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A three-dimensional hollow NiCo2O4 structure was successfully prepared with a precipitation-hydrothermal method. A balance between magnetic and dielectric losses was achieved by using a hollow NiCo2O4 structure loaded with benzotriazole (BTA), and thus the performance of electromagnetic waves was attenuated. The minimum reflection loss value of BTA@NiCo2O4 at 16.01 GHz was −35.39 dB when the absorber thickness was 2 mm, at which the absorption bandwidth for an RL of less than −10 dB is as high as 4.64 GHz. The absorption mechanism was characterized by the synergy among interfacial polarization, multiple reflection, and dipole polarization enhancement between NiCo2O4 and BTA. Interestingly, the epoxy/BTA@NiCo2O4 coating not only exhibited an outstanding microwave absorption (MA) performance but also has excellent anticorrosion and self-healing properties, as shown by the results of electrochemical impedance spectroscopy and confocal laser scanning microscopy. This work would be very helpful to the development of novel coatings with excellent MA performance and anticorrosion and self-healing properties.

Dissipative particle dynamics (DPD) simulations were applied to investigate the effect of SiO2 nanoparticles (SNPs) modified with different tertiary amine chain length and concentration on O/W emulsion properties, the influence mechanism was also revealed from the molecular level. On this basis, the influence of the modified SNPs volume fraction in the emulsion system was studied. The results showed that with the increase number of tertiary amine chain alkyl carbon, the stability of the original emulsion system was first enhanced and then weakened while the responsiveness of the protonated emulsion system was first weakened and then slightly enhanced, the number of tertiary amine chains modified on SNPs has the same influence rule on emulsion performance, which was determined by the hydrophobicity of modified SNPs. In addition, with the increase of the modified SNPs volume fraction in the emulsion system, the stability of the emulsion is gradually enhanced. However, when the volume fraction of SiO2 exceeds 3%, the amplitude of stability enhancement decreases. The increase in the interaction energy between oil droplets in the equilibrium process is caused by emulsion fusion, which in turn is affected by SNPs. The repulsive force between oil and water is greater than that between two oil drops, which is the reason for the oil drop fusion. The presence of SNPs can reduce the repulsive force between oil and water to different degrees, thus slowing down the fusion of emulsion.

In the present study, SiO2 nanoparticles were first hydrophobically modified and then added into anionic surfactant sodium dodecyl sulfate (SDS) stabilized water-based foam to improve the foam stability. The foam stability was experimentally evaluated by measuring surface tension, Zeta potential and half-life of the foam. The foam stabilizing mechanism was also studied from a micro perspective by molecular dynamics simulation through analyzing the equilibration configuration and MSD curve of both SDS surfactant and water molecules. The results show that foam exhibits an optimal stability when SiO2 concentration is 0.35 wt% under a specific surfactant concentration (0.5 wt%) in this work. The addition of SiO2 nanoparticles with suitable concentration could improve the adsorption between SDS molecules and nanoparticles, thus limiting the movement of SDS and restricting the movement of surrounding water molecules, which is beneficial to enhance the foam stability.

The exfoliation corrosion behaviour of 2024 aluminium alloy was investigated through exfoliation corrosion test, together with synchrotron radiation X-ray computed tomography (SR-CT) to achieve the 3D segmentation of precipitated phases, cracks and corrosion products. The results demonstrate that aging treatment has a significant effect on the distribution of the precipitated phases in the 2024-T4 aluminium alloy, and the precipitated phases continuously distributed along the grain boundary would lead to intergranular corrosion (IGC) which is easily evolved into exfoliation corrosion. In the 2024-T2 aluminium alloy, the longest crack was found to locate at the boundary between the inner grains structure and outer peripheral coarse grain (PCG) structure, which indicates that the corrosion is attributed to electrochemical property difference of two structures.

Experiment and molecular dynamics simulation were carried out to study the tunable stability of oil-containing SDS-stabilized Nitrogen-in-water foam. The experimental results show that the foam stability could be tuned by the concentrations of SDS and modified SiO2 nanoparticles. In the foam systems with a low SDS concentration (0.2 wt.%), the foams show poor stability and the foam stability was almost not affected by the addition of modified SiO2 nanoparticles. The foam stability was greatly improved at moderate SDS concentration (0.5 wt.%), it enhanced first and then weakened with the increase of modified SiO2 concentration, and the half-life time achieved a maximum value of 1292 s at 0.05 wt.% modified SiO2. However, at high SDS concentration (0.8 wt.%), the foam stability was pretty good except for when the modified SiO2 concentration is too high (>0.2 wt.%). The microscopic mechanism was obtained by investigating the structural and dynamic properties of the foam film. The simulation work showed consistent results of foam stability with the experimental results. Moreover, it also revealed that the concentration and configuration of SDS will affect its interaction with SiO2 and oil molecule, which is critical to foam stability.

The designability and adjustability of the pore structure are vital advantages of metal–organic framework (MOF) materials for separation. Their exploration in the field of membrane separation is still inadequate, especially for the regulation of the pore environment based on the inorganic secondary building unit (SBU). In this work, we have studied the effect of the pore environment regulated by the SBU on the gas separation performance of MOF membranes for the first time. The Fe3(μ3-O)(CH3COO)6 SBU of the parent framework (soc-MOF, a stable microporous Fe-MOF) was in situ modified with imidazole (IM) molecules to construct the soc-MOF-IM polycrystalline membrane. The exact location of the incorporated IM and the narrowed pore size are observed based on the determined crystal structure. The gas solubility, diffusivity and separation performance of the two membranes are evaluated. Compared to the soc-MOF membrane with a H2/CO2 selectivity of 6, the soc-MOF-IM polycrystalline membrane possesses a significantly enhanced H2/CO2 selectivity (48), which is mainly attributed to the triggered molecular sieving effect. Thanks to the facile introduction of functional molecules and precise adjustment of the pore environment, SBU modification can be a powerful strategy to improve the separation performance of MOF membranes.

Density functional theory was used to investigate the anticorrosion mechanism of Cr-doped nickel-base alloy in Br/O environment. The adsorption properties including adsorption energy, bond length a...

Molecular dynamics simulations are used to investigate the effects of temperature, strain rate and molecule length on the deformation of graphene/polyethylene composites. At higher temperature, the host molecules move easily to fit the strain during the deformation. When the strain rate is lower, atoms in the composite model are more relaxed to fit the strain, thus the yield stress of the composite model is smaller than that at a higher strain rate. Due to the longer the length of molecules, the relative movement between molecules is more difficult with the increase of the strain, resulting in a larger yield stress.

Defects in metal–organic frameworks (MOFs) can play an important role in the development of MOFs as promising reverse osmosis (RO) membranes for water desalination. By employing molecular dynamics ...

Pseudomorphic conversion of metal-organic frameworks (MOFs) enables the fabrication of nanomaterials with well-defined porosities and morphologies for enhanced performances. However, the commonly reported calcination strategy usually requires high temperature to pyrolyze MOF particles and often results in uncontrolled growth of nanomaterials. Herein, we report the controlled alkaline hydrolysis of MOFs to produce layered double hydroxide (LDH) while maintaining the porosity and morphology of MOF particles. The preformed trinuclear M3(μ3-OH) (M = Ni2+ and Co2+) clusters in MOFs were demonstrated to be critical for the pseudomorphic transformation process. An isotopic tracing experiment revealed that the 18O-labeled M3(μ3-18OH) participated in the structural assembly of LDH, which avoided the leaching of metal cations and the subsequent uncontrolled growth of hydroxides. The resulting LDHs maintain the spherical morphology of MOF templates and possess a hierarchical porous structure with high surface area (BET surface area up to 201 m2·g-1), which is suitable for supercapacitor applications. As supercapacitor electrodes, the optimized LDH with the Ni:Co molar ratio of 7:3 shows a high specific capacitance (1652 F·g-1 at 1 A·g-1) and decent cycling performance, retaining almost 100% after 2000 cycles. Furthermore, the hydrolysis method allows the recycling of organic ligands and large-scale synthesis of LDH materials.

Dissipative particle dynamics (DPD) simulations were applied to investigate the solution self-assembly and pH-responsive behavior of hydrophobic DCPD (dicyclopentadiene)-loaded microcapsules from triblock copolymers poly (1,2-ethanediol, homopolymer-b-2-Diethylaminoethylmethacrylate-b-methyl methacrylate) (PEG- b -PDMAEMA- b -PMMA). Results indicate that micelles with longer hydrophilic PEG blocks and shorter hydrophobic PMMA blocks were in favor of encapsulating hydrophobic DCPD. Cross-linking at the core/shell interface generates a chemically bonded network structure in the micelle and leads to a significant decrease of their thermodynamic mobility (i.e., the increase of stability). Both non cross-linked and cross-linked micelles show a good pH-responsive behavior. In particular, cross-linked micelles still have the ability to carry DCPD due to the incomplete dispersion even completely protonation of PDMAEMA, which indicates that the cross-linked micelles could be expected to realize the slow release of encapsulated DCPD agent.

Hydrophobic oil additives have been shown to be a unique class of chemicals in solution, which affect the stability of foam films. While the oil-induced destruction of a foam film has been largely ...

Self-assembly of polymer and surfactant mixtures has attracted great interests because of its potential applications, ranging from tertiary oil recovery to drug delivery. However, the mechanism by which the hydrolysis degree of polymers promotes morphology transition is still experimentally challenging. In this study, self-assembly of the cationic surfactant dodecyltrimethylammonium bromide (DTAB) and anionic polyelectrolyte partially hydrolyzed polyacrylamide (HPAM) mixture was investigated by coarse-grained molecular dynamics (CG MD) simulation. In the polymer-surfactant mixtures, a sphere-to-rod transition of aggregates was obtained with the increasing concentration of DTAB. The increase of HPAM hydrolysis degree can promote the morphological transition from spherical into rod-like aggregates. Our simulation revealed that the flexibility of HPAM chain and the electrostatic attraction between DTAB headgroups ( N(CH3)3+) and HPAM carboxylate ions ( COO−) exerted a crucial role in promoting the morphological transition of aggregates. These simulation results brought to light the molecular-level information of sphere-to-rod transitions in polymer-surfactant aggregates. This work is expected to trigger further studies on morphology transition of polymer-surfactant mixtures.

This study uses an all-atom computational model to investigate the temperature dependent heterogeneity and percolation in a nanofilm system of short linear epoxy chains on a solid graphene surface. The heterogeneity, which indicates having physical characters that vary within the nanofilm, is mainly manifested in distributions of volume, energy and the dynamic properties. Local glass transition temperatures, Tgs, from above properties depend largely on the separation to the graphene surface, and the glass transition of the nanofilm is asynchronous along the film normal. Distinct Tg increases and decreases are particularly observed in the solid and free interfaces, respectively, compared with the bulk. From the dynamic heterogeneity, percolation effect, which indicates the connectivity of mobile and immobile domains, of the nanofilm is also observed during glass transition by plotting internal atomic mobility distribution diagrams. A multi-stage percolation mechanism based on the glass transition state and the connection state of immobile and mobile domains of the nanofilm is developed. A relatively immobile domain near the graphene surface is observed, even at temperatures much higher than Tg, and it initiates the dynamic percolation. The interconnection of immobile domains after percolation accelerate the transition from the rubbery to the glassy state.

Density functional theory was used to investigate the adsorption of imidazole (IMD), benzotriazole (BTAH) and 2-mercaptobenzoxazole (MBO) on the grain boundary (GB) of Cu (100) surface. Results show that molecules prefer to adsorb on the grain boundary with the larger distortion degree and more adsorption sites. The main interaction of molecules and grain boundary is chemisorption through C, N, S Cu bonds in both perpendicular and parallel modes. Hydrogen bonds and the lateral dipole-dipole interactions are also found. Based on the adsorption behaviour, the coverage effect and charge redistribution might be two possible inhibition mechanisms of inhibitor molecules.

Membrane-based water desalination has drawn considerable attention for its potential in addressing the increasingly limited water resources, but progress remains limited due to the inherent constraints of conventional membrane materials. In this work, by employing state-of-the-art molecular simulation techniques, we demonstrated that two-dimensional hydrocarbon polymer membranes, materials that possess intrinsic and tunable nanopores, can provide opportunities as molecular sieves for producing drinkable water from saline sources. Moreover, we identified a unique relationship between the permeation and selectivity for membranes with elliptical pores, which breaks the commonly known trade-off between the pore size and desalination performance. Specifically, increase in the area of elliptical pores with a controlled minor diameter can offer an improved water flux without compromising the ability to reject salts. Water distributions and water dynamics at atomic levels with the potential of mean force profiles for water and ions were also analyzed to understand the dependence of permeation and selectivity on the pore geometry. The outcomes of this work are instrumental to the future development of ultrathin-film reverse osmosis membranes and provide guidelines for the design of membranes with more effective and efficient pore structures.

Coaxial titanium vanadium nitride core–sheath nanofibers (VN@TiN) with mesoporous structure are fabricated and explored as efficient Pt-free counter electrodes (CEs) for Dye-sensitized Solar Cells (DSCs). For these nanofibers, the TiN core is covered with a sheath of VN, and their boundary is a continuous series of TiVN solid solutions. Both electrochemical tests and density functional theory computations indicate that the combination of core-sheath nanofibers structure design and the formation of TiVN solid solutions significantly enhance the triiodide reduction activity of parental TiN and VN. Impressively, the devices employing VN@TiN core-sheath nanofibers CEs yield 8.98%, which is 17% higher than that device with Pt CE (7.64%). The design strategy developed in this study may promote a boom in a promising alternative CE for future large-scale application of DSCs.

Molecular dynamics simulations were used to investigate the aggregation of two partially overlapped graphene sheets in hexane, dodecane and eicosane. When partially overlapped graphene shee...

Nanofibrils from the self-assembly of the naturally occurring saponin glycyrrhizic acid (GA) can be used to produce an oil-in-water emulsion foam with a long-term stability. Through homogenization and aeration followed by rapid cooling, stable emulsion foams can be produced from the mixtures of sunflower oil and saponin nanofibrils. At high temperatures, the GA fibrils form a multilayer assembly at the interface, creating an interfacial fibrillar network to stabilize the oil droplets and air bubbles generated during homogenization. A subsequent rapid cooling can trigger the self-assembly of free GA fibrils in the continuous phase, forming a fibrillar hydrogel and thus trapping the oil droplets and air bubbles. The viscoelastic bulk hydrogel showed a high yield stress and storage modulus, which lead to a complete arrest of the liquid drainage and a strong slowdown of the bubble coarsening in emulsion foams. The jamming of the emulsion droplets in the liquid channels as well as around the bubbles was also found to be able to enhance the foam stability. We show that such stable foam systems can be destroyed rapidly and on demand by heating because of the melting of the bulk hydrogel. The reversible gel-sol phase transition of the GA hydrogel leads to thermoresponsive emulsion foams, for which the foam stability can be switched from stable to unstable states by simply raising the temperature. The emulsion foams can be further developed to be photoresponsive by incorporating internal heat sources such as carbon black particles, which can absorb UV irradiation and convert the absorbed light energy into heat. This new class of smart responsive emulsion foams stabilized by the natural, sustainable saponin nanofibrils has potential applications in the food, pharmaceutical, and personal care industries.

We present a simple approach for the fabrication of a full-thickness super-hydrophobic composite coating consisted of modified TiO 2 nanoparticles and polysiloxane resin. Scanning electron microscope (SEM), fourier transform infrared spectrometer (FTIR), contact angle meter and a simple self-made device were employed to characterize the surface morphologies, chemical compositions, contact angle and sliding angle of the modified TiO 2 nanoparticles and composite coating, respectively. Results show that for both the modified TiO 2 nanoparticles and the as-prepared composite coating the contact angle and sliding angle of is up to 152° and 0°, respectively. In addition, due to the coating design of full-thickness super-hydrophobicity, the composite coating also exhibited good thermal stability, abrasion resistance and corrosion resistance in the thermo-gravimetric analysis (TGA) experiment, abrasion test and immersion test, respectively.

Dissipative particle dynamics (DPD) simulation is used to study the effect of pH on the morphological transition in micelles assembled from dirhamnolipids (diRLs), and analyze the pH-driven mechanism and influence factors of micellar surface patterns. At pH4.0, various multilayer structures with homogeneous surface patterns are observed, whereas diRLs can self-assemble into novel anisotropic morphologies with phase-separated surface patterns at pH7.4, such as patchy spherical micelles, rod-like micelles with helical surface patterns and a lamellar phase with anisotropic surface patterns. The change in a surface pattern results from the diverse molecular arrangement in the course of assembly due to the deprotonation of carboxyl groups. Further studies show that influence factors, such as molecular structure, solvent selectivity and intramolecular interaction, are closely associated with the changes in surface patterns and topological structures. In detail, decreasing the critical packing parameter of rhamnolipids, increasing the solution polarity and weakening the compatibility between rhamnose rings and alkyl chains are all beneficial to the formation of phase-separated surface patterns. Remarkably, a wider variety of surface patterns (randomly anisotropic surface patterns) can be further obtained with the different factors mentioned above. This work is expected to extend the applications of diRLs to advanced functional materials like drug delivery, optoelectronics and nanofiltration membranes.

Density functional theory calculation was conducted to investigate the adsorption behavior and mechanism of benzotriazole (BTA) on the copper surface with the defects of vacancy, impurity, and grain boundary (GB). On the Cu (111) surface with vacancies, BTA tends to obliquely, rather than vertically, adsorb on the copper surface. The surface doped with Zn and O has stronger adsorption activity for negatively charged particles compared with the surface doped with Ni and S. For impurity and GB surface, the adsorption energy and transferred charge show that the oblique and horizontal adsorption configurations are more stable than the vertical adsorption of BTA. Our findings provide profound explanation for corrosion inhibitor protection of defective metal surface.

Molecular dynamics (MD) simulations were implemented to investigate the effect of single adatom (SA) and Stone-Wales (SW) defects on the longitudinal elastic properties of unidirectional carbon nanotube (CNT)/polypropylene (PP) composites. The longitudinal Young's moduli of individual CNTs and CNT/PP composites were calculated from uniaxial tension simulations, and the interfacial shear strengths (IFSSs) between CNTs and PP matrix were also extracted. The moduli of SA and SW defected CNT/PP composites decrease with the increase of the defect degree, and SW defects have a greater impact on the moduli than SA defects. Moreover, the intrinsic moduli of the CNTs with SA and SW defects also decrease due to the structural relaxations under tension loading as the defect degree increases. However, the IFSSs of SA and SW defected CNT/PP composites tardily decrease and increase with the increase of the defect degree, respectively. Analysis of the parametric loss ratios indicates that the longitudinal elastic properties of SA and SW defected CNT/PP composites strongly depend on that of the CNTs, and the variation of interfacial bonding characteristics caused by SA and SW defects might have a negligible effect.

Dissipative particle dynamics (DPD) simulations were applied to investigate the coating repair agent dicyclopentadience (DCPD) in pH-sensitive micelles. The results show micelles self-assembled from triblock copolymers with strong hydrophobic interaction are not conducive to loading DCPD, and only micelles with weak interaction parameter can encapsulate DCPD well. After protonation, the structure of micelle was disassembled and DCPD beads have a stronger ability to shrink polymer chains and exposed to water. This work provides mesoscopic insight into self-assembly and disassembly of desired agent-loaded micelle, and might be useful for the design of new materials for agent delivery.

Molecular dynamics simulations have been carried out to study the stability of gemini surfactant foam with different head groups. The results showed that the interaction strength between the polar head groups of the surfactants and water molecules increased from 12-3S-12 (sulfate) system, 12-3Sn-12 (sulfonate) system to 12-3L-12 (carboxylate) system, and the coordination number of water molecules around head increased. From the perspective of energy, the interface formation energy of 12-3L-12 system was smallest, which means that the foam stability was the best. These results indicated that the different head type had a significant effect on the stability of gemini surfactant foam.

Molecular dynamics simulations are used to investigate the effect of graphene dispersion on the equilibrium structure and deformation of graphene/eicosane composites. Two graphene sheets with four different interlayer distances are incorporated, respectively, into a eicosane matrix to form graphene/eicosane composites representing different graphene dispersions. With greater graphene dispersion, the “adsorption solidification” of the eicosane increases, where eicosane molecular lamination, orientation, and extension become more uniform and stronger. In addition, eicosane molecular motion is inhibited more in the direction perpendicular to graphene surfaces. When these graphene/eicosane composites are deformed, the free volume initially increases slowly due to small, scattered voids. After reaching the yield strains, the free volume rises sharply as the structures of composites are damaged, and small voids merge into large voids. The damage always occurs in the region of the composite with the weakest “adsorption solidification.” Since this effect is stronger when the graphene sheets are more dispersed, more complete dispersion results in higher composite yield stresses. Lessons from these simulations may provide some insights into graphene/polyethylene composites, where suitable models would require very long equilibration times.

Self-assembly of asymmetric block copolymers (BCPs) around active pore edges has emerged as an important strategy to produce smart membranes with tunable pathways for solute transport. However, thus far, it is still challenging to manipulate pore shape and functionality for directional transformation under external stimuli. Here, a versatile strategy by mesoscale simulations to design stimuli-responsive pores with various edge decorations in hybrid membranes is reported. Dopant BCPs are used as decorators to stabilize pore edges and extend their function in reconfiguring pores in response to repeated membrane stretching/shrinking caused by external stimuli. The decoration morphologies are predictable since the assemblies of dopant BCPs around pore edges are closely related to their self-assemblies in solution. The coassembly between different BCPs in the hybrid membrane for the control of pore morphology is featured, and the parameter settings, including block incompatibility and molecular architecture for the construction of a specific pore, are determined. Results show that harnessed dopant BCPs in the hybrid membrane can enhance pore formation and induce directional pore shape and functionality transformation. Diversified pore decorations exhibit potential that can be further explored in selective solute transport and the design of stimuli-responsive smart nanodevices.

In the lifting process of drainage gas recovery, external conditions and internal components of the foam are complex. We used molecular dynamics simulation to construct a series of fatty alcohol polyoxyethylene ether sulfate (AES) foam models that could represent various foams in different lifting stages from well to ground. The effect of temperature and pressure on foam stability was investigated. We found that there are two main reasons for foam instability in the first-half stage of the lifting process. Firstly, high temperature aggravated the molecule movement; some CH4 molecules entered the foam film and formed a molecular transport channel. Secondly, the interaction between the CH4 phase and condensate oil leads to some alkane molecules entering the gas–liquid interface. The calculation results and theoretical analysis will help to deepen the understanding of the performance of oily foams under harsh conditions.

Developing high-performance materials for efficient isolation of proteins is of great importance. Herein, the authors synthesized a series of magnetic Fe3O4@PS-ANTA-M2+ (M = Ni, Co, Cu and Zn) nanospheres, consisting of fine Fe3O4 nanoparticles encapsulated by functionalized polystyrene shell, where metal ions were complexed by Nα, Nα-Bis(carboxymethyl)-L-lysine hydrate for selectively immobilizing histidine (His)-tagged proteins. The structures of the Fe3O4@PS-ANTA-M2+ were studied by field scanning electron microscopy, transmission microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and vibrating sample magnetometer. The adsorption performance of the Fe3O4@PS-ANTA-M2+ was studied using bovine hemoglobin as a model protein. The thermodynamics of the binding process was studied by isothermal titration calorimetry tests. The resulting Fe3O4@PS-ANTA-Cu2+, Fe3O4@PS-ANTA-Ni2+, Fe3O4@PS-ANTA-Co2+ and Fe3O4@PS-ANTA-Zn2+ possessed adsorption capacities of 21200, 8080, 6640 and 5360 mg g−1, respectively, rendering them as the best adsorbents for protein purification. The adsorption isotherm was better fitted by Langmuir equation. To verify the selectivity, the Fe3O4@PS-ANTA-M2+ was practically employed to isolate His-tagged proteins from cell lysate. The results indicated that the samples showed outstanding adsorption capacity, selectivity and stability, and facile regeneration and separation, outperforming a commercial NTA-Ni column. These findings suggested that the Fe3O4@PS-ANTA-M2+ showed promising applications for specifically isolating proteins from complex biological systems.

The adsorption behavior of CO2, CH4 and their mixtures in bituminous coal was investigated in this study. First, a bituminous coal model was built through molecular dynamic (MD) simulations, and it was confirmed to be reasonable by comparing the simulated results with the experimental data. Grand Canonical Monte Carlo (GCMC) simulations were then carried out to investigate the single and binary component adsorption of CO2 and CH4 with the built bituminous coal model. For the single component adsorption, the isosteric heat of CO2 adsorption is greater than that of CH4 adsorption. CO2 also exhibits stronger electrostatic interactions with the heteroatom groups in the bituminous coal model compared with CH4, which can account for the larger adsorption capacity of CO2 in the bituminous coal model. In the case of binary adsorption of CO2 and CH4 mixtures, CO2 exhibits the preferential adsorption compared with CH4 under the studied conditions. The adsorption selectivity of CO2 exhibited obvious change with increasing pressure. At lower pressure, the adsorption selectivity of CO2 shows a rapid decrease with increasing the temperature, whereas it becomes insensitive to temperature at higher pressure. Additionally, the adsorption selectivity of CO2 decreases gradually with the increase of the bulk CO2 mole fraction and the depth of CO2 injection site.

Atomistic molecular dynamics simulations have been performed to explore the effect of interfacial bonding on the interphase properties of a nanocomposite system that consists of a silica nanoparticle and the highly cross-linked epoxy matrix. For the structural properties, results show that interfacial covalent bonding can broaden the interphase region by increasing the radial effect range of fluctuated mass density and oriented chains, as well as strengthen the interphase region by improving the thermal stability of interfacial van der Waals excluded volume and reducing the proportion of cis conformers of epoxy segments. The improved thermal stability of the interphase region in the covalently bonded model results in an increase of ∼21 K in the glass transition temperature (Tg) compared to that of the pure epoxy. It is also found that interfacial covalent bonding mainly restricts the volume thermal expansion of the model at temperatures near or larger than Tg. Furthermore, investigations from mean-square displacement and fraction of immobile atoms point out that interfacial covalent and noncovalent bonding induces lower and higher mobility of interphase atoms than that of the pure epoxy, respectively. The obtained critical interfacial bonding ratio when the interphase and matrix atoms have the same mobility is 5.8%. These results demonstrate that the glass transitions of the interphase and matrix will be asynchronous when the interfacial bonding ratio is not 5.8%. Specifically, the interphase region will trigger the glass transition of the matrix when the ratio is larger than 5.8%, whereas it restrains the glass transition of the matrix when the ratio is smaller than 5.8%.

Molecular dynamics simulations were carried out to investigate the influence of cations (Ca2+/Mg2+) on the stability of the foam system stabilized by sodium dodecyl polyoxyethylene sulfonate (A12E2SO3). First, the structure of A12E2SO3 monolayer at the air/water interface was studied through analyzing the distribution of A12E2SO3 headgroups and the orientation of surfactant molecules. Results show that the addition of Mg2+ can increase the distance between A12E2SO3 headgroups, broaden the distribution thickness of A12E2SO3 headgroups along z axis, and improve the orientation of A12E2SO3 molecules, which favored the foam stability. On the contrary, the addition of Ca2+ in the foam system made surfactant molecules more aggregated, which was detrimental to the foam stability. Second, the interaction of surfactant molecules and cations was also studied through calculating their binding/dissociation energy and mobility. Results reveal that the binding tendency of the head-Ca2+ ion-pair was stronger than that of the head-Mg2+ ion-pair, which disturbed the foam stability. Third, we studied the hydration of surfactant headgroups and cations through calculating the number and the mobility of hydrated water molecules around headgroups. Results show that due to the extra hydration of cations in the foam system, especially for that with the addition of Mg2+, the number of water molecules around headgroups was increased and their mobility was restricted, which was beneficial to the foam stability. In addition, two forms of hydrogen bond bridging structures (O1⋯H2O⋯O2 and O2⋯H2O⋯Os) were observed for the first time in anionic surfactants. The location and the formation probability of these structures were found to be related to the gauche conformation of A12E2SO3 headgroup backbones. It was also found that hydrogen bond bridging structures can affect the foam stability.

Most of existing nanocontainers suffer from tedious, complicated and unsustainable assembly process which restricts their application in corrosion protection as smart inhibitor carriers. In this study, we adopted the framework-hybridization approach to prepare a smart anticorrosion system (MBT@Ph-HPMO), with MBT inhibitor as cargo and phenylene-bridged hollow periodic mesoporous organosilica (Ph-HPMO) as nanocontainer. Results reveal that the π-π stacking between MBT and framework of Ph-HPMO serves as nature valve, which is supplemented by the molecular dynamic simulation. The encapsulated inhibitor was loaded into Ph-HPMO at neutral pH, demonstrating fast release in acidic environment. On-demand release of inhibitors from MBT@Ph-HPMO contributed to achieving in situ active corrosion protection. Anticorrosion performance of MBT@Ph-HPMO for copper alloy was evaluated in 3.5 wt% NaCl solution for a period of 30 days. The alloy exhibited the slightest corrosion damage in the corrosion medium with the addition of 0.24 wt% MBT@Ph-HPMO. This facile and versatile strategy will have broad applications in new class of nanocontainers fabrication and open up a new prospect for active corrosion protection.

Increasing demand for affordable desalinating water has stimulated the vigorous development of reverse osmosis (RO) membranes. To date, the performance of polymeric membranes is limited by the permeability–selectivity trade-off: more permeable membranes lead to a less ideal selectivity and vice versa. Significant efforts have been made to identify new classes of ultra-permeable nanoporous membranes, but such trade-off can still be commonly observed. In this study, we identify the key role of the surface uniformity and chemistry of permeation channels inside nanoporous membranes in mitigating the trade-off. By using highly tunable aluminosilicate nanotubes (AlSiNTs) as a model system, this study demonstrates that, by properly designing the interior surface of AlSiNTs, the materials can offer not only higher water permeability but also a better ability to reject salts. Detailed investigations on the capacity, dynamics, energetics, and distribution of water as well as the free energy landscapes for water molecules and ions are also carried out to understand the permeation mechanisms of species at an atomic level. The outcomes obtained herein can provide guidelines for the rational design of nanotube-based membranes, or porous materials in general, to achieve more efficient and effective desalination processes.

Ultrafiltration (UF) membranes have found great application in sewage purification and desalination due to their high permeation flux and high rejection rate for contaminants under low-pressure conditions, but the flux and antifouling ability of UF membranes needs to be improved. Tetrakis (4-carboxyphenyl) porphyrin (TCPP) has good hydrophilicity, and it is protonated under strongly acidic conditions and then forms strong hydrogen bonds with N, O and S, so that the TCPP would be well anchored in the membrane. In this work, NaHCO3 was used to dissolve TCPP and TMC (trimesoyl chloride) was used to produce a strong acid. Then, TCPP was modified in a membrane with a different rejection rate by a method similar to interfacial polymerization. Performance tests of TCPP/polysulfone (PSf) membranes show that for the membrane with a high BSA (bovine serum albumin) rejection, when the ratio of NaHCO3 to TCPP is 16:1 (wt.%), the pure water flux of membrane Z1 16:1 is increased by 34% (from 455 to 614 Lm&minus, 2h&minus, 1bar&minus, 1) while the membrane retention was maintained above 95%. As for the membrane with a low BSA rejection, when the ratio of NaHCO3 to TCPP was 32:1, the rejection of membrane B2 32:1 was found to increase from 81% to 96%. Although the flux of membrane B2 32:1 decreased, it remained at 638 Lm&minus, 1, which is comparable to the reported polymer ultrafiltration membrane. The above dual results are thought to be attributed to the synergistic effect of protonated TCPP and NaHCO3, where the former increases membrane flux and the latter increases the membrane rejection rate. This work provides a way for the application of porphyrin and porphyrin framework materials in membrane separation.

In order to effectively enhance the performances of supercapacitors (SCs), novel electrode materials with high energy density and long cycling lives are urgently needed. Herein, we provide an universal strategy to improve the cycling stablity of transition metal phosphides as supercapacitor electrodes. Ni1.4Co0.6P@C hierarchical core@shell microspheres with abundant electrochemical active sites for large energy storage and coated porous carbon shells for drastically improved conductivity and cycling stability are purposely prepared and obtained. Benefiting from its excellent structural and compositional advantages, the as-derived Ni1.4Co0.6P@C microspheres possess attractive electrochemical properties such as remarkably high specific capacitance (1571.3 F g−1 at 1 A g−1), good rate capability (80.2%, from 1 A g−1 to 25 A g−1), and outstanding cycling stability (retained 82.8% after 5000 cycles). The fabricated all-solid state asymmetric supercapacitor using Ni1.4Co0.6P@C spheres and hollow carbon nanospheres (HCNs) as electrodes delivers the energy density of 40.8 Wh∙kg−1 at a power density of 80.8 W kg−1 and excellent cycling stability (retained 89.3% after 10000 cycles), illustrating its promising application potentials.

Multigeometry nanoparticles with high complexity in composition and structure have attracted significant attention for enhanced functionality. We assess a simple but versatile strategy to construct hybrid nanoparticles with subdivided geometries through the cooperative assembly of diblock copolymer blends with asymmetric architectures. We report the formation of multicompartmental, vesicular, cylindrical, and spherical structures from pure AB systems. Then, we explore the assemblies of binary AB/AC blends, where the two incompatible, hydrophobic diblock copolymers subdivide into self-assembled local geometries, and the complexity of the obtained morphologies increases. We expand the strategy to ternary AB/AC/AD systems by tuning the effect of phase separation of different hydrophobic domains on the surface or internal region of the nanoparticle. The kinetic control of the coassembly in the initial stage is crucial for controlling the final morphology. The interactions of copolymers with different block lengths and chemistries enable the stabilization of interfaces, rims and ends of subdomains in the hybrid multigeometry nanoparticles. With further exploration of size and shape, the dependence of local geometry on the volume fraction is discussed. We show an efficient approach for controllable multigeometry nanoparticle construction that will be useful for multifunctional and hierarchical nanomaterials.

Multicompartment nanostructures, such as microcapsules with clearly separated shell and core, are not easily accessible by conventional block copolymer self-assembly. We assess a versatile computational strategy through cooperative assembly of diblock copolymer blends to generate spherical and cylindrical compartmentalized micelles with intricate structures and morphologies. The co-assembly strategy combines the advantages of polymer blending and incompatibility-induced phase separation. Following this strategy, various nanoassemblies of pure AB, binary AB/AC and ternary AB/AC/AD systems such as compartmentalized micelles with sponge-like, Janus, capsule-like and onion-like morphologies can be obtained. The formation and structural adjustment of microcapsule micelles, in which the shell or core can be occupied by either pure or mixed diblock copolymers, were explored. The mechanism involving the separation of shell and core copolymers is attributed to the stretching force differences of copolymers which drive the arrangement of different copolymers in a pathway to minimize the total interfacial energy. Moreover, by adjusting block interactions, an efficient approach is exhibited for regulating the shell or core composition and morphology in microcapsule micelles, such as the transition from the "pure shell/mixed core" morphology to the "mixed shell/pure core" morphology in the AB/AC/AD micelle. This mesoscale simulation study identifies the key factors governing co-assembly of diblock copolymer blends and provides bottom-up insights towards the design and optimization of new multicompartment micelles.

© 2017 American Chemical Society. Using dissipative particle dynamics simulation, we probe the tunable permeability of cross-linked microcapsules made from pH-sensitive diblock copolymers poly(ethylene oxide)-b-poly(N,N-diethylamino-2-ethyl methacrylate) (PEO-b-PDEAEMA). We first examine the self-assembly of non-cross-linked microcapsules and their pH-responsive collapse and then explore the effects of cross-linking and block interaction on the swelling or deswelling of cross-linked microcapsules. Our results reveal a preferential loading of hydrophobic dicyclopentadiene (DCPD) molecules in PEO-b-PDEAEMA copolymers. Upon reduction of pH, non-cross-linked microcapsules fully decompose into small wormlike clusters as a result of large self-repulsions of protonated copolymers. With increasing degree of cross-linking, the morphology of the microcapsule becomes more stable to pH change. The highly cross-linked microcapsule shell undergoes significant local polymer rearrangement in acidic solution, which eliminates the amphiphilicility and therefore enlarges the permeability of the shell. The responsive cross-linked shell experiences a disperse-to-buckle configurational transition upon reduction of pH, which is effective for the steady or pulsatile regulation of shell permeability. The swelling rate of the cross-linked shell is dependent on both electrostatic and nonelectrostatic interactions between the pH-sensitive groups as well as the other groups. Our study highlights the combination of cross-linking structure and block interactions in stabilizing microcapsules and tuning their selective permeability.

Molecular dynamics simulations are used to investigate the aggregation and behavior of two parallel graphene sheets (22.0–64.0 A in length) in dodecane. The dodecane layer formed on the graphene surface leads to an energy barrier which slows the rate of the graphene aggregation process when the two sheets are totally separated by dodecane molecules. The graphene sheets aggregate in dodecane only when portions of one graphene sheet are in contact with another sheet. The aggregation rate depends on the combined structures of the two graphene sheets. The aggregation rate for two parallel graphene sheets in half contact with one another is constant since the relative sheet geometry and spacing are nearly constant in the transition region between sheets where dodecane molecules are being displaced during aggregation. The aggregation rate for partially overlapped graphene sheets becomes progressively slower as aggregation continues since the area not overlapped decreases as the aggregation proceeds.

Dissipative particle dynamics (DPD) simulation has been used to study the effect of pH on the morphology transition of micelles assembled by monorhamnolipids (monoRLs). Results show that micellar structures and transition modes with increasing mass concentrations are multiform due to the changeable hydrophilicity of pH-responsive beads at different pH levels. Various chaotic multilayer aggregations of monoRLs are observed at low pH (pH4.0) whereas well-ordered single-layer structures are obtained at high pH (pH7.4). At medium pH region (4.0pH7.4), morphologies with semi-chaotic structures will transform from multilayer to single layer with increasing pH due to the hydrophilicity increase of micelles. In addition, three micellar transition modes are built by varying the hydrophilicity of pH-responsive beads and validated by solvent accessible surface areas (SASAs) as a function of mass concentrations. This work is expected to trigger further studies on the stimuli-driven phenomena of glycolipids.

A novel CO2/N2 switchable aqueous foam was developed using a CO2-responsive surfactant N,N-dimethyl-N-dodecyl amine (C12A) and a conventional surfactant sodium dodecyl sulfate (SDS). The performance and mechanism of this switchable foam were studied by both experiment and molecular simulation methods. Experimental results demonstrate that the foam stabilized by SDS/C12A surfactants has better stability and water carrying capacity than single C12A foam. The foam could be rapidly switched between stable and unstable states at ambient temperature with CO2 or N2 as the triggers. Simulation results shows that when CO2 was introduced, most of SDS and C12A molecules aggregated in the water phase, instead of adsorbing at the air-water interface to stabilize the foam films. The strong electrostatic attraction between protonated C12A and SDS molecules could account for the aggregation. Due to the presence of limited surfactants located at the air-water interface after introducing CO2, the foam bursts quickly.

Density functional theory and first-principles computational tensile test were used to investigate the intergranular-stress corrosion mechanism of brass in H2S environment. Results show that the complicated structure of grain boundary makes H2S and its decomposed corrosive ions adsorb on the surface more easily. The segregation of Zn atoms is conducive to the decomposition of H2S and the permeation of H atom. H permeation in the grain boundary can weaken the strength of metallic bond. GB structure, Zn segregation and H permeation all facilitate the intergranular-stress corrosion process of brass in H2S environment under the action of external stress.

Oil phase has strong hydrophobicity and weak interface tension in the foam system, which will destroy the internal structure of foam and reduce the intrinsic stability of the foam film. Coarse-grained molecular simulation techniques were employed to investigate the effect of oil phases on the structural instabilities of two typical foam systems, i.e., ionic sodium dodecyl sulfate (SDS) and nonionic pentaethylene glycol monododecyl ether (C 12 E 5 ). In both systems, the pseudo-emulsion film ruptures at a critical thickness, subsequently the oil phase enters the air-water interface subsequently. Instability mechanisms are obtained by analyzing dynamic processes of the foam systems. For the SDS foam system, an oil-bridge is formed in the foam film, which is attributed to the electrostatic repulsion between the SDS at the oil-water interface and that at the air-water interface, as well as the discontinuous distribution of SDS at the air-water interface caused by the structural reversal of SDS molecules. However, for the C 12 E 5 foam system, oil phase spreads at the air-water interfaces, which is caused by the continuous distribution of the C 12 E 5 molecules at the air-water interface and the attractive interaction between the neutral C 12 E 5 molecules at the air-water interface and that at the oil-water interface. The outcomes of this work shed light on the destructive mechanism of foam films induced by oil phase and provide guidelines for the design of novel oil-resistant foam system.

The redox-responsive hollow mesoporous silica sphere (HMSS) as smart nanocontainer demonstrates great potential for active agent storage and controlled release. In the present work, HMSS was firstly prepared by surfactant assisted selective etching method. Then, target corrosion inhibitors, 2-mercaptobenzothiazole (MBT) molecules, were loaded and encapsulated with redox-responsive supramolecular nanovalves, ZnO quantum dots. Results reveal that obtained HMSS exhibits a hierarchical mesoporous structure consisting of hollow cavity and mesoporous shell. Corrosion inhibitors were successfully loaded and capped in HMSS nanocontainers, showing on-demand release behavior under specific environment. Moreover, the release efficiency gradually increased with increasing dosage of the reducing agent. Therefore, the novel smart nanocontainers with redox-responsive characteristics will offer a great promise for the development of new generation nano delivery system for corrosion protection accompanying redox environment change.

Molecular dynamics simulations are used to investigate the behavior of two parallel graphene sheets fixed on one edge (lateral plane) in liquid dodecane. The interactions of these sheets and dodecane molecules are studied with different starting inter-sheet distances. The structure of the dodecane solvent is also analyzed. The results show that when the distance between the two graphene sheets is short (less than 6.8 A), the sheets will expel the dodecane molecules between them and stack together. However, when the distance between two sheets is large (greater than 10.2 A), the two sheets do not come together, and the dodecane molecules will form ordered layers in the interlayer spacing. The equilibrium distance between the graphene sheets can only take on specific discrete values (3.4, 7.8, and 12.1 A), because only an integer number of dodecane layers forms between the two sheets. Once the graphene sheets are in contact, they remain in contact; the sheets do not separate to allow dodecane into the interlayer spacing.