• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.388-388
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• 2011

Graphene, with its unique physical and structural properties, has recently become a proving ground for various physical phenomena, and is a promising candidate for a variety of electronic device and flexible display applications. The physical properties of graphene depend directly on the thickness. These properties lead to the possibility of its application in high-performance transparent conducting films (TCFs). Compared to indium tin oxide (ITO) electrodes, which have a typical sheet resistance of ~60 ${\Omega}/sq$ and ~85% transmittance in the visible range, the chemical vapor deposition (CVD) synthesized graphene electrodes have a higher transmittance in the visible to IR region and are more robust under bending. Nevertheless, the lowest sheet resistance of the currently available CVD graphene electrodes is higher than that of ITO. Here, we report an ingenious strategy, irradiation of MeV electron beam (e-beam) at room temperature under ambient condition,for obtaining size-homogeneous gold nanoparticle decorated on graphene. The nano-particlization promoted by MeV e-beam irradiation was investigated by transmission electron microscopy, electron energy loss spectroscopy elemental mapping, and energy dispersive X-ray spectroscopy. These results clearly revealed that gold nanoparticle with 10~15 nm in mean size were decorated along the surface of the graphene after 1.0 MeV-e-beam irradiation. The fabrication high-performance TCF with optimized doping condition showed a sheet resistance of ~150 ${\Omega}/sq$ at 94% transmittance. A chemical transformation and charge transfer for the metal gold nanoparticle were systematically explored by X-ray photoelectron spectroscopy and Raman spectroscopy. This approach advances the numerous applications of graphene films as transparent conducting electrodes.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.487-487
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• 2011

Recently graphene has emerged as a fascinating 2D system in condensed-matter physics as well as a new material for the development of nanotechnology. The unusual electronic band structure of graphene allows it to exhibit a strong ambipolar electric field effect with high mobility. These properties lead to the possibility of its application in high-performance transparent conducting films (TCFs). Compared to indium tin oxide (ITO) electrodes, which have a typical sheet resistance of ${\sim}60{\Omega}$/sq and ~85 % transmittance in the visible range (400?900 nm), the CVD-grown graphene electrodes have a higher/flatter transmittance in the visible to IR region and are more robust under bending. Nevertheless, the lowest sheet resistance of the currently available CVD graphene electrodes is higher than that of ITO. Here, we report an ingenious strategy, irradiation of MeV electron beam (e-beam) at room temperature under ambient condition, for obtaining size-homogeneous gold nanoparticle decorated on graphene. The nano-particlization promoted by MeV e-beam irradiation was investigated by transmission electron microscopy, electron energy loss spectroscopy elemental mapping, and energy dispersive X-ray spectroscopy. These results clearly revealed that gold nanoparticle with 10 ~ 15 nm in mean size were decorated along the surface of the graphene after 1.5 MeV-e-beam irradiation. A chemical transformation and charge transfer for the metal gold nanoparticle were systematically explored by X-ray photoelectron spectroscopy and Raman spectroscopy. This approach advances the numerous applications of graphene films as transparent conducting electrodes.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.90-90
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• 2009

박막 태양전지의 단락전류를 증가시키기 위해서는 투명전도 산화막의 표면 식각을 통한 광포획 특성 극대화가 중요하며, 일반적으로 스퍼터링법으로 제작된 투명전도 산화막의 표면 식각은 HCl solution을 이용한다. 본 연구는 투면전도 산화막 증착시 seed로 작용할 수 있는 colloidal 형태의 nanoparticle을 유리기판에 형성한 뒤 rf-magnetron sputtering 법을 이용하여 ZnO:Al(AZO) 투명전도 산화막을 증착하여 광학 전기적 특성 변화를 분석하였다. Nanoparticle을 사용하여 제조된 AZO 박막은 nanoparticle의 확산에 의한 전자농도의 향상이 보였으나, 이동도의 감소로 인해 전기적 특성에 큰 변화는 없었다. 반면 AZO 박막의 표면형상이 nanoparticle로 인해 변하여 박막의 광 포획을 위한 안개도가 향상됨을 확인 할 수 있었으며, 이로 인해 표면 형상 제어를 통한 박막 태양전지 적용을 위한 투명전도 산화막을 제작할 수 있었다.

• Carbon letters
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• v.20
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• pp.26-31
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• 2016

In this study, we report a general method for preparation of a one-dimensional (1D) arrangement of Au nanoparticles on single-walled carbon nanotubes (SWNTs) using biologically programmed peptides as structure-guiding 1D templates. The peptides were designed by the combination of glutamic acid (E), glycine (G), and phenylalanine (F) amino acids; peptides efficiently debundled and exfoliated the SWNTs for stability of the dispersion and guided the growth of the array of Au nanoparticles in a controllable manner. Moreover, we demonstrated the superior ability of 1D nanohybrids as flexible, transparent, and conducting materials. The highly stable dispersion of 1D nanohybrids in aqueous solution enabled the fabrication of flexible, transparent, and conductive nanohybrid films using vacuum filtration, resulting in good optical and electrical properties.

• Journal of Biomedical Engineering Research
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• v.35 no.4
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• pp.105-110
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• 2014

For the combination of MRI and magnetic particle hyperthermia(MPH), we investigated the relative heating efficiency with respect to the strength of the static magnetic field under which the magnetic nanoparticles are to be heated by RF magnetic field. We performed nanoparticle heating experiments at the fringe field of 3T MRI magnet with applying the RF magnetic field perpendicularly to the static magnetic field. The static field strengths were 0T, 0.1T, 0.2T, and 0.3T. To prevent the coil heat from conducting to the nanoparticle suspension, we cooled the heating solenoid coil with temperature-controlled water with applying heat insulators between the solenoid coil and the nanoparticle container. We observed significant decrease of heat generation, up to 6% at 0.3T(100% at 0T), due to the magnetic saturation of the nanoparticles of 15 nm diameter under the static field. We think MPH is still feasible at low magnetic field lower than 0.3T if stronger RF magnetic field generation is permitted.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.268.1-268.1
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• 2013

Immobilization of conducting nanoparticles on a nanogap comprising two electrodes spaced at a distance comparable to the particle size can be used as a simple and sensitive method of detecting the particles. In this work, we have examined the performance of the nanogap devices in the measurement of metallic nanoparticles, particularly gold nanoparticles (Au NPs). Detection of pM-level Au NPs in an aqueous suspension was quite straightforward irrespective of the existence of non-conducting materials. Speed of detection or the time necessary for the completion of the measurement, however, was strongly dependent upon the immobilization process. Active trapping process was found to be much more efficient and also effective in the detection of nanoparticles than its passive counterpart.

• Journal of Electrochemical Science and Technology
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• v.10 no.2
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• pp.223-230
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• 2019

A facile method for surface coating with $Li_2TiF_6$ which has a high lithium-ion conductivity, on $LiMn_2O_4$ spinel cathode material for high performance lithium ion batteries. The surface coating is performed by using a co-precipitation method with $Li_2CO_3$ powder and $H_2TiF_6$ solution under room temperature and atmospheric pressure without special equipment. Total coating amount of $Li_2TiF_6$ is carefully controlled from 0 to 10 wt.% based on the active material of $LiMn_2O_4$. They are evaluated by a systematic combination of analyses comprising with XRD, SEM, TEM and ICP. It is found that the surface modification of $Li_2TiF_6$ is very beneficial to high cycle life and excellent rate capability by reducing surface failure and supporting lithium ions transportation on the surface. The best coating condition is found to have a high cycle life of $103mAh\;g^{-1}$ at the 100th cycle and a rate capability of $102.9mAh\;g^{-1}$ under 20 C. The detail electrochemical behaviors are investigated by AC impedance and galvanostatic charge and discharge test.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.188-188
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• 2012

Graphene, with its unique physical and structural properties, has recently become a proving ground for various physical phenomena, and is a promising candidate for a variety of electronic device and flexible display applications. Compared to indium tin oxide (ITO) electrodes, which have a typical sheet resistance of ${\sim}60{\Omega}$/sq and ~85% transmittance in the visible range, the chemical vapor deposition (CVD) synthesized graphene electrodes have a higher transmittance in the visible to IR region and are more robust under bending. Nevertheless, the lowest sheet resistance of the currently available CVD graphene electrodes is higher than that of ITO. In this study, we report a creative strategy, irradiation of microwave at room temperature under vacuum, for obtaining size-homogeneous gold nano-particle doping on graphene. The gold nano-particlization promoted by microwave irradiation was investigated by transmission electron microscopy, electron energy loss spectroscopy elemental mapping. These results clearly revealed that gold nanoparticle with ${\geq}30$ nm in mean size were decorated along the surface of the graphene after microwave irradiation. The fabrication high-performance transparent conducting film with optimized doping condition showed a sheet resistance of ${\geq}100{\Omega}$/sq. at ~90% transmittance. This approach advances the numerous applications of graphene films as transparent conducting electrodes.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.114.1-114.1
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• 2011

Electrical sintering of the front electrode for crystalline silicon solar cells was performed applying a constant DC current to the printed lines. Conducting lines were printed on glass substrate by a drop-on-demand (DOD) inkjet printer and silver nanoparticle ink. Specific resistance and microstructure of sintered silver lines and were measured with varying DC current. To find the relation between temperature increase with changing applied current and specific resistance, temperature elevation was also calculated. Sintering process finished within a few milliseconds. Increasing applied DC current, specific resistance decreased and grain size increased after sintering. Achieved minimum specific resistance is approximately 1.7 times higher than specific resistance of the bulk silver.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.274-274
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• 2006

Recently, conjugated polymer solar cells have attracted a great deal of attention. In this work, we applied the various scanning probe techniques to characterize composite materials typically used to fabricate polymer solar cells: poly-3(hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and P3HT/PCBM/Au nanoparticle (NP) samples. The latter is studied due to the idea of using the gold NP surface plasmon to enhance the optical absorption of the composite films. AFM is used to characterize the film morphology whereas conducting AFM is used to study the charge transport properties at the nanoscale. We found that there is a direct correlation between the nanoscale charge transport measurements and the device efficiencies.