title: Force trace hysteresis and temperature dependence of bridging nanobubble induced forces between hydrophobic surfaces.
abstract: An atomic force microscope and the colloidal probe technique are used to probe the interaction between a hydrophobic particle and a hydrophobic surface in water. The characteristics of the observed force curves strongly suggest that a gas bubble is formed when the particle is moved toward the surface and that the bubble ruptures when the particle subsequently is retracted from the surface. We demonstrate that this type of interaction is not unique for hydrophobic surfaces in water since the interaction between hydrophilic surfaces in air provides very similar force curves. However, the interaction between hydrophobic surfaces vanish if water is replaced by an organic solvent with low polarity. The bridging bubble model is employed to explain the hysteresis observed between approach and retraction force traces and experimental conditions where the hysteresis can be almost eliminated are identified. Finally, it is demonstrated that the hydrophobic interaction is strongly temperature dependent and this dependence can be attributed mainly to the decreasing solubility of air in water with increasing temperature.
authors.affiliation: MEMPHYS, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark. esben.thormann@surfchem.kth.se
authors.forename: Esben
authors.initials: E
authors.lastname: Thormann
authors.forename: Adam C
authors.initials: AC
authors.lastname: Simonsen
authors.forename: Per L
authors.initials: PL
authors.lastname: Hansen
authors.forename: Ole G
authors.initials: OG
authors.lastname: Mouritsen
mesh_terms: D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D057927:Hydrophobic and Hydrophilic Interactions; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D013314:Stress, Mechanical; D013499:Surface Properties; D013500:Surface Tension; D013696:Temperature
chemical_list: D046911:Macromolecular Substances