title: Homoepitaxial branching: an unusual polymorph of zinc oxide derived from seeded solution growth.
abstract: The development of hydrothermal synthesis has greatly promoted bottom-up nanoscience for the rational growth of diverse zinc oxide (ZnO) nanostructures. In comparison with normal ZnO nanowires, ZnO nanostructures with a larger surface area, for instance, branched nanowires, are more attractive in the application fields of catalysis, sensing, dye-sensitized solar cells etc. So far the ZnO branched nanowires achieved by either one-step or multistep growth always present a boundary-governed nonepitaxial branch/stem interface. In this report, seeded growth of single-crystalline ZnO hexabranched nanostructures was achieved by selecting polyethylene glycol (PEG) as capping agent based on a low-temperature, laterally epitaxial solution growth strategy. We investigated the generality of this PEG-assisted growth process using different ZnO seed layers including continuous film, patterned dots, and vertically aligned nanowire arrays. It was revealed that PEG is a distinctive c-direction inhibitor responsible for the lateral growth and subsequent branching of ZnO due to its nonionic and nonacidic feature and weak reactivity in the solution system. All the obtained branched nanostructures are of single crystallinity in nature, which is methodologically determined by the homoepitaxial growth mode. This PEG-assisted process is versatile for diameter tuning and branch formation of ZnO nanowires by secondary growth. Our proof-of-concept experiments demonstrated that the ZnO hexabranched nanostructures presented superior photocatalytic efficiency for dye degradation relative to the normal ZnO nanowires.
authors: Nanotechnology, Institute of Microsystems Engineering (IMTEK), Albert Ludwigs University of Freiburg, Georges-Köhler-Allee 103, D-79110 Freiburg, Germany.
authors: Rajeevan
authors: R
authors: Kozhummal
authors: Yang
authors: Y
authors: Yang
authors: Firat
authors: F
authors: Güder
authors: Andreas
authors: A
authors: Hartel
authors: Xiaoli
authors: X
authors: Lu
authors: Umut M
authors: UM
authors: Küçükbayrak
authors: Aurelio
authors: A
authors: Mateo-Alonso
authors: Miko
authors: M
authors: Elwenspoek
authors: Margit
authors: M
authors: Zacharias
mesh_terms: D003460:Crystallization / Q000379:methods*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; C009495:titanium dioxide; D014025:Titanium; D015034:Zinc Oxide