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곽은혜,윤경병,정구환 한국물리학회 2014 Current Applied Physics Vol.14 No.12
We report a comparative study on diameter distribution of single-walled carbon nanotubes (SWNTs) grown using nanoporous templates having different pore sizes, namely, zeolite-L, ZSM-5, and MCM-41. The change in the tube diameter based on catalytic film thickness and growth temperature was systematically investigated. We prepared very thin Fe catalyst films with nominal thicknesses of 0.5, 0.7, 1, and 2 Å, and the growth temperature was varied from 850 to 925 C. We found that the SWNT mean diameter and size distribution width decreased with decreasing catalyst film thickness, growth temperature, and pore sizes of the templates. In addition, all SWNTs grown from the nanoporous templates have narrower diameter distribution compared to the SWNTs grown from SiO2 planar surface. The obtained results are straightforward and suggest that the template growth has potential for SWNT growth with very narrow diameter distribution.
Nonlinear Optical Zeolite Films for Second and Third Harmonic Generation
김현성,Tung Thanh Pham,윤경병 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.5
Methods to prepare novel second-order nonlinear optical (2O-NLO) materials composed of all-silica zeolite (silicalite-1) and a series of 2O-NLO molecules having high second order hyperpolarizability constants (βvalues) are reviewed. These methods include the development of novel methods to incorporate a series of hemicyanine (HC) molecules into the channels of silicaite-1 films in uniform orientations. The first method is to incorporate HC molecules tethered with long alkyl chains (octadecyl or longer) into the silicalite-1 channels with the long alkyl chain side first through the hydrophobic-hydrophobic interaction between the long alky chains and the silicalite-1 channels. The second method is to incorporate the HC molecule tethered with a medium length alkyl chain (nonyl) into the silicalite-1 channels with the medium length alkyl chain side first through hydrophobic-hydrophobic interaction between the medium length alky chain in the photoexcited state and the silicalite-1 channels. The third method is to incorporate the HC molecule tethered with propionic acid into the silicalite-1 channels with the propionic acid side last mediated by a tetrabultylammonium cation ionpaired to the propionate unit. A method to prepare a novel third-order nonlinear optical (3O-NLO) material composed of zeolite-Y and PbS or PbSe quantum dots is also reviewed. This Account thus describes a promising new direction to which the search for highly sensitive 2O-NLO and 3O-NLO materials has to be conducted and a new direction to which zeolite research and applications have to be expanded.
Depolarization of Luminescence from Dye Molecules in Solutions or Embedded in Zeolite Pores
Hyunjin Lim,이진석,윤경병,정현식 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61
Depolarization of luminescence from pyronine B dye molecules was studied using polarized photoluminescence spectroscopy. When the molecules were dissolved in a solvent, the viscosity and the electronic dipole moment of the solvent affected the depolarization ratio and the photoluminescence peak position, respectively. In addition, the concentration of the dye molecules also influenced the depolarization ratio and the photoluminescence. For pyronine B molecules embedded in zeolite-L crystals, the photoluminescence peak position was independent of the concentration, and the depolarization ratio showed a dependence on the concentration that was opposite to the case of dye molecules in a solvent. The energy transfer between the molecules or the re-absorption process is suggested to explain the experimental results.
Photoluminescence Study of Fluorophore-Containing Zeolite Rods
H. Lim,정현식,이진석,윤경병 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.II
We have studied the photoluminescence (PL) from pyronine-B (PyB$^{+}$) dye molecules inserted into the pores of various zeolites with different pore sizes. We observed that the PL spectrum blue-shifted as the pore size of the zeolite decreased. This can be explained by the quantum confinement effect. We also noticed that the luminescence of the dye molecules was affected by the type of solvent. In addition, we studied the optical anisotropy of PyB$^{+}$-containing zeolite rods by using polarized photoluminescence spectroscopy. A high anisotropic ratio of $\sim$9 was obtained from an oriented monolayer of PyB$^{+}$-containing zeolite L.