Water chain formation on rutile TiO2 (110) nanocrystal: A molecular dynamics simulation approach

Mesoscopic Model for Reversible Adsorption Stage of Albumin and Fibrinogen on TiO2 Surface

The competitive behavior of proteins in the reversible adsorption stage plays a crucial role in determining the composition of the protein layer and the subsequent biological responses to the biomaterial. However, such competitive adsorption is a mesoscopic process at physiological protein concentration, and neither a macroscopic experiment nor microscopic MD (molecular dynamics) simulation is suitable to clarify it. Here, we proposed a mesoscopic DPD (dissipative particle dynamics) model to illustrate the competitive process of albumin and fibrinogen on TiO2 surface with its parameters deduced from our previous MD simulation, and proved the model well retained the diffusion and adsorption properties of proteins in the competitive adsorption on the plane surface. We then applied the model to the competitive adsorption on the surfaces with different nanostructures and observed that when the nanostructure size is much larger than that of protein, the increase in surface area is the main influencing factor; when the nanostructure size is close to that of protein, the coordination between the nanostructure and the size and shape of protein significantly affects the competitive adsorption process. The model has revealed many mechanical phenomena observed in previous experimental studies and has the potential to contribute to the development of high-performance biomaterials.

Adsorption properties of albumin and fibrinogen on hydrophilic/hydrophobic TiO2 surfaces: A molecular dynamics study

In serval experimental researches, UV-induced hydrophilicity enabled better hemocompatibility in the TiO₂ surface, which was considered to be caused by the removal of the carboxylic acid contamination from the surface. In this paper, we altered the surface wetting property by applying the formate contamination on the rutile (110) surface, and systematically investigated the adsorption properties of albumin and fibrinogen on hydrophilic/hydrophobic TiO₂ surface. Unique contacts were found between the charged residues and the hydrophilic surface, anchoring the protein on the surface. The small size and the heart shape of albumin make it easy to cross the stable water layers near the surface. Besides, albumin has a higher proportion of charged residues, so it can form more unique contacts on the hydrophilic surface. Therefore, the albumin tends to adsorb on the hydrophilic surface. For the hydrophobic surface, the water layers near the surface are weakened, which helps the fibrinogen diffusing to the surface and adjusting its orientation. Although the hydrophobic surface cannot form the unique contacts, the larger size of fibrinogen can provide more residues to form enough ordinary contacts after adjusting, and then achieves stable adsorption. Therefore, fibrinogen tends to adsorb on the hydrophobic surface.

Gas separation using graphene nanosheet: insights from theory and simulation

The investigation of porous graphene, especially experimental research, is a challenging issue in related academic and technology and has become a hot topic in recent years. It is well known that the preparation of porous graphene is a difficult problem in experimental techniques. To prepare nanoporous graphene, much attention must focus on the quality of nanoporous structures and throughput array pores. Therefore, a comprehensive summary as much as possible has been made to provide a better understanding of the progress. A summary of synthesis techniques, the properties of nanoporous graphene membranes from the synthesis point of view, and potential applications of porous graphene and graphene oxide for gas separation on the basis of theoretical studies were given attention in this paper. Gas separation, including carbon dioxide capture, gas storage, natural gas sweetening, and flue gas purification through porous graphene, is of great interest. Porous graphene with narrow pore distribution provides exciting opportunities in gas separation processes.

Interaction between N-Methylmorpholine N-Oxide, Water, and the Titanium Dioxide Surface in the Lyocell Process

Interaction between N-methylmorpholine N-oxide (NMMO), H₂O, and the titanium dioxide (TiO₂) surface was studied by spectral tests and molecular dynamics simulations as the theoretical foundation for the development of functional lyocell. The molecular structure, movement, and arrangement of the NMMO and water molecules, as well as the interaction energies between them, were characterized. The results show that both water and NMMO molecules can interact with the TiO₂ surface, and the water molecule is stronger, which makes the water molecules near the TiO₂ surface different from that of the bulk solution. With the increase of the NMMO concentration, NMMO molecules compete with the water molecules adsorbed on the TiO₂ surface, and two adsorption conformations of NMMO on the TiO₂ surface were found. When the NMMO concentration is higher than 50%, the N-O bond of NMMO is the main position interacting with the TiO₂ surface, forming a more stable and complex adsorption molecular layer and enhancing the interaction between TiO₂ and the solution, and finally promote the dispersion of TiO₂ particle and increase the zero-shear viscosity of the lyocell solution. At the same time, the strong interaction also weakens the N-O bond of the NMMO molecules near the TiO₂ surface with the bond length increasing; however, the influence cannot cause instability of NMMO. UV spectra also shows that there is no NMMO decomposition due to the addition of TiO₂ during the dissolution process. In conclusion, NMMO can promote the dispersion of the TiO₂ nanoparticles in the solvent, and the stability of NMMO is not affected, which is the basis for the preparation of the functional lyocell fiber.

Formation and stability of water clusters at the molybdenum disulfide interface: a molecular dynamics simulation investigation

In this work structural properties and dynamic behavior of a water nano droplet on the molybdenum disulfide were considered. The simulation results show that water molecules form polygon clusters on the interface, and most of which are hexagonal. Structures of water clusters at the interface are seen in two forms of curved and flattened polygons, which result in the formation of hydrogen bonds between and in the adjacent layers, respectively. Most of the clusters have circular flattened structures. Calculations of the lifetime of hydrogen bonds of water molecules at the interface also show that hydrogen bonds between water molecules at the interface have a low stability. This leads to the permanent formation and breaking down of hydrogen bonds of water molecules which can cause movement of water molecules and, consequently, the displacement of the center of mass and droplet motion. Considering the changes in the center of mass of a water droplet at the MoS₂ interface display, the water droplet has a significant spontaneous motion.