Eun-Mee Kim

Advanced porous gold nanofibers for highly efficient and stable molecular sensing platforms.

Porous gold nanofibers are fabricated through templated electrochemical routes in porous alumina membranes. Gold-silver alloy is electrochemically deposited in the nanocylinders of the porous alumina templates and then the silver phase is selectively dealloyed. The resulting nanofibers present a nanoporous network with a pore dimension of approximately 10 nm and notable surface-enhanced Raman scattering (SERS) efficiencies which are at least seven times higher than from the smooth solid gold nanofibers without porosity. The relative SERS enhancement on porous gold is directly proved by imaging with a Raman microscope for conjugated porous gold/solid gold single nanorods.

A Facile Fabrication of Fe

Monodispersed superparamagnetic magnetite submicron particles were synthesized by using a one-step solvothermal method. Increasing the volume ratio of ethylene glycol/diethylene glycol (EG/DEG) shows a gradual increase in the size of primary nanograin and secondary Fe3O4 submicroparticles. To induce the photo-magnetic functionality, we have successfully synthesized the multifunctional core-shell (Fe3O4/ZnO) submicron particles by atomic layer deposition (ALD) method. Microstructure and magnetic properties of the multifunctional core/shell submicron particles are investigated by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), and photoluminescence spectroscopy.

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One-dimensional-magnetic nanostructures have recently attracted much attention because of their intriguing properties that are not displayed by their bulk or particle counterparts. One of the commonly used methods for generating ID-nanostructures is based on the electrodeposition of various materials in porous membranes. This technique has been applied to fabricate metallic nanowires as arrays of wires perpendicular to the substrate. They display unique magnetic properties (e.g., anisotropic magnetization). Electrodeposition is, however, of limited use for oxide-based magnetic materials, due to the difficulty involved in the formation of oxides through electrochemical deposition. We obtained zinc ferrite nanowires inside an anodic aluminum oxide (AAO) template using a novel technology fundamentally different from electrodeposition. First, fabricated zinc ferrite nanoparticles were injected in the AAO template and then annealed in air. The process of embedding particles into the pores was assisted by the magnetic field of a permanent magnet placed under the substrate. The physical and chemical properties of these zinc ferrite nanowires have been investigated by thermogravimetric analysis, infrared, X-ray diffraction, scanning electron microscope, and superconducting quantum interference device. The nanoparticles embedded into the pores exhibited superparamagnetic behavior with the blocking temperature of 15 K. After annealing, the particles formed nanowires and the hysteresis of the annealed samples increased significantly.