title: Self-Organizing Arrays of Size Scalable Nanoparticle Rings.
abstract: A central challenge in nano- and mesoscale materials research is facile formation of specific structures for catalysis, sensing, and photonics. Self-assembled equilibrium structures, such as three-dimensional crystals or ordered monolayers, form as a result of the interactions of the constituents. Other structures can be achieved by imposing forces (fields) and/or boundary conditions, which Whitesides termed "self-organization". Here, we demonstrate contact line pinning on locally curved surfaces (i.e., a self-assembled monolayer of SiO2 colloidal particles) as a boundary condition to create extended arrays of uniform rings of Au nanoparticles (NPs) on the SiO2 colloids. The mechanism differs from the well-known "coffee-ring" effect; here the functionalized NPs deposit at the contact line and are not driven by evaporative transport. Thus, NP ring formation depends on the hydrophobicity and wetting of the SiO2 colloids by the chloroform solution, ligands on the NPs, and temperature. The NP rings exhibit size scaling behavior, maintaining a constant ratio of NP ring-to-colloid diameter (from 300 nm to 2 μm). The resultant high-quality NP ring structures are expected to have interesting photonic properties.
authors: Department of Chemistry, ‡The James Franck Institute, §Department of Physics, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
authors: Ying
authors: Y
authors: Bao
authors: Department of Chemistry, ‡The James Franck Institute, §Department of Physics, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
authors: Thomas A
authors: TA
authors: Witten
authors: Department of Chemistry, ‡The James Franck Institute, §Department of Physics, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
authors: Norbert F
authors: NF
authors: Scherer
keywords: SiO2 monolayer; contact line; nanoparticle rings; scaling behavior; wetting