title: Plasmon hybridization reveals the interaction between individual colloidal gold nanoparticles confined in an optical potential well.
abstract: The understanding of interaction forces between nanoparticles in colloidal suspension is central to a wide range of novel applications and processes in science and industry. However, few methods are available for actual characterization of such forces at the single particle level. Here we demonstrate the first measurements of colloidal interactions between two individual diffusing nanoparticles using a colorimetric assay based on plasmon hybridization, that is, strong near-field coupling between localized surface plasmon resonances. The measurements are possible because individual gold nanoparticle pairs can be loosely confined in an optical potential well created by a laser tweezers. We quantify the degree of plasmon hybridization for a large number of individual particle pairs as a function of increasing salt concentration. The data reveal a considerable heterogeneity at the single particle level but the estimated average surface separations are in excellent agreements with predictions based on the classical theory of Derjaguin, Landau, Verwey, and Overbeek.
authors.affiliation: Department of Applied Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden. lianming.tong@chalmers.se
authors.forename: Lianming
authors.initials: L
authors.lastname: Tong
authors.forename: Vladimir D
authors.initials: VD
authors.lastname: Miljković
authors.forename: Peter
authors.initials: P
authors.lastname: Johansson
authors.forename: Mikael
authors.initials: M
authors.lastname: Käll
mesh_terms: D003102:Colloids / Q000737:chemistry*; D017979:Gold Colloid / Q000737:chemistry*; D008422:Materials Testing / Q000379:methods; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D020349:Surface Plasmon Resonance / Q000379:methods*
chemical_list: D003102:Colloids; D017979:Gold Colloid