Unraveling the Phase Behavior, Mechanical Stability, and Protein Reconstitution Properties of Polymer-Lipid Hybrid Vesicles.

Hybrid vesicles consisting of natural phospholipids and synthetic amphiphilic copolymers have shown remarkable material properties and potential for biotechnology, combining the robustness of polymers with the biocompatibility of phospholipid membranes. To predict and optimize the mixing behavior of lipids and copolymers, as well as understand the interaction between the hybrid membrane and macromolecules like membrane proteins, a comprehensive understanding at the molecular level is essential. This can be achieved by a combination of molecular dynamics simulations and experiments. Here, simulations of POPC and PBD22-b-PEO14 hybrid membranes are shown, uncovering different copolymer configurations depending on the polymer-to-lipid ratio. High polymer concentrations created thicker membranes with an extended polymer conformation, while high lipid content led to the collapse of the polymer chain. High concentrations of polymer were further correlated with a decreased area compression modulus and altered lateral pressure profiles, hypothesized to result in the experimentally observed improvement in membrane protein reconstitution and resistance toward destabilization by detergents. Finally, simulations of a WALP peptide embedded in the bilayer showed that only membranes with up to 50% polymer content favored a transmembrane configuration. These simulations correlate with previous and new experimental results and provide a deeper understanding of the properties of lipid-copolymer hybrid membranes.

Reduction-Driven 3D to 2D Transformation of Cu Nanoparticles.

The interaction between metal and metal oxides at the nanoscale is of uttermost importance in several fields, thus its enhancement is highly desirable. In catalysis, the performance of the nanoparticles is dependent on a wide range of properties, including its shape that is commonly considered stable during the catalytic reaction. In this study, highly reducible CeO2-x nanoparticles are synthesized aiming to provide Cu/CeO2-x nanoparticles, which are classically active catalysts for the CO oxidation reaction. It is observed that the Cu nanoparticles shape changes during reduction treatment (prior to the CO oxidation reaction) from a nearly spherical 3D to a planar 2D shape, then enhances the Cu-CeO2-x interaction. The spread of the Cu nanoparticles over the CeO2-x surface during the reduction treatment occurs due to the minimization of the total system energy. The shape change is accompanied by migration of O atoms from CeO2 surface to the border of the Cu nanoparticles and the change from the Cu0 to Cu+1 state. The spreading of the Cu nanoparticles influences on the reactivity results toward the CO oxidation reaction since it changes the local atomic order around Cu atoms. The results show a timely contribution for enhancing the interaction between metal and metal oxide.

Strain-Tunable Carbon Nanothread-Derived Membranes for Water Desalination.

Carbon nanothread-derived nanomeshes are highly flexible two-dimensional (2D) structures with tunable pore size and shape, which allows fine control of their transport properties when applied as membranes. In this work, we use molecular dynamics simulations to investigate the performance of several nanomesh structures as membranes for water desalination through reverse osmosis. Results show that these membranes can operate in a wide range of water flow rate, with an optimal point that yields 100% NaCl rejection and water permeability as high as 106 L·cm-2·day-1·MPa-1, higher than other nanoporous 2D materials reported in the literature. This promising performance is partially due to the elliptical pores of strained nanomeshes, which allow the passage of rotated water molecules while rejecting hydrated salt ions. Our results show that carbon nanothread-derived nanomeshes have great potential for application in water desalination processes and emphasize the importance of engineering pore shape in 2D materials when applied as reverse osmosis membranes.

First-principles study of carbon nanothreads derived from five-membered heterocyclic rings: thiophene, furan and pyrrole.

Carbon nanothreads are one-dimensional materials obtained by controlled compression of aromatic molecules. Benzene and other six-membered ring molecules are normally used as precursors, but recent experiments have shown that carbon nanothreads can also be synthesized from five-membered ring heterocyclic compounds such as thiophene and furan, with an improved control of the structure of the final material and potentially easier scalability. In this work we use Density Functional Theory calculations to unveil the structural, electronic and mechanical properties of carbon nanothreads derived not only from thiophene and furan, but also from pyrrole, aiming to encourage experimental efforts towards the synthesis of equivalent 1D materials. Our results show that these new structures are remarkably stable when compared to similar nanothreads derived from benzene and pyridine. The presence of heteroatoms may lead to significant variations on the electronic band gap of these materials compared to conventional nanothreads, without compromising their mechanical properties. These findings suggest that nanothreads derived from five-membered rings are suitable for the same applications proposed for conventional NTs and potential candidates for new ones.

Peering into the Formation of Template-Free Hierarchical Flowerlike Nanostructures of SrTiO3.

The development of efficient advanced functional materials is highly dependent on properties such as morphology, crystallinity, and surface functionality. In this work, hierarchical flowerlike nanostructures of SrTiO3 have been synthesized by a simple template-free solvothermal method involving poly(vinylpyrrolidone) (PVP). Molecular dynamics simulations supported by structural characterization have shown that PVP preferentially adsorbs on {110} facets, thereby promoting the {100} facet growth. This interaction results in the formation of hierarchical flowerlike nanostructures with assembled nanosheets. The petal morphology is strongly dependent on the presence of PVP, and the piling up of nanosheets, leading to nanocubes, is observed when PVP is removed at high temperatures. This work contributes to a better understanding of how to control the morphological properties of SrTiO3, which is fundamental to the synthesis of perovskite-type materials with tailored properties.

Formation and Mechanical Behavior of Nanocomposite Superstructures from Interlayer Bonding in Twisted Bilayer Graphene.

We report a comprehensive study on the design of two-dimensional graphene-diamond nanocomposite superstructures formed through interlayer covalent bonding of twisted bilayer graphene with commensurate bilayers. The interlayer bonding is induced by patterned hydrogenation that leads to the formation of superlattices of two-dimensional nanodiamond domains embedded between the two graphene layers. We generalize a rigorous algorithm for the formation of all possible classes of these superstructures: the structural parameters employed to design such carbon nanocomposites include the commensurate bilayer's twist angle, the stacking type of the nanodomains where the interlayer bonds are formed, the interlayer bond pattern, and the interlayer C-C bond density that is proportional to the concentration of sp3-hybridized interlayer-bonded C atoms. We also analyze systematically the mechanical behavior of these nanocomposite superstructures on the basis of molecular-dynamics simulations of uniaxial tensile straining tests according to a reliable interatomic bond-order potential. We identify a range of structural parameters over which the fracture of these superstructures is ductile, mediated by void formation, growth, and coalescence, contrary to the typical brittle fracture of graphene. We introduce a ductility metric as an order parameter for the brittle-to-ductile transition, demonstrate its direct dependence on the fraction of sp3-hybridized interlayer-bonded C atoms, and show that increasing the fraction of interlayer-bonded C atoms beyond a critical level in certain classes of these superstructures induces their ductile mechanical response.