Efficient heavy metal ion removal by fluorographene nanochannel templated molecular sieve: a molecular dynamics simulation study.

Environmental water contamination, particularly by heavy metal ions, has emerged as a worldwide concern due to their non-biodegradable nature and propensity to accumulate in soil and living organisms, posing a significant risk to human health. Therefore, the effective removal of heavy metal ions from wastewater is of utmost importance for both public health and environmental sustainability. In this study, we propose and design a membrane consisting of fluorographene (F-GRA) nanochannels to investigate its heavy metal ion removal capacity through molecular dynamics simulation. Although many previous studies have revealed the good performance of lamellar graphene membranes for desalination, how the zero-charged graphene functionalized by fluorine atoms (fully covered by negative charges) affects the heavy metal ion removal capacity is still unknown. Our F-GRA membrane exhibits an exceptional water permeability accompanied by an ideal heavy metal ion rejection rate. The superior performance of F-GRA membrane in removing heavy metal ions can be attributed to the negative charge of the F-GRA surface, which results in electrostatic attraction to positively charged ions that facilitates the optimal ion capture. Our analysis of the potential of mean force further reveals that water molecule exhibits the lowest free energy barrier relative to ions when passing through the F-GRA channel, indicating that water transport is energetically more favorable than ion. Additional simulations of lamellar graphene membranes show that graphene membranes have higher water permeabilities compared with F-GRA membranes, while robustly compromising the heavy meal ion rejection rates, and thus F-GRA membranes show better performances. Overall, our theoretical research offers a potential design approach of F-GRA membrane for heavy metal ions removal in future industrial wastewater treatment.

Potential toxicity of graphene (oxide) quantum dots via directly covering the active site of anterior gradient homolog 2 protein.

Graphene quantum dots (GQDs) have attracted significant attention in biomedicine, while extensive investigations have revealed a reverse regarding the potential biotoxicity of GQDs. In order to supplementing the understanding of the toxicity profile of GQDs, this study employs a molecular dynamics (MD) simulation approach to systematically investigate the potential toxicity of both GQDs and Graphene Oxide Quantum Dots (GOQDs) on the Anterior Gradient Homolog 2 (AGR2) protein, a key protein capable of protecting the intestine. We construct two typical simulation systems, in which an AGR2 protein is encircled by either GQDs or GOQDs. The MD results demonstrate that both GQDs and GOQDs can directly make contact with and even cover the active site (specifically, the Cys81 amino acid) of the AGR2 protein. This suggests that GQDs and GOQDs have the capability to inhibit or interfere with the normal biological interaction of the AGR2 active site with its target protein. Thus, GQDs and GOQDs exhibit potential detrimental effects on the AGR2 protein. Detailed analyses reveal that GQDs adhere to the Cys81 residue due to van der Waals (vdW) interaction forces, whereas GOQDs attach to the Cys81 residue through a combination of vdW (primary) and Coulomb (secondary) interactions. Furthermore, GQDs aggregation typically adsorb onto the AGR2 active site, while GOQDs adsorb to the active site of AGR2 one by one. Consequently, these findings shed new light on the potential adverse impact of GQDs and GOQDs on the AGR2 protein via directly covering the active site of AGR2, providing valuable molecular insights for the toxicity profile of GQD nanomaterials.

Magnesium Ion Gated Ion Rejection through Carboxylated Graphene Oxide Nanopore: A Theoretical Study.

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.

Villin headpiece unfolding upon binding to boridene mediated by the "anchoring-perturbation" mechanism.

We employ molecular dynamics (MD) simulations to investigate the influence of boridene on the behavior of a protein model, HP35, with the aim of assessing the potential biotoxicity of boridene. Our MD results reveal that HP35 can undergo unfolding via an "anchoring-perturbation" mechanism upon adsorption onto the boridene surface. Specifically, the third helix of HP35 becomes tightly anchored to the boridene surface through strong electrostatic interactions between the abundant molybdenum atoms on the boridene surface and the oxygen atoms on the HP35 backbone. Meanwhile, the first helix, experiencing continuous perturbation from the surrounding water solution over an extended period, suffers from potential breakage of hydrogen bonds, ultimately resulting in its unfolding. Our findings not only propose, for the first time to our knowledge, the "anchoring-perturbation" mechanism as a guiding principle for protein unfolding but also reveal the potential toxicity of boridene on protein structures.

Exceptional metal-semiconductor-metal transition of lead apatites via oxygen defect tuning.

Lead apatites, distinguished and compelling bulk materials with the stoichiometric arrangement as Pb10(POx)6Oy, are renowned for their structural complexity. Recently, the discovery of possible room-temperature superconductivity under ambient pressure in copper-substituted lead apatites has engendered considerable interest within both the physics community and beyond. Nevertheless, exploration of pristine Pb10(POx)6Oy parent structures has hitherto remained elusive. In this study, we employ density functional theory (DFT) calculations to investigate the effects of oxygen defects on the electronic structures of Pb10(POx)6Oy and Pb9Cu(POx)6Oy. We scrutinize two distinct categories of defects: oxygen atoms enmeshed within POx groups (Ox) and solitary oxygen atoms (Oy). Our investigation uncovers a profound influence of these defects on the band structure. Specifically, the introduction of Oy defects prompts a remarkable transition in Pb10(PO4)6Oy from a metal to semiconductor to metal state, accompanied by pivotal shifts in the principal electronic contributors from p orbitals of Oy to those of Pb atoms. Furthermore, the introduction of Ox defects in Pb10(POx)6O1 engenders metamorphosis in the band structure, transmuting it from a semiconductor to a metallic state. Significantly, our findings pinpoint the suitable range of x in the Pb10(POx)6O1 configuration as lying between 2 and 4. Additionally, our study also demonstrates that the oxygen defects (Ox/Oy) do not affect the metallic properties of copper-substituted lead apatites. This study elucidates the significant role of oxygen defects in modulating the electronic properties of apatite materials, offering insights into potential interdisciplinary applications. This establishes a crucial link between material composition and electronic behavior, revealing key mechanisms for engineering functionality in lead apatites and other advanced materials.

Graphene quantum dots blocking the channel egresses of cytochrome P450 enzyme (CYP3A4) reveals potential toxicity.

Graphene quantum dots (GQDs) have garnered significant attention, particularly in the biomedical domain. However, extensive research reveals a dichotomy concerning the potential toxicity of GQDs, presenting contrasting outcomes. Therefore, a comprehensive understanding of GQD biosafety necessitates a detailed supplementation of their toxicity profile. In this study, employing a molecular dynamics (MD) simulation approach, we systematically investigate the potential toxicity of GQDs on the CYP3A4 enzyme. We construct two distinct simulation systems, wherein a CYP3A4 protein is enveloped by either GQDs or GOQDs (graphene oxide quantum dots). Our results elucidate that GQDs come into direct contact with the bottleneck residues of Channels 2a and 2b of CYP3A4. Furthermore, GQDs entirely cover the exits of Channels 2a and 2b, implying a significant hindrance posed by GQDs to these channels and consequently leading to toxicity towards CYP3A4. In-depth analysis reveals that the adsorption of GQDs to the exits of Channels 2a and 2b is driven by a synergistic interplay of hydrophobic and van der Waals (vdW) interactions. In contrast, GOQDs only partially obstruct Channel 1 of CYP3A4, indicating a weaker influence on CYP3A4 compared to GQDs. Our findings underscore the potential deleterious impact of GQDs on the CYP3A4 enzyme, providing crucial molecular insights into GQD toxicology.

Moderate binding of villin headpiece protein to C3N3 nanosheet reveals the suitable biocompatibility of this nanomaterial.

Since its recent successful synthesis and due to its promising physical and chemical properties, the carbon nitrite nanomaterial, C3N3, has attracted considerable attention in various scientific areas. However, thus far, little effort has been devoted to investigating the structural influence of the direct interaction of this 2D nanomaterial and biomolecules, including proteins and biomembranes so as to understand the physical origin of its bio-effect, particularly from the molecular landscape. Such information is fundamental to correlate to the potential nanotoxicology of the C3N3 nanomaterial. In this work, we explored the potential structural influence of a C3N3 nanosheet on the prototypical globular protein, villin headpiece (HP35) using all-atom molecular dynamics (MD) simulations. We found that HP35 could maintain its native conformations upon adsorption onto the C3N3 nanosheet regardless of the diversity in the binding sites, implying the potential advantage of C3N3 in protecting the biomolecular structure. The adsorption was mediated primarily by vdW interactions. Moreover, once adsorbed on the C3N3 surface, HP35 remains relatively fixed on the nanostructure without a distinct lateral translation, which may aid in keeping the structural integrity of the protein. In addition, the porous topological structure of C3N3 and the special water layer present on the C3N3 holes conjointly contributed to the restricted motion of HP35 via the formation of a high free energy barrier and a steric hindrance to prevent the surface displacement. This work revealed for the first time the potential influence of the 2D C3N3 nanomaterial in the protein structure and provided the corresponding in-depth molecular-level mechanism, which is valuable for future applications of C3N3 in bionanomedicine.

Ultralow lattice thermal conductivities and excellent thermoelectric properties of hypervalent triiodides XI3 (X = Rb, Cs) discovered by machine learning method.

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.

Robust Mechanical Destruction to the Cell Membrane of Carbon Nitride Polyaniline (C3N): A Molecular Dynamics Simulation Study.

The drug-resistant bacteria, particularly multidrug-resistant bacteria, has emerged as a major global public health concern posing serious threats to human life and survival. Nanomaterials, including graphene, have shown promise as effective antibacterial agents owing to their unique antibacterial mechanism compared with traditional drugs. Despite the structural similarity to graphene, the potential antibacterial activity of carbon nitride polyaniline (C3N) remains unexplored. In this study, we employed molecular dynamics simulations to investigate the effects of the interaction between the C3N nanomaterial and the bacterial membrane to evaluate the potential antibacterial activity of C3N. Our results suggest that C3N is capable of inserting deep into the bacterial membrane interior, regardless of the presence or absence of positional restraints in the C3N. The insertion process also resulted in local lipid extraction by the C3N sheet. Additional structural analyses revealed that C3N induced significant changes in membrane parameters, including mean square displacement, deuterium order parameters, membrane thickness, and area per lipid. Docking simulations, where all the C3N are restraint to a specific positions, confirmed that C3N can extract lipids from the membrane, indicating the strong interaction between the C3N material and the membrane. Free-energy calculations further revealed that the insertion of the C3N sheet is energetically favorable and that C3N exhibits membrane insertion capacity comparable to that observed for graphene, suggesting their potential for similar antibacterial activity. This study provides the first evidence of the potential antibacterial properties of C3N nanomaterials via bacterial membrane damage and underscores the potential for its use as antibacterial agents in the future applications.

Highly Efficient CO2/C2H2 Separation by Porous Graphene via Quadrupole Gating Mechanism.

Acetylene (C2H2) is an important and widely used raw material in various industries (such as petrochemical). Generally, a product yield is proportional to the purity of C2H2; however, C2H2 from a typical industrial gas-production process is commonly contaminated by CO2. So far, the achievement of high-purity C2H2 separated from a CO2/C2H2 mixture is still challenging due to their very close molecular dimensions and boiling temperatures. Taking advantage of their quadrupoles with opposite signs, here, we show that the graphene membrane embedded with crown ether nanopores can achieve an unprecedented separation efficiency of CO2/C2H2. Combining the molecular dynamics simulation and the density functional theory (DFT) approaches, we discovered that the electrostatic gas-pore interaction favorably allows the fast transport of CO2 through crown ether nanopores while completely prohibiting C2H2 transport, which yields a remarkable permeation selectivity. In particular, the utilized crown ether pore is capable of allowing the individual transport of CO2 while completely rejecting the passage of C2H2, independent of the applied pressures, fed gases ratios, and exerted temperatures, featuring the superiority and robustness of the crown pore in CO2/C2H2 separation. Further, DFT and PMF calculations demonstrate that the transport of CO2 through the crown pore is energetically more favorable than the transport of C2H2. Our findings reveal the potential application of graphene crown pore for CO2 separation with outstanding performance.

MoS2-Plasmonic Nanocavities for Raman Spectra of Single Extracellular Vesicles Reveal Molecular Progression in Glioblastoma.

Extracellular vesicles (EVs) are continually released from cancer cells into biofluids, carrying actionable molecular fingerprints of the underlying disease with considerable diagnostic and therapeutic potential. The scarcity, heterogeneity and intrinsic complexity of tumor EVs present a major technological challenge in real-time monitoring of complex cancers such as glioblastoma (GBM). Surface-enhanced Raman spectroscopy (SERS) outputs a label-free spectroscopic fingerprint for EV molecular profiling. However, it has not been exploited to detect known biomarkers at the single EV level. We developed a multiplex fluidic device with embedded arrayed nanocavity microchips (MoSERS microchip) that achieves 97% confinement of single EVs in a minute amount of fluid (<10 µL) and enables molecular profiling of single EVs with SERS. The nanocavity arrays combine two featuring characteristics: (1) An embedded MoS2 monolayer that enables label-free isolation and nanoconfinement of single EVs due to physical interaction (Coulomb and van der Waals) between the MoS2 edge sites and the lipid bilayer; and (2) A layered plasmonic cavity that enables sufficient electromagnetic field enhancement inside the cavities to obtain a single EV level signal resolution for stratifying the molecular alterations. We used the GBM paradigm to demonstrate the diagnostic potential of the SERS single EV molecular profiling approach. The MoSERS multiplexing fluidic achieves parallel signal acquisition of glioma molecular variants (EGFRvIII oncogenic mutation and MGMT expression) in GBM cells. The detection limit of 1.23% was found for stratifying these key molecular variants in the wild-type population. When interfaced with a convolutional neural network (CNN), MoSERS improved diagnostic accuracy (87%) with which GBM mutations were detected in 12 patient blood samples, on par with clinical pathology tests. Thus, MoSERS demonstrates the potential for molecular stratification of cancer patients using circulating EVs.

Efficient seawater desalination in lamellar nanochannel-based boridene filtration membrane.

With the progressively increasing demand for freshwater, the shortage of global freshwater resources has become one of the most serious events that all humans are facing now. The reverse osmosis (RO) technology that achieves freshwater from seawater is a promising strategy. However, current RO membranes suffer from the bottleneck of low efficiency. In this work, we designed a RO membrane based on a novel two-dimensional nanomaterial, boridene, prepared by stacking them into lamellar nanochannels. We employed the molecular dynamics (MD) simulation approach to investigate the desalination performance of the designed boridene lamellar membrane. Our results showed that the water permeability through the boridene membrane increased following the incremental interlayer spacing. In addition, the boridene membrane exhibits high water permeability and ideal salt rejection, featuring water permeability far beyond those obtained from commercial RO membranes with two orders of magnitude enhancement. Further free energy calculations demonstrated that the water molecules are energetically more favorable to transport through the boridene lamellar nanochannels than ions. Therefore, our results highlight that the boridene lamellar nanochannel-based filtration membrane can be utilized as a potential outstanding candidate in RO membranes for future desalination applications.

The single-atom catalytic activity of the hydrogen evolution reaction of the experimentally synthesized boridene 2D material: a density functional theory study.

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 ([Formula: see text]) 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.

Insights into the thermodynamic-kinetic synergistic separation of propyne/propylene in anion pillared cage MOFs with entropy-enthalpy balanced adsorption sites.

Propyne/propylene (C3H4/C3H6) separation is an important industrial process yet challenged by the trade-off of selectivity and capacity due to the molecular similarity. Herein, record C3H4/C3H6 separation performance is achieved by fine tuning the pore structure in anion pillared MOFs. SIFSIX-Cu-TPA (ZNU-2-Si) displays a benchmark C3H4 capacity (106/188 cm3 g-1 at 0.01/1 bar and 298 K), excellent C3H4/C3H6 IAST selectivity (14.6-19.3) and kinetic selectivity, and record high C3H4/C3H6 (10/90) separation potential (36.2 mol kg-1). The practical C3H4/C3H6 separation performance is fully demonstrated by breakthroughs under various conditions. 37.8 and 52.9 mol kg-1 of polymer grade C3H6 can be produced from 10/90 and 1/99 C3H4/C3H6 mixtures. 4.7 mol kg-1 of >99% purity C3H4 can be recovered by a stepped desorption process. Based on the in situ single crystal analysis and DFT calculation, an unprecedented entropy-enthalpy balanced adsorption pathway is discovered. MD simulation further confirmed the thermodynamic-kinetic synergistic separation of C3H4/C3H6 in ZNU-2-Si.

Single-layered fluorinated graphene nanopores for H2/CH4 and H2/CO2 separation with high efficiency and selectivity.

The utilization of hydrogen gas (H2) as an energy resource is a critical alternative to relieve the current greenhouse effect exacerbated by the excessive use of fossil fuels. The production of pure H2 is usually achieved by its separation from H2/CH4 and H2/CO2 mixtures; however, such process still represents a great challenge due to the inevitable contamination that occurs after the membrane sieving. Here, we investigate the ability of a 2-dimensional material, a nanoporous fluorinated graphene (F-GRA), to perform the separation of H2/CH4 and H2/CO2 using molecular dynamics simulations. We generated three representative nanopores with different morphologies in F-GRA sheets to separately explore their sieving performances for the H2 separation in the H2/CH4 and H2/CO2 mixtures. Our results revealed that the three F-GRA pores have an excellent performance for the H2/CH4 separation, displaying a high permeance for H2 (over 104 GPU) and a complete rejection for CH4; these results suggest an ideal permeability and selectivity for these 2D systems. Additionally, two F-GRA pores, namely, pore2 and pore3, also displayed high separation performance in the case of the H2/CO2 mixture, while the remaining pore, namely, pore1, exhibit poor performance due to the tight obstruction of the CO2 gas inside the nanopore. Combined, our findings exploit the utilization of the nanoporous F-GRA 2D material for the separation of H2/CH4 and H2/CO2 gas mixtures, which might open new possibilities for the future of gas sieving membrane preparation.

Ionic Liquid Decelerates Single-Stranded DNA Transport through Molybdenum Disulfide Nanopores.

Nanopores in two-dimensional (2D) materials have emerged to offer in principle necessary spatial resolution for high-throughput DNA sequencing. However, their fidelity is severely limited by the fast DNA translocation. A recent experiment indicates that introducing ionic liquids could slow down DNA translocation in a MoS2 nanopore. However, the corresponding in-depth molecular mechanism underlying the experimental findings is not fully understood, which is crucial for the future improvement of rational DNA translocation control. Here, we computationally investigate and then experimentally identify the effect of BmimCl ionic liquid on the retardation of ssDNA translocation through a single-layer MoS2 nanopore. Our all-atom molecular dynamics simulations demonstrate that the strong interaction between Bmim+ and ssDNA offers a considerable dragging force to decelerate the electrophoretic motion of ssDNA in the BmimCl solution. Moreover, we show that Bmim+ ions exhibit preferential binding on the sulfur edges of the nanopore. These Bmim+ in the pore region can not only act as a steric blockage but also form π-π stackings with nucleobases, which provide a further restriction on the ssDNA motion. Therefore, our molecular dynamics simulation investigations deepen the understanding of the critical role of ionic liquid in DNA translocation through a nanopore from a molecular landscape, which may benefit practical implementations of ionic liquids in nanopore sequencing.

Crown Nanopores in Graphene for CO2 Capture and Filtration.

With growing concerns about global warming, it has become urgent and critical to capture carbon from various emission sources (such as power plants) and even directly from air. Recent advances in materials research permit the design of various efficient approaches for capturing CO2 with high selectivity over other gases. Here, we show that crown nanopores (resembling crown ethers) embedded in graphene can efficaciously allow CO2 to pass and block other flue gas components (such as N2 and O2). We carried out extensive density functional theory-based calculations as well as classical and ab initio molecular dynamics simulations to reveal the energetics and dynamics of gas transport through crown nanopores. Our results highlight that the designed crown nanopores in graphene possess not only an excellent selectivity for CO2 separation/capture but also fast transport (flow) rates, which are ideal for the treatment of flue gas in power plants.

Fluorinated graphene nanomaterial causes potential mechanical perturbations to a biomembrane.

Fluorinated graphene (F-GRA) has attracted great interest in biomedical applications. In this context, the direct interaction between F-GRA and various biomolecules is a vital process guiding the bio-function of this nanomaterial. Nevertheless, information regarding the interaction of F-GRA with biomolecules is scarce, particularly at the molecular level. In this study, using an in silico approach, we investigate the adsorption of F-GRA to a phospholipid bilayer to evaluate the potential effect of the nanomaterial to a biomembrane and its mechanism. Our results indicate that F-GRA can either slightly insert into the membrane or parallelly adhere on the membrane surface, different from the complete insertion of graphene. Detailed analysis confirms that the electrostatic forces dominantly mediate the adsorption process. F-GRA in its parallel binding pattern causes a partial enlargement in the membrane thickness via the disruption of the lipids' order parameters, indicating a mild mechanical influence to the membrane structure. Although the potential mechanical perturbation of F-GRA to membrane is detected, this impact is much weaker than graphene. These findings suggest the potentially weak physical perturbations of F-GRA to the cellular membrane, which may establish the basis for the future biomedical applications of this material after proper surface coating.

Unexpected hydrophobicity on self-assembled monolayers terminated with two hydrophilic hydroxyl groups.

Current major approaches to access surface hydrophobicity include directly introducing hydrophobic nonpolar groups/molecules onto the surface or elaborately fabricating surface roughness. Here, for the first time, molecular dynamics simulations show an unexpected hydrophobicity with a contact angle of 82° on a flexible self-assembled monolayer terminated only with two hydrophilic OH groups ((OH)2-SAM). This hydrophobicity, verified by a water slip phenomenon characterizing the friction on the (OH)2-SAM surface, is attributed to the formation of a hexagonal-ice-like H-bonding structure in the OH matrix of (OH)2-SAM, which sharply reduces the hydrogen bonds between the surface and the water molecules above. The unique simple interface presented here offers a significant molecular-level platform for examining the bio-interfacial interactions ranging from biomolecule binding to cell adhesion.

Membrane Insertion of MoS2 Nanosheets: Fresh vs. Aged.

Fresh two-dimensional molybdenum disulfide (MoS2) absorbs the hydrocarbon contaminations in the ambient air and makes surface aging. To understand how the surface aging influences the interactions between MoS2 and biomolecules is important in the biomedical applications. Here, employing all-atom molecular dynamics simulations, we investigated the interactions of the fresh and aged MoS2 nanosheets with the lipid membranes of different components. Our results demonstrate that both the fresh and aged MoS2 nanosheets can spontaneously insert into the bilayer membranes. However, the fresh MoS2 nanosheet displays significantly stronger interaction and then has a larger penetration depth than the aged counterpart, regardless of the lipid components. The calculations of potential mean forces through the umbrella sampling further confirm that the insertion of fresh MoS2 into the lipid membranes is more energetically favorable. Moreover, we found that the fresh MoS2 nanosheet can cause a larger damage to the integrity of lipid membranes than the aged one. This work provides insightful understandings of the surface-aging-dependent interactions of the MoS2 nanosheets with biomembranes, which could facilitate the design of novel MoS2-based nanodevices with advanced surface properties.