title: Controlling metal nanotoppings on the tip of silicide nanostructures.
abstract: Utilizing the difference in surface tension between SiO2 and metal catalysts (Mn2+, Ni2+), we show how metals form nanoshells, nanodiscs and nanospheres at the tips of the SiO2 nanostructures of nanocones, nanorods and nanowires. For the Mn2+ catalyst (i), SiO2-nanocones are formed with the hemispherical convex cap of the MnO/SiO2 composite. For the Ni2+ catalyst (ii), SiO2 nanowires are grown due to the concave shape of SiO2 surrounding the multi-faceted NiSi particles at their tip. For the Mn2+/Ni2+ catalyst (iii), SiO2 nanorods are formed with large-sized spherical ferromagnetic single Ni nanocrystals (50-200 nm in diameter) surrounded by the concave MnO2/SiO2 composite at the tip of the SiO2 nanorods. This large-sized spherical formation of the single Ni crystal is possible because Ni is able to be chemically reduced by Mn at 950 degrees C, well below the melting point of Ni (1455 degrees C) due to the alloying effect.
authors.affiliation: Department of Chemistry, Center for Superfunctional Materials, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea.
authors.forename: In Chul
authors.initials: IC
authors.lastname: Hwang
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kumar
authors.forename: Nam Dong
authors.initials: ND
authors.lastname: Kim
authors.forename: Young
authors.initials: Y
authors.lastname: Chun
authors.forename: Jung Woo
authors.initials: JW
authors.lastname: Lee
authors.forename: Pavan
authors.initials: P
authors.lastname: Kumar
authors.forename: Rudra S
authors.initials: RS
authors.lastname: Mana
authors.forename: Changhoon
authors.initials: C
authors.lastname: Choi
authors.forename: Jae Rhung
authors.initials: JR
authors.lastname: Lee
authors.forename: Kwang S
authors.initials: KS
authors.lastname: Kim
mesh_terms: D003460:Crystallization / Q000379:methods*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008670:Metals / Q000737:chemistry*; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances; D008670:Metals; D012825:Silicon