Ultrathin V2O5 nanosheets were successfully prepared through supercritical solvothermal reaction followed by annealing treatment. The formation of ultrathin nanosheets is owing to Ostwald ripening and the effect of supercritical fluids. As cathode material for lithium batteries, the ultrathin V2O5 nanosheets exhibit a capacity of 108 mA h g(-1) at a high rate of up to 10 C at 2.4-4 V and excellent cyclability with little capacity loss after 200 cycles. The enhanced rate performance is attributed to the shortened diffusion distance and the increased electrode-electrolyte contact area of the ultrathin nanosheet structure. It is also demonstrated that the supercritical solvothermal method is effective and facile to scalably synthesize ultrathin nanomaterials for lithium batteries.

The presence of thin aqueous films and their stability have a profound effect on the interactions between oil/brine/rock interfaces. In a previous report, we proposed that hydration forces, originating from the overlap of hydrated layers of different surfaces in the presence of sodium chloride, played an important role at short range. In the present work, divalent ions were introduced to the liquid films and, the mechanisms in improving oil recovery from low-salinity brine and the low-salinity effect at the molecular level were revealed. Through a direct force-measuring technique of chemical force microscopy (CFM), the functionalized atomic force microscopy (AFM) tips felt a solid surface to mimic the oil/rock interactions in brine. It was found that not only did the van der Waals and electrostatic forces have a great effect on this process due to the interactions between the charged interfaces of oil/water and water/solid, but also some important additional interactions appeared at short range under a variety of salinity concentrations or compositions. Taking into account the important role of structural forces under a small distance, the force profiles were fitted well with the theory of extended Derjaguin–Landau–Verwey–Overbeek (denoted by EDLVO) through a double-exponential or Gaussian model. Interestingly, low adhesion appeared in the presence of sodium sulfate, because hydration forces contributed to the resultant force depending on the intrinsic properties of the solvent or solute molecules, while in the presence of calcium chloride, high adhesion emerged due to the dispersion interaction between water and hydrocarbon molecules, as well as the reorientation or restructuring of water molecules with tiny breakage of hydrogen bonds. Therefore, on the basis of the EDLVO theory, additional forces were suggested to play an important part in short range, proposing a better understanding of the effect of divalent ions on the thin liquid films in the process of increasing oil recovery.

3,4-Dihydroxy-l-phenylalanine (l-DOPA) is considered to be responsible for the mussel adhesion to a variety of surfaces. A molecular level understanding of the interactions between DOPA molecules and surfaces with different wettability and chemistry, however, posts significant challenges to control marine antifouling. Here, different self-assembled monolayers (SAMs) on gold surfaces were fabricated: (i) OH-, (ii) COOH-, and (iii) CH3-terminations. The effect of surface wettability and chemistry on the adsorption of DOPA upon the series of surfaces was investigated in situ, showing that the adsorbed mass was lower and the water content of DOPA layer was higher on hydrophilic surfaces (including OH- and COOH-terminated SAMs) than that on hydrophobic ones (including CH3-terminated SAMs and gold surface). Direct evidence regarding the DOPA orientation and the interaction between DOPA and film surfaces were obtained: on the OH-terminated surface a flexible and loose structure formed via coordinate hydrogen bonds of the hydroxyl end groups of the surface interacting with carboxyl groups of DOPA, while for the CH3-terminated surface, DOPA molecules mainly adopt a flat conformation due to the formation of hydrophobic “bonds” between the hydrophobic functional groups of alkyl chains on surface and aromatic rings of DOPA molecules. This study led a new insight into the adsorption mechanisms based on the adsorption processes and layer structures, and it proposed novel concepts for the design of antifouling and adhesive surfaces.

Asphaltene desorption from silica-coated quartz crystal surface, in the presence of a highly charged amphiphilic macromolecule (polyacryloyloxyethyl-N,N-dimethyl-N-benzylammonium bromide, denoted as PASBn), was investigated through a quartz crystal microbalance with dissipation, atomic force microcopy, and ultraviolet spectroscopy measurements. The results showed that asphaltenes were displaced by PASBn even at a low concentration of 0.5 g/L, mainly attributed to the electrostatic, polar, and hydrophobic interactions between asphaltenes and PASBn, as well as the electrostatic interactions between PASBn and binding sites of the solid surface. In order to understand the processes of asphaltene desorption and PASBn adsorption, the random sequential adsorption model was introduced. Unfortunately, this classical model was not consistent with the kinetic process of asphaltenes exposed to PASBn aqueous solution, due to the complex adsorption–desorption processes, including the detachment of asphaltenes, subsequent transport of the detached ones to the bulk, and the adsorption of PASBn. Furthermore, a new kinetic model and a reasonable physical model were proposed to reveal the desorption mechanism of asphaltenes from the solid/liquid interface, providing a new way of improving heavy oil recovery.