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A novel three-dimensional graphene/polyaniline (3DGP) composite was achieved by a hydrothermal method from in situ polymerization of a polyaniline/graphene oxide composite and GO suspension. This 3DGP composite possesses a 3D porous network structure and large specific capacity of 648 F g−1 at a current density of 0.5 A g−1. In particular, the capability can reach 356 F g−1 even at 20.0 A g−1, 537 F g−1 at 1.0 A g−1 can also be achieved after 1000 cycles. Therefore, the 3DGP composite is a suitable and promising electrode material for supercapacitors.

Gold nanoparticles (AuNPs) are of biomedical importance, such as delivery vectors. Therefore, we used all-atom molecular dynamic simulations to study the interaction of AuNPs with cell membrane (DMPC bilayer). We observed that the AuNPs adhered spontaneously on the surface of the cellular membrane from the bulk phase, largely as a result of the AuNP-DMPC headgroup attraction. We calculated the potential of mean force for transferring an AuNP through a DMPC bilayer. It was observed that a high energetic barrier to AuNP was inserted into the hydrophobic core of the bilayer. The inclusion of AuNP induced local bilayer deformation and slowed fluidity of the lipid molecules in the vicinity of it. As the size of the AuNP increased, the lipids in the vicinity of the AuNP had larger local deformation and slower fluidity. We found that a nanoparticle-membrane complex was formed by the AuNP and its neighbor lipids. These neighbor lipids moved laterally together with AuNP. On average, they moved significantly more slowly than the other lipids. The nanoparticle-membrane complex not only provided a clue for endocytosis mechanism regulating the translocation of AuNPs across the cellular membrane but also helped us to better understand the endocytosis process.

By combining the gauge cell method and lattice model, we study the surface phase transition and adsorption behaviors of surfactants on a solid surface. Two different cases are considered in this work: macrophase transition and adsorption in a single-phase region. For the case of macrophase transition, where two phases coexist, we investigate the shape and size of the critical nuclei and determine the height of the nucleation barrier. It is found that the nucleation depends on the bulk surfactant concentration. Our simulations show that there exist a critical temperature and critical adsorption energy, below which the transition from low-affinity adsorption to the bilayer structure shows the characteristic of a typical first-order phase transition. Such a surface phase transition in the adsorption isotherm is featured by a hysteresis loop. The hysteresis loop becomes narrower at higher temperature and weaker adsorption energy and finally disappears at the critical value. For the case where no macrophase transition occurs, we study the adsorption isotherm and microphase separation in a single-phase region. The simulation results indicate that the adsorption isotherm in adsorption processes is divided into four regions in a log-log plot, being in agreement with experimental observations. In this work, the four regions are called the low-affinity adsorption region, the hemimicelle region, the morphological transition region, and the plateau region. Simulation results reveal that in the second region the adsorbed monomers aggregate and nucleate hemimicelles, while adsorption in the third region is accompanied by morphological transitions.

From lattice Monte Carlo simulations, we found that an intermediate state, which is called the bridge structure, may exist during the phase transition of confined amphiphile/water systems, such as a transition from the monolayers on each solid surface to bilayer structures between the adsorbed monolayers. Extensive simulation results show that the occurrence of the bridge phase during the monolayer/bilayer transitions depends on the transition path and surfactant architecture. In addition, it is suggested that the bridge structure found in this work may be one possible origin for long-range hydrophobic forces.

In this work, lattice Monte Carlo was used to study the effects of crowding on the self-assembly of surfactants. Simulation results show that crowding strongly shifts the critical micelle concentration (CMC) of surfactants from the bulk value. Two effects originated from crowding are found to govern the CMC shift: one is the depletion effect by crowding agents and the other is the available volume for micelle formation. The depletion effects inevitably result in the enrichment of surfactants in crowding-free regions and cause the decrease in CMC. On the other hand, the appearance of crowding agents decreases the available volume for micelle formation, which reduces the conformational entropy and impedes the micelle formation. Three factors, including the radius of crowding agents, the arrangement of crowding agents, and the volume fraction of crowding agents, are considered in this work to study the crowding effects. The trends of CMC shifts are interpreted from the competition between the depletion effects and the available volume for micelle formation.

It is known that the thermoacidophilic archaebacterium Sulfolobus acidocaldarius can grow in hot springs at 65-80 degrees C and live in acidic environments (pH 2-3); however, the origin of its unusual thermal stability remains unclear. In this work, using a vesicle as a model, we study the thermal stability and rupture of archaebacterial cell membrane. We perform a simulation investigation of the structure-property relationship of monolayer membrane formed by bolaform lipids and compare it with that of bilayer membrane formed by monopolar lipids. The origin of the unusually thermal stability of archaebacterial cell and the mechanism for its rupture are presented in molecular details.

In this work, we first show that there are only five independent interchange parameters in the surfactant-solvent-interface system in Larson's model, and then adsorption and morphology transition of surfactants on hydrophobic surfaces are studied by extensive lattice Monte Carlo simulations. In our simulations, we found that there exist six adsorbed morphologies: (1) premature admicelle, (2) hemisphere, (3) hemisphere-hemicylinder mixture, (4) wormlike hemicylinder, (5) perforated monolayer, and (6) monolayer. The surface morphologies and the amount of adsorption on hydrophobic surfaces are found to be affected obviously by two interchange parameters. One is the attractive interaction between tail groups and surface (chiTS), and the other is the solubility of head groups in bulk (chiHW). Phase diagrams in chiHW versus chiTS planes for surfactants with different hydrophobicities (chiTW) and for surfactants with different molecular structures are determined in this work, from which the transitions of surface morphologies and adsorption behaviors are discussed.