Calculated Interaction Energies Research Articles

Investigating Hydrogen Bonding Interactions in Aniline‐Acetone Binary Mixture through Molecular Dynamics Simulations

AbstractBinary liquid systems serve as valuable prototypes for comprehending biologically and chemically relevant properties of hydrogen bonds, revealing both noteworthy patterns and anomalies in their behaviour. Aniline, acetone and their binary mixtures with other liquids are used in various industrial processes, drug design, and as cleaning agents. This study is a molecular dynamics exploration of aniline and acetone binary mixture, over a concentration range of 9 : 1–1 : 9 for each component. The investigation includes employing techniques such as radial distribution function (RDF), coordination number calculation, hydrogen bond statistics, and graph theoretical analysis (GTA) through the NetworkX module in python, cluster analysis, Voronoi entropy calculation, interaction energy calculation and FTIR spectroscopy for all concentrations studied. The results uncover a compelling trend: a decrease in the number of hydrogen bonds as the concentration of acetone increases. Additionally, increased acetone concentration correlates positively with the breakdown of larger and more complex hydrogen‐bonded structures, indicating the formation of small hydrogen‐bond structures.

The crystal structures and Hirshfeld surface analysis of three new bromo-substituted 3-methyl-1-(phenylsulfonyl)-1H-indole derivatives

Three new 1H-indole derivatives, namely, 2-(bromomethyl)-3-methyl-1-(phenylsulfonyl)-1H-indole, C16H14BrNO2S, (I), 2-[(E)-2-(2-bromo-5-methoxyphenyl)ethenyl]-3-methyl-1-(phenylsulfonyl)-1H-indole, C24H20BrNO3S, (II), and 2-[(E)-2-(2-bromophenyl)ethenyl]-3-methyl-1-(phenylsulfonyl)-1H-indole, C23H18BrNO2S, (III), exhibit nearly orthogonal orientations of their indole ring systems and sulfonyl-bound phenyl rings. Such conformations are favourable for intermolecular bonding involving sets of slipped π–π interactions between the indole systems and mutual C—H...π hydrogen bonds, with the generation of two-dimensional monoperiodic patterns. The latter are found in all three structures, in the form of supramolecular columns with every pair of successive molecules related by inversion. The crystal packing of the compounds is additionally stabilized by weaker slipped π–π interactions between the outer phenyl rings (in II and III) and by weak C—H...O, C—H...Br and C—H...π hydrogen bonds. The structural significance of the different kinds of interactions agree with the results of a Hirshfeld surface analysis and the calculated interaction energies. In particular, the largest interaction energies (up to −60.8 kJ mol−1) are associated with pairing of antiparallel indole systems, while the energetics of weak hydrogen bonds and phenyl π–π interactions are comparable and account for 13–34 kJ mol−1.

Synthesis and characterization of La-doped SnO2 nanoparticles with different shape: A comprehensive study on morphology, structure, and photocatalytic efficiency for eco-friendly wastewater treatment

New controllable synthetic approach to obtain of La-doped SnO2 nanoparticles based on the combination of co-precipitation method with post synthetical hydrothermal treatment has been developed. Nanoparticles with various shape (3 nm spheres and 5 nm cubes) and structural parameters, i.e. different amount of oxygen vacancies and defects, and different dopant concentrations of 11 mol% and 33 mol% were fully characterized using XRD, FTIR, XPS and Raman spectroscopy, TEM, SSA evaluation, optical absorption spectra study, luminescence spectroscopy, including quantum chemical calculations.It was shown that hydrothermal treatment (240 °C during 6 h) promotes nanoparticle growth via the mechanism of oriented attachment. Original computational approach based on the calculation of interaction energies between ions and crystal facets was engaged to study the growth process.The presence of intrinsic photoluminescence (406, 414, 438, 460, 500 and 676 nm) for all obtained samples was established, determined by a complex set of different parameters for sub-10 nm nanoparticles.Photocatalytic efficiency of 95 % on the example of methylene blue under commercially available LED lamp described via quantum chemical modelling and tested on the example of a colorless antibiotic solution. A clear dependance of the morphological and structural parameters on the photocatalytic properties has been obtained and studied in detail.Novel concept based on a combination of chemical and computational method, for effective visible-light driven photocatalyst synthesis with potential antibacterial properties for complex eco-friendly wastewater treatment was proposed.

Thermodynamics of NaCl in dense water vapor via cross virial coefficients

Sodium chloride in the fluid phase is important for the chemistry of natural hydrothermal processes in the Earth’s crust and derived industrial utilizations, where thermodynamics is an essential part that can also to some extent fill in missing experimental data. The solubility of sodium chloride in crystalline form (halite) in water vapor is modeled using a novel combination of an accurate equation of state for pure water and a truncated virial equation for water mixed with sodium chloride. In the resulting Helmholtz energy expression, interactions between H2O and NaCl are incorporated through the second (B12), third (C112), and fourth (D1112) cross virial coefficients. The temperature dependence of the coefficients has been determined by regression to experimental data. Specifically, the temperature dependence of B12 is assumed to follow that of a square-well gas, whereas C112 and D1112 are calculated using purely exponential functions of inverse temperature. The temperature dependence of B12 is supported by independent calculations of ab initio interaction energies between H2O and NaCl. For water itself, all terms in the virial equation are collectively modeled by the IAPWS-95 equation of state. For sodium chloride, interactions between two or more NaCl molecules are disregarded. The model shows quantitative agreement with available solubility data in the vapor–halite coexistence region, which implies that the water vapor density is approximately less than 130kgm−3. Its theoretical basis ensures that predictions are reliable in regions where experimental data are missing. The direct calculation of cross virial coefficients is overall useful for modeling geochemical fluids with low solute concentrations, including systems with multiple solvents.

Noncovalent and Covalent O-H···O Interactions in PPh3O Cocrystals: A Correlation Study Involving QTAIM, SAPT, NBO, and IBSI Methods.

PPh3O.hemihydrate polymorphs and 11 assorted PPh3O cocrystals collectively constitute a reliable stock to pursue a systematic analysis aiming to investigate the impacts of some vital issues on the TPPO.H-bond donor aggregates. The issues highlighted herein are (i) effect of varying acidity of H-bond donors on the degeneracy of lone pairs of the H-bond acceptor (PPh3O), (ii) effectiveness of the |V(r)|/G(r) and H(r)/ρ(r) parameters as a covalency metric, (iii) 3c-4e bonding in the covalent PPh3O.nitric acid cocrystal, (iv) salient features of H-bond interaction energy and an interplay of its components, (v) an intrinsic bond strength scale for the PPh3O cocrystals, and (vi) reliable empirical relations between several bond descriptors for a quick estimation of interaction energy. To be specific about point (vi), we have propounded two promising avenues for a fast semiquantitative calculation of interaction energy from an endearing nonenergetic parameter, viz., bond length: dO-H···O → ρBCP (MAPE = 2.36%) → ESAPT0 (MAPE = 9.26%), and dO-H···O → IBSI (MAPE = 1.87%) → ESAPT0 (MAPE = 9.66%). All the aforesaid issues have been explored in detail through the QTAIM, NBO, and IBSI analyses (M06-2X-D3/def2-TZVP level), as well as by the SAPT study at the SAPT0/aug-cc-pVDZ platform. The statistically valid correlation studies can be particularly conducive for practical purposes as a transformative extension of the established facts into postulates for the unknown cocrystals.

Theoretical Spectroscopic Study of Normal Raman and Charge Transfer Surface-Enhanced Raman Scattering (SERS) Spectra of the Adsorbed l- and d-Cysteine on the Chiral Au34 and Ag4@Au30 Nanoclusters: Chirality Discrimination.

In this work, the discrimination of the enantiomers of cysteine (l- and d-CYS) using the chiral Au34 and Ag4@Au30 clusters was theoretically investigated in the gas phase and water. Two modes were considered for the interaction of each enantiomer with the clusters (via only its S atom or its S atom and NH2 group, simultaneously). The interaction energy (Eint) and adsorption energy (Ead) for the complexation of each enantiomer with the clusters for each interaction mode were calculated. Considering the calculated interaction energies, the interaction of d-CYS with Au34 is stronger than that of l-CYS with the same cluster. Also, it was observed that the substitution of the Au4 core of the Au34 cluster with the Ag4 cluster caused the increase of the interaction energy of l-CYS with the Ag4@Au30 cluster compared to the Au34 cluster, while the reverse trend was observed for d-CYS. Quantum theory of atoms in molecules (QTAIM) analysis was employed to calculate the interaction paths and their related bond critical points (BCPs) between the CYS enantiomers and the clusters to explain the difference between the interaction energy of the enantiomers with the clusters. The IR, normal Raman (NR), and surface-enhanced Raman scattering (SERS) spectra of the enantiomers interacting with the Au34 and Ag4@Au30 clusters were calculated, and the discrimination between l-CYS and d-CYS using the calculated spectra was explained. It was found that the discrimination of the enantiomers based on their interaction with the clusters is controlled by the charge transfer between the enantiomers and the clusters.

Molecular docking and molecular dynamics simulation decoding molecular mechanism of EDCs binding to hERRγ.

Human estrogen-related receptor γ (hERRγ) is a key protein involved in various endocrines and metabolic signaling. Numerous environmental endocrine-disrupting chemicals (EDCs) can impact related physiological activities through receptor signaling pathways. Focused on hERRγ with 4-isopropylphenol, bisphenol-F (BPF), and BP(2,2)(Un) complexes, we executed molecular docking and multiple molecular dynamics (MD) simulations along with molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) and solvation interaction energy (SIE) calculation to study the detailed dynamical structural characteristics and interactions between them. Molecular docking showed that hydrogen bonds and hydrophobic interactions were the prime interactions to keep the stability of BPF-hERRγ and hERRγ-BP(2,2)(Un) complexes. Through MD simulations, we observed that all complexes reach equilibrium during the initial 50ns of simulation, but these three EDCs lead to local structure changes in hERRγ. Energy results further identified key residues L268, V313, L345, and F435 around the binding pockets through CH-π, π-π, and hydrogen bonds interactions play an important stabilizing role in the recognition with EDCs. And most noticeable of all, hydrophobic methoxide groups in BP(2,2)(Un) is useful for decreasing the binding ability between EDCs and hERRγ. These results may contribute to evaluate latent diseases associated with EDCs exposure at the micro level and find potential substitutes. Autodock4.2 was used to conduct the molecular docking, sietraj program was performed to calculate the energy, and VMD software was used to visualize the structure. Amber18 was conducted to perform the MD simulation and other analyses.

Purification of graphite from spent carbon cathodes through the reduction of the mechanical entrainment of cryolite using polyaluminium chloride as a flocculant

Spent carbon cathodes (SCCs) generated during electrolytic aluminum production pose significant environmental hazards. To optimize resource utilization, flotation is used as an early process for the clean recovery of valuable graphite from waste cathodes. However, the mechanical entrainment in flotation restricts the further improvement of product purity, resulting in an increase in waste gas and wastewater discharge in the subsequent purification process. In this study, to increase the fixed carbon content of flotation products, flocculant was first applied to the flotation separation of SCCs, and polyaluminum chloride (PAC) was used to flocculate cryolite with high impurity content to reduce mechanical entrainment in the flotation process. Zeta potential measurements, particle size analysis, optical microscopy, and scanning electron microscopy confirmed the agglomeration of cryolite under the action of PAC. Additionally, the DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory was used to estimate the interaction energy to further explain the mechanism underlying cryolite agglomeration. Interaction energy calculation revealed that the attraction energy between particles was dominant at the PAC concentration of 2000 mg/L. Flotation experiments indicated that under a constant pulp pH of 7.8, the absence of sodium silicate, and a stirring speed of 1200 rpm, mechanical entrainment decreased from 91.53 ± 1.53 g/L to 69.80 ± 1.90 g/L, and the carbon grade of the product increased from 83.07 ± 0.28% to 88.94 ± 0.30%. Overall, the proposed purification method provides a new approach for the efficient recovery of graphite in waste cathodes, which is of great significance for the sustainable development of graphite resources.

Unveiling intermolecular mechanism and electronic properties between asphaltene and deep eutectic solvent for enhanced oil recovery using first principles calculation

Electronic structure and interaction energy calculations offer critical insights into non-bonded interactions in solute–solvent systems that can be used to extract heavy oil, particularly asphaltene, in enhanced oil recovery. The present study examines deep eutectic solvent (DES) interaction with asphaltene through first-principles calculations, revealing the role of hydrogen bonds, overall system stability, and its mechanism. The analysis reveals that the inclusion of asphaltene makes the DES-asphaltene structure less stable, i.e., increasing wettability with DES. DES formed non-bonded interactions with asphaltene's aliphatic segments but excluded aromatic rings due to strong π-π interactions. Among the studied DESs, DES1 (choline chloride and urea, 1:2 ratio) exhibited a strong interaction with asphaltene (-103.946 kJ/mol) and formed a hydrogen bond. All systems show negative binding energies, which indicate stability. Notably among them, DES2 (choline chloride and thiourea, 1:2) and DES3 (choline chloride and ethylene glycol, 1:2) displayed remarkable stability with asphaltene, evident in a widened band gap of 2.182 and 2.157 eV, respectively.

Experimental and theoretical study for the sorption of Ni2+ and Cd2+ onto phosphoryl functionalized aluminum silicate composite

Phosphoryl functionalized Aluminum silicate (ASP) composite sorbent was synthesized using sol–gel technique and characterized with different techniques. The synthesized sorbent was tested for the sorption of Ni2+ and Cd2+ in aqueous solution at both single- and binary-solute systems under simulated conditions using batch technique. Batch experiments were executed as a function of pH, initial metal ion concentration and temperature. Structural and surface morphology of the synthesized sorbent were determined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The studied kinetic models suggested that the sorption of Ni2+ and Cd2+ onto ASP was found to follow the pseudo-second order and the Langmuir-Freundlich model was the best model to depict the sorption isotherms. The sorption equilibria of both ions were analyzed using two diverse statistical physics models (homogeneous and heterogeneous monolayer models). A Theoretical scrutiny of statistical physics calculations indicated that Ni2+ and Cd2+ sorption was multi-ionic where two sorption sites were involved but with a diverse contribution degree. The removal nature of Ni2+ and Cd2+ was endothermic and the calculated sorption amounts at saturation implied that Ni2+> Cd2+. Calculated interaction energies indicated the participation of physical forces in the sorption of both ions onto the synthesized sorbent surface and the variation of these sorption energies confirmed that both sorption sites participated in the removal of Ni2+ and Cd2+ but through different interactions type. Ions sorption capacity was increased with the temperature owing to increase in thermal agitation. This study reveals that phosphoryl functionalized aluminum silicate is an efficient sorbent that can be used for the sorption of Ni2+ and Cd2+ from aqueous solutions in both single- and binary -solute systems.

Benchmarking ANI potentials as a rescoring function and screening FDA drugs for SARS-CoV-2 Mpro

Here, we introduce the use of ANI-ML potentials as a rescoring function in the host–guest interaction in molecular docking. Our results show that the “docking power” of ANI potentials can compete with the current scoring functions at the same level of computational cost. Benchmarking studies on CASF-2016 dataset showed that ANI is ranked in the top 5 scoring functions among the other 34 tested. In particular, the ANI predicted interaction energies when used in conjunction with GOLD-PLP scoring function can boost the top ranked solution to be the closest to the x-ray structure. Rapid and accurate calculation of interaction energies between ligand and protein also enables screening of millions of drug candidates/docking poses. Using a unique protocol in which docking by GOLD-PLP, rescoring by ANI-ML potentials and extensive MD simulations along with end state free energy methods are combined, we have screened FDA approved drugs against the SARS-CoV-2 main protease (Mpro). The top six drug molecules suggested by the consensus of these free energy methods have already been in clinical trials or proposed as potential drug molecules in previous theoretical and experimental studies, approving the validity and the power of accuracy in our screening method.

Crystal structure, Hirshfeld surface analysis, calculations of crystal voids, inter-action energy and energy frameworks as well as density functional theory (DFT) calculations of 3-[2-(morpholin-4-yl)eth-yl]-5,5-di-phenyl-imidazolidine-2,4-dione.

In the title mol-ecule, C21H23N3O3, the imidazolidine ring slightly deviates from planarity and the morpholine ring exhibits the chair conformation. In the crystal, N-H⋯O and C-H⋯O hydrogen bonds form helical chains of mol-ecules extending parallel to the c axis that are connected by C-H⋯π(ring) inter-actions. A Hirshfeld surface analysis reveals that the most important contributions for the crystal packing are from H⋯H (55.2%), H⋯C/C⋯H (22.6%) and H⋯O/O⋯H (20.5%) inter-actions. The volume of the crystal voids and the percentage of free space were calculated to be 236.78 Å3 and 12.71%, respectively. Evaluation of the electrostatic, dispersion and total energy frameworks indicates that the stabilization is dominated by the nearly equal electrostatic and dispersion energy contributions. The DFT-optimized mol-ecular structure at the B3LYP/6-311 G(d,p) level is compared with the experimentally determined mol-ecular structure in the solid state. Moreover, the HOMO-LUMO behaviour was elucidated to determine the energy gap.

Investigation of Phe-tRNA interaction with EF-Tu in GDP/GTP nucleotide bound states: a molecular dynamics simulation study

Elongation factor Tu (EF-Tu) is an important class of translational GTPases (trGTPases) involved in the elongation process. EF-Tu functions by forming the tight complex with the aminoacyl-tRNA (aa-tRNA: transfer RNA carrying an amino acid) in the GTP-bound active state and subsequently transports the aa-tRNA to the A-site (aminoacyl-site) of the ribosome. The correct interaction between mRNA's codon and aa-tRNA anticodon triggers GTP hydrolysis, resulting in the transition of EF-Tu from the active state to the inactive state (EF-Tu bound to GDP). This, in turn, results in the dissociation of EF-Tu:GDP from the tRNA and ribosome. However, the conformational changes and interactions responsible for the tight complex formation between EF-Tu and aa-tRNA in the GTP-bound state and the disruption of the interaction between EF-Tu and aa-tRNA in the GDP-bound state are not well understood. Therefore, to explore the conformational changes in the EF-Tu:Phe-tRNA complex and to get insight into the interaction between Phe-tRNA (tRNA carrying Phenylalanine) and EF-Tu in GDP/GTP nucleotide bound state, 200 ns MD (molecular dynamics) simulation have been carried out. The RMSD, RMSF, cluster, and DSSP analyses suggest that the GTP-bound state attains a more favorable conformation, which may facilitate EF-Tu’s interactions with the tRNA and ribosome. Further investigation of the non-bonded interaction energy calculation revealed the significance of domainII in interaction with the Phe-tRNA in a GTP-bound state. In addition, the H-bonds calculated between the tRNA’s Phe (Phenylalanine attached to the tRNA is considered) and domainII highlights the contribution of Val285 in recognizing tRNA’s Phe by forming an H-bond throughout the simulation time in the GTP bound state. Overall these results provide insight into how GTP nucleotide influences the interaction between EF-Tu and Phe-tRNA.

A theoretical study on 1H-indole-2,3-dione complexes with lithium, sodium, and potassium cations.

A comparative study of the change in different properties of electronic and structural of the free 1H-indole-2,3-dione molecule and its complexes has been obtained. HOMA analysis was performed to investigate the effects of lithium sodium and potassium cations on the aromaticity of lithium sodium and potassium complexes of 1H-indole-2,3-dione. Several 1H-indole-2,3-dione complexes with lithium, sodium, and potassium cations were optimized at the B3LYP/6-311G(d,p) level. The cation and π interaction has been investigated from different aspects, including interaction energy calculations, charge transfer values, and changes in the aromaticity of the ring upon complexation. The charge transfer and natural population analysis for the complexes were performed with the natural bond orbital (NBO) analysis. The properties of bond critical points in complexes were studied by applying the quantum theory of atoms in molecules (QTAIM). Finally, the aromaticity change of phenyl induced upon complex formation was evaluated by applying the harmonic oscillator model of aromaticity (HOMA). [Li-INa]+ and [[Li-INb]+ were optimized with the wB97XD function using a version of Grimme's D2 dispersion model, and the absorption energy was compared with the calculation made with the B3LYP functional.

Prediction of Binding Pose and Affinity of Nelfinavir, a SARS-CoV-2 Main Protease Repositioned Drug, by Combining Docking, Molecular Dynamics, and Fragment Molecular Orbital Calculations.

A novel in silico drug design procedure is described targeting the Main protease (Mpro) of the SARS-CoV-2 virus. The procedure combines molecular docking, molecular dynamics (MD), and fragment molecular orbital (FMO) calculations. The binding structure and properties of Mpro were predicted for Nelfinavir (NFV), which had been identified as a candidate compound through drug repositioning, targeting Mpro. Several poses of the Mpro and NFV complexes were generated by docking, from which four docking poses were selected by scoring with FMO energy. Then, each pose was subjected to MD simulation, 100 snapshot structures were sampled from each of the generated MD trajectories, and the structures were evaluated by FMO calculations to rank the pose based on binding energy. Several residues were found to be important in ligand recognition, including Glu47, Asp48, Glu166, Asp187, and Gln189, all of which interacted strongly with NFV. Asn142 is presumably regarded to form hydrogen bonds or CH/π interaction with NFV; however, in the present calculation, their interactions were transient. Moreover, the tert-butyl group of NFV had no interaction with Mpro. Identifying such strong and weak interactions provides candidates for maintaining and substituting ligand functional groups and important suggestions for drug discovery using drug repositioning. Besides the interaction between NFV and the amino acid residues of Mpro, the desolvation effect of the binding pocket also affected the ranking order. A similar procedure of drug design was applied to Lopinavir, and the calculated interaction energy and experimental inhibitory activity value trends were consistent. Our approach provides a new guideline for structure-based drug design starting from a candidate compound whose complex crystal structure has not been obtained.

Polyaspartic acid, an eco-friendly regulator for the improvement of coking coal flotation: applications and mechanism

ABSTRACT In this study, a novel approach is to apply polyaspartic acid (PASP) as an eco-friendly regulator for the flotation of coking coal, which is different from the conventional use of oil collectors only. Flotation trails showed that adding PASP contributes to a two-way improvement in the yield and ash content of clean coal. SEM-EDS observations directly revealed that adding PASP significantly reduces the coating of high-ash fine slimes on the surface of low-ash coal particles. Contact angle detections and zeta potential analysis presented that the preferential adsorption of PASP hardly affects the adsorption of sodium oleate (NaOL) on the surface of low-ash coal particles but significantly weakens the adsorption of NaOL on the surface of high-ash fine slimes, leading to a remarkably hydrophobic difference. Particle interaction energy calculations verified that adding PASP enlarges the energy barrier between low-ash coal particle and high-ash fine slime. Hence, it can be arrived that the preferential adsorption of PASP affects the adsorption of NaOL on the surface of high-ash fine slime, widens the hydrophobic difference, enlarges the energy barrier between low-ash coal particle and high-ash fine slime, reduces the high-ash fine slime coating, therefore leading to a better flotation performance of lean coal.

Plasma pretreatment to enhance the sedimentation of ultrafine kaolinite particles: Experiments and mechanisms

Coal-slime water treatment not only has a direct impact on the reuse of water as well as the recovery of coal-slime, but also has an essential significance for the sustainable development of a green ecology and carbon neutrality. In this study, the sedimentation behavior of ultrafine kaolinite particles (the main component of high-ash fine slime) using plasma pretreatment was investigated via sedimentation tests, turbidity detections and high-speed camera observations. The results showed that with plasma pretreatment, the arrival time of the maximum (final) thickness of the thickening layer considerably shortens, the final thickness of the thickening layer slightly decreases, and the turbidity of the supernatant significantly reduces. The mechanism of the plasma pretreatment method for the enhanced sedimentation of ultrafine kaolinite particles was elaborated via laser particle size analysis, microscopic observations, zeta potential determinations, and particle interaction energy calculations. The results showed that with plasma pretreatment, the zeta potential of kaolinite particles lowers, and the decrease in repulsive electrostatic force strengthens the coagulation of kaolinite particles, therefore making kaolinite flocs more compact and enhancing the sedimentation process of ultrafine kaolinite particles. And the enhanced sedimentation mechanism of ultrafine kaolinite particles via plasma pretreatment was drawn.

Reduction of slime coating: effects of sodium silicate and sodium carbonate on lean coal flotation in sodium oleate system

High-ash fine slime has an adverse effect on coal flotation. In this study, the roles of sodium silicate (SS) and sodium carbonate (SC) in the facilitating effect on lean coal flotation (a type of coking coal) were studied when sodium oleate (NaOL) was used as a collector through flotation tests, Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS) observations, turbidity measurements, and particle interaction energy calculations. The flotation tests found that SS has a stronger capacity than SC for the improvement of flotation performance of lean coal. Moreover, SEM-EDS observations and turbidity measurements showed that SS presents a stronger weakening effect for the coating of high-ash fine slime on the surface of low-ash coal particles than SC. Furthermore, the particle interaction energy calculations verified that the increase in the energy barrier for the attachment between low-ash coal particle and high-ash fine slime caused by SS is larger than SC, providing theoretical supports for the experiments. Compared to kerosene as a collector, based on the similar ash content, the yield of clean coal increases greatly with the synergistic effect of SS and NaOL. In summary, SS is an appropriate dispersant for lean coal flotation in sodium oleate system.

Shape-Assisted Self-Assembly of Hexa-Substituted Carpyridines into 1D Supramolecular Polymers.

The extent of the influence that molecular curvature plays on the self-assembly of supramolecular polymers remains an open question in the field. We began addressing this fundamental question with the introduction of "carpyridines", which are saddle-shaped monomers that can associate with one another through π-π interactions and in which the rotational and translational movements are restricted. The topography displayed by the monomers led, previously, to the assembly of highly ordered 2D materials even in the absence of strong directional interactions such as hydrogen bonding. Here, we introduce a simple strategy to gain control over the dimensionality of the formed structures yielding classical unidimensional polymers. These have been characterized using well-established protocols allowing us to determine and confirm the self-assembly mechanism of both fibers and sheets. The calculated interaction energies are significantly higher than expected for flexible self-assembling units lacking classical "strong" non-covalent interactions. The versatility of this supramolecular unit to assemble into either supramolecular fibers or 2D sheets with strong association energies highlights remarkably well the potential and importance of molecular shape for the design of supramolecular materials and the applications thereof.

Oil Detachment Mechanism in Natural Surfactant Flooding from Silica Surface: Molecular Dynamics Simulation

Summary International regulations have compelled Europe and the United States to phase out certain traditional surfactants to mitigate the use of toxic and nonbiodegradable chemicals. Sodium cocoyl propionate (SCA), as a natural surfactant with high performance, has been proved to have the potential to replace traditional surfactants in previous studies. However, its performance has not fully met practical application requirements. Therefore, in this paper, molecular dynamics (MD) simulation was used to study the detachment behavior and mechanism of SCA, lauryl dimethylamine oxide (OA-12), emulsifier OP-10, and SOO (combination of SCA, OA-12, and OP-10) on crude oil (dodecane, C12) at different temperatures (80–120°C) and salinities (20 000–200 000 mg/L). The complex interaction mechanism between surfactant molecules and C12 molecules was revealed by analyzing the simulated snapshot, radial distribution function (RDF), mean square displacement (MSD), and interaction energy. The simulated snapshot captures the conformational evolution of surfactant molecules at different time points, emphasizing the spatiotemporal and spatial changes of their dynamic behavior. A comparison of two desorption modes reveals that dispersive adsorption displacement and concentrated adsorption displacement are two possible desorption mechanisms. RDF analysis shows that the probability of SOO molecules near C12 remains high even at high-salinity and -temperature conditions. MSD analysis showed that the diffusion capacity of SOO was the highest at 100°C, reaching 1.52867×10 –5 cm2/ps. The calculation of interaction energy results reveals that SOO has a strong adsorption capacity for C12, which is mainly due to the effect of van der Waals (vdW) force. This is because the C12 molecules are inert, and their molecular movement is mainly determined by the polar groups of the surfactant. The main contribution of this study is to provide a natural surfactant with superior performance as a viable alternative, offering experimental settings for further improvement in SCA performance. This research provides theoretical guidance for on-site applications of SCA and SOO to enhance oil recovery.