Water Molecules Research Articles

Nanoscale insights into NASH under high-velocity fluids erosion: A molecular dynamics study

The poor durability of geopolymer is a major factor hindering its application, and erosion from high-velocity fluids exacerbates this drawback. This study aimed to characterize the microstructural features of geopolymer under high-velocity fluids erosion and investigate the influence of harmful ions on erosion damage. Models of geopolymer/water solution and geopolymer/NaCl solution were constructed to simulate the erosion of geopolymer by high-velocity fluids. The results indicated that under high-velocity fluids erosion, most of the atoms on the surface of the geopolymer experienced leaching, indicating destruction of the substrate. Additionally, water molecules in solution were able to form hydrogen bonds to the substrate surface, accelerating its degradation. Under NaCl solution erosion, Na ions interacted with the exposed bridging oxygen in the geopolymer, and ion exchange occurred between Na ions and the substrate, making the substrate more unstable and leaching more pronounced. The findings of this study provide nanoscale insights into the erosion resistance of geopolymer that could guide the development of new erosion-resistant materials and methods.

Density functional simulation of water molecule with Ab-initio pseudo potential

Density functional simulation of water molecule with Ab-initio pseudo potential

A comparative study of nickel and cadmium coordination polymers: Framework topology and proton conductivity

Two new coordination polymers (CPs), [Ni2(dip)2(obb)2]⋅2H2O, and [Cd2(dip)2(obb)2(H2O)]⋅5.5H2O, were successfully synthesized via hydrothermal processes utilizing the organic linkers 4,4′-oxybisbenzoate (obb) and 2,6-di(1H-imidazole-1-yl)pyridine (dip). The unique structures of both CPs were confirmed by single-crystal X-ray diffraction studies. Ni-CP presents an intricate three-fold interpenetrated 3D framework, featuring a rare cag topology centered around dinuclear nodes. In contrast, Cd-CP exhibits a distinctive non-interpenetrated 2D framework with an unusual kIa topology. Despite Cd-CP's water coordination and the inclusion of substantial guest water molecules, it unexpectedly exhibited lower proton conductivity than Ni-CP, which is non-porous and contains much less water content.

Density functional simulation of water molecule with Ab-initio pseudo potential

Density functional simulation of water molecule with Ab-initio pseudo potential

The Dependence of Hydrophobic Interactions on the Shape of Solute Surface.

According to our recent studies on hydrophobicity, this work is aimed at understanding the dependence of hydrophobic interactions on the shape of a solute's surface. It has been observed that dissolved solutes primarily affect the structure of interfacial water, which refers to the top layer of water at the interface between the solute and water. As solutes aggregate in a solution, hydrophobic interactions become closely related to the transition of water molecules from the interfacial region to the bulk water. It is inferred that hydrophobic interactions may depend on the shape of the solute surface. To enhance the strength of hydrophobic interactions, the solutes tend to aggregate, thereby minimizing their surface area-to-volume ratio. This also suggests that hydrophobic interactions may exhibit directional characteristics. Moreover, this phenomenon can be supported by calculated potential mean forces (PMFs) using molecular dynamics (MD) simulations, where different surfaces, such as convex, flat, or concave, are associated with a sphere. Furthermore, this concept can be extended to comprehend the molecular packing parameter, commonly utilized in studying the self-assembly behavior of amphiphilic molecules in aqueous solutions.

Zinc(II) and copper(II) halide complexes of 2-(aminomethyl)aniline

The syntheses and structures of 2-(aminomethyl)aniline (2-AMAn) complexes of CuX2 and ZnX2 (X = Cl, Br) are reported: [(2-AMAn)ZnCl2] (1), [(2-AMAn)ZnBr2] (2), [(2-AMAn)2ZnCl2] (3), [(2-AMAn)2ZnBr2] (4), [(2-AMAn)2CuCl]Cl (5) and [(2-AMAn)2Cu(H2O)2]Br2 (6). Compounds 1 and 2 are isomorphous and crystallize in the monoclinic space group Ia with two coordinated halide ions and one chelating 2-AMAn ligand. Compounds 3 and 4 are also isomorphous and crystallize in the monoclinic space group P21/n with two monodentate 2-AMAn ligands and two coordinated halide ions. All four Zn(II) complexes are slightly distorted tetrahedral in geometry. The Cu(II) complexes are structurally distinct from the Zn(II) complexes. 5 crystallizes in the monoclinic space group P21/n and is strongly distorted square pyramidal in geometry with two chelating 2-AMAn ligands, one coordinated chloride ion and one dissociated chloride ion. The bromide compound, 6, crystallizes in the monoclinic space group P21/c, also with two chelating 2-AMAn ligands, but with two coordinated water molecules and both bromide ions dissociated in the lattice.

Elucidating the dynamics behavior of PFASs at the water and hydrophobic low-melting mixture solvents interphase

In this work, we studied the interphase dynamics of hydrophobic low-melting mixture solvents (LoMMSs) for the advanced remediation of per- and polyfluoroalkyl substances (PFASs) in wastewater systems by using classical molecular dynamics (MD) simulations. We showed the interaction between widely prevalent PFAS-specifically perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) and an innovative LoMMS composed of cineole (CIN) and linoleic acid (LNA) at equimolar ratios. Our investigations reveal that the interphase diffusion of PFASs through the LoMMS is a multi-stage process involving diffusion, interface sorption, and subsequent migration into the bulk aqueous phase. The simulations underscore a robust affinity between the PFASs molecules and the LoMMS, with the displacement of PFASs from the water interface marked by the formation of complex hydrogen-bonded networks. This intricate interplay results in a significant reorganization of water molecules, leading to potential clustering at the interface and compression of the fluid phase. These findings not only substantiate the efficacy of LoMMSs in PFASs extraction but also highlight the need to account for competitive interactions at the water interface, which could impede the absorption kinetics. By providing a detailed molecular-level narrative of the interphase capture phenomena, this study paves the way for designing efficient, low-toxicity LoMMS-based systems for the targeted removal of PFASs from contaminated water sources.

Ab initio study of the adsorption of O, O2, H2O and H2O2 on UO2 surfaces using DFT+U and non-collinear magnetism

In order to model correctly the corrosion of spent nuclear fuel under disposal conditions, it is important to understand its behavior in the presence of oxidants. To advance in this direction, we consider the oxidation of UO2. We investigate computationally the adsorption of various species on its three most stable surfaces: (111), (110), and (100), with emphasis on incorporating a full non-collinear PBE+U approach. Various species, namely O, O2, H2O and H2O2 are considered due to their relevance for the oxidation of UO2. The dissociation energy and an estimate for the dissociation barrier for O2 were obtained, using the preferred adsorption configurations of O and O2. The adsorption configurations for H2O in our study compare well with previous studies that used collinear approximations, both in terms of relative stability of configurations and bond lengths. Differences in adsorption energies were found, which may be important for reaction kinetics. Dissociative reactions in which the water molecule splits in hydrogen and hydroxyl occur only on one of the three surfaces. The hydrogen further reacts with a surface oxygen to also form a hydroxyl group. Not surprisingly, we find that H2O2 binds more strongly to the three surfaces than water (lower formation energy), and similar to H2O adsorption, dissociative reactions may occur. The dissociated hydrogen reacts with a surface oxygen to form a hydroxyl group and the hydroperoxyl molecule binds with a surface uranium. Our study, which includes a detailed study of electron transfer, magnetic structure and the preferred adsorption configurations, gives insight into the uranium oxidation states and the influence of surface geometry on adsorption. The findings contribute to a more comprehensive understanding of the early stages of UO2 oxidation.

Laminated graphene oxide and hydrotalcite membranes via alternating spray-deposition with stable desalting performance

Laminated graphene oxide (GO) membrane has great potential for desalination, but achieving good stability in salt retention and water permeation is still a challenge. The “compact” sieving structure and the “loose” permeating structure of the GO membranes offer synergetic effects for high-performance desalination. Here, a composite desalination membrane involving two two-dimensional layered nanomaterials with opposite charges has been reported. The multi-layered GO (MLGO) and hydrotalcite (HT) were then alternated in a spray-coating on a PDA-modified substrate to construct multiple structures. Different assembly regions were identified by in-situ morphology monitoring, which showed that MLGO and HT were connected by electrostatic attractions. Also, the composite membrane showed high salt retention, permeability and long-term performance stability. The water flux of the composite membrane increased from 2.8 L m−2 h−1 bar−1 to 3.6–5.2 L m−2 h−1, which was due to the increases in the interlayer spacing distances and the introduction of new permeable spaces. After a 400 h continuous filtration test, the Na2SO4 retention remained stable. The water fluxes were in the range of 2.0–3.0 L m−2 h−1 bar−1, which corresponded to an increase by 42.9 %–114.3 % in comparison with the pure MLGO membrane. As compared with the MLGO membrane, molecular dynamics (MD) simulations revealed that more water molecules passed through the MLGO-HT membrane with a shorter pathway length and higher speed than MLGO membrane. The present study demonstrated the potential of a composite with 2D materials for desalination applications.

Zr-BTB nanosheets assist in optimizing the structure of forward osmosis membranes to enhance the lithium concentration performance

Recently, low-energy forward osmosis (FO) technology has been employed in the lithium concentration stage during the extraction of lithium from brine sources. The interlayer FO membrane is renowned for its exceptional structural characteristics; however, challenges remain in selecting suitable interlayer materials and exploring their control mechanisms on amine monomers. As interlayer materials, traditional 3D nanomaterials are prone to detachment, while traditional 2D materials without micropores can increase the transmission resistance of water molecules. This study introduces a novel FO membrane utilizing Zr-BTB nanosheets with 5.4 Å micropores as the interlayer material. Based on detection and simulation calculations, it was found that the increase in steric hindrance and interaction forces jointly slowed the diffusion of amine monomers in the presence of the Zr-BTB interlayer. This results in a thinner separation layer, facilitating water transport. The interlayer also plays crucial roles in preventing defective pore formation in the separation layer and assisting in intercepting salt ions. The Zr-BTB interlayer membrane exhibited a water flux of 29.14 L m−2 h−1 and a reverse salt flux of 0.16 g m−2 h−1, which are superior to those of many FO membranes reported in the field. The prepared membrane also has excellent performance in lithium concentration applications, and its separation mechanism was explored by MD simulations.

Ions effect on tunable coacervate and its relevance to the Hofmeister series

Ion induced self-assembly allows a better understanding of the natural self-assemblies such as proteins, colloids and polymers, etc. However, little is known about ions mediated tunable coacervates. Herein, we show that the Hofmeister series of ions can be used to explain the tunable coacervates induced by different types of ions. The assembly of benzenesulfonate and polyetheramine undergoes the transformation from bilayer vesicles to the network structure of bottom coacervate with the increased concentration of inorganic salt, and the tunable coacervates of surfactants was found to be highly dependent on the ion species in solution. The affinity and compatibility of cations and surfactant follows Li+ > Na+ > K+, which determines the disturbance range of water molecules in the hydration shell of surfactant, resulting in different states of the final aggregates varying from precipitate, upper coacervate to bottom coacervate. The chaotropic anions (e.g., I−) have more pronounced dehydration effect on surfactants compared with kosmotropic anions (e.g., F−), and the ability of anions induced the transition from the bottom to the upper coacervate follows I−> Br− > Cl− >F−. Since the structural transformation of bottom coacervate requires conformational entropy, the release of water molecules is thermodynamically favorable for the transition of coacervates, which is also verified by the fact that the occurrence of dehydration drives the bottom coacervate upward to the upper coacervate during the heating process. These results provide a close link between the Hofmeister series and the controllable coacervates, which is of importance for further progress in ion specificity effects and creates a basic physicochemistry skeleton to understand this important phenomenon.

Constructing novel GO microcomposite membranes with β-CD based microporous nanosheets for efficient dye/salt separation

Constructing novel GO microcomposite membranes with β-CD based microporous nanosheets for efficient dye/salt separation

A bilayer composite hydrogel with simultaneous high load bearing and superior lubrication by dopamine modified nano-hydroxyapatite

A bilayer composite hydrogel with simultaneous high load bearing and superior lubrication by dopamine modified nano-hydroxyapatite

Molecular dynamics simulation studies elucidating interaction mechanisms and structures of salt–brine interfacial systems derived from magnesium sulfate subtype salt lakes

Salt–brine interfacial systems widely occur in the process of salt crystallization and separation, where the interfacial interaction plays a crucial role in influencing salt crystal growth, product purity and brine recovery rates. In the present study, molecular dynamics simulations were employed to investigate the interaction mechanisms and structures of salt–brine interfacial systems derived from the magnesium sulfate–subtype salt lakes. The results indicate that the type of salts was the key factor that affects salt–brine interfacial interactions. The strength of interfacial interaction in hydrated salt–brine systems was found to be more than twice that of ionic salt–brine systems. This can be attributed to two characteristics observed in hydrated salt–brine systems: the incompact and undulating surface structure of hydrated salts and the hydrogen bonding between water molecules on hydrated salt and brine surfaces. In all the seven interfacial systems, no accumulation of Li+ ions at the interface was observed, and there were no significant structure changes in bulk brines except the variations in hydration numbers of K+ ions. These findings provide insights into atomic-level mechanisms governing the interfacial interactions between different types of salts and brines, thus providing a theoretical guidance for enhancing the salt crystallization and separation process.

Temperature-dependent structural changes in xylanase II from Trichoderma longibrachiatum

Endo-β-1,4-xylanases degrade heteroxylans that constitute the lignocellulosic plant cell wall. This enzyme is widely used in the food, paper, textile, and biorefinery industries. Temperature affects the optimum activity of xylanase and is an important factor in its application. Various structural analyses of xylanase have been performed, but its structural influence by temperature is not fully elucidated. To better understand the structural influence of xylanase due to temperature, the crystal structure of xylanase II from Trichoderma longibrachiatum (TloXynII) at room and cryogenic temperatures was determined at 2.1 and 1.9 Å resolution, respectively. The room-temperature structure of TloXynII (TloXynIIRT) showed a B-factor value 2.09 times higher than that of the cryogenic-temperature structure of TloXynII (TloXynIICryo). Subtle movement of the catalytic and substrate binding residues was observed between TloXynIIRT and TloXynIICryo. In TloXynIIRT, the thumb domain exhibited high flexibility, whereas in TloXynIICryo, the finger domain exhibited high flexibility. The substrate binding cleft of TloXynIIRT was narrower than that of TloXynIICryo, indicating a distinct finger domain conformation. Numerous water molecule networks were observed in the substrate binding cleft of TloXynIICryo, whereas only a few water molecules were observed in TloXynIIRT. These structural analyses expand our understanding of the temperature-dependent conformational changes in xylanase.

Novel 5-(2-chloro-quinolin-3-yl)-[1,3,4]thiadiazol-2-ylamines and their copper(II) metallates: Preparation, spectroscopy, X-ray crystallography, nucleic acid/albumin binding, DNA cleavage and in vitro cytotoxicity

Copper(II) metallates of 2-chloroquinoline-3-carboxaldehyde-4(N)-substituted thiosemicarbazone (CuQ1, CuQ2, CuQ3, CuQ4) were synthesized, characterized by Fourier-Transform Infrared (FT-IR), Ultraviolet–Visible (UV–Vis), Electron Paramagnetic Resonance (EPR) and Mass spectrometry. The true nature of the ligands and a representative complex was confirmed by X-ray single crystal analysis. During the complexation, the ligands underwent cyclisation to form thiadiazole and two units of thiadiazole were coordinated to copper ion through N2-nitrogen atom. The remaining sites were occupied with two chloride ions and a water molecule which led to a square pyramidal geometry around copper ion. Absorption and emission titration methods confirmed the partial intercalative mode of binding interaction between CT-DNA and the metal complexes. The interaction between complexes and BSA led to the formation of ground state fluorophore-quencher complex by following static quenching mechanism. In vitro cytotoxic effect of the ligands and complexes were done by taking Human cervical cancer (HeLa) cells and toxicity of the test compounds were analyzed by using normal human kidney cell (HEK). The complexes CuQ2, CuQ3 and CuQ4 showed better cytotoxic activity against HeLa cells as compared with the standard cisplatin. Among the complexes, CuQ3 exhibited higher activity with least IC50 value (17 µM).

Unveiling the dynamic and thermodynamic interactions of hydrocortisone with β-cyclodextrin and its methylated derivatives through insights from molecular dynamics simulations

Cyclodextrins (CDs) can enhance the stability and bioavailability of pharmaceutical compounds by encapsulating them within their cavities. This study utilized molecular dynamics simulations to investigate the interaction mechanisms between hydrocortisone (HC) and various methylated CD derivatives. The results reveal that the loading of HC into CD cavities follows different mechanisms depending on the degree and position of methylation. Loading into βCD and 6-MeβCD was more complete, with the hydroxyl groups of HC facing the primary hydroxyl rim (PHR) and the ketone side facing the secondary hydroxyl rim (SHR). In contrast, 2,3-D-MeβCD and 2,6-D-MeβCD showed a different loading mechanism, with the ketone side facing the PHR and the hydroxyl groups facing the SHR. The root mean square fluctuation (RMSF) analysis demonstrated that methylation increases the flexibility of CD heavy atoms, with 3-MeβCD and 2,3-D-MeβCD exhibiting the highest flexibility. However, upon inclusion of HC, 3-MeβCD, 2,3-D-MeβCD, 2-MeβCD, and 6-MeβCD showed a significant reduction in flexibility, suggesting a more rigid structure that effectively retains HC within their cavities. The radial distribution function revealed a significant reduction in the number of water molecules within the innermost layer of the methylated CD cavities, particularly in TMeβCD, indicating a decrease in polarity. The presence of HC led to the release of high-energy water molecules, creating more favorable conditions for HC loading. Conformational analysis showed that methylation caused a partial decrease in the area of the PHR, a significant decrease in the area of the middle rim, and a notable decrease in the area of the SHR. The loading of HC increased the area of the PHR in most derivatives, with the most pronounced increase observed in 2,6-D-MeβCD and 6-MeβCD. The analysis of interaction energies and binding free energies demonstrated that the binding of HC to methylated CD derivatives is thermodynamically more favorable than to βCD, with the strongest association observed for 6-MeβCD, 2-MeβCD, and 2,3-D-MeβCD.

WATER-RESPONSIVE SELF-HEALING MEMBRANE MODIFIED WITH POLYETHYLENEIMINE (PEI)/POLY (ACRYLIC ACID) (PAA)

The self-healing membrane has received substantial research attention in recent years due to its ability to overcome the difficulty in detecting the exact damage location of the membrane at a microscopic level. The healing effect of a self-healable membrane often requires the help of an external stimulus. This study reported the fabrication of a water-responsive self-healing membrane using polyethyleneimine (PEI)/poly(acrylic acid) (PAA) coated on polyethersulfone (PES) membrane via layer-by-layer (LbL) method. Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray (EDX) were performed to observe the successful attachment of PEI and PAA onto the PES surface. The topographical analysis was performed using scanning electron microscopy (SEM) to visualize the healing performance. Apart from the instrumental analysis, pure water flux (PWF) was conducted to quantify the healing efficiency of the membrane. The best self-healing performance of the fabricated PEI/PAA self-healing membrane at 5.0 mg/mL concentration of PEI and PAA solutions displayed a healing efficiency of 70 % after being immersed into distilled water for 24 hours, compared to the concentrations of 1.0 mg/mL (19.8 %) and 3.0 mg/mL (34.3 %). This could be attributed to the higher amounts of PAA to form hydrogen bonds with surrounding water molecules, and subsequently promotes healing performance as hydrogen bonds are the basis for the self-healing process. This study proposes a newly develop water-stimulus PEI/PAA self-repairing membrane which contributes to the energy-efficient membrane filtration process.

Engineering hydrophobic protective layers on zinc anodes for enhanced performance in aqueous zinc-ion batteries

Aqueous zinc-ion batteries possess substantial potential for energy storage applications; however, they are hampered by challenges such as dendrite formation and uncontrolled side reactions occurring at the zinc anode. In our investigation, we sought to mitigate these issues through the utilization of in situ zinc complex formation reactions to engineer hydrophobic protective layers on the zinc anode surface. These robust interfacial layers serve as effective barriers, isolating the zinc anode from the electrolyte and active water molecules and thereby preventing hydrogen evolution and the generation of undesirable byproducts. Additionally, the presence of numerous zincophilic sites within these protective layers facilitates uniform zinc deposition while concurrently inhibiting dendrite growth. Through comprehensive evaluation of functional anodes featuring diverse functional groups and alkyl chain lengths, we meticulously scrutinized the underlying mechanisms influencing performance variations. This analysis involved precise modulation of interfacial hydrophobicity, rapid Zn2+ ion transport, and ordered deposition of Zn2+ ions. Notably, the optimized anode, fabricated with octadecylphosphate (OPA), demonstrated exceptional performance characteristics. The Zn//Zn symmetric cell exhibited remarkable longevity, exceeding 4000 h under a current density of 2 mA cm−2 and a capacity density of 2 mA h cm−2. Furthermore, when integrated with a VOH cathode, the complete cell exhibited superior capacity retention compared to anodes modified with alternative organic molecules.

Theoretical Investigations of Hydrolysis Mechanisms of N(SiMe3)3.

Tris(trimethylsilyl)amine (N(SiMe3)3) is one of the most important intermediate products in the indirect synthesis of ammonia (NH3) from nitrogen (N2), which could be hydrolyzed to NH3 under mild conditions. Herein, the hydrolysis mechanism of N(SiMe3)3 has been systematically investigated using density functional theory (DFT) with explicit combined implicit water models. Under neutral conditions, the active barrier of the hydrolysis of N(SiMe3)3 is 17.6 kcal mol-1 in water solvent. The attacking of proton to N center and OH group to Si from water is decoupled for the stabilization of OH group by solvent water molecules, which lower the hydrolysis energy barriers. Furthermore, under acid conditions, N(SiMe3)3 is easily coordinated with proton to form [NH(SiMe3)3]+, and the energy barrier of the hydrolysis reaction could be reduced to 11.5 kcal mol-1 of the first stage, making it being promoted according to the chemical equilibrium. Thus, the results provide an explanation for the possible mechanism of the quantitative conversion of N(SiMe3)3 to NH3 under mild conditions. The decoupled hydrolysis mechanism may play important role in other hydrolysis processes.