• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.360-364
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• 2018

A facile method to fabricate freestanding CuO nanoleaves and CuO nanowires-based films was demonstrated. $Cu(OH)_2$ nanoleaves and nanowires were prepared by a hydrolysis reaction in aqueous solution including pyridine and NaOH with the tailored concentrations at room temperature. The films of freestanding CuO nanoleaves and CuO nanowires can be successfully obtained via the simple vacuum infiltration following a thermal dehydration reaction. The morphologies and crystallinity of the $Cu(OH)_2$ nanoleaves/nanowires and CuO nanoleaves/nanowires were characterized by XRD, SEM, TEM and FT-IR. The films fabricated with freestanding CuO nanoleaves and nanowires in this study may be applicable for building high-efficiency organic binder-free devices, such as gas sensors, batteries, photoelectrodes for water splitting and so on.

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.392-397
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• 2014

CuO nanotubes are synthesized using $TeO_2$ nanorod templates for application to $H_2S$ gas sensors. $TeO_2$ nanorod templates were synthesized by using the VS method through thermal evaporation. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction showed that the synthesized nanotubes were monoclinic-structured polycrystalline CuO with diameter and wall thickness of approximately 100~300 nm and 5~10 nm, respectively. The CuO nanotube sensor showed responses of 136~325% for the $H_2S$ concentration of 0.1~5 ppm at room temperature. These response values are approximately twice as high as that of the CuO nanowire sensor for the same concentrations of $H_2S$ gas. Along with the investigation of the performance of the sensors, the mechanisms of $H_2S$ gas sensing of the CuO nanotubes are also discussed in this study.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.609-609
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• 2013

나노선은 대표적인 일차원 나노구조로 높은 부피-표면적 비율과, 조절 가능한 밴드갭 에너지, 뛰어난 광학적/전기적 특성으로 인해 다양한 잠재적 응용처를 가지며, 많이 연구되고 있다. 특히 ZnO 나노선은 대표적인 광촉매로, 높은 감광성과 높은 부피-표면적 비율 등의 특징을 가지지만, 상대적으로 넓은 밴드갭 에너지 때문에 가시광선 영역을 사용하지 못하는 단점이 있다. 본 연구에서는 CuS 나노입자/ZnO 나노선 이종구조를 간단한 두 가지의 방법으로 합성하였다. ZnO 나노선은 간단한 수열합성 방법으로 합성하였고, 그 위에 CuS 나노입자를 successive ionic layer adsorption and reaction (SILAR) 방법으로 증착하였다. 합성된 나노 구조는 기존의 ZnO 구조와는 달리 가시광 영역에서도 향상된 광촉매 특성을 보였으며, 이는 ZnO와 CuS사이의 interfacial charge transfer (IFCT)에서 기인한 것이다. SEM, TEM, XRD를 통해 CuS/ZnO 이종구조의 형태와 결정구조, 구성성분을 분석할 수 있었고, Acid Orange 7의 광분해 실험을 통해 향상된 광촉매 특성을 확인 할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.249-249
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• 2013

Surface-enhanced Raman spectroscopy (SERS) is a sensitive approach to detect and to identify a variety of molecules. To enhance the Raman signal, optimization of the gap between nanostructures is quite important. One-dimensional materials such as nanowires, nanotubes, and nanograsses have great potential to be used in SERS due to their unique sizes and shape dependent characteristics. In this study we investigate a simple way to fabricate SERS substrates based on randomly grown copper oxide (CuO) nanowires. CuO nanograss is fabricated on pre-cleaned Cu foils. Cu oxidized in an ammonium ambient solution of 2.5 M NaOH and 0.1 M $(NH_4)_2S_2O_8$ at $4^{\circ}C$ for 10, 30, and 60 minutes. Then, Cu(OH)2 nanostructures are formed and dried at $180^{\circ}C$ for 2 h. With the drying process, the Cu(OH)2 nanostructure is transformed to CuO nanograss by dehydration reaction. CuO nanograss are grown randomly on Cu foil with the average length of 10 ${\mu}m$ and the average diameter of a 100 nm. CuO nanograsses are covered by Ag with various thicknesses from 10 to 30 nm using a thermal evaporator. Then, we immerse uncoated and Ag coated CuO nanowire samples of various oxidation times in a 0.001M methanol-based 4-mercaptopyridine (4-Mpy) in order to evaluate SERS enhancement. Raman shift and SERS enhancement are measured using a Raman spectrometer (Horiba, LabRAM ARAMIS Spectrometer) with the laser wavelength of 532 nm. Raman scattering is believed to be enhanced by the interaction between CuO nanograss and Ag island film. The gaps between Ag covered CuO nanograsses are diverse from <10 nm at the bottom to ~200 nm at the top of nanograsses. SERS signal are improved where the gaps are minimized to near 10s of nanometers. There are many spots that provide sufficiently narrow gap between the structures on randomly grown CuO nanograss surface. Then we may find optimal enhancement of Raman signal using the mapping data of average results. Fabrication of CuO nanograss based on a solution method is relatively simple and fast so this result can potentially provide a path toward cost effective fabrication of SERS substrate for sensing applications.

• Korean Journal of Materials Research
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• v.30 no.3
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• pp.131-135
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• 2020

Silver nanowire (AgNW) networks have been adopted as a front electrode in Cu(In,Ga)Se2 (CIGS) thin film solar cells due to their low cost and compatibility with the solution process. When an AgNW network is applied to a CIGS thin film solar cell, reflection loss can increase because the CdS layer, with a relatively high refractive index (n ~ 2.5 at 550 nm), is exposed to air. To resolve the issue, we apply solution-processed ZnO nanorods to the AgNW network as an anti-reflective coating. To obtain high performance of the optical and electrical properties of the ZnO nanorod and AgNW network composite, we optimize the process parameters - the spin coating of AgNWs and the concentration of zinc nitrate and hexamethylene tetramine (HMT - to fabricate ZnO nanorods. We verify that 10 mM of zinc nitrate and HMT show the lowest reflectance and 10% cell efficiency increase when applied to CIGS thin film solar cells.

• Transactions on Electrical and Electronic Materials
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• v.11 no.5
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• pp.234-237
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• 2010

Nanoenergetic materials were synthesized and the thermite reaction between the CuO nanowires and the deposited nano-Al by Joule heating was studied. CuO nanowires were grown by thermal annealing on a glass substrate. To produce nanoenergetic materials, nano-Al was deposited on the top surface of CuO nanowires. The temperature of the first exothermic reaction peak occurred at approximately $600^{\circ}C$. The released heat energy calculated from the first exothermic reaction peak in differential scanning calorimetry, was approximately 1,178 J/g. The combustion of the nanoenergetic materials resulted in a bright flash of light with an adiabatic frame temperature potentially greater than $2,000^{\circ}C$. This thermite reaction might be utilized to achieve a highly reliable selective area crystallization of amorphous silicon films.

• Journal of the Korean institute of surface engineering
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• v.37 no.6
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• pp.313-318
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• 2004

Vertically-aligned and uniformly-distributed CuO nanowires were formed on copper-coated Si substrates by wet chemical process, immersing them in a hot alkaline solution. The effects of hydrogen plasma treatment on the field emission characteristics of CuO nanowires were investigated. It was found that hydrogen plasma treatment enhanced the field emission properties of CuO nanowires by showing a decrease in turn-on voltage, and an increase in emission current density, and stability of current-voltage curves. However, the excessive hydrogen plasma treatment made the I-V curves unstable. It was confirmed by XPS (X-ray Photoelectron Spectroscopy) analysis that hydrogen plasma treatment deoxidized CuO nanowires, thereby the work function of the nanowires decreased from 4.35 eV (CuO) to 4.1 eV (Cu). It is thought that the decrease in the work function enhanced the field emission characteristics. It is well-known that the lower the work function, the better the field emission characteristics. The results suggest that the hydrogen plasma treatment is very effective in achieving enhanced field emission properties of the CuO nanowires, and there may exist an optimal hydrogen plasma treatment condition.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.433.2-433.2
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• 2014

그래핀(graphene)은 탄소나노튜브(CNTs)에 비해 가격 경쟁력이 있고 우수한 광투과성과 전기 및 열 전도성을 갖고 있어 반도체 소재, 방열 소재, 접점 소재 등에 적용 가능성이 높은 재료로 주목받고 있다. 특히 모바일 디바이스의 소형화, 고집적화 등의 이슈로 인해 그래핀 소재의 방열 소재 적용을 위해 다양한 연구가 진행되고 있다. 한편 산화 구리 나노선(CuO Nanowire)은 전기 및 열전도도가 우수하고 1차원 나노 구조는 부피대비 큰 표면적, 종횡비가 커서 뛰어난 열전도 구조로서 방열 소재로 응용되기 좋은 조건을 갖고 있다. 본 연구에서는 2차원 구조의 그래핀 나노플레이트(Graphene Nanoplatelet)와 1차원 구조의 CuO NW를 하이브리드화를 통해 열전도도 향상를 개선시키고자 하였다. 소재 합성은 GNP에 Cu 무전해 도금을 진행한 후 열산화 방식을 적용하여 CuO NW를 직접 성장시키는 방식으로 진행하였다. 합성된 GNP-CuONWs 다차원 나노구조체의 열전도도 측정은 에폭시에 분산시켜 레이져 플레쉬법을 이용하였다. 미세 구조 관찰 결과, CuO NW 성장 거동은 열처리 온도 및 시간 그리고 O2 가스의 순환 환경이 주요인자로 작용하는 것을 확인하였다. 열전도도 향상은 다차원 구조의 특성으로 인해 면접촉과 선접촉이 동시에 이루어졌기 때문인 것으로 분석되었으며, 이러한 CuO NWs morphology와 열전도도 향상과의 상관 관계에 대해 논의할 것이다.

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2283-2288
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• 2010

Nanostructured copper compounds were grown by electrochemical anodization of copper foil in aqueous NaOH under varying conditions including electrolyte concentration, reaction temperature, current density, and reaction time. Their morphology and atomic composition were investigated by using SEM, TEM, XRD, EDS and XPS. At the conditions ([NaOH] = 1 M, $20^{\circ}C$, $2\;mA\;cm^{-2}$), wire-like orthorhombic $Cu(OH)_2$ nanobundles with an average width of 100 - 300 nm and length of $10\;{\mu}m$ were synthesized with the preferential [100] growth direction. Furthermore, when the concentration decreased to 0.5 M NaOH, the 1D nanobundle structure became narrower and longer without any change in compositions or crystalline structure. Side reaction pathways appeared to compete with the 1D nanostructure formation channels: the formation of CuO nanoleaves at $50^{\circ}C$ via the sequential dehydration of $Cu(OH)_2$, CuO/$Cu_2O$ aggregates in 4 M NaOH, and $Cu_2O$ nanoparticles and CuO nanosheets at lower current density.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.3
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• pp.193-199
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• 2013

In this work, thin film type Cu/ZnO nanostructure catalysts were fabricated by several synthetic routes in order to maximize the performance of the micro reforming system. For this work, various Cu/ZnO nanostructure catalysts could be synthesized by means of four approaches which are chemical vapor method, wet solution method and their hybrid method. The reforming performance of these as-synthetic catalysts was evaluated as compared to the conventional catalysts. Among the as-synthetic nanostructures, sphere type catalysts with specific surface of $18.6m^2/g$ showed the best performance of hydrogen production rate of 30ml/min at the feed rate of 0.2ml/min. This work will give the first insight on thin film type Cu/ZnO nanostructure catalyst for micro reforming system for hydrogen production of portable electronic systems.