• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.312-319
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• 2021

Photothermal therapy is a treatment that necrotizes selectively the abnormal cells, in particular cancer cells, which are more vulnerable to heat than normal cells, using the heat generated when irradiating light. In this study, we synthesized a reduced graphene oxide with carboxyl groups (CRGO)-gold nanorod (AuNR) nanocomposite for photothermal treatment. Graphene oxide (GO) was selectively reduced and exfoliated at high temperature to synthesize CRGO, and the length of AuNR was adjusted according to the amount of AgNO₃, to synthesize AuNR with a strong absorption peak at 880 nm, as an ideal photothermal agent. It was determined through FT-IR, thermogravimetric and fluorescence analyses that more carboxyl groups were conjugated with CRGO over RGO. In addition, CRGO exhibited excellent stability in aqueous solutions compared to RGO due to the presence of carboxylic acid. The CRGO-AuNR nanocomposites fabricated by electrostatic interaction have an average size of ~317 nm with a narrow size distribution. It was confirmed that under radiation with a near-infrared 880 nm laser which has an excellent tissue transmittance, the photothermal effect of CRGO-AuNR nanocomposites was greater than that of AuNR due to the synergistic effect of the two photothermal agents, CRGO and AuNR. Furthermore, the results of cancer cell toxicity by photothermal effect revealed that CRGO-AuNR nanocomposites showed superb cytotoxic properties. Therefore, the CRGO-AuNR nanocomposites are expected to be applied to the field of anticancer photothermal therapy based on their stable dispersibility and improved photothermal effect.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.32.1-32.1
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• 2009

본 연구에서는 산화 그라핀을 환원하여 얻은 그라핀 분말의 고온 XRD 패턴를 통해 그라핀의 열팽창계수를 정량하였다. 산화 그라핀은 Hummer method에 의해 제조되었다. 또한 그라핀은 산화그라핀을 1273K에서 열처리하여 얻어졌다. 1273K에서 그라핀의 열팽창계수($32.9{\pm}1.0$ X 10-6 K-1)는 원료인 흑연(30.3 X 10-6 K-1) 보다 8.6% 더 크게 나타내는것을 알 수 있었다. 그라핀은 화학적 처리에 의한 급격한 면간 팽창과 열처리에 의한 aggregation에 의해 심하게 굴곡지고 적층된 morphology를나타냈다. 이는 박리효과에 의한 것으로 XRD 패턴을 통해그라핀의 층수가 흑연보다 훨씬 적은 것을 알 수 있었다. 이에 따라 면간 규칙적인 배열을 보이는 흑연과는 달리 그라핀은 흑연구조에서 흔히 보이는 disorder 구조인turbostratic 적층 구조를 나타나고 면간인터렉션이 약화되어 열팽창계수가 크게 나타난다고 생각된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.23-23
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• 2007

고체산화물연료전지(SOFC)는 연료가 갖는 화학에너지를 연소과정 없이, 공기와 $H_2$, CO, $CH_4$와 같은 환원성 가스를 공급받아 $700^{\circ}C-850^{\circ}C$에서 전기화학적 반응을 통하여 직접 전기를 얻는 방식이다. SOFC는 여러장의 단위 셀을 적층하여 스택을 구성하는데, 스택 제조시 단전지에 공급되는 산화, 환원 가스의 누출이나 흡입을 막기 위하여 밀봉재를 사용한다. 이러한 밀봉재는 완벽한 밀봉, 열에 대한 안정성, 충격에 견디는 저항성 등의 기계적인 특성 및 구성요소와의 최소한의 열팽창계수차를 가져야 한다. 따라서 본 연구에서는 $SiO_2-R_2O_3$-RO계에서 $R_2O_3$, RO의 변화에 따른 밀봉 특성 및 열팽창계수에 미치는 영향을 조사하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.689-696
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• 2010

The Because of its high thermal efficiency, the direct injection (DI) diesel engine has emerged as a promising potential candidate in the field of transportation. However, the amount of nitrogen oxides ($NO_x$) increases in the local high-temperature regions and that of particulate matter (PM) increases in the diffusion flame region during diesel combustion. In the de-$NO_x$ system the Lean $NO_x$ Trap (LNT) catalyst is used, which absorbs $NO_x$ under lean exhaust gas conditions and releases it in rich conditions. This technology can provide a high $NO_x$-conversion efficiency, but the right amount of reducing agent should be supplied to the catalytic converter at the right time. In this research, the emission characteristics of a diesel engine equipped with a micro-reformer that acts as a reductants-supplying equipment were investigated using an LNT system, and the effects of the exhaust-gas temperature were also studied.

• Journal of the Korean Vacuum Society
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• v.1 no.1
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• pp.176-182
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• 1992

t-Stress and junction leakage current characteristics of CVD-tungsten have been investigated. Stressversus continuous annealing temperature plot. shows hysteresis curve where the stress level of the cooling curveis higher than that of the heating curve. It is found that the thermal and intrinsic stress of tungsten film depositedby SiH4 reduction is higher than that by Hz reduction.The tungsten film deposited by SiHl reduction is in the tensile stress state below 700"Cnd the stress ofthe film decreses with increasing annealing temperature. The stress state changes into compressive stress atabout 700"Cnd the compressive stress increases rapidly with increasing temperature.Leakage current of the n+/p diode increases rapidly especially in the range of 400-450$^{\circ}$C with increasingdeposition temperature of the CVD-W by SiH4 reduction, which is due to the Si consumption by W encroachment.On the other hand leakage current of the n+/p diode slightly increases with increasing SiH4/WF6 ratio.h increasing SiH4/WF6 ratio.

• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.83-91
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• 1993

The eletrochemical behavior of light lanthanide complexes has been investigated by several electrochemical techniques in alkaline solutions. The composition of the complexes was determined by spectrophotometric method to be 1 : 1 and reduction mechanism was two steps 1 electron transfer reaction. The half wave potential of first peak depended on pH and cathodic current showed remarkably adsorptive properties. The results of DC and CV investigation demonstrated the quise-reversible nature of the electron transfer. The anion radical formed after first one electron reduction process, dimerizes to form dimer. The apparent irreversible behavior of the second wave is a result of the existence of a fast protonation following the second electron transfer. An exhaustive electrolysis was carried out at controlled potential of -1.80 V, deep blue color of the solution became progressively weaker, and then the solution became colorless solution. The final product of an exhaustive electrolysis is electro-inactive. The appearance of four steps may be explained by the fact the reduction of Ln-OCP elucidated ECEC mechanism.

• Journal of Korean Society of Forest Science
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• v.49 no.1
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• pp.1-5
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• 1980

In this study, enzymatic saccharification of substrates from Alnus hirsuta Ruper (8-14 years). Quercus acutissima Carruthers, Betula platyphylla var. japonica Nera, Populus euramericana Guiner and Platanus orientalis L. were investigated using crude cellulase preparations of Trichoderma viride Pers. ex. Fr. SANK 16374, and conduced on the optimum treated conditions of the cellulase sacchrification and reactivation of residue of digested substrates. The Trichoderma viride cellulase was produced by the submerged culture process and produced in the culture fluid was salted out quantitatively by the use of ammonium sulfate. The method of dilignification from wood (5 species) was treated by the peracetic acid(PA) method. The reducing sugar was determined by the dinitrosalicylic acid (DNS) method. 1. The results of tests carried out for 96 hr. (Figure 1), show conclusively the initial substrates from 5 species ($S_3$) which has been rendered highly reactive form and the mean rate of reducing sugar was 28.3 %. 2. The results of tests carried out for 96 hr., the reactivation of residue of digested substrates (improvement in the quality of the substrate through preheating in air at $190^{\circ}C$. for 45 min. followed by milling was (60 mesh size) at the same substrate level, increased concentrations of cellulase at the same substrate level, and increased concentrations of cellulase increases the rate of hydrolysis considerably. 3. Figure 1. shows conclusively that the residue of digested substrates ($S_1$ dried at $60^{\circ}C$) which has been rendered extremly resistant to cellulase action can be reactivated into a highly reactive form ($S_2$), almost comparable to that of the initial substrates ($S_3$). And the reducing sugar formation did not show statistically significent differences at 5% levels by initial substrates and the residue of digested substrates (preheating in air at $190^{\circ}C$. for 45 min. fallowed by milling was (60 mesh size).

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.307-313
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• 2011

금속산화물을 이용한 2단계 산화/환원 반응은 GTL, CTL 의 반응원료인 합성가스 및 수소 생산기술이다. 이 기술은 메탄을 환원제로 사용함으로써 비교적 저온에서 산화/환원 반응을 할 수 있는 장점이 있다. 하지만 반복 사이클의 시연에서 금속산화물의 소결현상으로 인한 활성저하가 이 기술의 문제점 중의 하나이다. 본 연구에서는 2.5 kW Xenon arc lamp 가 설치된 solar simulator를 사용 하였으며, 무기물 다공성 폼 (SiC foam)및 유기물 다공성 폼 (Ni, Cufoam)에 $CeO_2/ZrO_2$ 를 코팅하여 연속적인 합성가스 및 수소 생산 가능성을 알아보았다. 반응 전 후의 $CeO_2/ZrO_2$ 의 결정 구조를 SEM 과 XRD 를 통해 분석하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.137-137
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• 2013

본 연구에서는 반도체 검사 장비인 프로브 카드의 핵심 부품인 프로브 니들의 팁 부분의 내마모성을 향상시키기 위하여 무전해 Ni-B-W 합금 도금 실험을 실시하였다. 무전해 Ni-B-W 합금 도금 실험에서 여러 가지 제어인자 중 도금욕의 pH와 온도 그리고 환원제의 농도 등을 변수로 하였다. 도금욕 pH와 온도에 따른 전착속도 및 물성 변화를 관찰하였으며, 환원제 농도 변화에 의한 open circuit potential의 변화를 측정하였다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.477-478
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• 2003

에너지 사용의 증대에 따라 대기중으로의 질소산화물 배출양이 증가하고 있으며, 이에 따른 산성비, 광화학 스모그등 많은 피해가 나타나고 있다. 이러한 질소산화물중 고정원에서 배출되는 질소산화물은 선택적 촉매환원법에 의해 제거가 되고 있다. 선택적 촉매 환원법에 사용되고 있는 촉매는 주로 V$_2$O$_{5}$/TiO$_2$ 계열로써 300 ~ 40$0^{\circ}C$ 영역에서 최적의 반응을 보인다(H. Bosch and F. Janssen, 1988). 그러나 촉매의 내구성 증진, 재가열에 따른 에너지 절감등의 이유로 저온에서 우수한 활성을 보이는 촉매의 개발이 필요하다. (중략)