title: Long-ranged attraction between charged polystyrene spheres at aqueous interfaces.
abstract: We report an optical and atomic force microscopic study of interactions between charged polystyrene spheres at a water-air interface. Optical observations of bonded particle clusters and formation of circular chainlike structures at the interface demonstrate that the interaction potential is of dipole origin. Atomic force microscope phase images show patchy domains on the colloidal surface, indicating that the surface charge distribution is not uniform as is commonly believed. Such surface heterogeneity introduces in-plane dipoles, leading to an attraction at short interparticle distances.
authors.affiliation: Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Susheng
authors.initials: S
authors.lastname: Tan
authors.forename: Tai-Kai
authors.initials: TK
authors.lastname: Ng
authors.forename: Warren T
authors.initials: WT
authors.lastname: Ford
authors.forename: Penger
authors.initials: P
authors.lastname: Tong
mesh_terms: D003102:Colloids / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D011137:Polystyrenes / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D003102:Colloids; D011137:Polystyrenes; D014867:Water