A Molecular Dynamics Study Of Nanobubble And Hydrophobic Interactions

Hydrophobic interaction plays an important role in a wide variety of chemical and biophysical phenomena,such as protein folding,capillary evaporation,self-assembly of biomolecules in cells,colloidal assemblies,water permeation in nanoscale channels and gating of ion channels.Long-range hydrophobic interactions will lead to the generation of surface nanobubble and surface nanopancake.Both theoretic and experimental works have proved the existance of surface nanobubble.Surface nanobubble and surface nanopancake have potential applications in gas storage and clean fuel cell.Recently,methane fuel cell has been fabricated according to the theory of hydrogen fuel cell.Methane storage is the key technology in the fabrication of fuel cell,one of which is high-density methane adsorption on surface.Understanding the mechanism of methane adsorption on surface in water is helpful to increasing the efficiency of methane fuel cell and optimization of gas separation devices.A fascinating phenomenon in hydrophobic interacton is the so-called nanoscale dewetting transition,namely,water drying between nanoscale hydrophobic surfaces when two hydrophobic objects approach each other and reach a critical distance,or even the space between them is large enough to accommodate several layers of water molecules.The reduction of water molecules between two solvated inert surfaces will lead to long-range hydrophobic attraction.Using molecular dynamics simulations,we have investigated the hydrophobic interactions and influence of nitrogen molecules on the critical distance of dewetting between the nanoscale hydrophobic plates.We show that dewetting transition is very sensitive to the distribution of nitrogen molecules.The nitrogen molecules prefer to aggregate in the vicinity of the two hydrophobic plates and exclude water molecules.Furthermore,our simulation results indicate that the effective range of hydrophobic attraction between two nanoscale plates is enhanced by the aggregated nitrogen molecules.In particular,we find that the distribution patterns of nitrogen molecules are very different when the inter-plate region is filled with water or dewetting.These findings are helpful to understand effects of gas molecules dissolved in water on hydrophobic interactions.