Nanosheets are exceptional solid lubricants whose performance is regulated by substrate adhesion. Using molecular dynamics simulations combined with the recently proposed phononic friction theory, we reveal how adhesion controls friction by dictating stick-slip dynamics of the sliding tip. Adhesion, through variation of nanosheet out-of-plane compliance, can modulate tip-nanosheet potential landscape anisotropy and contact stiffness to govern the tip oscillation amplitude, frequency, and damping coefficient. Synergistic enhancement of dynamic determinants amplifies as adhesion reduces, driving vigorous anisotropic sliding and significantly higher phononic energy dissipation. These findings establish a complete physical pathway from interfacial adhesion to frictional response, providing valuable guidance for designing advanced lubricant system through interfacial engineering.

Layered graphene oxide (GO) films are promising structural materials, but their strength and ductility are limited by weak, porous interfaces that lose load transfer during interlayer sliding. Here we report a nacre-like reduced graphene oxide/melamine (rGO/Mel) film coupling dense lamellar stacking with strong, constrained yet dynamically reconfigurable noncovalent interactions. Melamine is introduced between GO sheets and retained after hydroiodic acid reduction, while the reduced sheets form flatter, more compact stacks with smaller interlayer spacing. Melamine’s triazine rings interact with graphitic domains through π–π stacking, and its amine groups form reversible hydrogen bonds with residual oxygen-containing groups, sustaining shear transfer while allowing controlled sliding. Under tensile loading, rGO/Mel exhibits pronounced post-yield strain hardening associated with nanosheet straightening, interfacial reorientation and continued molecular bridging. The optimized film reaches a tensile strength of 262.7 MPa, a strain at break of 5.0 % and a toughness of 6.0 MJ m⁻3. These values represent increases of 538 %, 317 % and 2900 % over pure GO, respectively. Molecular dynamics simulations support this picture by showing more stable interlayer contact and melamine-assisted shear transfer in rGO/Mel. This work shows that constrained noncovalent interfaces can turn interlayer sliding from a failure pathway into a source of strain hardening in layered nanocomposites.

As carbon dioxide (CO2) injection plays an increasingly important role in greenhouse gas mitigation and enhanced oil recovery (EOR), a fundamental understanding of CO2-oil interfacial dynamics is essential for optimizing miscibility and displacement efficiency. In this study, molecular dynamics simulations (MD) are employed to systematically investigate interfacial evolution in CO2-alkane systems, with particular emphasis on the effects of pressure, temperature, and alkane chain length, among which chain length exerts the most pronounced influence on interfacial behavior. Results show that increasing pressure significantly enhances interfacial mass transfer and reduces the density of the alkane bulk phase, whereas increasing temperature promotes CO2 escape from the oil phase, leading to a corresponding density increase under constant-pressure conditions. Compared with short-chain alkanes, long-chain alkanes exhibit weaker pressure sensitivity and narrower interfacial characteristic lengths, which are primarily attributed to their more ordered molecular structures and tighter packing. These structural features effectively suppress CO2 dissolution, resulting in lower solubility and reduced oil swelling capacity. The minimum miscibility pressure (MMP) is determined using the vanishing interfacial tension (VIT) method. The results reveal that long-chain alkanes possess lower configurational entropy and higher interfacial stability, which increases resistance to CO2-oil miscibility and fundamentally accounts for the observed increase in MMP with alkane chain length. Overall, this work provides molecular-level insights into the interfacial evolution and miscibility mechanisms of CO2-oil systems, offering valuable theoretical guidance for optimizing CO2 injection pressure and composition-dependent strategies in EOR applications.

The confinement effect at nanoparticle (NP)-polymer matrix interface is vital to the determination of nanocomposite functionalities and varies due to thermal modulation. Nevertheless, fundamental understanding of the nanoconfinement and temperature effect on it has yet to be clarified in terms of the impacts of the interfacial interaction and/or molecular mobility. Using molecular dynamics (MD) simulations and theoretical models we characterized the temperature-dependent mass density and chain orientation of polymer near a gold NP (AuNP)-polyethylene (PE) interface. The interfacial van der Waals (vdW) interaction is found to generate compressive stress concentrations and local density peaks, which diminish with rising temperature due to the thermal expansion mismatch between AuNP and PE. Furthermore, it is established that the vdW interaction also exerts a rotational moment on polymer chain segments (PCSs) causing a trend of PCSs to orient parallel/perpendicular to the AuNP surface. This tendency is most pronounced at room temperature but diminishes with temperature deviations due to the molecular mobility changes. The study provides a theoretical framework for optimizing the nanocomposite properties by tailoring interfacial structures.

Bilayer graphene exhibits intriguing physical and mechanical properties that are suitable for advanced electronic device applications. By introducing a new degree of freedom through interlayer twisting, exotic phenomena such as superconductivity can arise. However, in practical experiments, manual manipulation is often required to fabricate such a configuration and therefore, scaled production of magic angle bilayer graphene is challenging. In this work, we propose utilizing the grain boundaries and accompanying localized out-of-plane deformation in graphene to facilitate twisted bi-layer graphene formation. Based on molecular dynamics simulations, the structure folding process along the boundary line is examined where a lower energetic cost is found. Once stabilized, the folded bilayer structure shows twist angles that differ visibly from the conventional AA or AB stacking modes and can achieve twist angles close to the 1.1° magic angle. This observation suggests a potential novel strategy for synthesizing stable twisted bilayer graphene or other two dimensional van der Waals heterostructures with greater efficiency.

Ubiquitous nitrate (NO3−) in groundwater sources is considered a hazard compound for human health. Photo-catalytic reduction by Ag-TiO2/formic acid/visible light represents an emerging method for NO3− removal without secondary pollution. In this contribution, the removal of NO3− by photo-catalytic reduction and the selectivity of N2 were systematically investigated under varied conditions, including concentrations of Ag-TiO2, NO3−, and formic acid (HCOOH). The removal efficiency of NO3− reached 84.47%, 82.68% of which was converted to N2 under the optimal conditions: NO3− at 50 mg-N/L, Ag-TiO2 at 1.0 g/L, HCOOH at 20.05 mmol/L, and reaction time at 120 min. The removal of NO3− was enhanced mainly by CO2− rather than by photo-generated electrons or HCOO−. The results of this study indicated that the production of ·CO2− by Ag-TiO2 and HCOOH under visible light catalysis can achieve efficient NO3− removal.

Twisted bilayer van der Waals materials have become a transformative framework for the design of quantum and electronic devices, yet their counterparts, the twisted bilayer non-van der Waals materials, remain largely unexplored. Here, we report the first molecular-dynamics simulation evidence of the spontaneous formation of twisted bilayer ice with moiré patterns. Unlike the twisted bilayer van der Waals materials which can be produced by manually twisting one monolayer relative to another, twisted-bilayer-ice formation hinges on the structural adaptability of hydrogen bonds to achieve thermodynamic stability. First-principles molecular-dynamics simulations confirm the thermal stability of the twisted bilayer ice with two different moiré patterns, one with commensurate twist angle of 21.8° and another 27.8°. A phase diagram illustrates the stability region of twisted bilayer ice, providing guidance for future experimental validation. This work not only expands the family of two-dimensional ices but also advances the notion of twisted bilayer hydrogen-bonding materials, thereby offering opportunities to investigate emergent properties and potential applications of twisted bilayer non-van der Waals materials.

High-efficiency degradation and conversion of cellulosic biomass into biofuels and bio-based chemicals are critical to human society for sustainable development. Long-term challenges in deciphering how mechanical external force activates nanocellulose hydrolysis at the molecular level have hindered the wider application of mechanochemistry in high-efficiency degradation technologies. Here, combining multiscale modeling and in situ experimental characterization, we revealed the mechanochemistry hidden in the mechanically activated nanocellulose degradation behaviors, that artificial kink defects enable hydrolysis acceleration. The localized plastic deformation and nonlinear molecular geometry at kink defects drive hydrolysis processes toward the lower-barrier reaction pathway and facilitate hydrolysis accessibility. The proposed two-step mechanochemical hydrolysis strategy, introducing more artificial kink defects and preferential reaction sites via mechanical pretreatment, realizes substantial enhancement of hydrolysis efficiency. This study provides a framework for anticipating how mechanical external force, microstructure defects, and molecular geometric mutation contribute to the mechanochemical degradation of cellulosic biomass with more sustainability and bioeconomy.

Supercritical carbon dioxide (scCO2) has emerged as a promising agent in enhanced oil recovery (EOR) due to its ability to reduce interfacial tension and enhance oil mobility in reservoirs. Water is ubiquitous in oil reservoirs, yet the underlying mechanisms governing scCO2 transport in the presence of water within nanoscale channels remain inadequately understood. Using molecular dynamics simulations combined with analytical models, this study explores the two-phase flow behavior of scCO2 and water in confined nanochannels, emphasizing the effects of water saturation (Sw) and channel wettability. It is found that in hydrophilic nanochannels, water preferentially adsorbs onto channel walls, forming thin films that coalesce into a water bridge at higher Sw. This water bridge drastically impedes scCO2 transport, reducing the flow capacity by up to 95%. Conversely, hydrophobic nanochannels exhibit water clustering in the channel center, which facilitates a higher scCO2 mobility. At elevated Sw, the flow pattern transitions from Poiseuille to Couette flow, further mitigating the decline in the scCO2 transport capacity. Analytical models accurately predict these behaviors, highlighting the interplay among channel wettability, Sw, and nanoscale confinement in dictating scCO2 transports. This research deepens our understanding of scCO2-water interactions and offers a theoretical foundation for optimizing scCO2-EOR processes under realistic reservoir conditions.

Surfactants are critical in the enhanced oil recovery (EOR) process due to their ability to reduce oil–water interfacial tension (IFT), thereby improving EOR efficiency. While betaine surfactants have emerged as promising candidates for achieving ultralow IFT values (∼10−3 mN/m), their standalone performance is often limited by inherent interfacial packing defects arising from their molecular architecture. In this study, we employ systematic molecular dynamics simulations to investigate the synergistic effects of blending betaine surfactants [alkyl sulfobetaine (ASB) and xylyl substituted alkyl sulfobetaine (XSB)] with nonionic surfactants Span80 or Tween80, aiming to explore the IFT reduction capability and to understand the interfacial behavior for potential application in EOR. The results indicate that when the two betaines are blended with Tween80, they compete for water molecule adsorption on the aqueous side and incorporate water molecules into the interfacial film. This disrupts the film’s ability to isolate water molecules, thus producing an antagonistic effect. In contrast, blending betaines with Span80 yields favorable interactions: at low concentrations, Span80 primarily increases intermolecular spacing between adjacent betaines to reduce electrostatic forces, generating synergistic effects. At higher concentrations, Span80 adapts to interfacial vacancies by enhancing the rigidity and angle of its hydrophobic chains, exhibiting good interfacial effects. Notably, ASB/Span80 and XSB/Span80 systems achieved ultralow IFT values but due to structural differences, XSB has relatively weaker synergy with Span80 than ASB, nonetheless it still outperforms other single or mixed surfactant systems in IFT reduction capability.

An advanced photochemical reduction system involving the UV/Fe(III)–oxalate system was developed for the reduction of nitrate (NO3−) to harmless N-gaseous species, primarily nitrogen (N2), by carbon dioxide radical (·CO2−) generated in the presence of dissolved oxygen (DO). Electron paramagnetic resonance (EPR) analyses confirmed the presence of both ·CO2− and ·OH radicals. Systematic investigations were conducted on various operational parameters, such as the initial Fe(III) concentration, oxalate concentration, and pH levels, to assess their impacts on the efficiency and products of NO3− reduction. Notably, solution pH played a significant role in influencing the NO3− reduction efficiency and the final products. At pH 2, approximately 75% of NO3− was converted into N2 with an 80% selectivity. In the pH range of 3 to 5, a remarkable NO3− removal rate of about 90% was achieved. Furthermore, higher concentrations of Fe(III) (2 mM) and oxalate (10 mM) were found to enhance NO3− removal to 91.95% and 88.71%, respectively. The presence of DO increased the oxidative potential in the reaction system, subsequently enhancing the selectivity conversion of NO3− to N2. In summary, the UV/Fe(III)–oxalate system exhibits significant potential for effective removal of NO3− while achieving high selectivity for the production of N2 in water remediation applications.

Graphene nanoplatelets (GNPs) have significant potential as reinforcement agents in metallic materials. Understanding the interfacial structure between GNPs and an aluminum matrix (AlM) is crucial for this composite (GNPs/AlMC) design and application. Studies on the effects of heat treatment on the interfacial character and its influence on mechanical properties at the atomic scale are, therefore, of high importance. This study presents molecular dynamics simulations investigating the effects of heat treatment on the interfacial structural evolution between GNPs and AlM and how such behavior tunes mechanical performance. The results show that the number of interfacial bonds increases significantly when the heat treatment temperature reaches 900 K, below which it stays at low level. Compared with the heat treatment temperature, the pressure has less effect on the interfacial bonds of GNPs/AlMCs. Moreover, defective GNPs with pores at certain heat treatment temperatures promote the formation of Al-C bonds at the interface and improve the mechanical properties of GNPs/AlMCs. These findings underscore the potential for utilizing heat treatment and defect engineering to improve interfacial bonding and achieve improved mechanical performance in GNPs/AlMCs.

Hygroscopicity and the resulting pronounced structural deformation and mechanical attenuation limit the applications of wood and nanocellulose materials. Understanding the micromechanical mechanisms of interfibrillar hydration from the perspective of interfacial hygromechanics is a prerequisite for achieving tailored macroscopic properties. Here, we demonstrated a counterintuitive mechanism that weak hydration interfaces can simultaneously strengthen and toughen nanocellulose materials due to the transition of interfacial deformation mode. The interfibrillar sliding barrier and shear strength are undoubtedly reduced by increasing interfacial hydration and shift from stick–slip motion at low humidity to more continuous slip at high moisture content. These transitions in the shear response suppress local deformation at the interface, facilitate the homogenization of fibril deformation, and ultimately enhance the interfacial load transfer capability of long fibrils through the cooperativity of hydrogen bonds. The redistribution of local stress across the interface also reduces the strain concentration in fibrils, promoting fibril pullout and bridging. This novel mechanism is applicable to other hydrogen bond-dominated building blocks for the bottom-up design of advanced nanocomposites that are both strong and tough.

Vanadium oxides have aroused attention as cathode materials in aqueous zinc-ion batteries (AZIBs) due to their low cost and high safety. However, low ion diffusion and vanadium dissolution often lead to capacity decay and deteriorating stability during cycling. Herein, vanadium dioxides (VO2) nanobelts are coated with a single-atom cobalt dispersed N-doped carbon (Co-N-C) layer via a facile calcination strategy to form Co-N-C layer coated VO2 nanobelts (VO2@Co-N-C NBs) for cathodes in AZIBs. Various in-/ex situ characterizations demonstrate the interfaces between VO2 layers and Co-N-C layers can protect the VO2 NBs from collapsing, increase ion diffusion, and enhance the Zn2+ storage performance. Additional density functional theory (DFT) simulations demonstrate that Co─O─V bonds between VO2 and Co-N-C layers can enhance interfacial Zn2+ storage. Moreover, the VO2@Co-N-C NBs provided an ultrahigh capacity (418.7 mAh g-1 at 1 A g-1), outstanding long-term stability (over 8000 cycles at 20 A g-1), and superior rate performance.

Seawater desalination is one of the most promising solutions to fresh water shortage all over the world.The rapid development of nanotechnology led to the boom of nanoporous membranes for water purifica-tion.Recent theoretical and experimental studies reported ultra-high water permeability and salt rejection in nanoporous monolayer graphene.However,the difficulty of precisely creating nanometer-scale pores and con-trolling their distribution greatly limits its industrial application.Through molecular dynamics(MD)simulation,the monolayer quasi-tetragonal phase fullerene(qTPC60)was found to have tremendous potential as ultra-per-meable membranes for desalination due to their unform pore distribution.The monolayer fullerene membranes exhibit high water permeability compared to conventional polymer filtration membranes.The work offers in-sights into the molecular mechanism of sieving,and the MD simulations show that Na+and Cl-ions have large energy barriers.This 2D monolayer carbon material with unique structure exhibits great potential in seawater desalination.

Exploring new reverse osmosis (RO) membranes that break the permeability-selectivity trade-off rule is the ultimate goal in seawater desalination. Both nanoporous monolayer graphene (NPG) and carbon nanotube (CNT) channels have been proposed to be promising candidates for this purpose. From the perspective of membrane thickness, both NPG and CNT can be classified into the same category, as NPG is equivalent to the thinnest CNT. While NPG has the advantage of a high water flux rate and CNT is excellent at salt rejection performance, a transition is expected in practical devices when the channel thickness increases from NPG to infinite-sized CNTs. By employing molecular dynamics (MD) simulations, we find that as the thickness of CNT increases, the water flux diminishes but the ion rejection rate increases. These transitions lead to optimal desalination performance around the cross-over size. Further molecular analysis reveals that this thickness effect originates from the formation of two hydration shells and their competition with the ordered water chain structure. With the increase in CNT thickness, the competition-dominated ion path through CNT is further narrowed. Once above this cross-over size, the highly confined ion path remains unchanged. Thus, the number of reduced water molecules also tends to stabilize, which explains the saturation of the salt rejection rate with the increasing CNT thickness. Our results offer insights into the molecular mechanisms of the thickness-dependent desalination performance in a one-dimensional nanochannel, which can provide useful guidance for the future design and optimization of new desalination membranes.

Understanding the mechanisms of oil/brine/rock interfacial interactions from a nanoscale perspective is essential for enhanced oil recovery (EOR) techniques employed in the exploration of shale oil. Under formation conditions, both metal cations and water molecules could form bridging connections between rock surfaces and the polar oil components, which are referred to as hydrated ion bridges (HIB) and water bridges (WB). In this work, we have comprehensively analyzed the interaction and destruction of various HIB and WB systems. Quasi-static pulling processes were investigated based on first-principles calculations. We found that ions can increase the oilrock interaction strength, especially for the divalent ions. Various different contributions to interfacial energy were scrutinized from several different approaches. Our results show that water-valeric acid could be the most probable destruction sites at oil/brine/rock interface. Hydrogen bonds and van der Waals interactions were visualized in an intuitive way, which enhance our comprehension on the interaction and destruction of HIB and WB connections. These findings may provide an in-depth insight into oil/brine/rock interfacial interactions and theoretical support for the effective oil extraction.

Phenine nanotubes (PNTs) have recently been synthesized as a promising new one-dimensional material for high-performance electronics. The periodically distributed vacancy defects in PNTs result in novel semiconducting properties, but may also compromise their mechanical properties. However, the role of these defects in modifying the structural and mechanical properties is not yet well understood. To address this, we conducted systematic molecular dynamics simulations investigating the structural evolution and mechanical responses of PNTs under various conditions. Our results demonstrated that the twisting of linear carbon chains in both armchair and zigzag PNTs led to interesting structural transitions, which were sensitive to chiralities and diameters. Additionally, when subjected to tensile and compressive loading, PNTs' cross-sectional geometry and untwisting of linear carbon chains resulted in distinct mechanical properties compared to carbon nanotubes. Our findings provide comprehensive insights into the fundamental properties of these new structures while uncovering a new mechanism for modifying the mechanical properties of one-dimensional nanostructures through the twisting-untwisting of linear carbon chains.

Uncontrollable dendrite growth and side reactions resulting in short operating life and low Coulombic efficiency have severely hindered the further development of aqueous zinc-ion batteries (AZIBs). In this work, we designed to grow zeolitic imidazolate framework-8 (ZIF-8) uniformly on CuO nanosheets (NSs) and prepared carbon-coated CuZn alloy NSs (CuZn@C NSs) by calcination under H2/Ar atmosphere. As reflected by extended X-ray absorption fine structure (EXAFS), density functional theory (DFT), and in-situ Raman, the Cu—Zn and Zn—N bonds present in CuZn@C NSs act as zincophilic sites to uniformly absorb Zn ions and inhibit the formation of Zn dendrites. At the same time, CuZn@C NSs hinder the direct contact between zinc anode and electrolyte, preventing the occurrence of side reactions. More impressively, the symmetric cells constructed with CuZn@C NSs anodes exhibited excellent zinc plating/exfoliation performance and long life cycle at different current densities with low voltage hysteresis. In addition, low polarization, high capacity retention, and long cycle life over 1000 cycles at 5 A·g−1 were achieved when CuZn@C NSs were used as anodes for CuZn@C/V2O5 full cells.

In-situ conversion process (ICP) appears to be a promising approach to enhance hydrocarbon recovery of shale reservoirs. During the ICP, the pore-networks gradually generate underground and serve as the conduits for the storage and transport of hydrocarbon, which finally decides the recovery ability of the reservoir. Reactive molecular dynamics simulations are used to study the pyrolysis behavior of kerogen under the reservoir conditions. The pyrolysis proceeds in four stages: energy accumulation, oil window, gas window, and steady stage. And during this process, the kerogen pyrolytic pore-networks form under the combined actions of chemical bond breaking and physical deformation. Further analysis demon-strates that the structural characteristic is dependent on the maturities of kerogen and pyrolysis tem-perature. Low-maturity kerogen creates high-quality pore-networks (-15% porosity), while the pores in medium-and high-maturity kerogen are scarce and isolated (-1% porosity). In the simulation, the optimal pyrolysis temperature of pyrolysis is about 2300 K to develop high-quality pore-networks. In addition, a conversion relationship between the simulation temperatures and ICP engineering temper-atures is established using Arrhenius equations, and the optimal temperature for ICP engineering is suggested to be-730 K. (c) 2021 Elsevier Ltd. All rights reserved.