• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.151-152
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• 2007

탄소나노튜브(CNTs)는 우수한 물리적, 화학적, 기계적 특성으로 다양한 분야에서 연구가 진행 되고있다. 특히, field emission displays (FEDs)로의 응용을 위해서는 기본적으로 sodalime glass 위에 직접 CNTs를 성장시켜야 하며, 소자 응용을 위해 기판인 sodalime glass를 왜곡시키는 온도보다 낮은 온도에서 CNT의 수직 성장이 이루어져야 한다. 본 연구에서는 Hot-filament plasma enhanced chemical vapor deposition (HF-PECVD)를 이용하여 합성온도를 400, 450, 500, $550^{\circ}C$로 변화시켰으며 촉매 층인 Ni의 두께를 5~40 nm까지 조절하여 탄소나노튜브를 합성하였다. 저온에서 합성된 탄소나노튜브는 FE-SEM을 이용하여 성장 형태 및 표면 특성을 확인하였으며, 미세구조는 HR-TEM을 이용하여 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.299.1-299.1
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• 2013

넓은 표면적을 갖는 탄소나노튜브(CNT)는 기체 분자의 흡착 성능이 기존의 다른 흡착제에 비해 우수한 것으로 알려져 있으나, CNT의 물리/화학적 성질은 튜브의 직경과 기하 구조에 의해 큰 차이를 나타내며 정제가 매우 까다롭다는 단점을 가지고 있다. CNT와 외형적으로 매우 흡사한 질화붕소 나노튜브(BNNT)의 경우, 구조와 직경에 상관없이 열적, 화학적 안정성이 우수하여 $CO_2$를 비롯한 다른 공해 물질들의 제거제나 흡착제로서 응용 가능성이 매우 높다. 본 연구진은, BN-결함을 도입한 BNNT 벽면에서의 $CO_2$ 흡착 반응과 $CO_2$를 에너지 물질인 HCOOH와 $H_2CO_3$로 전환하는 반응에 대한 양자화학 이론 계산 연구를 수행하였다. 그 결과, $CO_2$에 대한 $B_N$-BNNT 흡착 성능이 튜브의 직경에 상관없이 매우 우수하였고, $B_N$-BNNT 벽면상에 흡착된 $CO_2$가 물 분자와 반응할 경우 HCOOH와 $H_2CO_3$로의 전환반응이 효과적으로 진행되었다. 이러한 이론 계산 연구 결과는 BN-BNNT가 $CO_2$ 흡착제 및 에너지 전환 촉매로의 응용 가능성을 훌륭히 제시하고 있다.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.112-117
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• 2021

In this study, a method of self-assembly of peptides based on irreversible covalent bonds was studied by mimicking a biological covalent bond, dityrosine bond. A tyrosine-rich short peptide monomer having the sequence of Tyr-Tyr-Leu-Tyr-Tyr (YYLYY) was selected to achieve a high-density of dityrosine bond. The peptide nanoparticles covalently self-assembled with dityrosine bonds were synthesized by one-step photo-crosslinking of a peptide using a ruthenium catalyst under visible light. The effect of the concentration of each component for the size of the peptide nanoparticle was studied using dynamic light scattering, UV-Vis spectroscopy, and transmission electron microscopy. As a result, the synthesis conditions for size of the peptide nanoparticles ranging from 130 nm to 350 nm were optimized.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.732-738
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• 2011

Effect of metal oxide catalysts and ionic liquids on the synthesis of methyl carbamate(MC) and dimethyl carbonate (DMC) from urea and methanol was investigated in a high pressure reaction system. In closed system, MC yield from urea and methanol reached almost 100% at reaction temperature over $150^{\circ}C$ without catalyst, whereas DMC yield of 1.5% under was obtained irrespective of catalysts used. In DMC synthesis from MC and methanol, $ZnCl_{2}$ showed the highest catalytic activity and led to the DMC yield of 16.3% under optimal conditions. Furthermore, DMC yield can be enhanced by the simultaneous application of ionic liquids with nano-sized catalysts in semi-continuous reaction system.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.5
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• pp.207-212
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• 2014

An ultrathin sheet-like carbon nanostructure provides an important model of a two-dimensional graphite structure with strong anisotropy in physical properties. As an easy and cheap route for mass production, RF thermal plasma synthesis of freestanding carbon nanosheet from $CH_4$ (Methane) and $C_3H_8$ (Propane) is presented. Using vapor synthesis process with RF inductively thermal plasma, carbon nanosheets were obtained without catalysts and substrates. The synthesized carbon nanosheets were characterized using transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis. The carbon nanosheets synthesized using methane and propane generally showed 5~6 and 15~16 layers with a wrinkled morphology and size of approximately 100 nm.

• Journal of the Korean Vacuum Society
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• v.22 no.6
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• pp.291-297
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• 2013

ZnO nanowires were synthesized by vapor-liquid-solid (VLS) process using ZnO and graphite powders on the sapphire substrate coated with an Au film as a catalyst. ZnO nanowires had two prominent emission bands; i) near-band edge (NBE) emission band at 380 nm, and ii) a relatively stronger deep level (DL) emission band ($I_{NBE}/I_{DL}$ <1). In order for the ZnO nanowires to be utilized as an effective material for UV emitting devices, the photoluminescence intensity of NBE needs to be improved with the decreased intensity of DL. In the current study, hydrogen plasma treatment was performed to improve the photoluminescence characteristics of ZnO nanowires. With the hydrogen plasma treatment time of more than 120 sec, the extent of performance improvement was gradually decreased. However, the intensity ratio of NBE to DL ($I_{NBE}/I_{DL}$) was significantly improved to about 4 with a relatively short plasma treatment time of 90 sec, suggesting hydrogen plasma treatment is a promising approach to improve the photoluminescence properties of ZnO nanowires.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.3
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• pp.91-94
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• 2007

Single-crystalline $SnO_2$ nanowires were successfully grown on Si(001) substrates via vapor-liquid-solid mechanism in a thermal chemical vapor deposition. Large quantity of $SnO_2$ nanowires were synthesized at temperature ranges of $950{\sim}1000^{\circ}C$ in Ar atmosphere. It was found that the grown $SnO_2$ nanowires are of a tetragonal rutile structure and single crystalline by diffraction and transmission electron microscopy measurements. Broad emission located at about 600 m from the grown nanowires was clearly observed in room temperature photoluminescence measurements, indicating that the emission band originated from defect level transition into $SnO_2$ nanowires.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.1
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• pp.23-28
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• 2019

The Titanium oxide ($TiO_2$) is an attractive ceramic material which shows non-toxic, high refractive index, catalytic activity and biocompatibility, and can be fabricated at a low cost due to its high chemical stability and large anisotropy. $TiO_2$ nanoparticles have been prepared by sol-gel method. The pH of solution can affect the $TiO_2$ crystallinity during the formation of nanoparticles. The prepared nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, photoluminescence spectroscopy in order to investigate their structural and photoluminescence properties. Through these analysis, the size of $TiO_2$ nanoparticles were found to be smaller than 5 nm. As the crystallinity of the nanoparticles increased, the emission of PL in the 550 nm region increased. Therefore, luminescence characteristics can be improved by controlling the crystallinity of the $TiO_2$ nanoparticles.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.51-56
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• 2023

Composite membranes consisting of TiO₂ nanoparticles (NPs) and porous polymers have been widely utilized in photocatalytic water treatment because the composite membranes can allow an easy recovery of NPs after the photocatalytic reaction as well as the reduction of fouling in the membrane. However, the photocatalytic efficiency of the immobilized TiO₂ NPs in the composite membranes has been discussed to a limited degree. In this study, we prepared polyethersulfone (PES)/TiO₂ composite membranes to study the photocatalytic decomposition of organic dyes under light illumination. The decomposition kinetics of dye molecules by the PES/TiO₂ composite membranes and colloidal TiO₂ NPs have been compared to discuss the photocatalytic efficiency of NPs before and after their immobilization on the polymer membrane.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.191-191
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• 2013

금속 산화물 촉매 입자는 특정한 파장에 의해서 활성화되면서 전자-정공 쌍을 생성한다. 광촉매원리를 이용하면 전자 정공 제공을 통해 기존의 물질 주위에 활성 라디칼을 생성하고 물질의 특성을 변화시킬 수 있다. 이런 독특한 특성을 이용한 금속산화물의 다양한 연구가 물리, 화학, 재료, 생명 분야에서 이루어지고 있다. 본 연구에서는 광촉매 입자와 대기압 플라즈마와의 특성을 활용하여 발생되는 물리적 특성과 재료적인 특성을 이용한 응용 연구에 대한 내용을 다루고 있다. 특히 광촉매로 가장 많이 사용되는 $TiO_2$가 $200^{\circ}C$ 이하 저온 플라즈마 방전가스에 의해 상변화되는 현상을 다루고 이에 대한 구체적인 재료 분석을 실시 하였다. 즉, 저온의 알곤과 알곤/산소 대기압 플라즈마에 의해 처리된 $TiO_2$의 결정성 변화에 대해서 조사하였고 이를 이용하여 유사 작용제의 분해에 대한 연구를 하였다. 신경작용제(VX: nerve agent)의 유사작용제인 말라치온(Malathion)뿐만 아니라 셀룰로우즈(cellulose) 계의 복잡한 구조의 화학유기물 등을 대기압 플라즈마를 이용해 분해시킬 수 있음을 알 수 있었다. 본 연구에서는 대기압 플라즈마와 금속산화물의 결정성 변화에 대한 분석을 통해 기능성화된 촉매입자를 이용한 효과적인 화학물질의 분해를 소개하고, 대기압 플라즈마의 나노 소재기술로의 높은 응용가능성도 함께 살펴보았다.