title: Controlling the locus of bubble nucleation by dissolved gases in heterogeneous liquid-liquid systems.
abstract: We have examined the nucleation of chemically generated nitrogen gas bubbles in microheterogeneous systems, using optical microscopy on a model system consisting of a single liquid-liquid interface. Results clearly show that bubble nucleation occurs in both the aqueous and oil phases, despite the nitrogen production reaction being a purely aqueous phase process. A theoretical model is developed which describes the time evolution of the nitrogen concentration profile, and this reveals that bubbles in the oil are a result of homogeneous nucleation of dissolved N(2) transported across the interface into a (supersaturated) diffusion layer. We further show that bubble nucleation in the oil can be inhibited or eliminated by adding water-soluble surfactants, which facilitates aqueous phase bubble nucleation and then acts as highly effective nitrogen sinks, severely reducing the flux of dissolved gas across the water-oil interface.
authors.affiliation: Key Centre for Polymers and Colloids, School of Chemistry, F11, The University of Sydney, NSW 2006, Australia.
authors.forename: Pramith
authors.initials: P
authors.lastname: Priyananda
authors.forename: Brian S
authors.initials: BS
authors.lastname: Hawkett
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Warr
mesh_terms: D004058:Diffusion; D005740:Gases / Q000737:chemistry*; D008853:Microscopy; D008962:Models, Theoretical; D009584:Nitrogen / Q000737:chemistry*; D009821:Oils / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D005740:Gases; D009821:Oils; D013501:Surface-Active Agents; D014867:Water; D009584:Nitrogen