• Clean Technology
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• v.19 no.3
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• pp.320-326
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• 2013

Nano-sized PtRu-Ni/VC and PtRu-Sn/VC electrocatalysts were synthesized by a one-step radiation-induced reduction (RIR) (30 kGy) process using distilled water as the solvent and Vulcan XC-72 as the supporting material. The obtained electrocatalysts were characterized by transmission electron microscopy (TEM), scanning electron microscope energy dispersive spectroscopic (SEM-EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The catalytic efficiency of electrocatalysts was examined for oxygen reduction, MeOH oxidation and CO stripping decreased in the following order, Hydrogen stripping : PtRu-Sn/VC > PtRu-Ni/VC > PtRu/VC$^{(R)}$ (E-TEK). MeOH oxidation : PtRu-Sn/VC > PtRu-Ni/VC > PtRu/ VC$^{(R)}$ (E-TEK). Unit cell performance : PtRu-Sn/VC > PtRu-Ni/VC > PtRu/VC$^{(R)}$ (E-TEK) catalysts.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.399-399
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• 2012

최근 그래핀 연구와 더불어 2차원 구조의 나노소재에 대한 관심이 급증하면서 육각형의 질화붕소(hexagonal boron nitride; h-BN) 나노시트(nanosheet)[1]나 붕소 탄화질화물(boron caronitride;BCN) 나노시트[2, 3]와 같은 2차원 구조체에 대한 연구가 활발히 진행되고 있다. 그 중 BCN은 반금속(semimetal)인 흑연(graphite)과 절연체인 h-BN이 결합된 나노시트로 원소의 구성 비율에 따라 전기적 특성을 제어할 수 있다는 장점이 있다. 따라서 다양한 나노소자로의 응용을 위한 연구가 활발히 진행되고 있다. 본 연구에서는 열 화학기상증착법(thermal chemical vapor deposition)을 이용하여 폴리스틸렌(polystyrene)과 보레인 암모니아(borane ammonia)를 사용하여 BCN 나노시트를 합성하였다. 합성된 BCN 나노시트의 구조적 특징과 화학적 조성 및 결합 상태를 주사전자현미경(scanning electron microscopy), 투과전자현미경(transmission electron microscopy), X-선 광전자 분광법(X-ray photoelectron spectroscopy), 라만 분광법(Raman spectroscopy)을 통해 조사하였고, 이온성 용액법 (ionic liquid)[4]을 이용하여 전계효과 특성을 측정하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.242-242
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• 2012

Transparent oxide semiconductors are increasingly becoming one of good candidates for high efficient channel materials of thin film transistors (TFTs) in large-area display industries. Compare to the conventional hydrogenated amorphous silicon channel layers, solution processed ZnO-TFTs can be simply fabricated at low temperature by just using a spin coating method without vacuum deposition, thus providing low manufacturing cost. Furthermore, solution based oxide TFT exhibits excellent transparency and enables to apply flexible devices. For this reason, this process has been attracting much attention as one fabrication method for oxide channel layer in thin-film transistors (TFTs). But, poor electrical characteristic of these solution based oxide materials still remains one of issuable problems due to oxygen vacancy formed by breaking weak chemical bonds during fabrication. These electrical properties are expected due to the generation of a large number of conducting carriers, resulting in huge electron scattering effect. Therefore, we study a novel technique to effectively improve the electron mobility by applying environmental annealing treatments with various gases to the solution based Li-doped ZnO TFTs. This technique was systematically designed to vary a different lithium ratio in order to confirm the electrical tendency of Li-doped ZnO TFTs. The observations of Scanning Electron Microscopy, Atomic Force Microscopy, and X-ray Photoelectron Spectroscopy were performed to investigate structural properties and elemental composition of our samples. In addition, I-V characteristics were carried out by using Keithley 4,200-Semiconductor Characterization System (4,200-SCS) with 4-probe system.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.475-479
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• 2004

$TiO_2$ thin films were grown on Si (100) substrates by atomic layer deposition using $[Ti(OPr^i )_2(dmae)_2]$ and water as precursors. The thickness, chemical composition, crystalline structure, and morphology of the deposited films were investigated by transmission electron microscopy, UV spectrometry, X-ray photoelectron pectroscopy, X-ray diffraction, and atomic force microscopy. The results show that $TiO_2$ ALD using $[Ti(OPr^i )_2(dmae)_2]$ as a precursor is self-controlled at temperatures of 100-300$^{\circ}C$. At the growth temperatures below 300$^{\circ}C$, the surface morphology of the $TiO_2$ films is smooth and uniform. The $TiO_2$ film was grown with a preferred orientation toward the [101] direction at 400$^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2694-2698
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• 2012

Materials on the scale of nanoscale have widely been used as research topics because of their interesting characteristics and aspects they bring into the field. Out of the many metal oxides, zinc oxide (ZnO) was chosen to be fabricated as nanofibers using the electrospinning method for potential uses of solar cells and sensors. After ZnO nanofibers were obtained, calcination temperature effects on the ZnO nanofibers were studied and reported here. The results of scanning electron microscopy (SEM) revealed that the aggregation of the ZnO nanofibers progressed by calcination. X-ray diffraction (XRD) study showed the hcp ZnO structure was enhanced by calcination at 873 and 1173 K. Transmission electron microscopy (TEM) confirmed the crystallinity of the calcined ZnO nanofibers. X-ray photoelectron spectroscopy (XPS) verified the thermal oxidation of Zn species by calcination in the nanofibers. These techniques have helped us deduce the facts that the diameter of ZnO increases as the calcination temperature was raised; the process of calcination affects the crystallinity of ZnO nanofibers, and the thermal oxidation of Zn species was observed as the calcination temperature was raised.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.309-314
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• 2010

The surface modified $LiMn_2O_4$ materials with Li-Fe composites were prepared by a sol-gel method to improve the electrochemical performance of $LiMn_2O_4$ and were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and transmission electron microscopy (TEM)-EDS. XRD results indicate that all the samples (modified and pristine samples) have cubic spinel structures, and XRD, XPS, and TEM-EDS data reveal the formation of $Li(Li_xFe_xMn_{2-2x})O_4$ solid solution on the surface of particles. For the electrochemical properties, the modified material demonstrated dramatically enhanced reversibility and stability even at elevated temperature. These improvements are attributed to the formation of the solid solution, and thus-formed solid solution phase on the surface of $LiMn_2O_4$ particle reduces the dissolution of Mn ion and suppresses the Jahn-Teller effect.

• Journal of the Korean Chemical Society
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• v.61 no.4
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• pp.168-178
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• 2017

$La/TiO_2$ - graphene composites were synthesized in this study, and applied to the photocatalytic degradation of Rhodamine B (RhB) under UV-visible light irradiation. X-ray diffraction (XRD), surface analysis, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) analysis demonstrated that $La/TiO_2$ nanoparticles were well distributed on the surface of graphene, and formed the heterostructure of $La/TiO_2$-graphene. Compared to the pure $TiO_2$, $La/TiO_2$-graphene composites displayed much higher photocatalytic activities in RhB degradation under UV-visible light irradiation. The photocatalytic data of $La/TiO_2$-graphene composites exhibit extended light absorption in the visible light region, and possess better charge separation capability than that of pure $TiO_2$. The high photocatalytic activity was attributed to the composite's high adsorptivity, extended light absorption, and increased charge separation efficiency, due to the excellent electrical properties of graphene, and the large surface contact between graphene and $La/TiO_2$ nanoparticles.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.59.1-59.1
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• 2015

In the Linford group at Brigham Young University we have recently developed three new sets of materials for three different areas of separations science: thin layer chromatography (TLC), high performance liquid chromatography (HPLC), and solid phase microextraction (SPME). First, via microfabrication we have grown patterned carbon nanotube (CNT) forests on planar substrates that we have infiltrated with inorganic materials such as silicon nitride. The coatings on the CNTs are conformal and typically deposited in a process like low pressure chemical vapor deposition. The resulting materials have high surface areas, are porous, and function as effective separation devices, where separations on our new TLC plates are typically significantly faster than on conventional devices. Second, we used the layer-by-layer (electrostatically driven) deposition of poly (allylamine) and nanodiamond onto carbonized poly (divinylbenzene) microspheres to create superficially porous particles for HPLC. Many interesting classes of molecules have been separated with these particles, including various cannabinoids, pesticides, tricyclic antidepressants, etc. Third, we have developed new materials for SPME by sputtering silicon onto cylindrical fiber substrates in a way that creates shadowing of the incoming flux so that materials with high porosity are obtained. These materials are currently outperforming their commercial counterparts. Throughout this work, the new materials we have made have been characterized by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, scanning electron microscopy, transmission electron microscopy, etc.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.49-49
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• 2009

Nanocomposites of gold nanoparticles and multi-walled carbon nanotubes (MWNTs) were prepared by electrostatic interaction. Gold nanopartic1es were stabilized by polyvinylpyrrolidone (PVP), sodium dodecyl sulfate (SDS) and poly(sodium-4-styrenesulfonate) (PSS) in aqueous medium, and MWNTs were modified by poly(diallyldimethylammonium)chloride (PDDA) in water. The as-perpared Au-MWNT nanocomposites were structurally and electrically characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), UV/Vis spectroscopy, X-ray photoelectron spectroscopy (XPS) and cyclo voltammetry (CV). UV/Vis spectra of Au-MWNT nanocomposites showed the characteristic surface plasmon bands in the range of ~515nm, depending on the stabilizers. There is only slight change on the band shape with variation of stabilizing agents for gold nanoparticles. Through FE-SEM and TEM images, the distribution of gold, nanoparticles on the sidewalls of MWNTs was deliberately investigated on Au-MWNT nanocomposites treated with different stabilizers. XPS and CV showed redistribution of electron densities and changes in the binding energy states of nanopartic1es in nanocomposite respectively.

• Journal of the Korean Electrochemical Society
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• v.15 no.2
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• pp.90-94
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• 2012

We report nanostructure electrodes with $TiO_2$ as a core and carbon as a shell ($TiO_2$@C) for oxygen reduction in alkaline solution. The structure of core-shell electrodes is characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction method, and X-ray photoelectron microscopy. The electrochemical properties of the $TiO_2$@C electrodes are characterized using a potentiostat and compared with those of carbon supported Pt catalyst. In particular, the core-shell electrode with dominant pyridinic-N component exhibits an imporved electrocatalytic activity for oxygen reduction reaction in alkaline solution.