Search

While nanoporous graphene oxide (GO) is recognized as one of the most promising reverse osmosis desalination membranes, limited attention has been paid to controlling desalination performance through the large GO pores, primarily due to significant ion leakage resulting in the suboptimal performance of these pores. In this study, we employed a molecular dynamics simulation approach to demonstrate that Mg2+ ions, adhered to carboxylated GO nanopores, can function as gates, regulating the transport of ions (Na+ and Cl−) through the porous GO membrane. Specifically, the presence of divalent cations near a nanopore reduces the concentration of salt ions in the vicinity of the pore and prolongs their permeation time across the pore. This subsequently leads to a notable enhancement in salt rejection rates. Additionally, the ion rejection rate increases with more adsorbed Mg2+ ions. However, the presence of the adsorbed Mg2+ ions compromises water transport. Here, we also elucidate the impact of graphene oxidation degree on desalination. Furthermore, we design an optimal combination of adsorbed Mg2+ ion quantity and oxidation degree to achieve high water flux and salt rejection rates. This work provides valuable insights for developing new nanoporous graphene oxide membranes for controlled water desalination. [ABSTRACT FROM AUTHOR]

Despite long‐term efforts for exploring antibacterial agents or drugs, potentiating antibacterial activity and meanwhile minimizing toxicity to the environment remains a challenge. Here, it is experimentally shown that the functionality of reduced graphene oxide (rGO) through copper ions displays selective antibacterial activity that is significantly stronger than that of rGO itself and no toxicity to mammalian cells. Remarkably, this antibacterial activity is two‐orders‐of‐magnitude greater than the activity of its surrounding copper ions. It is demonstrated that rGO is functionalized through the cation–π interaction to massively adsorb copper ions to form a rGO–copper composite and result in an extremely low concentration level of surrounding copper ions (less than ≈0.5 µm). These copper ions on rGO are positively charged and strongly interact with negatively charged bacterial cells to selectively achieve antibacterial activity, while rGO exhibits the functionality to not only actuate rapid delivery of copper ions and massive assembly onto bacterial cells but also result in the valence shift in the copper ions from Cu2+ into Cu+, which greatly enhances the antibacterial activity. Notably, this rGO functionality through cation–π interaction with copper ions can similarly achieve algaecidal activity but does not exert cytotoxicity against neutrally charged mammalian cells. [ABSTRACT FROM AUTHOR]

We theoretically and experimentally show that, with water being adsorbed, the graphene oxide (GO) is converted to a spontaneously dynamic covalent material under ambient conditions, where the dominated epoxy and hydroxyl groups are mediated by water molecules to spontaneously break/reform their C–O bonds to achieve dynamic oxygen migration. This dynamic material presents structural adaptivity for response to biomolecule adsorption. Both density functional theory calculations and ab initio molecular dynamics simulations demonstrate that this spontaneously dynamic characteristics is attributed to the adsorption of water molecules, which sharply reduces the barriers of these oxygen migration reactions on GO to the level less than or comparable to the hydrogen bonding energy in liquid water. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR), a pivotal process in hydrogen fuel cells crucial for enhancing fuel cell performance through suitable catalysts, remains a challenging aspect of development. This study explores the catalytic potential of germanene on Al (111), taking advantage of the successful preparation of stable reconstructed germanene layers on Al (111) and the excellent catalytic performance exhibited by germanium-based nanomaterials. Through first-principles calculations, we demonstrate that the O2 molecule can be effectively activated on both freestanding and supported germanene nanosheets, featuring kinetic barriers of 0.40 and 0.04 eV, respectively. The presence of the Al substrate not only significantly enhances the stability of the reconstructed germanene but also preserves its exceptional ORR catalytic performance. These theoretical findings offer crucial insights into the substrate-mediated modulation of germanene stability and catalytic efficiency, paving the way for the design of stable and efficient ORR catalysts for future applications. [ABSTRACT FROM AUTHOR]

Identifying the oxidation structure of two-dimensional interfaces is crucial to improve surface chemistry and electronic properties. Beyond graphene with only phenyl rings, a novel carbon-nitrogen material, C3N, presents an intrinsic heterogeneous surface morphology where each phenyl ring is encircled by six nitrogen atoms, yet its atomistic oxidation structure remains unclear. Here, combining a series of density functional theory calculations and ab initio molecular dynamics simulations, we demonstrate that thermodynamically favorable oxidation loci are confined to the phenyl ring, and kinetic transformations of oxidation structures are feasible along the phenyl ring, whereas those toward nitrogen atoms are proven to be extremely difficult. These results are attributed to the lower barrier of oxygen atom migration along the phenyl ring, while the significantly high barriers toward nitrogen atoms are due to the heterogeneous potential energy surface for oxygen–C3N interaction. This work highlights the significance of surface morphology on the characteristics of oxidation structure, offering insights into tunable electronic properties via confined interfacial oxidation. [ABSTRACT FROM AUTHOR]

Understanding how nanomaterials interact with cell membranes is related to how they cause cytotoxicity and is therefore critical for designing safer biomedical applications. Recently, graphene (a two-dimensional nanomaterial) was shown to have antibacterial activity on Escherichia coli, but its underlying molecular mechanisms remain unknown. Here we show experimentally and theoretically that pristine graphene and graphene oxide nanosheets can induce the degradation of the inner and outer cell membranes of Escherichia coli, and reduce their viability. Transmission electron microscopy shows three rough stages, and molecular dynamics simulations reveal the atomic details of the process. Graphene nanosheets can penetrate into and extract large amounts of phospholipids from the cell membranes because of the strong dispersion interactions between graphene and lipid molecules. This destructive extraction offers a novel mechanism for the molecular basis of graphene's cytotoxicity and antibacterial activity. [ABSTRACT FROM AUTHOR]

The evaporation of a tiny amount of water on the solidsurfacewith different wettabilities has been studied by molecular dynamicssimulations. From nonequilibrium MD simulations, we found that, asthe surface changed from hydrophobic to hydrophilic, the evaporationspeed did not show a monotonic decrease as intuitively expected, butincreased first, and then decreased after it reached a maximum value.The analysis of the simulation trajectory and calculation of the surfacewater interaction illustrate that the competition between the numberof water molecules on the water–gas surface from where thewater molecules can evaporate and the potential barrier to preventthose water molecules from evaporating results in the unexpected behaviorof the evaporation. This finding is helpful in understanding the evaporationon biological surfaces, designing artificial surfaces of ultrafastwater evaporating, or preserving water in soil. [ABSTRACT FROM AUTHOR]

Thermal conductivity and power factor are key factors in evaluating heat transfer performance and designing thermoelectric conversion devices. To search for materials with ultralow thermal conductivity and a high power factor, we proposed a set of universal statistical interaction descriptors (SIDs) and developed accurate machine learning models for the prediction of thermoelectric properties. For lattice thermal conductivity prediction, the SID-based model achieved the state-of-the-art results with an average absolute error of 1.76 W m−1 K−1. The well-performing models predicted that hypervalent triiodides XI3 (X = Rb, Cs) have ultralow thermal conductivities and high power factors. Combining first-principles calculations, the self-consistent phonon theory, and the Boltzmann transport equation, we obtained the anharmonic lattice thermal conductivities of 0.10 and 0.13 W m−1 K−1 for CsI3 and RbI3 in the c-axis direction at 300 K, respectively. Further studies show that the ultralow thermal conductivity of XI3 arises from the competition of vibrations between alkali metal atoms and halogen atoms. In addition, at 700 K, the thermoelectric figure of merit ZT values of CsI3 and RbI3 are 4.10 and 1.52, respectively, at the optimal hole doping level, which indicates hypervalent triiodides are potential high performance thermoelectric materials. [ABSTRACT FROM AUTHOR]

Reducing the ignition temperature of aromatic volatile organic compounds (VOCs) is a long-term pursuit for environmental pollution treatment and industrial application. In this paper, the toluene catalytic combustion was ignited at ultra-low temperature of 73 °C over a poplar wood monolithic catalyst with highly dispersed Pd particles coated by nano-thick graphited carbon layer via in-situ carbonization. Combing the characterizations and DFT calculations, the satisfying catalytic performance could be attributed to two aspects: (i) the unrestricted mass transfer of reactant and the high dispersity of Pd were simultaneously ensured in the straight micrometer-channel with abundant surface anchoring groups of poplar wood; (ii) the nano-thick graphited carbon layer on Pd significantly enhanced the oxygen activation. Given the low cost of economic wood and facile preparation technique, this work opened up new alternative for the preparation of highly dispersed noble metal catalyst and the low temperature catalytic combustion of aromatic VOCs in industry. [ABSTRACT FROM AUTHOR]

The molecular scale signal conversion, transmission, and amplification by a single external charge through a water-mediated Y-shaped nanotube have been studied using molecular dynamics simulations. Our results show that the signal converting capability is highly sensitive to the magnitude of the charge, while the signal transmitting capability is independent of the charge signal. There is a sharp two-state-like transition in the signal converting capacity for both positive and negative charges. When the charge magnitude is above a threshold (|q| ≥ ∼0.7 e), the water dipole orientations in the main tube can be effectively controlled by the signaling charge (i.e., signal conversion), and then be transmitted and amplified through the Y-junction, despite the thermal noises and interferences between branch signals. On the other hand, the signal transmitting capability, characterized by the correlation between the two water dipole orientations in the two branches, is found to be always larger than 0.6, independent of charge signals, indicating that the water-mediated Y-tube is an excellent signal transmitter. These findings may provide useful insights for the future design of molecular scale signal processing devices based on Y-shaped nanotubes. [ABSTRACT FROM AUTHOR]

Thermoelectrics (TEs) have been considered a sustainable and eco-friendly energy technology. However, due to limitations in energy conversion efficiency, TE devices have not yet been widely adopted. Here, we proposed a class of TE materials, trigonal XPt2Se3 (X = K, Rb), with the same crystal structure as Bi2Te3. At room temperature, with quartic anharmonicity correction, the lattice thermal conductivity (κL) of KPt2Se3 and RbPt2Se3 in the x-direction is only 0.57 and 0.46 W m−1 K−1, respectively. The ultralow κL arises from their layered structure, strong lattice anharmonicity, weak bonding nature, rattling motion of guest alkali metal atoms, and large scattering space. Simultaneously, the large density of states contributes to large power factors. At 800 K, both under n-type and p-type doping, KPt2Se3 exhibits ZT values that can exceed 4 in specific directions, while RbPt2Se3's ZT values can surpass 3, which is significantly higher than traditional TE materials. Our research not only elucidates that the layered trigonal crystals XPt2Se3 (X = K, Rb) represent a category of potential TE materials with ultralow κL and high TE performance but also provides directions for exploring TE materials. [ABSTRACT FROM AUTHOR]

All-inorganic perovskite quantum dots (PeQDs) have aroused great research interest in white light-emitting diodes (WLED) due to their excellent optoelectronic properties, but the poor stability, caused by dynamically binding long-chain capping ligands, hinders their future practical applications. To address this issue, here, we exploit short-chain butyric acid (BA) to replace long-chain oleic acid (OA) as capping ligand of CsPbX3 PeQDs by a hot-injection method. The addition of BA not only makes the morphology of CsPbBr3 PeQDs uniform and improves the crystallinity but also effectively suppresses nonradiative recombination, achieving a near unit photoluminescence quantum yield of 96%. The BA capped CsPbBr3 PeQDs exhibit high stability up to 180 d stored in ambient environment and also significantly improved resistance against polar solvent, ultra-violet lamp irradiation, and heat, which is rationalized by the strong binding capacity and shortened distance of BA to the PeQDs through ab initio calculations. Furthermore, by combining green-emission CsPbBr3 and red-emission CsPbBr0.8I2.2 PeQDs with blue GaN chip, we achieved WLEDs with excellent luminous properties, showing their great potential in practical application of wide-color-gamut display and lighting. [ABSTRACT FROM AUTHOR]

In this study, we report a facile strategy to prepare polyaniline and graphene nanopieces (PANI@GNP) nanocomposite by the oxidative polymerization of the aniline pre-assembled on the GNP surface. The morphology, chemical structure and interfacial interaction of the synthesized samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and x-ray photoelectron spectroscopy (XPS). The resulting PANI@GNP nanocomposite with a 0.33:1 mass ratio of PANI to GNP, has a large specific surface area, electron doping interface, excellent conductivity and reversible redox activity. The PANI@GNP symmetrical supercapacitor with the unique π-π electronic interaction demonstrates 351.7 F/g of specific capacitance; 57.5% of the rate property when the the current density increases from 1 to 10 A/g; the capacity retained 80% of the initial value in constant current charge–discharge mode (at the current density of 10 A/g) after 2000 cycles. This scalable preparation process makes PANI@GNP nanocomposite promising application in electrochemical devices. [ABSTRACT FROM AUTHOR]

G-quadruplexes (GQs) are guanine-rich, non-canonical nucleic acid structures that play fundamental roles in biological processes. The topology of GQs is associated with the sequences and lengths of DNA, the types of linking loops, and the associated metal cations. However, our understanding on the basic physical properties of the formation process and the stability of GQs is rather limited. In this work, we employed ab initio, molecular dynamics (MD), and steered MD (SMD) simulations to study the interaction between loop bases and ions, and the effect on the stability of G-quadruplex DNA, the Drude oscillator model was used in MD and SMD simulations as a computationally efficient manner method for modeling electronic polarization in DNA ion solutions. We observed that the binding energy between DNA bases and ions (K+/Na+) is about the base stacking free energies indicates that there will be a competition among the binding of M+-base, H-bonds between bases, and the base-stacking while ions were bound in loop of GQs. Our SMD simulations indicated that the side loop inclined to form the base stacking while the loop sequence was Thy or Ade, and the cross-link loop upon the G-tetrads was not easy to form the base stacking. The base stacking side loop complex K+ was found to have a good stabilization synergy. Although a stronger interaction was observed to exist between Cyt and K+, such an interaction was unable to promote the stability of the loop with the sequence Cyt. [ABSTRACT FROM AUTHOR]

MoSH is a representative example of a Janus two-dimensional monolayered system consisting of a molybdenum atomic layer sandwiched between sulfur and hydrogen atomic layers. Extensive experimental and theoretical efforts have suggested the great promise of the MoSH material, but the validity of the MoSH model (with a Mo–S–H ratio of 1:1:1) remains uncertain. While various experiments have established the Mo-to-S ratio to be close to 1:1, the hydrogen content has remained elusive even with the use of state-of-the-art characterization techniques due to its lightweight nature. In this study, we present a theoretical investigation aiming to determine the positions and ratios of the hydrogen atoms on MoSHx (with x ranging from 0 to 3) as well as assess their structural stability. By evaluating the energetic, mechanical, and thermodynamic properties, we confirm the existence of stable MoSHx structures within a critical range of hydrogen atom ratios, specifically 0.5 ≤ x ≤ 2.0. Additionally, as the hydrogen atom ratio increases, we observe a transition in the preferred adsorption sites of hydrogen atoms from the center of the hexagonal ring composed of molybdenum and sulfur atoms to the upper region of the molybdenum atoms. This study offers critical insight into the structural characteristics and stability of Janus monolayer MoSHx, contributing to the advancement and application of Janus MoSHx in various fields. [ABSTRACT FROM AUTHOR]

[Display omitted] Water dissociation is of fundamental importance in scientific fields and has drawn considerable interest in diverse technological applications. However, the high activation barrier of breaking the O H bond within the water molecule has been identified as the bottleneck, even for the water adsorbed on the graphene oxide (GO). Herein, using the density functional theory calculations, we demonstrate that the water molecule can be spontaneously dissociated on GO supported by the (1 1 1) surface of the copper substrate (Copper-GO). This process involves a proton transferring from water to the interfacial oxygen group, and a hydroxide covalently bonding to GO. Compared to that on GO, the water dissociation barrier on Copper-GO is significantly decreased to be less than or comparable to thermal fluctuations. This is ascribed to the orbital-hybridizing interaction between copper substrate and GO, which enhances the reaction activity of interfacial oxygen groups along the basal plane of GO for water dissociation. Our work provides a novel strategy to access water dissociation via the substrate-enhanced reaction activity of interfacial oxygen groups on GO and indicates that the substrate can serve as an essential key to tuning the catalytic performance of various two-dimensional material devices. [ABSTRACT FROM AUTHOR]

Structural phase transition materials have attracted extensive attention in various fields due to their tunable physical properties. Transition metal dichalcogenide (TMD) nanomaterial is a critical representation. However, the phase transition of Janus MoSH, a sub-member of TMD nanomaterial, remains poorly understood. In this study, we employed a theoretical approach to investigate the phase transition of MoSH monolayer. Our results reveal temperature-dependent structural phase transitions of MoSH from 2H to 1T′. As the temperature reaches a critical value, a spontaneous structural phase transition occurs from 2H to 1T′ phase. Remarkably, our study identifies the 1T′ phase of MoSH as the most stable phase (including energetic, mechanical, dynamic, and thermodynamic stability) at most temperature ranges, and we provide insight into the reaction pathway of MoSH from 2H to 1T′ phase. Moreover, the structural phase transition of MoSH with hydrogen vacancies is also temperature-dependent, with the critical temperature decreasing with the incremental number of vacancies. Overall, our findings not only reveal the temperature-dependent structural phase transition of MoSH but also confirm the stable structure of MoSH in 1T′ phase at room temperature, which is significant for potential applications of 2D MoSH nanomaterial. [ABSTRACT FROM AUTHOR]

Functional nanoscale structures consisting of a DNA molecule coupled to graphene or graphene oxide (GO) have great potential for applications in biosensors, biomedicine, nanotechnology, and materials science. Extensive studies using the most sophisticated experimental techniques and theoretical methods have still not clarified the dynamic process of single-stranded DNA (ssDNA) adsorbed on GO surfaces. Based on a molecular dynamics simulation, this work shows that an ssDNA segment could be stably adsorbed on a GO surface through hydrogen bonding and π-π stacking interactions, with preferential binding to the oxidized rather than to the unoxidized region of the GO surface. The adsorption process shows a dynamic cooperation adsorption behavior; the ssDNA segment first captures the oxidized groups of the GO surface by hydrogen bonding interaction, and then the configuration relaxes to maximize the π-π stacking interactions between the aromatic rings of the nucleobases and those of the GO surface. We attributed this behavior to the faster forming hydrogen bonding interaction compared to π-π stacking; the π-π stacking interaction needs more relaxation time to regulate the configuration of the ssDNA segment to fit the aromatic rings on the GO surface. [ABSTRACT FROM AUTHOR]

A correction to the article "Destructive extraction of phospholipids from Escherichia coli membranes by graphene nanosheets" that was published in the November 26, 2013 issue is presented.

Context : Previous theoretical studies have suggested that two-dimensional (2D) MBene materials might display adequate monatomic catalytic activity for the hydrogen evolution reaction (HER). Recently, a study reported the experimental synthesis of a 2D MBene (Mo4/3B2), re-defined as boridene, albeit no effort has been devoted to explore the single-atom catalytic activity for HER of this experimentally synthesized 2D material. Therefore, we herein investigate the single-atom HER performance of the boridene. Interestingly, with Mo defects mixed with single Au and Zn atoms shows excellent hydrogen evolution performance, and the change in the Gibbs free energy ( Δ G H ) value is close to 0 eV, which can even match the performance of Pt-based materials. Through analysis of the charge density difference and density of states, the mechanism affecting the HER performance is explained at the electronic level. This work provides a new direction for the use of the Mo4/3B2 monolayer two-dimensional materials in the field of single-atom catalysis for HER. Methods: This study used the DFT calculations in Vienna ab initio simulation package. The GGA-Perdew-Burke-Ernzerhof functional with DFT-D2 correction is used to describe the exchange–correlation interactions. The projection augmented wave is used with the plane wave cutoff of 500 eV. The convergences of energy and force are 10−5 eV and 0.01 eV/Å, respectively. A vacuum layer with a height of 20 Å is set in the Z direction. For geometry optimization, self-consistent, and DOS calculations, the k-point grids sampled in Brillouin zones are 3 × 3 × 1, 9 × 9 × 1, and 9 × 9 × 1, respectively. The AIMD simulation is performed in the canonical ensemble (NVT), and the temperature was maintained at 300 K by Nosé-Hoover thermostats with a time step of 2.0 fs. [ABSTRACT FROM AUTHOR]

Single transition‐metal atom coordinated graphite carbon nitride, including the metal atom doped g‐C3N4 system, displays catalytic activity comparable to that of the noble metal Pt catalyst with outstanding performance. Herein, we investigate the single atom catalytic performance of g‐C3N3 embedded by a single transition metal atom (M−C3N3; M=Mn, Fe, Co, Ni, Cu, Rh, Pd, Ag, and Pt) for hydrogen evolution reaction (HER) using density functional theory (DFT) calculations. The results indicate that all the M−C3N3 catalysts are thermally and dynamically stable systems. By comparing the Gibbs free energies, we found that the Rh−C3N3 catalyst exhibits the best HER electrocatalytic performance among the investigated systems. Subsequently, analysis of electronic structure indicates that the Rh−C3N3 system displays a metallic behavior, which is a beneficial feature for an adequate HER electrocatalyst. Finally, the charge density difference of the Rh−C3N3 structure further supports the rationality of our results. This study provides a new candidate of low‐cost, high‐performance, and highly active non‐noble metal electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel Janus Monolayer 1T'-MoSF is found through theoretical calculations. • Janus Monolayer 1T'-MoSF has high energetic, mechanical, dynamical, and thermodynamic stability. • Janus Monolayer 1T'-MoSF exhibits significant anisotropy, and superior mechanical flexibility. Janus monolayers of transition-metal dichalcogenides (TMDs) have garnered significant attention in various scientific fields due to their exceptional physical properties. Among the known Janus monolayer TMDs, MoSX holds particular significance, with X typically representing chalcogen atoms. The successful synthesis of MoSH has pushed the boundaries of X beyond the conventional chalcogens. Nevertheless, it remains an open question whether other elements can also yield stable Janus monolayer MoSX. Herein, we employ theoretical methods to undertake a comprehensive evaluation of the stability of Janus monolayer MoSX (X = Li, Be, B, C, N, F, Na, Mg, Al, Si, P, Cl). The analysis of stability encompasses various aspects, including energetic, mechanical, dynamical, and thermodynamic features. Interestingly, our investigations have revealed the existence of a hitherto undiscovered stable 1T'-MoSF structure. Remarkably, this structure exhibits significant anisotropy, providing superior mechanical flexibility due to its low Young's modulus. In addition, despite the dynamical instability of 2H/1T-MoSN and the mechanical instability of 2H/1T-MoSC/Mg, they could potentially exist under specific conditions. This theoretical study not only provides insights into the structural characteristics and stability of novel Janus monolayer MoSX, but also extends the Janus monolayer MoSX family, which would be valuable to future applications of Janus TMDs. [ABSTRACT FROM AUTHOR]

Recent experiments have shown the coexistence of both large unoxidized and oxidized regions on graphene oxide (GO), but the underlying mechanism for the formation of the GO atomic structure remains unknown. Now, using density functional calculations, 52 oxidation pathways for local pyrene structures on GO were identified, and a kinetic profile for graphene oxidation with a high correlation between oxidation loci was proposed, which is different from the conventional view, which entails a random distribution of oxidation loci. The high correlation is an essential nature of graphene oxidation processes and can be attributed to three crucial effects: 1) breaking of delocalized π bonds, 2) steric hindrance, and 3) hydrogen-bond formation. This high correlation leads to the coexistence of both large unoxidized and oxidized regions on GO. Interestingly, even in oxidized regions on GO, some small areas of sp2-hybridized domains, similar to 'islands', can persist because of steric effects. [ABSTRACT FROM AUTHOR]

Recent experiments have shown the coexistence of both large unoxidized and oxidized regions on graphene oxide (GO), but the underlying mechanism for the formation of the GO atomic structure remains unknown. Now, using density functional calculations, 52 oxidation pathways for local pyrene structures on GO were identified, and a kinetic profile for graphene oxidation with a high correlation between oxidation loci was proposed, which is different from the conventional view, which entails a random distribution of oxidation loci. The high correlation is an essential nature of graphene oxidation processes and can be attributed to three crucial effects: 1) breaking of delocalized π bonds, 2) steric hindrance, and 3) hydrogen-bond formation. This high correlation leads to the coexistence of both large unoxidized and oxidized regions on GO. Interestingly, even in oxidized regions on GO, some small areas of sp2-hybridized domains, similar to 'islands', can persist because of steric effects. [ABSTRACT FROM AUTHOR]

The scarcity of freshwater is of great challenge that the world is facing nowadays. The advances of nanomaterial based on the reverse osmosis (RO) technology provide new possibilities for desalination. In this study, using molecular dynamics simulation, we propose and design an excellent RO membrane composed of fluorinated graphene (F-GRA) nanochannels, by which the exceptionally high water permeation (reaching up to 61.1 L/cm2/day/MPa) and the almost complete ion rejection are achieved. Notably, F-GRA nanochannel membranes exhibit a desalination performance much more promising than many other nanomaterials in previously theoretical studies. This superior desalination performance of F-GRA channels is attributed to the negatively charged surface and hydrophobicity of F-GRA, where the electrostatic interactions (attraction or repulsion) between ions and F-GRA surface cause the ideal ion rejection and the ultralow water friction on F-GRA mediated by its hydrophobicity results in the excellent water penetration. Moreover, potential of mean force calculations further reveal that the water molecule reflects the lowest free energy barrier relative to ions when traversing through the F-GRA channel, indicating the energetical favorability of the successful water transport instead of ions. Our theoretical study offers a fascinating approach of molecular sieving design usable for future desalination. • Fluorinated graphene (F-GRA) nanochannel based membrane is constructed. • The F-GRA membrane presents an excellent desalination performance with the high water permeability and the high ion rejection. • The superior water permeability and ion rejection are resulted from the negatively charged surface and hydrophobicity of F-GRA. • The desalination performance of F-GRA nanochannel is investigated from the molecular level. [ABSTRACT FROM AUTHOR]

Abstract: Galilean invariance is a fundamental property; however, although the dynamics of lattice Boltzmann equation in the hydrodynamic limit is Galilean invariant, this property is usually not taken into account in the treatment of the fluid–solid interface. Here, we show that consideration of Galilean invariance in fluid–solid interfacial dynamics can greatly enhance the computational accuracy and robustness in a numerical simulation. Surprisingly, simulations are so vastly improved that the force fluctuation is very small and a time average becomes unnecessary. [Copyright &y& Elsevier]

Dynamic covalent interfaces (DCIs) can autonomously adjust their internal structures and dynamically respond to changes in the external environment, thus holding broad application prospects in drug delivery, molecular detection, and interface catalysis. However, the dynamic properties of such DCIs greatly rely on the localized exchanges or formations of chemical bonds, seriously constraining the adaptive response efficiency. To transcend the limitations of the dynamic two-dimensional (2D) scales, employing the experimentally synthesized biphenylene monolayer as a prototype, we systematically study the hydroxyl-assisted globally spontaneous dynamic oxygen migration on biphenylene interface based on the first-principles calculations and machine-learning-based molecular dynamics (MLMD) simulations. The calculated results indicate that the stable dangling oxygen atoms on the biphenylene monolayer can attract the proton in the interfacial water, which in turn undergoes a water dissociation process and produces hydroxyl groups on the biphenylene interface. Assisted by the hydroxyl groups, the dangling oxygen atoms can achieve long-range migration, exhibiting notably low energy barriers (0.09 eV, 0.04 eV) due to the reversible proton transfer reactions. Therefore, the local dynamic covalent behaviors of oxygen atoms on the biphenylene interface are broken with the oxygen atoms migrating between the adjacent C 4 rings. More importantly, the charge density difference and Bader charge analysis demonstrate that the presence of hydroxyl groups significantly enhance the stability of the dangling oxygen, effectively reducing energy barriers of oxygen migration compared to epoxy on the biphenylene interface. Furthermore, the MLMD trajectories visually show the process of realizing large-area DCIs on the biphenylene monolayer. Our work not only clarifies the oxygen-related dynamic behavior of the biphenylene interface, but also provides new ideas for the realization of large-area dynamic covalent materials (DCMs) on other carbon-based or 2D materials. With the assistance of the hydroxyl groups, the dangling oxygen atoms can exchange positions with the neighboring hydroxyl groups through the carbon-oxygen bonds breaking/reforming and the reversible proton transfer reactions. As a result, the globally spontaneous dynamic oxygen migration on the biphenylene monolayer is realization with the oxygen atoms migrating between the adjacent C 4 rings. [Display omitted] • The dangling oxygen atoms can exchange positions with the neighboring hydroxyl groups. • The carbon-oxygen bonds are reforming and the proton transfer reactions are reversible. • The limited distributions of the oxygen atoms on biphenylene can be broken. • The globally spontaneous dynamic oxygen migration is confirmed by the MLMD trajectory. • The underlying mechanism is analyzed through the charge density difference and Bader charge. [ABSTRACT FROM AUTHOR]

[Display omitted] • The graphitic carbon nitride (g-C 3 N 4) shows unique geometrical characterizes to anchoring metal trimer clusters. • They have excellent catalytic performances for yielding NH 3 products with limiting potential of 0.02–0.50 V involving kinetic barrier of 0.03–0.46 eV. • The establish the relationship between surficial activities and electronic properties. As a cleaner and more energy-efficient alternative, the electrochemical reduction of N 2 to NH 3 under mild conditions has emerged as a promising avenue for environmental protection. However, developing catalysts with both high activity and selectivity has been a challenging task. The advent of atomically dispersed catalysts is revolutionizing the field of catalysis. Drawing inspiration from the successful fabrication of Ru trimer on graphitic carbon nitride (g-C 3 N 4) nanosheets, herein, we adopted a series of trimeric metal clusters anchored on g-C 3 N 4 monolayer (TM 3 @g-C 3 N 4 , TM = 3 d , 4 d and 5 d transition metal atom), as well as utilized the criteria range to describe the stability, activity, energy cost and selectivity of supported trimers for N 2 reduction reaction based on ab initio calculations combined with multi-level screening strategies. Finally, 5 candidate TM 3 @g-C 3 N 4 (TM = Rh, Ru, V, Mo, and Re) exhibits decent catalytic activity with limiting potential ranging of –0.50 – –0.02 V. These spatially confined triatomic metal centers demonstrated proficiency in activating N 2 molecules while exhibiting tunable surficial reactivity through modulation of the metal elements and interfacial electron coupling between trimers and underlying substrates. More importantly, a structure–activity relationship was established, which provides crucial insights for precise design of highly efficient atomically-precise catalysts at an atomic level for hydrogen fuel storage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Iodine vacancy did not create midgap states in CsPbI 3 perovskites. • The carriers separation was governed by both surface defects and dipolar stabilizer. • The excited dynamics of electron relaxation was explored. • We explained the mechanism of dipolar passivator regulating carriers lifetime. The surface properties including both defect-modified and surface functionalization by dipolar molecules has a significant influence on the dynamics of charge carriers within metal halide perovskites (MHPs), which is crucial for achieving highly efficient and stable optoelectronic devices. Herein, we considered the sulfobetaine (SFB) as a model structure of dipolar molecular stabilizer, and systematically explored the surface defects and SFB passivation to regulate geometrical/electronic structures of perovskites, as well as its impact on spatial separation of photogenerated carriers by first-principles calculations. We further utilized time-dependent ab initio nonadiabatic molecular dynamics to simulate the photogenerated carrier dynamical behavior and elucidate the exact influence of surface iodine vacancy and SFB passivators have in tuning excited state lifetime. These theoretical results provide insight into physical mechanism behind defect passivation via dipolar stabilizers, promising routes towards improved optoelectronic applications for MHPs. [ABSTRACT FROM AUTHOR]

Bismuth-based compounds have been identified as a class of promising candidates for the realization of high-performance thermoelectrics, derived from their exceptional electrical conductivity and intrinsic low lattice thermal conductivity κ L. Here, we employed first-principles calculations, self-consistent phonon theory, and compressive sensing technique in conjunction with the Boltzmann transport equation to investigate the anharmonic thermoelectric properties of full-heusler bismuth compounds Cs x Rb 3 − x Bi. As the Cs content increases, the κ L of Cs x Rb 3 − x Bi decreases due to impurity scattering effects, and then increases. Among them, at 300 K, Rb 3 Bi has the largest κ L of 0.69 Wm−1K−1, while Cs 2 RbBi has the smallest κ L of 0.45 Wm−1K−1, both of which are lower than the κ L of traditional bismuth-based thermoelectric materials. The ultralow κ L originates from the strong lattice anharmonicity. In addition, the coexistence of high dispersion and flat band edges leads to high thermoelectric power factor at optimal doping concentration. As a result, the largest thermoelectric figure of merit ZT values of 2.59 (4.19) at 300 (500) K were obtained for CsRb 2 Bi at optimal hole doping level. These findings suggest that Cs x Rb 3 − x Bi compounds are superior for thermal management and thermoelectric applications. • At finite temperatures, Cs x Rb 3 − x Bi compounds are not only mechanically stable but also dynamically stable. • The κ L of Rb 3 Bi, CsRb 2 Bi, Cs 2 RbBi, and Cs 3 Bi are 0.69, 0.47, 0.45, and 0.56 Wm−1K−1, respectively, at 300 K. • The p-type doped CsRb 2 Bi exhibits a ZT value of 2.59, while at 500K, the ZT value reaches 4.19. • The ultra-low κ L of CsRb 2 Bi originates from the rattling vibration of Bi atoms, which manifests as an 'avoided crossing' phenomenon. [ABSTRACT FROM AUTHOR]

Alcohols are important products in chemical industry, but separating them from their aqueous solutions is very difficult due to the hydrophilic nature of alcohols. Based on molecular dynamics simulations, we observe a striking nanoscale drying phenomenon and suggest an energy-saving and efficient approach toward alcohol/water separation by using single-walled carbon nanotubes (SWNTs). We use various common linear alcohols including C1-C6 1-alcohols and glycerol for demonstration (the phenol is also used as comparison). Our simulations show that when SWNTs are immersed in aqueous alcohols solutions, although the alcohols concentration is low (1 M), all kinds of alcohols can induce dehydration (drying) of nanotubes and accumulate inside wide [(13, 13)] and narrow [(6, 6) or (7, 7)] SWNTs. In particular, most kinds of alcohols inside the narrow SWNTs form nearly uniform 1D molecular wires. Detailed energetic analyses reveal that the preferential adsorption of alcohols over water inside nanotubes is attributed to the stronger dispersion interactions of alcohols with SWNTs than water. Interestingly, we find that for the wide SWNT, the selectivity for 1-alcohols increases with the number of alcohol's carbon atoms (Ncarbon) and exhibits an exponential law with respect to Ncarbon for C1-C5 1-alcohols; for narrow SWNTs, the selectivity for 1-alcohols is very high for methanol, ethanol, and propanol, and reaches a maximum when Ncarbon = 3. The underlying physical mechanisms and the implications of these observations for alcohol/water separation are discussed. Our findings provide the possibility for efficient dehydration of aqueous alcohols (and other hydrophilic organic molecules) by using SWNT bundles/membranes. [ABSTRACT FROM AUTHOR]

The friction at the liquid-solid interfaces is widely involved in various phenomena ranging from nanometer to micrometer scales. By the molecular dynamic (MD) simulation, the friction properties of liquid-solid interfaces at the molecular level are calculated via the Green-Kubo relation. It is found that the system size will influence the value of the friction coefficient, especially for the solid surfaces with the larger polar charge. The value of the friction coefficient decreases with the increase in the system size and converges at large system sizes. The large polar charge will lead to a significant friction coefficient. However, the diffusion of water molecules on this surface is almost a constant, indicating that the diffusion coefficient seems to be independent of the system size and polar charge. This work provides insights for the selection of the system size in modeling the frictional properties of hydrophobic/hydrophilic surfaces. [ABSTRACT FROM AUTHOR]

Generally, the interface friction on solid surfaces is regarded as consistent with wetting behaviors, characterized by the contact angles. Here using molecular dynamics simulations, we find that even a small charge difference (≤0.36 e) causes a change in the friction coefficient of over an order of magnitude on two-dimensional material and lipid surfaces, despite similar contact angles. This large difference is confirmed by experimentally measuring interfacial friction of graphite and MoS2 contacting on water, using atomic force microscopy. The large variation in the friction coefficient is attributed to the different fluctuations of localized potential energy under inhomogeneous charge distribution. Our results help to understand the dynamics of two-dimensional materials and biomolecules, generally formed by atoms with small charge, including nanomaterials, such as nitrogen-doped graphene, hydrogen-terminated graphene, or MoS2, and molecular transport through cell membranes. The interface friction on solid surfaces is generally regarded as consistent with the wetting behaviour. Here the authors use molecular dynamics simulations and experiments to show that a small surface charge difference causes a change in the solid/water friction coefficient of over an order of magnitude, while the contact angles stay similar. [ABSTRACT FROM AUTHOR]

• Higher oxidization degree of GO membrane favors water permeation. • Optimal microstructures for highly separating water from ethanol were uncovered. • With low O/C ratio, diffusion effect governs water permeation behavior. • With high O/C ratio, preferential adsorption governs water permeation process. Molecular dynamics (MD) simulations were employed to investigate water-ethanol separation through monolayer graphene oxide (GO) membranes with different pore sizes and O/C ratios. The ultrahigh water flux and infinite water separation factors were achieved. The separation properties under 50/50 w/w water-ethanol mixtures reveal that higher O/C ratios favor water selectivity, and water flux is enhanced with O/C ratio and pore size. With the help of highest oxidization, water largely sorption amount governs permeation process. On the contrary, with low oxidization degree of GO membrane, water diffusion effect becomes dominant factor of permeation. We screen an optimal microstructure of GO membrane which equipped with an adequately sized pore (D = 2.4 Å) and a highest O/C ratio (R = 0.49). This optimal one D2.4Å_R0.49 achieves the highest water flux and fully ethanol rejection in the mimicked experimental system. This simulation study elucidates the role of O/C ratio and pore diameter in water-ethanol separation through porous GO membranes on the microscopic level and uncovers the governing effects for water permeation and also suggests a potential candidate as a water-ethanol separation membrane. [ABSTRACT FROM AUTHOR]

• The anion plays a crucial function in controlling the GO interlayer spacing. • The ion bridge is chiefly responsible for the reducing of the GO interlayer spacing. • The ion bridge is composed of one anion sandwiched by two cations. • The effect of the number of ion bridges on the GO interlayer spacing is investigated. Interlayer spacing of graphene oxide (GO) membranes can be precisely controlled using cations, which has been extensively used in nanofiltration membrane. However, no report definitely discloses the specific performance of anion in treating GO membrane, although cations and anions naturally coexist in aqueous solution. Subjectively, anion might have weak/reverse effect in maintaining the interlayer of negatively charged GO, which is yet confirmed by no evidence. In this work, combining molecular dynamics simulations and density functional theory calculations, we have discovered a long-time unexplored effect that anion can also sustain the GO membrane interlayer — specifically, two types of ion bridges (confined within two neighboring GO sheets), one composed of one anion intercalated into two cations and the other composed of two anions sandwiched by two cations, can effectively and stably fix the interlayer spacing of GO membrane. Our calculations revealed that the ion bridges greatly enhance the interaction between two neighboring GO sheets, making them highly stabilize in aqueous solution. Moreover, free energy calculations and density functional theory calculations further confirm the critical role of ion bridge in controlling the interlayer spacing of GO membrane. Our findings highlight, for the first time, the undiscovered control of GO membrane interlayer with anions via forming an ingenious ion bridge, rather than the preconceived weak/reverse effect of anions, which could inspire the future application of anions (and ion bridge) in membrane design. [ABSTRACT FROM AUTHOR]

Highlights • Presence of salt influences the solute association behavior in nanoconfined solutions. • Dispersion, reversible and aggregation states are still observed. • Increase of salt concentration promotes the formation and growth of clusters. • Transformation of solute association states occurs due to ion polarization. • Tails are more in alignment along radius direction at higher salt concentrations. Abstract Using molecular dynamics simulations, we have studied the effects of salt on the association behavior of solute molecules in nanoconfined aqueous solutions. Three types of solute association states – dispersion, reversible and aggregation states – are still observed in nanoconfined aqueous solutions in the presence of salt. With the increase of ion concentration, the tendency toward the formation of larger clusters is enhanced and the solute critical aggregation number decreases. We even found the transformation of solute association state from the dispersion to the reversible state or from the reversible to the aggregation state within an intermediate range of solute number. This phenomenon is similar to the salting out process and is attributed to the decrease of free water molecules induced by the ion polarization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rutile MnO 2-δ film is used to demonstrate the regulation of the orbital occupation. • Orbital polarization change in MnO 2-δ films is obtained by reductvie annealing. • Significant enhanced magnetic moments in MnO 2-δ films can be detected below 50 K. Effectively manipulating the orbital configuration is an emerging method to design quantum functional materials with novel electronic ground states. Here, we report the realization of orbital polarization change in rutile MnO 2-δ epitaxial thin films by reductive treatments such as CaH 2 coating annealing and hydrogen atmosphere annealing. These treated samples show significant lattice expansion due to the generation of oxygen vacancies and incorporation of H, and the mixed valence states of Mn2+ and Mn3+ are formed with the decrease in the Mn valence state. The X-ray linear dichroism results show that the electron occupied state of Mn in the treated film samples changes from 3d 3z 2 -r 2 to 3d x 2 -y 2, which means that the deprivation of oxygen atoms in the oxygen octahedron of MnO 6 causes a change of orbital polarization. The resulting high spin state in the treated MnO 2-δ films greatly enhances the magnetic properties of the films. This work not only demonstrates how the oxygen atoms in the edge-shared oxygen octahedron of rutile structures are replaced by reduction but also extends the study of orbital polarization and magnetic ground state control in oxide epitaxial films. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pristine C 3 N monolayer shows stronger O 2 physisorption than pristine graphene. • The most preferable O 2 dissociation is an indirect two-step path with chemisorbed O 2. • Two dangling C-O bonds on the para-carbon site is the most stable oxidized structure. • Pristine C 3 N monolayer is more susceptible to oxidation than pristine graphene. • Electronic properties can be altered significantly due to the presence of two chemisorbed O atoms. The oxygen dissociation and the oxidized structure on the pristine C 3 N monolayer in exposure to air are the inevitably critical issues for the C 3 N engineering and surface functionalization yet have not been revealed in detail. Using the first-principles calculations, we have systematically investigated the possible O 2 adsorption sites, various O 2 dissociation pathways and the oxidized structures. It is demonstrated that the pristine C 3 N monolayer shows more O 2 physisorption sites and exhibits stronger O 2 adsorption than the pristine graphene. Among various dissociation pathways, the most preferable one is a two-step process involving an intermediate state with the chemisorbed O 2 and the barrier is lower than that on the pristine graphene, indicating that the pristine C 3 N monolayer is more susceptible to oxidation than the pristine graphene. Furthermore, we found that the most stable oxidized structure is not produced by the most preferable dissociation pathway but generated from a direct dissociation process. These results can be generalized into a wide range of temperatures and pressures using ab initio atomistic thermodynamics. Our findings deepen the understanding of the chemical stability of 2D crystalline carbon nitrides under ambient conditions, and could provide insights into the tailoring of the surface chemical structures via doping and oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The GO humidity sensor fabricated by a simple way. • The GO humidity sensor with ultrafast response and recovery time less than 0.3s. • Protons generated from oxygen-containing groups and water molecules revealed. • An array of sensors was successfully fabricated to demonstrate its application. • LEDs lighted up by power-generating device made from humidity sensors. Next-generation humidity sensor, as one of the smart devices in artificial skin or flexible electronics, will need to be self-powered, flexible, fast and accurately detecting in the microenvironment. Although various flexible humidity sensors have already been demonstrated, most of them rely on large external power sources to operate, and still suffer from slow response, poor selectivity in environmental stimuli, and expensive and complicated procedures. Here, we realize a self-powered humidity sensor with ultrafast response and recovery time of less than 0.3 s by flexible GO film. Importantly, of all state-of-the-art humidity sensors, this is the fastest response for humidity sensor. Moreover, the sensor has a high sensitivity within a wide range of RH from 33% to 98%, and an excellent selective response to humidity under multiple environmental stimuli, due to its moist-induced generator. Theoretical computations reveal that protons generated spontaneously from oxygen-containing groups and water molecules, have a fast diffusion behavior as Grotthuss hopping. In particular, we build four real-time measurement systems capable of respiration monitoring of human, smart leaf surface humidity sensor, and energy harvesting. Our work provides a simple way to fabricate next-generation self-powered sensor using GO film with outstanding humidity sensor performance. [ABSTRACT FROM AUTHOR]

Combining the molecular dynamics (MD) simulations and the free-energy-based thermodynamic analysis, we analyze the role of alkyl chain length on the nucleation of alcohol molecules with the mono-hydroxyl in nanoconfined solution. The free energy formulae and thermodynamic equilibrium equation are parameterized by fitting the theoretical equilibrium equation to MD simulation results. We find that alcohol molecules with the varied alkyl chain length show different nucleation states, i.e. , dispersion, reversible and aggregation states, corresponding to the total free energy G c o n f i n e (n , N) with a single minimum at n ∼ 1, two minima at n ∼ 1 and N separated by a maximum, and a local minimum at n ∼ N , respectively. The alcohol molecule with a longer alkyl chain tends to aggregate into a cluster at a lower solute number in nanoconfined solution. Besides, the free energy of cluster formation in nanoconfined solution G c l u s t e r (n) also depends on the alkyl chain length, and three regions can be identified: For the shorter alkyl chain, such as ethanol, there is no local maximum on G c l u s t e r (n), indicating that alcohol molecules tend to be dispersed in water; For the intermediate alkyl chain length, such as 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol, the critical nucleation number n c and nucleation barrier G b monotonically decrease with the increase of alkyl chain length; For the longer alkyl chain, n c ∼ 1 and G b ∼ 0 k B T suggest that alcohol molecules, such as 1-heptanol, can aggregate into clusters easily. Our work deepens the understanding of the alkyl chain length effect on the nucleation behavior of alcohol molecules in nanoconfined solution. [ABSTRACT FROM AUTHOR]

Abstract: Using all-atom molecular dynamics (MD) simulation, we have investigated the adsorption of protein GA module (GA53) onto graphene oxide (GO), compared with similar adsorption onto pristine graphene (PG). We find that: (1) the protein GA53 can be easily and firmly adsorbed onto the surface of GO and PG, but the binding sites are not specific; the main difference is that the secondary structure of GA53 can be well preserved in protein–GO system, while GA53 will partially lose its secondary structure after adsorbed on PG. (2) in protein–GO system, hydroxyl and epoxy groups increase the distance between protein and GO, which weaken their vdW interactions, meanwhile, hydrogen bonds and electrostatic interactions enhance their binding affinity. In protein–PG system, strong vdW interactions between residues of GA53 and PG have destroyed its secondary structure. (3) π–π stacking interactions still exist between aromatic residues and both the basal plane of GO and PG. In comparison with PG, our results suggest that GO presents better biocompatibility to preserve protein secondary structure when simultaneously absorbing protein. [Copyright &y& Elsevier]

• A systematic increase in the adsorption energy of organic molecules on graphene in the presence of underlaying metal substrates is shown. • For the case of strong binding, such as Pd(111)-graphene contact, benzene is adsorbed obliquely on graphene with a large tilt angle of about 6 ∘. • With metal surface supported, the adsorption energy of OMs on graphene increases linearly with the number of methyl groups, regardless of the dispersion correction method used. • When compressive stress is applied to graphene, the adsorption energy of molecules increases. [Display omitted] We perform a comparative theoretical study of benzene and its homologues (toluene, para-xylene, and mesitylene) adsorbed on Cu/Al/Pd(111)-supported graphene using density functional theory (DFT). The long-range attraction is handled by semiempirical dispersion correction method (PBE-D3) and ab initio van der Waals density functionals (vdW-DF2, optB86b-vdW, optB88-vdW, and SCAN-rVV10). Our results show a systematic increase in the adsorption energy of organic molecules on graphene in the presence of underlaying metal substrates. In the case of strong metal-graphene contact, such as Pd(111)-graphene, the adsorption energy of benzene even increases 0.44 eV, which presents suitable platform for filtering harmful molecules such as benzene. Besides, we find out that the dispersion-corrected functionals play a fundamental role in the structure and adsorption energy. Furthermore, the adsorption energy increases linearly with the number of methyl groups on the benzene ring. [ABSTRACT FROM AUTHOR]

[Display omitted] • A prior exploration of the potential biological effect of a carbon nitride (C 3 N 3). • The moderate adsorption of C 3 N 3 nanosheet to membrane. • The molecular insights and mechanism of the interaction between C 3 N 3 and membrane. • The specific attraction between C 3 N 3 pores and lipid heads. Recently, the novel hole-containing carbon nitride C 3 N 3 nanomaterial was successfully synthesized, featuring outstanding and unique mechanical and electrical properties. However, to fully exploit this nanomaterial in biomedical applications, information regarding its biocompatibility is necessary. Herein, by using all-atom molecular dynamics simulations, we evaluate the interactions between a C 3 N 3 nanosheet and a critical cellular component, that is, a lipid membrane bilayer. Our results indicate that the C 3 N 3 nanosheet is able to interact with the lipid bilayer surface without affecting the membrane's structural integrity. Moreover, our results showed that the C 3 N 3 nanosheet is adsorbed on the surface of the lipid bilayer without inflicting any structural damage to the membrane, regardless of the conditions of the system (that is, with and without restrains in the C 3 N 3 nanosheet). Also, we found that both energy contributions, namely vdW and Coulomb energies, conjointly mediated the C 3 N 3 adsorption process. In comparison and as expected, pristine graphene significantly disturbed the membrane structure. Perpendicularly-oriented-sheet simulations described the significance of the surface charges of the C 3 N 3 nanosheet in prohibiting its insertion into the membrane. Detailed analysis indicated that the electrostatic attraction between the pores in the C 3 N 3 structure and the lipid head amino groups stabilized the interaction restricting the insertion of the C 3 N 3 structure deeper into the membrane. Our results suggested the importance of the negatively charged C 3 N 3 pores when interacting with lipid membranes. Our findings shed light on the potential compatibility of C 3 N 3 with biomembranes and its underlying molecular mechanism, which might provide a useful foundation for the future exploration of this 2D nanomaterial in biomedical applications. [ABSTRACT FROM AUTHOR]

We develop a new Gibbs free energy-based association model and perform series of molecular dynamics (MD) simulations to study the association behavior of Lennard-Jones (LJ) particles in nanoconfined aqueous solution. In the association model, the total Gibbs free energy is the sum of free energy cost in the nucleation of a densely packed cluster with an isotropic shape and a radius dependent interfacial tension coefficient, and the translation entropy of dispersed particles outside the cluster. Two key theoretical expressions – total Gibbs free energy formula and the thermodynamic equilibrium equation – are obtained to estimate the cluster aggregation number for a given LJ particle number and the corresponding total Gibbs free energy. Using MD simulations, we observe that the association state transforms from the stable dispersion state, through the reversible state, finally to the stable aggregation state as the LJ particle number increases. In the reversible state, the system reversibly switch in between the dispersion and aggregation states. The existence of three types of association states is also found for LJ particles with the varied well depth. According to our model, the Gibbs free energy curve shows from a single minimum, through two minima, finally to a single minimum, leading to the transformation of association states. The occurrence of reversible state transition is attributed to the free energy barrier of the order of thermal fluctuation in water between the dispersion and aggregation states. These findings deepen the understanding of nucleation/aggregation of hydrophobic gas molecules or particles in solution under nanoconfinement. • LJ particles show dispersion, reversible, aggregation states in nanoconfined solution. • Three association states still exist even if the well depth changes. • A Gibbs free energy-based association model is developed. • The Gibbs free energy profile shows two minima in the reversible state. • The free energy barrier is the order of thermal fluctuation. [ABSTRACT FROM AUTHOR]