• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.880-884
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• 2011

ZnO nanorods were grown by hydrothermal method. Two kinds of seed layers, Au film and island seed layers were prepared to investigate the effect of seed layer on ZnO nanorods. The ZnO nanorod on Au island seed layer has more unifom diameter and higher density compared to that of ZnO nanorod on Au film seed layer. The ZnO nanorods on Au island seed layer were annealed at various temperatures ranging from 300 to $850^{\circ}C$. The pinholes at the surface of the ZnO nanorods is formed as the annealing temperature is increased. It is noted that the pyramid structure on the surface of ZnO nanorod is observed at $850^{\circ}C$. The intensity of ZnO (002) diffraction peak in X-ray diffraction pattern and intensity of near band edge emission (NBE) peak in photoluminescence (PL) are increased as the ZnO nanorods were annealed at the temperature of $300^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.209-209
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• 2010

금(Au) 또는 은(Ag) 금속 나노입자의 모양, 크기, 분포 상태를 조절하여 가시광선과 적외선, 자외선 영역에서 강한 표면 플라즈몬 효과을 이용할 수 있는데, 최근 이러한 금속 나노입자의 표면플라즈몬 효과를 이용하여 태양광 소자의 성능을 향상시키는 연구가 매우 활발하게 이루어지고 있다. 그 중, 높은 효율과 낮은 제작비용 그리고 간단한 공정과정의 장점을 갖고 있어서 크게 주목 받고 있는 염료감응태양전지에서도 금(Au) 또는 은(Ag) 금속 나노입자을 이용하기 위한 많은 연구가 진행되고 있다. 그 예로, Au가 코팅된 $TiO_2$ 기반의 염료감응태양전지구조를 제작하여, 입사된 빛이 표면플라즈몬 효과를 통해, Au에서 여기된 전자들이 Au/$TiO_2$ 사에의 schottky 장벽을 통과하여 $TiO_2$의 전도대 전자들의 밀도가 증가하여, charge carrier generating rate을 높여 소자의 광변환 효율의 향상을 증명하였다. 이에 본 연구에서는, $TiO_2$보다 높은 전자 이동도(mobility)와 직선통로(direct path way)의 장점을 갖고 있는 ZnO nanorod에서의 charge carrier generating rate을 높일 수 있도록, 비교적 가격이 저렴한 Ag nanoparticle을 코팅하였다. ZnO nanorod 제작은 낮은 온도에서 간단하게 성장시킬 수 있는 hydrothermal 방법을 이용하였다. 기판위에 RF magnetron 스퍼터를 이용하여 AZO seed layer를 증착한 후, zinc nitrate $Zn(NO_3)_2{\cdot}6H_2O$과 hexamethylentetramines (HMT)으로 혼합된 용액을 사용해 ZnO nanorods를 성장시켰다. 이 후, Ag를 형성할 수 있도록 열증기증착법을 이용하여 코팅하였다. Ag의 증착시간에 따른 ZnO nanorods에서의 코팅된 구조와 형태를 관찰하기 위해 field emission scanning electron microscopy (FE-SEM)을 이용하여 측정하였으며, 결정성을 조사하기 위해 X-ray diffraction (XRD)을 이용하여 분석하였다. 또한 입사된 빛에 의해, 여기된 ZnO 전도대 전자들이 다시 재결합을 통해 방출되는 photoluminescence 양을 scanning PL 장비를 통해 측정하여 Ag가 코팅된 ZnO nanorod의 광특성을 분석하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.126-126
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• 2011

수직으로 정렬된 1차원 ZnO nanorod arrays (NRAs)는 효율적인 반사방지 특성의 기하학적 구조를 갖고 있어, 크기와 모양 그리고 정렬형태의 다양한 설계를 통해 빛의 흡수율과 광 추출효율을 증가시켜 광전소자 및 태양광 소자의 성능을 향상시킬 수 있으며, 최근 이러한 연구에 대한 관심이 집중되고 있다. 본 연구에서는 ZnO NRAs의 넓은 표면적과 불연속적인 독특한 표면을 활용하여 광학적 특성을 효과적으로 개선하였다. 실험을 위해, thermal evaporator를 사용하여 Au와 Ag 그리고 e-beam evaporator를 사용하여 $SiO_2$를 ZnO NRAs 표면에 여러 가지 조건으로 증착하여, 독특한 계층 나노구조의 형성과 광학적 특성을 관찰하였다. 표면 roughness가 큰 FTO/glass 위에 수열합성법을 통해 끝이 뾰족하고, 비스듬히 정렬된 ZnO nano-tip array에 Au를 증착할 경우 ZnO/Au core/shell 구조가 형성되며, Au의 광 흡수율이 매우 크게 증가함을 관찰할 수 있었다. 반면 flat한 표면위에 빽빽하게 수직으로 정렬된 ZnO NRAs를 성장시켜 그 위에 Ag를 증착할 경우, evaporated Ag flux가 ZnO nanorod의 사이에 scattered 되어 ZnO nanorod 기둥의 측면에 직경이 50 nm 이하인 nanoparticles이 decorated 되어 국소표면플라즈몬 현상이 관찰되었으며, 이러한 효과를 통해 입사되는 빛의 흡수율을 효과적으로 증가시킬 수 있었다. 또한, ZnO NRAs의 표면에 $SiO_2$를 e-beam evaporator를 이용하여 증착할 경우, 자연적으로 vapor flux와 ZnO nanorod 사이에 oblique angle이 $80^{\circ}$ 이상으로 증가하여 $SiO_2$ nanorods가 자발적으로 형성되어 ZnO/$SiO_2$ branch 계층형태의 나노구조를 제작할 수 있었다. 이러한 구조는 유효 graded refractive index profile로 인해 기존의 ZnO NRAs보다 개선된 반사방지 특성을 나타냈다. 이러한 계층 나노구조의 광학적 특성을 시뮬레이션을 통해 이론적으로 분석을 통해 광전자 소자의 성능의 개선에 대한 적용 가능성을 조사하였다.

• 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 Korean Vacuum Society Conference
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• 2012.08a
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• pp.111-111
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• 2012

In this talk, we represent a novel approach to investigating intra-nanorod surface plasmon coupling with control over block compositions. The multi-component rod-like nanostructures, which consist of optically active components (Au and Ag) and optically less active component (for example, Ni) in UV-vis-NIR spectral window, showed interesting optical response depending on each block length and the total length of the structure. By controlling the composition and relative lengths of the blocks that comprise these structures, we can tailor the overall optical properties. Depending on the relative fraction of Au and Ag blocks, the intensity of the transverse modes varied without noticeable peak shifts. However, the strong intraparticle surface plasmon coupling resulted in the collective appearance of longitudinal LSP modes, including higher-order modes. The experimental observations were confirmed by theoretical calculation, using a discrete dipole approximation method. In addition, we will briefly discuss how single nanorod solar cells can be synthesized by using by using electrochemical deposition and AAO hard templates.

• Journal of Microbiology and Biotechnology
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• v.24 no.9
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• pp.1291-1299
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• 2014

Recently, multifunctional nanomaterials have been developed as nanotherapeutic agents for cellular imaging and targeted cancer treatment because of their ease of synthesis and low cytotoxicity. In this study, we developed a multifunctional, two-component nanorod consisting of gold (Au) and nickel (Ni) blocks that enables dual-fluorescence imaging and the targeted delivery of small interfering RNA (siRNA) to improve cancer treatment. Fluorescein isothiocyanate-labeled luteinizing hormone-releasing hormone (LHRH) peptides were attached to the surface of a Ni block via a histidine-tagged LHRH interaction to specifically bind to a breast cancer cell line, MCF-7. The Au block was modified with TAMRA-labeled thiolated siRNA in order to knock down the vascular endothelial growth factor protein to inhibit cancer growth. These two-component nanorods actively targeted and internalized into MCF-7 cells to induce apoptosis through RNA interference. This study demonstrates the feasibility of using two-component nanorods as a potential theranostic in breast cancer treatment, with capabilities in dual imaging and targeted gene delivery.

• Clean Technology
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• v.20 no.2
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• pp.141-145
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• 2014

In this study, we studied optical properties on the layer-by-layer (LbL) assemblies consisting of Au nanorods and organic dyes. For this purpose, poly (allylamine hydrochloride), PAH and poly (styrene sulfonate), PSS were selected as ionic polymers and rhodamine B isothiocyanate (RB) was utilized as an organic dye based on its spectral overlap with plasmon band of Au nanorods. In the view point of assembling methods, RB was covalently attached to PAH, then, LbL structure of Au [PSS/PAH]2/PSS/PAH-RB was prepared by sequential coating of PAH, PSS, PAH-RB on Au nanorods. Since the prepared LbL assembly exhibits both plasmonic and fluorescent properties, we studied the mutual nanorod-dye properties by dissolving Au nanorods.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.126-126
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• 2010

본 연구에서는 catalyst-free 유기금속 화학증착법 (MOCVD)를 이용하여 사파이어 (0001)면 위에 직접 InN nanorods를 성장하였다. InN 박막의 성장에서 TMIn과 $NH_3$를 전구체로 사용하였으며, 캐리어 가스로는 질소를 사용하였다. 성장 전, 기판에 $1100^{\circ}C$에서 3분간 nitridation 처리를 거친 후 온도를 낮춰 $630{\sim}730^{\circ}C$의 온도범위 에서 InN 박막을 성장하였다. 이때 $710^{\circ}C$의 온도에서 박막은 columnar growth의 특성을 보였으며 동일조건에서 80분간 성장시킨 결과 InN nanorods가 성장되었다. 성장시킨 InN nanorod는 X-선 회절 측정법, 주사 전자 현미경 그리고 투과 전자 현미경을 이용하여 그 특성을 분석하였다. 투과 전자 현미경을 통한 분석결과 지름이 150~200 nm이며 그 길이는 수 ${\mu}m$인 InN nanorod가 성공적으로 성장되었음을 확인하였다. 또한 X-선 회절 측정법과 주사 전자 현미경을 통한 분석에서 이들 nanorods가 대부분 c 방향으로 수직하게 정렬되어 있음을 확인하였다. 또한 Ti/Au (120/80 nm)를 전극으로 사용하여 개개의 nanorod의 전기적 특성을 분석한 결과 linear한 I-V특성이 관찰되었으며 비저항은 평균적으로 $0.0024\;{\Omega}cm$ 이었다. transfer 특성의 측정결과 -50V까지 게이트 전압을 인가하여도 드레인 전류의 변화는 매우 적어 doping level이 상당히 높다고 예상가능하다. 또한 mobility는 $133\;cm^2/Vs$로 도출되었다.

• Progress in Superconductivity
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• v.11 no.1
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• pp.47-51
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• 2009

For many large-scale applications of high-temperature superconducting materials, large critical current density ($J_c$) in high applied magnetic fields are required. A number of methods have been reported to introduce artificial pinning centers in $YBa_2Cu_3O_{7-{\delta}}$ films for enhancement of their $J_c$. We studied the microstructures and characteristic of $YBa_2Cu_3O_{7-{\delta}}$ films fabricated on $SrTiO_3$ (100) substrates with ZnO nanorods as pinning centers. Au catalyst nanoparticles were synthesized on STO substrates with self assembled monolayer to control the number of ZnO nanorods. The density of Au nanoparticles is approximately $240{\sim}260{\mu}m^{-2}$ with diameters of $41{\sim}49nm$. ZnO nanorods were grown on STO by hot-walled PLD with Au nanoparticles. Typical size of ZnO nanorod was around 179 nm in diameter and $2{\sim}6{\mu}m$ in length respectively. YBCO films deposited directly on STO substrates show the c-axis orientation, while YBCO films with ZnO nanorods exhibit any mixed phases without any typical crystal orientation.

• Applied Chemistry for Engineering
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• v.27 no.6
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• pp.599-605
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• 2016

Recently, photodynamic and photothermal therapies have received increasing attention as an effective cancer treatment. In this study, a gold nanorod (AuNR) colloidal solution was synthesized as a hyperthermia agent for photothermal therapy and also modified with photosensitizer (PS) for photodynamic therapy. PEG (polyethylene glycol) and FA (folic acid) ligand were also introduced into AuNR for the long circulation in human body and efficient targeting of cancer cells, respectively and AuNRs were modified with FA-PEG and poly-${\beta}$-benzyl-L-aspartate (PBLA) block copolymers through a 3,4-dihydroxy hydrocinnamic acid (HCA) linker. A series of AuNRs with various aspect ratios were synthesized by controlling the feeding ratio of $AgNO_3$. The physicochemical property and morphology of synthesized AuNR100 and FA-PEG-$P(Asp)_{50}$-HCA-AuNR100 were analyzed by UV-visible spectrophotometer, $^1H$ NMR, XPS measurements, TEM. The surface modified AuNR carrier with biocompatibility could be applied for the effective diagnosis as well tumor phototherapy.