title: Self-assembled nanoparticle deposits formed at the contact line of evaporating micrometer-size droplets.
abstract: We report on the formation of self-assembled rings of Co Pt3 nanoparticles (ring diameter ranging from 0.6 to 1.5 microm, particle diameter 6 nm ) formed in an evaporating thin film. The latter was achieved on the surface of water by spreading a binary mixture composed of two solutions: nitrocellulose dissolved in amyl acetate and Co Pt3 particles stabilized by hexadecylamine dissolved in hexane. The self-assembly process of the nanometer-sized particles into micrometer-sized rings results from phase separation in a thin film of the mixed solutions, leading to a bilayer, and the subsequent decomposition during solvent evaporation of the top hexadecylamine-rich layer into droplets. Finally, the evaporation of the remaining solvent from these droplets gives rise to a retraction of their contact line. The Co Pt3 particles located at the contact line follow its motion and self-assemble along this line.
authors.affiliation: Institute of Physics, University of Oldenburg, D-26111 Oldenburg, Germany. leonid.govor@uni-oldenburg.de
authors.forename: Leonid V
authors.initials: LV
authors.lastname: Govor
authors.forename: Günter
authors.initials: G
authors.lastname: Reiter
authors.forename: Jürgen
authors.initials: J
authors.lastname: Parisi
authors.forename: Gottfried H
authors.initials: GH
authors.lastname: Bauer