cell lines were more sensitive to these Pd(II)-porphyrins than the fibroblast cell line (L929). Moreover, 3-PdTPyP was more photototoxic to A375 cells (IC50 = 0.43 μM), whereas 4-PdTPyP was more photototoxic to B16-F10 cells (IC50 = 0.51 μM). These findings suggest that these porphyrins are promising PS for future PDT research focused on skin cancer.

Time-dependent underwater interaction between polyhydroxyalkanoate coatings and functionalized surfaces

Polyhydroxyalkanoates (PHAs), a family of naturally occurring biodegradable polyester, are considered environmentally friendly alternatives to conventional commodity plastics derived from petrochemicals.; however, their molecular interaction in water has not been elucidated. Here, we investigated the surface- and contact time-dependent underwater interaction characteristics of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)), the most common PHA, using a surface forces apparatus (SFA). We found that PHA showed weak adhesion with functionalized surface and cohesion for a short-contact time (<30 mins) in the water. The adhesion to the functionalized surface was strong in the order of mica (negatively charged hydrophilic), APTES (positively charged hydrophilic), and PS (hydrophobic). However, the adhesive strength of PHA to the functionalized surfaces increased as contact time increased, which may be attributed to chain rearrangement, reorientation, or van der Waals forces of PHA in water. We also confirmed results similar to those for SFA by bulk testing on hydrophilic surfaces. As PHAs have attracted people’s attention as eco-friendly and biocompatible polymers, these results provide insights for the development of PHA-based composite, as well as for the biodegradation and fate of PHA post-use.

Molecular and Energetic Descriptions of the Plasma Protein Adsorption onto the PVC Surface: Implications for Biocompatibility in Medical Devices.

Protein adsorption on material surfaces plays a key role in the biocompatibility of medical devices. Therefore, understanding the complex interplay of physicochemical factors driving this kind of biofouling is paramount for advancing biomaterial design. In this study, we investigated the interaction of the most prominent plasma proteins with polyvinyl chloride (PVC) as one of the ubiquitous materials in medical devices. Through molecular docking, we identified human serum albumin (HSA) as a plasma protein with the highest affinity for adsorption onto the PVC surface with the binding energy of -25.9 kJ mol-1. Subsequently, utilizing triplicate molecular dynamics (MD) simulations (0.5 μs each), we quantitatively analyzed the interactions between HSA and PVC, probing potential structural changes in the protein upon adsorption. Our findings revealed that water-mediated hydrogen bonds and van der Waals forces are key contributors in stabilizing HSA onto the surface of PVC without significant alteration to its secondary and tertiary structures. The observed distribution of water molecules further highlights the importance of the hydration layer in facilitating and modulating protein-polymer interactions. We further evaluated the thermodynamic properties governing the adsorption process by calculating the potential of mean force (PMF) along the direction normal to the surface. The computed Gibbs free energy of adsorption at 300 K (-507.4 kJ/mol) indicated a thermodynamically favored and spontaneous process. Moreover, our investigations across different temperatures (290 to 310 K) consistently showed an enthalpy-driven adsorption process.

Theory of electrotuneable mechanical force of solid-liquid interfaces: A self-consistent treatment of short-range van der Waals forces and long-range electrostatic forces.

Elucidating the mechanical forces between two solid surfaces immersed in a communal liquid environment is crucial for understanding and controlling adhesion, friction, and electrochemistry in many technologies. Although traditional models can adequately describe long-range mechanical forces, they require substantial modifications in the nanometric region where electronic effects become important. A hybrid quantum-classical model is employed herein to investigate the separation-dependent disjoining pressure between two metal surfaces immersed in an electrolyte solution under potential control. We find that the pressure between surfaces transits from a long-range electrostatic interaction, attractive or repulsive depending on the charging conditions of surfaces, to a strong short-range van der Waals attraction and then an even strong Pauli repulsion due to the redistribution of electrons. The underlying mechanism of the transition, especially the attractive-repulsive one in the short-range region, is elucidated. This work contributes to the understanding of electrotunable friction and lubrication in a liquid environment.

Synergetic studies on the influence of the integrated cellulose on the adsorption of selenite and selenite by cellulose/phillipsite composite: Steric and energetic assessments

Natural zeolite of the phillipsite phase was integrated into biocomposite with cellulose fibers (CF/Ph) and characterized as an effective and environmental adsorbent for both selenite (Se (IV)) and selenate (Se (VI)). The retention studies were performed based on the experimental factors in addition to both classic and advanced equilibrium modeling. The composite showed enhanced retention properties for both Se (IV) (196.4 mg/g) and Se (VI) (144.7 mg/g) as compared to raw phillipsite (Se (IV) (142.13 mg/g) and Se (VI) (113 mg/g)) and cellulose (Se (IV) (42.5 mg/g) and Se (VI) (6.4 mg/g)). Based on the synergetic parameters, the integration process enhanced the quantities of the existing active sites at a considerable rate (Nm = 57.3 mg/g (Se (IV)) and 48 mg/g (Se (VI))) as compared to phillipsite and cellulose. The number of the two adsorbed selenium ions is about 4, demonstrating multi-ionic uptake of them in vertical orientations. The energetic investigation (9–11 kJ/mol) validates the retention of two forms of selenium by mainly physical mechanistic processes (dipole bonding and/or van der Waals forces and/or hydrogen bonding). Regarding the thermodynamic functions, the reported behaviors demonstrate the exothermic and spontaneous uptake of both selenite (Se (IV)) and selenate (Se (VI)) by CF/Ph. Also, the composite possesses remarkable recyclability and higher efficiency as compared to several studied structures and can be applied in realistic remediation process even in existence of other chemical contaminants.