In this paper, flower-, star-, and chain-like hierarchically nanostructured nickel crystals as well as [Ni(N2H4)2]Cl2 nanorods were first synthesized by a simple reduction method. This method is template-free, environmentally benign, and can be carried out at low temperature (60 °C) with high efficiency on a large scale. Investigation of the growth kinetics has proved that the crystal sizes are sensitive to the reaction temperature and reaction time. Various nickel nanostructures can be achieved by the oriented growth of preferred nickel crystal planes. The magnetic properties of the flower-like nickel nanocrystals were also characterized with the results of much enhanced coercivity (Hc) and decreased saturation magnetization (Ms).

Surprisingly oxidation resistant icosahedral FePt nanoparticles showing hard-magnetic properties have beenfabricated by an inert-gas condensation method with in-flight annealing. High-resolution transmission electronmicroscopy (HRTEM) images with sub-Angstrom resolution of the nanoparticle have been obtained withfocal series reconstruction, revealing noncrystalline nature of the nanoparticle. Digital dark-field methodcombined with structure reconstruction as well as HRTEM simulations reveal that these nanoparticles haveicosahedral structure with shell periodicity. Localized lattice relaxations have been studied by extracting theposition of individual atomic columns with a precision of about (0.002 nm. The lattice spacings of (111)planes from the surface region to the center of the icosahedra are found to decrease exponentially with shellnumbers. Computational studies and energy-filtered transmission electron microscopy analyses suggest thata Pt-enriched surface layer is energetically favored and that site-specific vacancies are formed at the edges offacettes, which was experimentally observed. The presence of the Pt-enriched shell around an Fe/Pt coreexplains the environmental stability of the magnetic icosahedra and strongly reduces the exchange couplingbetween neighboring particles, thereby possibly providing the highest packing density for future magneticstorage media based on FePt nanoparticles.

A series of highly uniform one-dimensional Ni nanochains, with diameters ranging from 20 to 200 nm, have been synthesized by a facile, template-free, wet chemical method at diverse temperature and magnetic field. Our results indicate that the crystallite size, diameter and length of the prepared nanochains depend critically on the reaction temperature. The characteristic thermodynamic cohesive energies, ΔED and ΔEL, are obtained for the formation of the Ni nanochains. In addition, the chain length also depends on the applied field because of the Zeeman energy of the magnetic Ni nanoparticles. For the morphology control, an external field is required in order to obtain axially aligned rather than dendritic nanochains. The size-dependent magnetic properties are studied systematically. The saturation magnetization is shown to reduce inversely with the chain diameter, attributable to a core-shell structure. The thickness of the shell which encloses the ferromagnetic Ni core is determined to be about 2.3-3.4 nm.

Synthesis and manipulation of advanced bimetallic nanomaterials via a green and low-cost wet chemical route are of great importance for the industrialization potential. Materials design integrating the synthesis of nanomaterials through an environmentally benign route with a simple manipulation method is a challenge. The CoPt hollow nanochains have been successfully synthesized in aqueous solution with shell thickness of about 5 nm and tunable length from 300 nm to 2 μm. The as-prepared CoPt hollow nanochains can be easily aligned by the external magnetic fields and can be attached onto substrates, such as silicon wafer. The synthesis strategy is characterized by room temperature reaction (300 K), low cost, and utilization of facile reagents (water as solvent). Growth kinetics investigation shows the magnetostatic interactions between Co clusters together with the spontaneous galvanic replacement between Co clusters and Pt ions are indispensable for the formation of aligned hollow nanochains. Magnetic measurements indicate that the shape anisotropy of 1D aligned nanochains plays a dominant role on the good controllable behavior.