• Title/Summary/Keyword: Magnetic nanostructures

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Gold Shell Nanocluster Networks in Designing Four-Branch (1×4) Y-Shape Optical Power Splitters

  • Ahmadivand, Arash;Golmohammadi, Saeed
    • Journal of the Optical Society of Korea
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    • v.18 no.3
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    • pp.274-282
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    • 2014
  • In this study, closely spaced Au nanoparticles which are arranged in nanocluster (heptamer) configurations have been employed to design efficient plasmonic subwavelength devices to function at the telecommunication spectrum (${\lambda}$~1550 nm). Utilizing two kinds of nanoparticles, the optical properties of heptamer clusters composed of Au rod and shell particles that are oriented in triphenylene molecular fashion have been investigated numerically, and the cross-sectional profiles of the scattering and absorption of the optical power have been calculated based on a finite-difference time-domain (FDTD) method. Plasmon hybridization theory has been utilized as a theoretical approach to characterize the features and properties of the adjacent and mutual heptamer clusters. Using these given nanostructures, we designed a complex four-branch ($1{\times}4$) Y-shape splitter that is able to work at the near infrared region (NIR). This splitter divides and transmits the magnetic plasmon mode along the mutual heptamers arrays. Besides, as an important and crucial parameter, we studied the impact of arm spacing (offset distance) on the guiding and dividing of the magnetic plasmon resonance propagation and by calculating the ratio of transported power in both nanorod and nanoshell-based structures. Finally, we have presented the optimal structure, that is the four-branch Y-splitter based on shell heptamers which yields the power ratio of 23.9% at each branch, 4.4 ${\mu}m$ decaying length, and 1450 nm offset distance. These results pave the way toward the use of nanoparticles clusters in molecular fashions in designing various efficient devices that are able to be efficient at NIR.

Deterministic manipulation and visualization of near field with ultra-smooth, super-spherical gold nanoparticles by atomic force microscopy

  • KIM, MINWOO;LEE, JOOHYUN;YI, GI-RA;LEE, SEUNGWOO;SONG, YOUNG JAE
    • Proceedings of the Korean Vacuum Society Conference
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    • 2015.08a
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    • pp.111.1-111.1
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    • 2015
  • As an alternative way to get sophisticated nanostructures, atomic force microscopy (AFM) has been used to directly manipulate building primitives. In particular, assembly of metallic nanoparticles(NPs) can provide various structures for making various metamolecules. As far, conventionally made polygonal shaped metallic NPs showed non-uniform distribution in size and shape which limit its study of fundamental properties and practical applications. In here, we optimized conditions for deterministic manipulation of ultra-smooth and super-spherical gold nanoparticles (AuNPs) by AFM. [1] Lowered adhesion force by using platinum-iridium coated AFM tips enabled us to push super-spherical AuNPs in linear motion to pre-programmed position. As a result, uniform and reliable electric/magnetic behaviors of assembled metamolecules were achieved which showed a good agreement with simulation data. Furthermore, visualization of near field for super-spherical AuNPs was also addressed using photosensitive azo-dye polymers. Since the photosensitive azo-dye polymers can directly record the intensity of electric field, optical near field can be mapped without complicated instrumental setup. [2] By controlling embedding depth of AuNPs, we studied electric field of AuNPs in different configuration.

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Implementation of magnetic Fe3O4@ZIF-8 nanocomposite to activate sodium percarbonate for highly effective degradation of organic compound in aqueous solution

  • Sajjadi, Saeed;Khataee, Alireza;Soltani, Reza Darvishi Cheshmeh;Bagheri, Nafiseh;Karimi, Afzal;Azar, Amirali Ebadi Fard
    • Journal of Industrial and Engineering Chemistry
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    • v.68
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    • pp.406-415
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    • 2018
  • Here, as-synthesized $Fe_3O_4$ nanoparticles were incorporated into the zeolitic imidazolate framework (ZIF-8) lattice to activate sodium percarbonate (SPC) for degradation of methylene blue (MB). The reaction rate constant of $Fe_3O_4@ZIF-8/SPC$ process ($0.0632min^{-1}$) at acidic conditions (pH = 3) was more than six times that of the $Fe_3O_4/SPC$ system ($0.009min^{-1}$). Decreasing the solute concentration, along with increasing SPC concentration and $Fe_3O_4@ZIF-8$ nanocomposite (NC) dosage, favored the catalytic degradation of MB. The $Fe_3O_4@ZIF-8$ NC after fifteen consecutive treatment processes showed the excellent stability with a negligible drop in the efficiency of the system (<10%). The reaction pathway was obtained via GC-MS analysis.

Fabrication of Fe Nanodot Using AAO Prepatterned by Laser Interference Lithography (레이저 간섭 석판술로 전처리된 AAO을 이용한 Fe 나노점 제작)

  • Hwang, H.M.;Kang, J.H.;Lee, S.G.;Lee, J.
    • Journal of the Korean Magnetics Society
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    • v.17 no.3
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    • pp.137-140
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    • 2007
  • The ordering of nanopores in AAO has been improved by using laser interference lithography. After growing Fe and Cu on this substrate in vacuum and removing AAO, Fe nanodots are fabricated. The nanopores in AAO and nanodots are ordered in one dimension following the prepatterning. It has been confirmed from the magnetic hysteresis loop that the Fe nanodots have vortex structure and the dipolar interaction is dominant among them.

Growth of Amorphous SiOx Nanowires by Thermal Chemical Vapor Deposition Method (열화학 기상 증착법에 의한 비정질 SiOx 나노와이어의 성장)

  • Kim, Ki-Chul
    • Journal of Convergence for Information Technology
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    • v.7 no.5
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    • pp.123-128
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    • 2017
  • Nanostructured materials have received attention due to their unique electronic, optical, optoelectrical, and magnetic properties as a results of their large surface-to-volume ratio and quantum confinement effects. Thermal chemical vapor deposition process has attracted much attention due to the synthesis capability of various structured nanomaterials during the growth of nanostructures. In this study, silicon oxide nanowires were grown on Si\$SiO_2$(300 nm)\Pt(5~40 nm) substrates by two-zone thermal chemical vapor deposition with the source material $TiO_2$ powder via vapor-liquid-solid process. The morphology and crystallographic properties of the grown silicon oxide nanowires were characterized by field-emission scanning electron microscope and transmission electron microscope. As results of analysis, the morphology, diameter and length, of the grown silicon oxide nanowires are depend on the thickness of the catalyst films. The grown silicon oxide nanowires exhibit amorphous phase.

Spin Wave Interference in Magnetic Nanostructures

  • Yang, Hyun-Soo;Kwon, Jae-Hyun;Mukherjee, Sankha Subhra;Jamali, Mahdi;Hayashi, Masamitsu
    • Proceedings of the Korean Magnestics Society Conference
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    • 2011.12a
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    • pp.7-8
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    • 2011
  • Although yttrium iron garnet (YIG) has provided a great vehicle for the study of spin waves in the past, associated difficulties in film deposition and device fabrication using YIG had limited the applicability of spin waves to practical devices. However, microfabrication techniques have made it possible to characterize both the resonant as well as the travelling characteristics of spin waves in permalloy (Py). A variety of methods have been used for measuring spin waves, including Brillouin light scattering (BLS), magneto-optic Kerr effect (MOKE), vector network analyzer ferromagnetic resonance (VNA-FMR), and pulse inductive microwave magnetometry (PIMM). PIMM is one of the most preferred methodologies of measuring travelling spin waves. In this method, an electrical impulse is applied at one of two coplanar waveguides patterned on top of oxide-insulated Py, producing a local disturbance in the magnetization of the Py. The resulting disturbance travels down the Py in the form of waves, and is inductively picked up by the other coplanar waveguide. We investigate the effect of the pulse width of excitation pulses on the generated spin wave packets using both experimental results and micromagnetic simulations. We show that spin wave packets generated from electrical pulses are a superposition of two separate spin wave packets, one generated from the rising edge and the other from the falling edge, which interfere either constructively or destructively with one another, depending upon the magnitude and direction of the field bias conditions. A method of spin wave amplitude modulation is also presented by the linear superposition of spin waves. We use interfering spin waves resulting from two closely spaced voltage impulses for the modulation of the magnitude of the resultant spin wave packets.

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