• Electronic Materials Letters
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• 제14권6호
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• pp.739-748
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• 2018

ZnS nanowalls, microspheres and rice-shaped nanoparticles have been successfully grown on graphene oxide (GO) sheets by the hydrothermal method. The morphologies, structures, chemical compositions and optical properties of the as-synthesized GO/ZnS have been characterized by X-ray power diffraction, energy dispersive spectrometer, scanning electron microscope, Raman spectra, photoluminescence spectroscopy and ultraviolet-visible absorption spectroscopy. It was found that the concentration of CTAB and the reaction temperature were important in the formation of GO/ZnS microstructures. The photocatalytic activity of the as-synthesized GO/ZnS was investigated through the photocatalytic degradation of textile dyeing waste. Results showed that the catalytic activity of the GO/ZnS porous spheres to methyl orange and methylene blue is higher than those of other samples. The degradation rates of methyl orange and methylene blue by porous spheres in 50 min were 97.6 and 97.1%, respectively. This is mainly attributed to the large specific surface area of GO/ZnS porous spheres and high separation efficiency between photogenerated electron and hole pairs.

• 한국입자에어로졸학회지
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• 제13권1호
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• pp.33-40
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• 2017

Cobalt-iron oxides have emerged as alternative electrode materials for supercapacitors because they have advantages of low cost, natural abundance, and environmental friendliness. Graphene loaded with cobalt ferrite ($CoFe_2O_4$) nanoparticles can exhibit enhanced specific capacitance. In this study, we present three-dimensional (3D) crumpled graphene (CGR) decorated with $CoFe_2O_4$ nanoparticles. The $CoFe_2O_4$-graphene composites were synthesized from a colloidal mixture of GO, iron (III) chloride hexahydrate ($FeCl_3{\cdot}6H_2O$) and cobalt chloride hexahydrate ($CoCl_2{\cdot}6H_2O$) respectively, via one step aerosol spray pyrolysis. Size of $CoFe_2O_4$ nanoparticles was ranged from 5 nm to 10 nm when loaded onto 500 nm CGR. The electrochemical performance of the $CoFe_2O_4$-graphene composites was examined. The $CoFe_2O_4$-graphene composite electrode showed the specific capacitance of $253F\;g^{-1}$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.175.2-175.2
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• 2014

Graphene (G) has been modified with palladium, copper, and manganese oxide nanoparticles (NPs), and their catalytic applications have been studied in C-C coupling reactions and methylmercaptan (CH3SH) decomposition reactions. In this research, graphite oxide (GO) sheets were exfoliated and oxidized from graphite powder and impregnated with metal precursors including Pd2+, Cu2+, and Mn2+. The thermal treatments of the metal impregnated GO in preferred gas environments produced Pd NPs on graphene (Pd/G), PdO NPs on GO (PdO/GO), and CuOx and MnOx NPs on graphene (CuOx/MnOx/G). In case of Pd/G and PdO/GO, the TEM images show that, although the mean size of the Pd NPs changed significantly before and after the C-C coupling reaction, that of the PdO NPs didn't, implying that the PdO/GO was superior to Pd/G in terms of the recyclability. Also, we demonstrate that the CuOx/MnOx/G exerts the excellent catalytic efficiency in CH3SH decomposition reaction comparing with conventional catalysts. The chemical and electronic structural changes were investigated using XRD and XPS.

• 공업화학
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• 제28권6호
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• pp.705-713
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• 2017

독창적 물질인 $Bi_2WO_6-GO-TiO_2$ 나노복합체를 쉬운 수열법에 의해 성공적으로 합성하였다. 수열반응을 하는 동안, 그래핀 시트 위에 $Bi_2WO_6$와 $TiO_2$를 도포하였다. 합성한 $Bi_2WO_6-GO-TiO_2$ 복합체형 광촉매는 X-선 회절법(XRD), 주사전자현미경(SEM), 에너지 분산 X-선(EDX) 분석, 투과전자현미경(TEM), 라만분광법, UV-Vis 확산반사 분광법(UV-vis-DRS), 및 X-선 광전자분광기(XPS)에 의하여 특성화하였다. $Bi_2WO_6$ 나노입자는 불규칙한 dark-square block 나노 플페이트 형상을 보였으며, 이산화티탄 나노입자는 퀜텀 도트 사이즈로 그래핀 시트 위 표면을 덮고 있었다. 로다민 비의 분해는 농도감소의 측정과 함께 UV 분광법에 의하여 관찰하였다. 합성된 물질의 광촉매 반응은 Langmuir-Hinshelwood 모델과 띠 이론으로 설명하였다.

• 폴리머
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• 제36권5호
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• pp.656-661
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• 2012

케이지 구조의 POSS-$NH_3{^+}$를 이용하여 팔라듐 입자들의 자기 조직화로 인한 구조가 제어된 Pd-POSS 나노입자를 제조하였다. 또한 흑연을 강산과 산화제를 이용하여 산화된 그래핀 옥사이드(GO)를 합성한 후 얻어진 GO와 NaBH4와의 반응을 통하여 그래핀을 제조하였다. 합성된 그래핀과 acrylic acid와 라디칼 중합 반응을 통하여 그래핀 표면에 poly(acrylic acid)(PAA)가 결합된 PAA-grafted graphene을 얻었다. Pd-POSS와 PAA-grafted graphene을 이용한 나노복합체는 POSS-$NH_3{^+}$로 인하여 양전하를 띠는 Pd-POSS 나노입자와 PAA로 인하여 음전하를 띠는 PAA-grafted graphene와의 정전기적 인력을 이용하여 제조하였다. Pd-POSS 나노입자가 PAA로 치환된 그래핀 표면에 정전기적 인력으로 결합되어 있고, 나노복합체의 열적 안정성은 PAA와 PAA-grafted graphene 보다 우수한 것을 확인할 수 있었다. 제조된 Pd-POSS/PAA-grafted graphene 나노복합체의 구조 및 형태와 열적 안정성은 FE-SEM, AFM, TEM, EDX, FTIR과 TGA를 통하여 분석하였다.

• Bulletin of the Korean Chemical Society
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• 제35권7호
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• pp.1979-1984
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• 2014

We have developed an efficient method to generate highly active Pd and PdO nanoparticles (NPs) dispersed on graphene and graphene oxide (GO) by an impregnation method combined with thermal treatments in $H_2$ and $O_2$ gas flows, respectively. The Pd NPs supported on graphene (Pd/G) and the PdO NPs supported on GO (PdO/GO) demonstrated excellent carbon-carbon cross-coupling reactions under a solvent-free, environmentally-friendly condition. The morphological and chemical structures of PdO/GO and Pd/G were fully characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). We found that the remarkable reactivity of the Pd/G and PdO/GO catalysts toward the cross-coupling reaction is attributed to the high degree of dispersion of the Pd and PdO NPs while the oxidative states of Pd and the oxygen functionalities of graphene oxide are not critical for their catalytic performance.

• 전기화학회지
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• 제27권1호
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• pp.15-31
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• 2024

The antimalarial drug hydroxychloroquine sulphate (HCQ) has taken much attention during the first COVID-19 pandemic phase for the treatment of severe acute respiratory infection (SARI) patients. Hence it is interest to study the electrochemical properties and photocatalytic degradation of the HCQ drug. Copper oxide (CuO) nanoparticles, graphene oxide (GO) and CuO/GO NC (nanocomposite) modified carbon paste electrodes (MCPE) are used for the detection of HCQ in an aqueous medium. Electrochemical behaviour of HCQ (20 μM) was observed using CuO/MCPE, GO/MCPE and CuO/GO NC/MCPE in 0.1 M phosphate buffer at pH 7 with a scan rate of 20 to 120 mV s^-1 by cyclic voltammetry (CV). Differential pulse voltammetry (DPV) of HCQ was performed for 0.6 to 16 μM HCQ. The CuO/GO NC/MCPE showed a reasonably good sensitivity of 0.33 to 0.44 μA μM cm^-2 with LOD of 69 to 92 nM for HCQ. Furthermore, the CuO/GO NC was used as a catalyst for the photodegradation of HCQ by monitoring its UV-Vis absorption spectra. About 98% was degraded in about 34 min under visible light and after 4 cycles it was 87%. The improved photocatalytic activity may be attributed to decrease in bandgap energy and enhanced ability for the electrons to migrate. Thus, CuO/GO NC showed good results for both sensing and degradation applications as well as reproducibility.

• 세라미스트
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• 제23권2호
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• pp.200-210
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• 2020

Supported catalysts are at the heart of manufacturing essential chemical, agricultural and pharmaceutical products. While the longevity of such systems is critically hinged on the durability of metal nanoparticles, the conventional deposition/dispersion techniques are difficult to enhance the stability of the metal nanoparticles due to the lack of control over the interaction between metal-support. Regarding this matter, ex-solution has begun to be recognized as one of the most promising methodologies to develop thermally and chemically robust nanoparticles. By dissolving desired catalysts as a cation form into a parent oxide, fine and uniformly distributed metal nano-catalysts can be subsequently grown in situ under reductive heat treatment, which is referred to ex-solution. Over the several years, ex-solved analog has resulted in tremendous progress in the chemical-electrochemical applications due to the exceptional robustness coupled with ease synthesis. Herein, we describe the ex-solution process in detail which therein introducing the unique characteristics of ex-solved particles that distinguish them from conventionally dispersed nanoparticles. We then go through the history of science regarding the ex-solution phenomena and summarize several major research achievements which embrace the ex-solved nanoparticles to markedly promote the catalytic performances. In conclusion, we address the remaining challenges and the future perspectives of this rapidly growing field.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.134-134
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• 2016

The effect of different thermal treatments on the sub-50 nm copper nanoparticles is examined in the aspects of chemical, electrical and surface morphology. The copper nanoparticles are chemically synthesized and fabricated for paste-type solution. Simple bar coating method is practiced as a deposition process to form copper thin film on a typical slide glass. Deposited copper thin films are annealed by two different routes: general tube furnace with 99.99 % Ar atmosphere and selective laser sintering process. The thermal behavior of the different thermal-treated copper thin films is compared by SEM, XRD, FT-IR and XPS analysis. In this study, the laser sintering process ensures low annealing temperature, fast working speed and ambient-accessible route. Moreover, the laser-sintered copper thin film shows good electrical property and enhanced chemical stability than conventional thermal annealing process. Consequently, the proposed laser sintering process can be compatible with plastic substrate for flexible applications.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.176.1-176.1
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• 2014

Graphene has attracted an increasing attention due to its extraordinary electronic, mechanical, and thermal properties. Especially, the two dimensional (2D) sheet of graphene with an extremely high surface to volume ratio has a great potential in the preparation of multifunctional nanomaterials, as 2D supports to host metal nanoparticles (NPs). Copper oxide is widely used in various areas as antifouling paint, p-type semiconductor, dry cell batteries, and catalysts. Although the copper oxide(II) has been well known for efficient catalyst in C-N cross-coupling reaction, copper oxide(I) has not been highlighted. In this research, CuO and Cu2O nanoparticles (NPs) dispersed on the surface of grapehene oxide (GO) have been synthesized by impregnation method and their morphological and electronic structures have been systemically investigated using TEM, XRD, and XAFS. We demonstrate that both CuO and Cu2O on graphene presents efficient catalytic performance toward C-N cross coupling reaction. The detailed structural difference between CuO and Cu2O NPs and their effect on catalytic performance are discussed.