Massive Fabrication of Free-Standing One-Dimensional Co/Pt Nanostructures and Modulation of Ferromagnetism via a Programmable Barcode Layer Effect

Massive fabrication of free-standing Co/Pt magnetic barcode nanowires with well-defined interfaces and layer thicknesses is obtained after freeing them from porous templates. Such barcodes display bamboo-like shapes with identical motifs either inside or out of the templates. The ferromagnetism of these barcode nanowires can be modulated easily depending on the cobalt segments and shape anisotropies. Further enhancements of the ferromagnetism of Co/Pt barcodes are also accomplished through interfacial alloying processes via a thermally induced phase transition

One-Dimensional Octacyanomolybdate-Based Cu(II)−Mo(V) Bimetallic Assembly with a Novel Rope-Ladder Chain Structure

A new type of one-dimensional cyanide-bridged Cu(II)−Mo(V) bimetallic assembly, [Cu(cyclam)]3[Mo(CN)8]2·5H2O (cyclam = 1,4,8,11-tetraazacyclotetradecane), was prepared by self-assembling Mo(CN)83- and Cu(cyclam)2+ ions in a 2:3 stoichiometric ratio. The overall molecular view is delineated as a novel rope-ladder chain structure. It displays a dominant ferromagnetic behavior within a pentanuclear Cu3Mo2 unit (Jp = 3.88 cm-1). Interunit ferromagnetic interactions (Jc = −0.03 cm-1) through a longer magnetic pathway of Cu−Mo and weak antiferromagnetic couplings (zJ‘ = −0.46 cm-1) resulting from interchain interactions are obtained

One-Dimensional Octacyanomolybdate-Based Cu(II)−Mo(V) Bimetallic Assembly with a Novel Rope-Ladder Chain Structure

A new type of one-dimensional cyanide-bridged Cu(II)−Mo(V) bimetallic assembly, [Cu(cyclam)]3[Mo(CN)8]2·5H2O (cyclam = 1,4,8,11-tetraazacyclotetradecane), was prepared by self-assembling Mo(CN)83- and Cu(cyclam)2+ ions in a 2:3 stoichiometric ratio. The overall molecular view is delineated as a novel rope-ladder chain structure. It displays a dominant ferromagnetic behavior within a pentanuclear Cu3Mo2 unit (Jp = 3.88 cm-1). Interunit ferromagnetic interactions (Jc = −0.03 cm-1) through a longer magnetic pathway of Cu−Mo and weak antiferromagnetic couplings (zJ‘ = −0.46 cm-1) resulting from interchain interactions are obtained

Shape Evolution of Single-Crystalline Iron Oxide Nanocrystals

Shape- and size-controlled synthesis of single-crystalline maghemite (γ-Fe2O3) nanocrystals are performed by utilizing a solution-based one-step thermolysis method. Modulating the growth parameters, such as the type and amount of capping ligands as well as the growth time, is shown to have a significant effect on the overall shape and size of the obtained nanocrystals and on the ripening process itself. The resulting shapes of the novel structures are diverse, including slightly faceted spheres, diamonds, prisms, and hexagons, all of which are in fact truncated dodecahedron structures with different degrees of truncation along the {111}, {110}, or {100} faces. Spherical nanocrystals are easily assembled into the three-dimensional superlattices, demonstrating the uniformity of these nanocrystals. The size-dependent magnetic properties are examined, and large hexagon-shaped γ-Fe2O3 nanocrystals are shown to be ferrimagnetic at room temperature

Shape Evolution of Single-Crystalline Iron Oxide Nanocrystals

Shape- and size-controlled synthesis of single-crystalline maghemite (γ-Fe2O3) nanocrystals are performed by utilizing a solution-based one-step thermolysis method. Modulating the growth parameters, such as the type and amount of capping ligands as well as the growth time, is shown to have a significant effect on the overall shape and size of the obtained nanocrystals and on the ripening process itself. The resulting shapes of the novel structures are diverse, including slightly faceted spheres, diamonds, prisms, and hexagons, all of which are in fact truncated dodecahedron structures with different degrees of truncation along the {111}, {110}, or {100} faces. Spherical nanocrystals are easily assembled into the three-dimensional superlattices, demonstrating the uniformity of these nanocrystals. The size-dependent magnetic properties are examined, and large hexagon-shaped γ-Fe2O3 nanocrystals are shown to be ferrimagnetic at room temperature

Phase- and Size-Controlled Synthesis of Hexagonal and Cubic CoO Nanocrystals

Highly crystalline, phase- and size-controlled CoO nanocrystals of hexagonal and cubic phases have been prepared by thermal decomposition of Co(acac)3 in oleylamine under an inert atmosphere. Kinetic and thermodynamic control for the precursor formation leads to two different seeds of hexagonal and cubic phases at higher temperatures. The crystal size of both CoO phases can be easily manipulated by changing the precursor concentration and reaction temperature

Redox−Transmetalation Process as a Generalized Synthetic Strategy for Core−Shell Magnetic Nanoparticles

Although multicomponent core−shell type nanomaterials are one of the highly desired structural motifs due to their simultaneous multifunctionalities, the fabrication strategy for such nanostructures is still in a primitive stage. Here, we present a redox−transmetalation process that is effective as a general protocol for the fabrication of high quality and well-defined core−shell type bimetallic nanoparticles on the sub-10 nm scale. Various core−shell type nanomaterials including Co@Au, Co@Pd, Co@Pt, and Co@Cu nanoparticles are fabricated via transmetalation reactions. Compared to conventional sequential reduction strategies, this transmetalation process has several advantages for the fabrication of core−shell type nanoparticles:  (i) no additional reducing agent is needed and (ii) spontaneous shell layer deposition occurs on top of the core nanoparticle surface and thus prevents self-nucleation of secondarily added metals. We also demonstrate the versatility of these core−shell structures by transferring Co@Au nanoparticles from an organic phase to an aqueous phase via a surface modification process. The nanostructures, magnetic properties, and reaction byproducts of these core−shell nanoparticles are spectroscopically characterized and identified, in part, to confirm the chemical process that promotes the core−shell structure formation