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ABSTRACT: One of the most important magnetic materials, ferrite nanoparticles, has extensively been studied because of their potential
applications in magnetic storage media and magnetic resonance imaging (MRI). The magnetic properties of these nanoparticles
can significantly change depending on their shape. 8 nm manganese ferrite nanoparticles were synthesized by thermal decomposing
the metal complex and surfactant. The process of embedding MnFe2O4 nanoparticles into the pores of the anodic aluminum oxide (AAO) was assisted by the magnetic field of the permanent magnet
that was placed directly under the substrate in the vacuum. The nanowires formed in the pores from the ferrite nanoparticles
were annealed at 400°C and 600°C in an Ar gas atmosphere in order for the morphology to transform. The morphology of the manganese
ferrite nanoparticles before and after annealing was observed using a field-emission scanning electron microscope. The coercivity
and squareness of the hysteresis loop of the annealed ferrite that resulted from the morphological changes increased when
the annealing temperature increased.
Keywordsferrite nanoparticles–magnetic property–anodic aluminum oxide
Electronic Materials Letters 04/2012; 5(2):87-90. · 1.82 Impact Factor
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ABSTRACT: Helix-coiled gold nanowires were fabricated by a templating route using unique composite templates consisting of anodic aluminum oxide (AAO) nanotubular membrane and confined mesoporous silica therein. A different degree of confinement energy induces a different degree of helix curvature of confined porous silica nanochannels in an AAO, which works as a hard template for the electrochemical deposition of gold, thereby rationally enabling a different degree of helix curvature of gold nano-replicas. From surface-enhanced Raman scattering experiments, we first found that helix-coiled gold nanowires show more distinctly enhanced molecule sensing efficiency than those from simple smooth gold nanowires, and gold nanowires with the narrower lateral width show more enhanced molecule sensing efficiency than those of thicker width helix nanowires.
Journal of Nanoscience and Nanotechnology 04/2012; 12(4):3501-5. · 1.56 Impact Factor
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ABSTRACT: We report a novel photofunctional magnetic nanoparticle that is strategically designed and prepared by simple modification process. Photofunctionality is provided by the photosensitizer (PS) of [5,15-bis(phenyl)-10,20-bis(4-methoxycarbonylphenyl)porphyrin]platinum that generates singlet oxygen in high quantum yield. The PS molecules are covalently bonded to the surface of magnetic nanoparticles. Microstructure and magnetic and photophysical properties of the photofunctional magnetic nanoparticles are investigated by transmission electron microscopy, vibrating sample magnetometry, and time-resolved spectroscopic methods. The results show that the immobilized PS molecules retain their optical and functional properties including the high efficiency of singlet oxygen generation. Generation quantum yield (ΦΔ) and releasing yield (ηΔ) of singlet oxygen from the prepared photofunctional magnetic nanoparticles are 0.47 and 0.42, respectively. Furthermore, the photofunctional magnetic nanoparticles have good solubility and stability in water, which are induced by the surface modification process. The photocatalytic experiment is demonstrated by utilizing the oxidation reaction of 2,4,6-trichlorophenol with the photofunctional magnetic nanoparticles.
02/2011;
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IEEE Transactions on Magnetics - IEEE TRANS MAGN. 01/2011; 47(10):3369-3372.
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ABSTRACT: Internal mesostructures of silica nanofibers were dramatically changed through controlled interfacial interactions of confined lyotropic block copolymer systems in nanocylinders, which were further used as structure-directing templates for the fabrication of porous gold nanofibers with unprecedented nanoarchitectures.
Chemical Communications 03/2010; 46(10):1760-2. · 6.17 Impact Factor
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ABSTRACT: 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.
Nanotechnology 09/2009; 20(32):325604. · 3.98 Impact Factor
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ABSTRACT: Mesoporous silica nanofibers containing CdS quantum dots (QDs) were fabricated by the confined self-assembly of a lyotropic mesophase within the nanochannels of porous alumina. The resulting mesoporous nanofibers show unique internal mesostructures that depend on the size of the incorporated CdS QDs. Porous nanochannels of the composite nanofibers are shown to form a circularly wound assembly perpendicular to the long fiber axis with small QDs incorporated. As the diameter of the CdS QDs within the silica nanofibers increases, the circularly wound nanochannels become disordered. This unique mesoporous structure is further perturbed by increasing the amount of incorporated CdS QDs. The perturbed mesostructure inside the nanofibers results in an enhanced efficiency of nitrogen gas adsorption and spectral changes of the incorporated QD emissions. Such perturbed nanochannels inside the nanofibers can be utilized as a preferred mesostructure for adsorbing gas molecules and removing surface emission states of the CdS QDs.
10/2005;
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ABSTRACT: Unique starlike CdS particles were prepared from the lyotropic triblock copolymer solution system. The starlike CdS consists of a spherical core and dozens of the attached conical nanolobes. From the comparative studies with the spherical and rod-shaped CdS nanoparticles, the unique photophysical property is presented for the starlike CdS particle. The experimental results suggest that the photogenerated charge carriers at the tip-edge region of the conical nanolobe in the starlike CdS system diffuse into the thicker inner part including the core region, which is possibly due to the decreasing excited state potential gradient from the tip edge to the thicker inner part. This type of charge carrier diffusion dynamics from the surrounding to the thicker inner part in this anisotropic morphology of the starlike CdS semiconductor closely resembles the energy transfer dynamics in the organic dendrimers.
The Journal of Physical Chemistry B 05/2005; 109(13):6204-9. · 3.70 Impact Factor
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ABSTRACT: For newly synthesized ternary Zintl phase LiSbTe2, absorption, fluorescence, and excitation spectra indicate that it has an Eg of 4.46 eV, and there is an absorption band around 300 nm below the band gap and a Stokes-shifted fluorescence band around 390 nm. At both room temperature and 77 K, power dependent steady-state and time-resolved fluorescence studies result in the appearance of another fluorescence band at about 450 and 520 nm. As the photon power increases, the 390 nm band is blue shifted at the saturation stage with the saturation of the 520 nm band as well. Along with fluorescence lifetime data, the results imply that the 390 and 450 nm bands correspond to shallow trapped exciton state and deep self-trapped exciton state originating from lattice distortion, respectively, and the 520 nm band is from the surface trap state coupled to the frozen solvent environment. The upper limit distance between the trap sites corresponding to 390 nm band is estimated to be about 17.6 nm by the dielectric function calculation of the gas phase model.
Chemical Physics. 256(3):295-305.
