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Hong C.-S.,National Kaohsiung Normal University | Chu S.-Y.,National Cheng Kung University | Chu S.-Y.,Institute of Nanotechnology and Microsystems Engineering | Chu S.-Y.,Center for Micro Nano Science and Technology | And 3 more authors.
Journal of Applied Physics | Year: 2011

Two different methods, the conventional direct oxide synthesized method and the two-step indirect synthesized (IS) method, were employed to synthesize the 0.75Pb (Fe2/3W1/3)O3-0.25 PbTiO3 ceramics. The low-field dielectric responses were investigated using the empirical law and the Curie-Weiss law. The temperature-dependent local ordering parameters were derived from the experimental results using the spin-glass model and the modified-Landau theory separately. According to the experimental data and the fitting results, it is concluded that the temperature-dependent local order parameters are changed from a short-range-ordered relaxor to a long-range-ordered ferroelectric state using the IS method. On the basis of the physical concepts of the spin-glass model, the modified-Landau theory and the ordering models, it is suggested that local polarizations are affected not only by degree of ordering but also by space charge polarization. In contrast, the glassy behavior of local polarization is affected only by degree of ordering but has nothing to do with space charge polarization. It is because local fields induced by space charge polarization have the same effect on local polarizations and are neutralized when calculating the correlation between neighboring polar microregions. On the other hand, the freezing process of local polarizations is affected by both degree of ordering and space charge polarization because local polarization affected by local fields cannot be neutralized when calculating the individual behavior of local polarization. © 2011 American Institute of Physics.

Hwang C.C.,National Cheng Kung University | Wang Y.C.,Center for Micro Nano Science and Technology | Kuo Q.Y.,Center for Micro Nano Science and Technology | Lu J.M.,National Center for High Performance Computing
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2010

The mechanical behavior of multi-walled carbon nanotubes (MWNTs), being fixed at both ends under uniaxial tensile loading, is investigated via the molecular dynamics (MD) simulation with the Tersoff interatomic potential. It is found that Young's modulus of the MWNTs is in the range between 0.85 and 1.16 TPa via the curvature method based on strain energy density calculations. Anharmonicity in the energy curves is observed, and it may be responsible for the time-dependent properties of the nanotubes. Moreover, the number of atomic layers that is fixed at the boundaries of the MWNTs will affect the critical strain for jumps in strain energy density vs. strain curves. In addition, the boundary conditions may affect "yielding" strength in tension. The van der Waals interaction of the double-walled carbon nanotube (DWNT) is studied to quantify its effects in terms of the chosen potential. © 2009 Elsevier B.V. All rights reserved.

Tsai M.-F.,Center for Micro Nano Science and Technology | Chang S.-H.G.,National Cheng Kung University | Cheng F.-Y.,National Cheng Kung University | Shanmugam V.,Center for Micro Nano Science and Technology | And 3 more authors.
ACS Nano | Year: 2013

Photothermal cancer therapy using near-infrared (NIR) laser radiation is an emerging treatment. In the NIR region, two biological transparency windows are located in 650-950 nm (first NIR window) and 1000-1350 nm (second NIR window) with optimal tissue transmission obtained from low scattering and energy absorption, thus providing maximum radiation penetration through tissue and minimizing autofluorescence. To date, intensive effort has resulted in the generation of various methods that can be used to shift the absorbance of nanomaterials to the 650-950 nm NIR regions for studying photoinduced therapy. However, NIR light absorbers smaller than 100 nm in the second NIR region have been scant. We report that a Au nanorod (NR) can be designed with a rod-in-shell (rattle-like) structure smaller than 100 nm that is tailored to be responsive to the first and second NIR windows, in which we can perform hyperthermia-based therapy. In vitro performance clearly displays high efficacy in the NIR photothermal destruction of cancer cells, showing large cell-damaged area beyond the laser-irradiated area. This marked phenomenon has made the rod-in-shell structure a promising hyperthermia agent for the in vivo photothermal ablation of solid tumors when activated using a continuous-wave 808 m (first NIR window) or a 1064 nm (second NIR window) diode laser. We tailored the UV-vis-NIR spectrum of the rod-in-shell structure by changing the gap distance between the Au NR core and the AuAg nanoshell, to evaluate the therapeutic effect of using a 1064 nm diode laser. Regarding the first NIR window with the use of an 808 nm diode laser, rod-in-shell particles exhibit a more effective anticancer efficacy in the laser ablation of solid tumors compared to Au NRs. © 2013 American Chemical Society.

Chung C.-K.,Center for Micro Nano Science and Technology | Liao M.-W.,Center for Micro Nano Science and Technology | Lee C.-T.,Center for Micro Nano Science and Technology | Chang H.-C.,Center for Micro Nano Science and Technology
Nanoscale Research Letters | Year: 2011

Nanoporous alumina which was produced by a conventional direct current anodization [DCA] process at low temperatures has received much attention in various applications such as nanomaterial synthesis, sensors, and photonics. In this article, we employed a newly developed hybrid pulse anodization [HPA] method to fabricate the nanoporous alumina on a flat and curved surface of an aluminum [Al] foil at room temperature [RT]. We fabricate the nanopores to grow on a hemisphere curved surface and characterize their behavior along the normal vectors of the hemisphere curve. In a conventional DCA approach, the structures of branched nanopores were grown on a photolithography-and-etched low-curvature curved surface with large interpore distances. However, a highcurvature hemisphere curved surface can be obtained by the HPA technique. Such a curved surface by HPA is intrinsically induced by the high-resistivity impurities in the aluminum foil and leads to branching and bending of nanopore growth via the electric field mechanism rather than the interpore distance in conventional approaches. It is noted that by the HPA technique, the Joule heat during the RT process has been significantly suppressed globally on the material, and nanopores have been grown along the normal vectors of a hemisphere curve. The curvature is much larger than that in other literatures due to different fabrication methods. In theory, the number of nanopores on the hemisphere surface is two times of the conventional flat plane, which is potentially useful for photocatalyst or other applications. PACS: 81.05.Rm; 81.07.-b; 82.45.Cc. © 2011 Chung et al.

Huang C.-C.,Center for Micro Nano Science and Technology | Tsai C.-Y.,National Cheng Kung University | Sheu H.-S.,National Synchrotron Radiation Research Center | Chuang K.-Y.,Center for Micro Nano Science and Technology | And 6 more authors.
ACS Nano | Year: 2011

A new magnetic nanoparticle was synthesized in the form of Gd 3+-chelated Fe3O4@SiO2. The Fe 3O4 nanoparticle was octahedron-structured, was highly magnetic (∼94 emu/g), and was the core of an encapsulating mesoporous silica shell. DOTA-NHS molecules were anchored to the interior channels of the porous silica to chelate Gd3+ ions. Because there were Gd3+ ions within the silica shell, the transverse relaxivity increased 7-fold from 97 s-1 mM-1 of Fe3O4 to 681 s -1 mM-1 of Gd3+-chelated Fe3O 4@SiO2 nanoparticles with r2/r1 = 486. The large transversal relaxivity of the Gd3+-chelated Fe 3O4@SiO2 nanoparticles had an effective magnetic resonance imaging effect and clearly imaged lymph nodes. Physiological studies of liver, spleen, kidney, and lung tissue in mice infused with these new nanoparticles showed no damage and no cytotoxicity in Kupffer cells, which indicated that Gd3-chelated Fe3O4@SiO 2 nanoparticles are biocompatible. © 2011 American Chemical Society.

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