• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2010년도 추계학술발표논문집 1부
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• pp.470-473
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• 2010

Graphene, consisting of a single layer of carbon in a two-dimensional lattice, has been emerging as a fascinating material with many unique physical, chemical and mechanical properties. In this study, graphenes were prepared by a chemical method. To develop high performance polymer nanocomposites reinforced by graphenes, adequate dispersion of the fillers and strong interfacial bonding between the fillers and the polymer matrix are essential. The purpose of this study was to examine the influence of introducing amine groups on the surfaces of graphenes. FT-IR spectroscopy, SEM were used to confirm the functionalization. Epoxy nanocomposites comprising the graphenes were prepared and their characteristics were investigated by DSC, DMA and TMA. Fracture surfaces of the nanocomposites were investigated by SEM. The functionalized graphenes induced strong interfacial bonding than the pristine graphenes and resulted in considerable improvements in the performance of the nanocomposites.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.12-12
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• 2011

Interfacing functional materials with electrical or biological systems is of prime importance in terms of expanding applicative fields and obtaining high performances of devices. Herein, I report the functionalization of graphenes through supramolecular assembly and their electrochemical applications into fuel cells, supercapacitors, and biosensor devices. The solution processable nanohybridization of graphenes by functional materials such as ionic liquids, polyelectrolytes, block copolymers, and biomaterials, described herein would pave the way to obtain high performances of flexible energy and biosensor devices as well as to overcome the existing technology barriers.

• 폴리머
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• 제35권3호
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• pp.265-271
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• 2011

Hummers와 Offeman 방법을 이용하여 흑연으로부터 graphene oxide(GO)를 합성하였다. Hydrazine hydrate를 사용하여 GO를 환원시켜 reduced graphene oxide (RGO)를 합성하였으며, 말단에 amine이 치환된 유기화제를 사용하여 관능기화 그래핀을 합성하였다. 합성된 GO, RGO, 그리고 관능기화 그래핀의 구조를 확인하기 위하여 FTIR과 $^{13}C$ NMR를 이용하였다. 합성된 시료들의 안정성, 모폴로지 및 다양한 유기용매 내에서의 분산도를 각각 조사하였다. AFM 사진으로부터 GO와 RGO는 한층 또는 두층 두께의 그래핀으로 이루어졌으며, 관능기화 그래핀들의 평균두께는 약 2.26~3.30 nm임을 알았다. 관능기화 그래핀들의 열 안정성은 RGO보다 낮았다. 관능기화 그래핀들은 용액상태에서 흑연의 특성 피크가 관찰되지 않는 것으로 보아 클로로포름과 톨루엔에 좋은 분산성을 가지는 것으로 확인되었다.

• Bulletin of the Korean Chemical Society
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• 제31권8호
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• pp.2261-2264
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• 2010

In this work, mechanical and electrical properties of graphenes (GP)/carbon nanotubes (CNTs) co-reinforced high density polyethylene (HDPE) matrix composites were studied. The microstructure, morphologies, and electric properties of the composites were evaluated by XRD, TEM, and 4-probe methods, respectively. It was found that the electric resistivity of 0.5 wt %-GP/HDPE was immeasurable, and 2.0 wt %-CNTs/HDPE showed high resistivity ($6.02{\times}10^4{\Omega}{\cdot}cm$). Meanwhile, GP (0.5 wt %)/CNTs (2.0 wt %)/HDPE showed excellent low resistivity ($3.1{\times}10^2{\Omega}{\cdot}cm$). This result indicates that the co-reinforcement systems can dramatically decrease electric resistivity of the carbon/polymer nanocomposites.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.40-40
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• 2010

Employing synchrotron radiation based photoemission spectroscopy (PES) and scanning tunneling microscopy (STM), our group have investigated Si surfaces, various graphenes and molecular nanolayers. In this talk, I introduce recent results on the surface related systems. All experiments have been performed at the surface science beamlines, 3A2 and 7B1, in Pohang Accelerator Laboratory, where high resolution PES (HRPES) and angle resolved PES (ARPES) are available. Metals or molecules are adsorbed and sometimes extreme ultraviolet is irradiated onto surfaces to give them special functions. I show several examples for surface functionalzation and how to characterize solid surface using the analysis techniques. In particular, lots of ARPES and STM data are provided from graphenes, a strong candidate for replacing Si and conducting oxide currently used in many electronic and optical devices.

• Elastomers and Composites
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• 제52권4호
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• pp.272-279
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• 2017

The heterocoagulation of latex is a simple and useful method to fabricate various polymer nanocomposites in which a precise control of the colloid stability is essential. In this work, a multi-layered graphenes (MLGs)/poly(styrene-co-butyl acrylate) (P(S-co-BA)) nanocomposite having an excellent dispersion of MLGs was prepared via the sudden heating heterocoagulation process. The P(S-co-BA) component was obtained by emulsion polymerization. This process can effectively shorten the process and particles growth steps. The colloid stability of these dispersions was controlled by factors such as ionic charge, temperature, and reaction times. The influence of these factors on heterocoagulation was evaluated and the properties of the nanocomposites were investigated. The conductivity of the MLGs/P(S-co-BA) nanocomposites increased from -11.53 to -5.70 S/cm for an increase in MLG content from 0.01 to 5 wt%. Moreover, percolation threshold was observed in the case of 0.01 wt% MLGs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.76.2-76.2
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• 2015

I will present my research group's recent investigation on how the localized plasmon of a nanoparticle interacts with another plasmon, and with nearby molecules. First, I will demonstrate the use of scattering-type scanning near-field microscopy (s-SNOM) to directly visualize the capacitive / conductive coupling in dimeric nanoparticles and heterometallic nanorods. Second, I will talk about the use of gap-plasmons to locally induce photochemical reactions, and to follow chemical kinetics of individual organic molecules using the gap-plasmons. As a last topic, I will talk about the use of near-field coupling between a scanning probe and graphenes to visualize / identify the stacking domains (e. g., ABA versus ABC-type stacking in triple layer) hidden in multilayer graphenes.

• 센서학회지
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• 제21권6호
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• pp.425-428
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• 2012

This paper presents the fabrication and characterization of graphene based hydrogen sensors. Graphene was synthesized by annealing process of Ni/3C-SiC thin films. Graphene was transferred onto oxidized Si substrates for fabrication of chemiresistive type hydrogen sensors. Au electrode on the graphene shows ohmic contact and the resistance is changed with hydrogen concentration. Nanoparticle catalysts of Pd and Pt were decorated. Response factor and response (recovery) time of hydrogen sensors based on the graphene are improved with catalysts. The response factors of pure graphene, Pt and Pd doped graphenes are 0.28, 0.6 and 1.26, respectively, at 50 ppm hydrogen concentration.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.8-8
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• 2011

During the last half decade, chemically modified graphene (CMG) has been studied in the wide range of applications, such as polymer composites, energy-related materials, sensors, 'paper'-like materials, field-effect transistors (FET), inks, actuators, and biomedical applications due to its excellent electrical, mechanical, and thermal properties. Chemical modification of graphene oxide, which is generated from graphite oxide, which is produced by simple oxidation of graphite, has been a promising route to achieve mass production of CMG platelets via their colloidal suspensions. Graphene oxide contains a range of reactive oxygen functional groups, which renders it a good candidate for use in the aforementioned applications (among others) through chemical functionalizations. In this presentation, I will discuss my recent research activities on the fundamental chemistry of graphite oxide, as well as novel applications based on CMGs. Topics will include the chemical structure of CMGs and colloidal suspensions of CMG platelets, as well as a wide variety of applications.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.127-127
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• 2012

We carried out the high-resolution dielectric mapping of graphenes on $SiO_2$/Si substrate, using the scattering Apertureless Near-Field Scanning Optical Microscopy (s-ANSOM) in both visible (633 nm) and infrared (3.6 um) wavelengths. In the visible wavelength, the dielectric contrasts are almost proportional to the number of the graphene layers, which indicates that the near-field interaction between the tip and individual graphene layers leads to an image charge oscillation in two-dimension. In the infrared region, on the other hand, we observe unique layer-specific contrasts that do not linearly increase with number of layers. It is attributed to the layer-dependent band- structure of graphenes.