Ki-Sub Kim

Korea National University of Transportation, Sŏul, Seoul, South Korea

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Publications (69)130.6 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We have investigated the motion of a C60 molecule absorbed on sinusoidal graphene nanoflake (GNF) via molecular dynamics simulations. Since C60 deposited on sinusoidal GNF is favorable on energetic grounds, the C60 molecule moved toward one of the valleys of sinusoidal GNF without energy barrier. So no sooner the C60 molecule was deposited on the sinusoidal GNF, then the C60 molecule immediately began to move toward the valley of the sinusoidal GNF. Since the position of the C60 molecule can be changed by externally applied force fields and has a binding energy of 0.754 eV in the valley of sinusoidal GNF, the sinusoidal C60/GNF can be applied to a switchable nonvolatile memory device. This work provides the probability of alternative ‘bucky shuttle’ memory based on the sinusoidal C60/GNF hybrid nanostructure.
    Journal of Nanoscience and Nanotechnology 07/2015; 15(7). DOI:10.1166/jnn.2015.10375 · 1.34 Impact Factor
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    ABSTRACT: CdTe nanowires were synthesized from individual nanoparticles via self-assembly at a specific wavelength of light. The wavelength of 500 nm resulted in a self-assembly of nanoparticles into nanowires. Most of the produced nanowires were straight and long in shape and their length ranged from 300 nm to 20 μm. The oxidation of Te2– in CdTe nanoparticles under the visible light resulted in the assembly of nanowires consisting of several layers of individual nanoparticles. Transmission electron microscopy and scanning electron microscopy were performed to characterize the synthesized nanostructures. Energy-dispersive X-ray demonstrated the atomic percentage of nanowires. Photoluminescence showed that the wavelength of the nanostructures is slightly blue-shifted from 555 to 548 nm.
    Journal of Nanoscience and Nanotechnology 07/2015; 15(7):5346-5349. DOI:10.1166/jnn.2015.10396 · 1.34 Impact Factor
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    ABSTRACT: This paper presents the schematics and the energetics of nonvolatile-nanomemory-element based on carbon nanotube (CNT) on graphene nanoribbon (GNR) array using interatomic interaction potential function. The system proposed was composed of short outer CNT and long core CNT placed on two GNRs with a gap. The short outer CNT, which can be formed by electro-burning or electron-beam stripping, shuttles between two GNRs along the core CNT under the alternatively applied force fields. When the outer CNT settles on the GNRs, the local energy minima are achieved from the attractive van der Waals potential energies and then, since the outer CNT shuttle remains its position on the GNR without external force fields, the proposed system can operate a nonvolatile memory device. To switch this CNT shuttle system, the external force fields to overcome the restoring force exerted by van der Waals attractions should be applied.
    Journal of Computational and Theoretical Nanoscience 03/2015; 12(3). DOI:10.1166/jctn.2015.3740 · 1.03 Impact Factor
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    ABSTRACT: We address the simple schematics of graphene-nanoflake shuttle-memory and investigate its energetic and dynamic properties. The internal dynamics of a related model system, consisting of a graphene-nanoflake on a patterned graphene nanoribbon, are investigated via classical molecular dynamics simulations. The van der Waals interactions between the graphene-nanoflake and the patterned graphene nanoribon make bistable potential energy wells in the larger surface area regions of the patterned graphene nanoribbon, and then the graphene-flake keeps its seat on one of the bistable positions, which is the place where the binary data is archived. This graphenenanoflake shuttle can be a tunable two-level system, where transitions between the bistable positions can be induced by applying an electric field. Nanostructures composed of graphene-nanoflake on graphene-nanoribbon are applicable to ultra-fast response oscillators, switches, sensors, and quantum computing, as well as nonvolatile memory.
    Journal of Computational and Theoretical Nanoscience 01/2015; 12(1). DOI:10.1166/jctn.2015.3690 · 1.03 Impact Factor
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    ABSTRACT: Cadmium telluride (CdTe) nanowires were successfully synthesized from individual nanoparticles and the evolutionary process was investigated. Slow oxidation of Te2− in CdTe nanoparticles resulted in the generation of ribbons consisting of several layers of individual nanocrystals. The length of nanowires ranged from 1 to 8 μm. The presence of unusual shapes of multiparticle assemblies, such as bouquet, dog-bone, and ribbon bunches was observed as intermediate stages. The images of nanoribbons were analysed based on transmission electron microscopy and scanning electron microscopy. The suggested synthetic procedure provides a viable pathway for the fabrication of nanomaterials with helical conformations.
    Journal of Nanoscience and Nanotechnology 01/2015; 15(1). DOI:10.1166/jnn.2015.8366 · 1.34 Impact Factor
  • 12/2014; 20(4):349-353. DOI:10.7464/ksct.2014.20.4.349
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    ABSTRACT: Ionic liquids (ILs) have been proposed as potential inhibitors for preventing gas hydrate formation because their ion pairs effectively interrupt the hydrogen bonding between water molecules. ILs also have broad inhibitory capabilities depending on the specific cation and anion combinations. The final structural design of ILs for hydrate inhibition must be performed after an inhibition mechanism is suggested. In this study, the inhibitory thermodynamic effects of ILs were measured by the hydrate–aqueous liquid–liquid carbon dioxide (CO2) equilibrium, and the experimental results were analyzed based on the hydration free energy of ILs calculated through molecular dynamics study. 1-Hydroxyethyl-1-methylpyrrolidinum chloride showed the best inhibitory performance of the suggested candidates. The anions mostly contributed to the thermodynamic inhibition, but the cations had a marginal impact on CO2 hydrate inhibition. Through fundamental understanding of the inhibition mechanism by both experimental and computational approaches, it is highly possible to provide crucial information for effective ILs to be designed as the CO2 hydrate inhibitor.
    Fluid Phase Equilibria 11/2014; 382:270–278. DOI:10.1016/j.fluid.2014.09.019 · 2.24 Impact Factor
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    ABSTRACT: Cadmium telluride (CdTe) nanowires were successfully synthesized from individual nanoparticles via self-assembly, and the evolutionary process was investigated. The oxidation of tellurium ions in CdTe nanoparticles under dark conditions led to the assembly of straight nanowires made of several layers of individual nanoparticles. Transmission electron microscopy and scanning electron microscopy were performed to characterize the synthesized nanostructures. The length of the NWs assembled from CdTe NPs ranged from 0.5 to 30 μm. Unlike generally prepared NWs, these NWs were made from individual NPs layered on top of each other. Remarkably, the assembly of individual NPs formed bundles during the intermediate steps before they unraveled into individual NWs. Both control of the amount of stabilizer and oxidation of Te ions acted as driving forces to form NWs. Thus, small modifications in synthesis yielded a major difference in the final nanomaterial structure. The suggested synthetic procedure provides a viable pathway for the fabrication of nanomaterials.
    Journal of Nanoscience and Nanotechnology 11/2014; 14(11). DOI:10.1166/jnn.2014.10005 · 1.34 Impact Factor
  • Ki-Sub Kim, Byung Heung Park
    09/2014; 12(3):245-251. DOI:10.7733/jnfcwt.2014.12.3.245
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    ABSTRACT: We report the concept of combining ionic liquids (ILs) with polymer inhibitors to more effectively inhibit methane hydrate formation. The new inhibitors extended the induction time and decreased the growth rate of the hydrate. It was found that the presence of a hydroxyl group on IL provided the most powerful inhibition effect by forming hydrogen bonds between IL and water molecules.
    RSC Advances 11/2013; 3(43):19920-19923. DOI:10.1039/c3ra43891k · 3.71 Impact Factor
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    ABSTRACT: We investigated the phase equilibrium boundary of tri-n-butylphosphine oxide (TBPO) semiclathrate hydrates incorporated with CH4, CO2, and H2. TBPO aqueous solutions with a molality (m) of (1.61 and 1.98) mol·kg–1 were used for hydrate formation, which corresponded to the clathrate structures of TBPO·34.5H2O and 28H2O, respectively. The phase boundary at both concentrations was shifted to the promotion region represented by lower pressures and higher temperatures, compared to each simple gas hydrate. In particular, TBPO + CO2 double hydrate presented mild hydrate stabilization conditions of <1 MPa at (280 to 285) K. Additionally, the dissociation enthalpy (ΔHd) calculated from the phase boundary curves for the TBPO + CO2 double hydrates was almost the same as that for tetra-n-butylammonium bromide (TBAB) + CO2 double hydrate (219.5 kJ·mol–1 for m = 1.61 mol·kg–1 and 211.6 kJ·mol–1 for m = 1.98 mol·kg–1). These results demonstrate that the TBPO + CO2 double hydrate could be used as refrigerants for cold storage and transportation.
    Journal of Chemical & Engineering Data 11/2013; 58(12):3494–3498. DOI:10.1021/je400773k · 2.05 Impact Factor
  • Ki-Sub Kim, Zion Hwang, Jeong Won Kang
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    ABSTRACT: We investigate the dynamics behaviors of single-layered graphene sheet resonator at constant temperature via classical molecular dynamics simulations. The simulation results show that the graphene sheet resonator works in a mixed behavior, partly chaotic and partly regular, which is due to the interaction between the self-rippling of the graphene sheet and the applied gate forces. However in spite of the partial chaotic motions, the existence of regular signature can allow the development of tunable resonators. Hence the resonance frequencies as a function of the applied fate force can be regressed by the power function, this result shows the tenability of the graphene sheet resonator by controlling electrical direct current bias of the gate. Graphene resonators as ultra-sensitive sensors can be well-modeled using the tension variations induced by the applied gate force.
    Journal of Computational and Theoretical Nanoscience 08/2013; 10(8):1879-1885. DOI:10.1166/jctn.2013.3143 · 1.03 Impact Factor
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    ABSTRACT: We investigate ultrahigh sensitivity accelerometers based on graphene-nanoribbon-resonators including an attached mass by performing molecular dynamics simulations. Sensing acceleration can be achieved by detecting the resonance frequency (f) or the resonance frequency shift (Δf) of the graphene-nanoribbon-resonator. The acceleration as a function of frequency was regressed by a power function and shown to have a linear relationship on a log–log scale. As the attached mass increased, the sensitivity decreased whereas the sensing range remained constant. When the reference frequency (f Max) was defined as the limit of the sensing range, acceleration could be sensed by fitting the function of f/f Max regardless of the attached mass. When Δf/f Max ≥ 0 8, acceleration rapidly increased with increasing Δf/f Max, and then the acceleration could be very sensitively detected from small changes of Δf/f Max.
    Journal of Computational and Theoretical Nanoscience 08/2013; 10(8):1886-1891. DOI:10.1166/jctn.2013.3144 · 1.03 Impact Factor
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    ABSTRACT: A tunable graphene-resonator was investigated using classical molecular dynamics modeling and simulations. The fundamental resonance frequency variation of the graphene resonator was found to be very closely related to the average tension acting on both its edges. The initial stain-induced tension could be adjusted by using the mismatch between the negative thermal expansion coefficient of the graphene and the positive thermal expansion coefficient of the substrate, and the deflection-induced tension could be controlled by an electrostatic capacitive force due to the gate voltage. For very small initial axial-strains, the tunable range reached above several hundred gigahertz. As the initial axial-strain on the graphene-resonator increased, both the tunability and the tunable range decreased. The fundamental resonance frequency as a function of the calculated gate voltage was in good agreement with previous experiments. Considering the variables that affect the tension variation, this graphene-resonator is suitable for use as an ultra-sensitive accelerometer, thermo-sensor or weight scale, as well as many other types of sensor.
    Current Applied Physics 06/2013; 13(4):789–794. DOI:10.1016/j.cap.2012.12.007 · 2.03 Impact Factor
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    ABSTRACT: We presented simple schematics of a nanoscale inertial measurement unit based on the self-retraction motion of the graphene flakes. When an external force is applied to the nanoscale graphite flake, the inertial force exerted on the movable layer can telescope it, then the self-restoring force also arises as the van der Waals force between the interlayers of the flake, which each suspended flake can automatically and fully retract back onto the top of the graphite platform immediately after the externally applied force is released. Since the van der Waals force linearly increases with the increasing size of the flake, the sensing limitation can be controlled. When the external force does not exceed the retracting force, this addressed nanoscale inertial measurement unit can be semi-permanently used. Therefore, the size and the thickness of the graphene flake should be carefully selected with a tradeoff. These graphite flakes can be utilized as a basic structure in various nanoelectromechanical devices, such as switch and memory, linear and angular accelerometers, and pressure sensors.
    Physica E Low-dimensional Systems and Nanostructures 05/2013; 50:44–50. DOI:10.1016/j.physe.2013.02.025 · 1.86 Impact Factor
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    ABSTRACT: A tunable graphene-nanoribbon (GNR)-resonator was investigated via classical molecular dynamics simulations. Resonance frequencies increased with increasing externally applied gate-force and axial-strain, and could be tuned above several hundred GHz. Tunable resonance frequencies achieved from the gate force were higher than those achieved from the axial-strain. The operating frequencies of GNR-resonators without axial-strain or with small axial-strains were most widely tuned by the gate, and almost linearly increased with increasing mean deflection. As the axial strain increased, the tunable ranges of the GNR-resonators were exponentially decreased, although the operating frequencies increased. GNR-resonators without axial-strain could be applied to wide-range-tuners, whereas GNR-resonators with high axial-strain could be applied to high-frequency-fine-tuners.
    Current Applied Physics 03/2013; 13(2):360–365. DOI:10.1016/j.cap.2012.08.009 · 2.03 Impact Factor
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    ABSTRACT: Molecular dynamics methods are used to model the vibrational behavior of a suspended graphene-resonator that absorbs a finite mass at constant temperature. The effective molecular dynamics simulations easily estimate the fundamental frequency shifts of the suspended graphene with attached mass. The resonance frequency of the graphene-resonator can be functionalized by both the attached mass and the applied force. The results obtained from the molecular dynamics simulations were in good agreement with those of previous related experimental and theoretical works. For this graphene-based scaled nanobalance, the possible frequency-shift ranges increased with increasing applied force and with decreasing attached mass, they then reached 75–80% of the fundamental resonance frequency of a bare graphene-resonator. The mass sensitivity of the graphene-resonator reached ∼10−24 g and a logarithmically linear relationship was found in the frequency-vs-mass curves for attached masses of 10−21–10−19 g.
    Computational Materials Science 02/2013; 67:329–333. DOI:10.1016/j.commatsci.2012.09.017 · 1.88 Impact Factor
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    ABSTRACT: We propose schematics for an ultra-sensitive pressure sensor based on graphene-nanoribbon (GNR) and investigate its electromechanical properties using classical molecular dynamics simulations and piezo-electricity theory. Since the top plate applied to the actual pressure is large whereas the contact area on the GNR is very small, both the sensitivity and the sensing range can be adjusted by controlling the aspect ratio between the top plate and the contact point areas. Our calculation shows that the electrical conductivity of GNRs can be tuned by the applied pressure and the electric conductance of the deflected GNR linearly increases with increasing applied pressure for the linear elastic region in low pressure below the cut-off point. In the curves for both the deflection and potential energy, the linear elastic regime in low pressure was explicitly separated with the non-linear elastic regime in high pressure. The proposed GNR-based nanoelectromechanical devices have great potential for application as electromechanical memory, relay or switching devices.
    Physica E Low-dimensional Systems and Nanostructures 01/2013; 47:6–11. DOI:10.1016/j.physe.2012.10.010 · 1.86 Impact Factor
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    ABSTRACT: We investigated the tension and strain energy variations as a function of the axial strain in static conditions in graphene nanoribbon resonators and the resonance frequency change with tensile loading in dynamic conditions via classical molecular dynamics simulations. This theoretical study presents the application of graphene nanoribbon resonators tuned by tensile loading as ultrahigh frequency devices. The non-linear mechanical properties of the resonators were found, and for small axial strains, the mechanical properties of the graphene nanoribbon, such as strain-energy vs. axial-strain and frequency vs. strain or tension, were estimated by the classical continuum theory. The resonance frequencies increased with increasing axial strain, and such a relation could be regressed by a linearly increasing line on a log–log scale. The increasing resonance frequency due to increasing tension could be regressed by a square root function.
    Computational Materials Science 12/2012; 65:216–220. DOI:10.1016/j.commatsci.2012.07.027 · 1.88 Impact Factor
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    ABSTRACT: CdTe nanoribbons feature their unique optical properties compared with CdTe nanoparticles. Slow oxidation of tellurium ions on CdTe nanoparticles resulted in the organization of individual nanoparticle into nanoribbons. The light-controlled self-assembly of CdTe nanoparticles led to twisted ribbons. It was found that irradiation improved the oxidation of tellurium ions. Transmission electron microscopy (TEM) were performed to characterize the synthesized nanostructures and showed nanowires were twisted after self-assembly. The photoluminescence was slightly blue-shifted from 550 to 544 nm. This synthetic procedure could potentially provide a key step toward the fabrication of nanowires.
    12/2012; 50(6). DOI:10.9713/kcer.2012.50.6.1082

Publication Stats

1k Citations
130.60 Total Impact Points

Institutions

  • 2012–2013
    • Korea National University of Transportation
      • Department of Chemical and Biology Engineering
      Sŏul, Seoul, South Korea
  • 2011–2012
    • Chungbuk National University
      • Department of Chemical Engineering
      Chinsen, Chungcheongbuk-do, South Korea
  • 2001–2007
    • Korea Advanced Institute of Science and Technology
      • Department of Chemical and Biomolecular Engineering
      Seoul, Seoul, South Korea