In this study, partially dry transfer is investigated to solve the problem of fully dry transfer. Partially dry transfer is a method in which multiple layers of graphene are dry-transferred over a wet-transferred graphene layer. At a wavelength of 550 nm, the transmittance of the partially dry-transferred graphene is seen to be about 3% higher for each layer than that of the fully dry-transferred graphene. Furthermore, the sheet resistance of the partially drytransferred graphene is relatively lower than that of the fully dry-transferred graphene, with the minimum sheet resistance being 179 Ω/sq. In addition, the fully dry-transferred graphene is easily damaged during the solution process, so that the performance of the organic photovoltaics (OPV) does not occur. In contrast, the best efficiency achievable for OPV using the partially dry-transferred graphene is 2.37% for 4 layers.

The reduced graphene oxide (rGO)/activated carbon (AC) composites are coated on the aluminum substrate using spray coating technique to fabricate nanocarbon-based supercapacitor. Polymer-based solid-state xanthan-gum/Na2SO4 electrolyte is also introduced to increase stability of the supercapacitor. The electrochemical properties of the supercapacitor are evaluated using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge tests. The highest capacitance value of the rGO/AC composite-based supercapacitor is 120 F/g. The rGO/AC composite-based supercapacitor has also retained ~ 85% of its initial capacitance value after 3000 galvanostatic charge/discharge cycles.

We report potentiometric performances of ion-to-electron transducer based on reduced graphene oxide (RGO) for application of all-solid-state potassium ion sensors. A large surface area and pore structure of RGO are obtained by a hydrothermal self-assembly of graphene oxide. The extensive electrochemical characterization of RGO solid contact at the interface of ionselective membrane and gold electrode shows that the potassium ion-selective electrode based on RGO had a high sensitivity (53.34 mV/log[K+]), a low detection of limit (− 4.24 log[ K+], 0.06 mM) a good potential stability, and a high resistance to light and gas interferences. The potentiometric K+- sensor device was fabricated by combining of screen-printed electrodes and a printed circuit board. The K+- sensor device accurately measures the ion concentration of real samples of commercial sports drinks, coke and orange juice, and then transfers the collected data to a mobile application through a Bluetooth module. The screen-printed ion sensors based on RGO solid contact show a great potential for real-time monitoring and point-of-care devices in human health care, water-treatment process, and environmental and chemical industries.

Chemical incorporation of epoxy-modified graphitic layers in epoxy/novolac phenolic resin matrices was carried out through co-curing of epoxy and novolac resins using triphenylphosphine as catalyst. First, (3-glycidyloxypropyl) trimethoxysilane (GPTMS) was grafted on graphene oxide (GO) surface to obtain epoxidized GO layers. Then epoxy resin and GPTMS-modified GO were incorporated into thermosetting reaction using novolac resin in the presence of triphenylphosphine. Covalent attachment of GPTMS-modified GO to the resin matrices resulted in a hybrid composite with high thermal characteristics. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction, and Raman spectroscopy were used for approving modification of GO with GPTMS. The images resulted from scanning and transmission electron microscopies exhibited GO layers with lots of creases turning to smooth layers with a few thin ripples after modification with GPTMS. TGA results showed that thermal characteristics of resins were improved by the addition of GPTMS-modified GO. Char residue of the hybrid composites containing 0.5 and 1 wt% of GPTMS-modified GO reached 28.1 and 34.3%, respectively. Also, their maximum thermal degradation temperature was also increased by the incorporation of GPTMS-modified GO.

In this paper, nitrogen-doped reduced graphene oxide(rGO) is obtained by thermal annealing of nitrogen-containing compounds and graphene oxide (GO) manufactured by modified Hummers' method. We use melamine as a nitrogen-containing compound and treat GO thermally with melamine at over 800 ~ 1,000℃ and 1 ~ 3 hr under Ar atmosphere. The electrical conductivity of doped rGO is measured by 4-point probe method. As a result, nitrogen contents on rGO are found to be in the range of 2.5 to 12.5 at% depending on the doping conditions after thermal annealing. The main doping site on graphene oxide is changed from pyridinic-N and pyrrolinic N to the graphitic site as the heat treatment temperature increases. The electrical conductivity of doped rGO increases as the N doping content increases. As the thermal treatment time increases, the change of both total doping contents and doping sites is slight and the surface resistance is remarkably reduced, which is caused by healing effects of doped graphene oxide at high temperature.

Graphene and Fe3O4 were bound by electrostatic attraction and prepared by effective reduction through microwave treatments. As a result of fabricating graphene with Fe3O4 as a composite material, it has been confirmed that it contributes to the structural improvement in graphene stabilization and at the same time, it shows improved electrochemical performance through improved charge transfer. It was also confirmed that the crystalline Fe3O4 was uniformly dispersed in the rGO sheet, effectively blocking the reaggregation due to the van der Waals interaction between the neighboring rGO sheets. The structural analysis of prepared composites was confirmed by transmission electron microscopy, and X-ray diffractometer. Electrochemical properties of composites were studied by cyclic voltammetry, galvanostatic charge–discharge curves, and electrochemical impedance spectroscopy. The Fe3O4 (0.4 M)/rGO composite showed a high specific capacitance of 972 F g−1 at the current density of 1 A g−1 in 6 M KOH electrolyte, which is higher than that of the pristine materials rGO (251 F g−1) and Fe3O4 (183 F g−1). Also, the prepared composites showed a very stable cyclic behavior at high current density, as well as an improvement in comparison with pristine materials in terms of resistance.

The aluminum (Al)/copper oxide (CuO) complex is known as the most promising material for thermite reactions, releasing a high heat and pressure through ignition or thermal heating. To improve the reaction rate and wettability for handling safety, nanosized primary particles are applied on Al/CuO composite for energetic materials in explosives or propellants. Herein, graphene oxide (GO) is adopted for the Al/CuO composites as the functional supporting materials, preventing a phase-separation between solvent and composites, leading to a significantly enhanced reactivity. The characterizations of Al/CuO decorated on GO(Al/CuO/GO) are performed through scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping analysis. Moreover, the functional bridging between Al/CuO and GO is suggested by identifying the chemical bonding with GO in X-ray photoelectron spectroscopy analysis. The reactivity of Al/CuO/GO composites is evaluated by comparing the maximum pressure and rate of the pressure increase of Al/CuO and Al/CuO/GO. The composites with a specific concentration of GO (10 wt%) demonstrate a well-dispersed mixture in hexane solution without phase separation.

그래핀, 제올라이트, metal-organic frameworks (MOF)s 등 다양한 나노 소재를 이차원 나노쉬트 형태로 제조하고, 이를 이용한 초박막 고성능 분리막을 개발하고자 하는 연구가 활발히 진행되고 있다. 특히, 산화그래핀의 경우, 2000년대 초반에 관련 연구가 시작된 이후, 다양한 합성 및 박막 코팅 기술이 축적되어 있어 빠른 속도로 분리막 분야에 응용되고 있다. 다층으로 적층된 산화그래핀 박막은 층간 거리를 조절함에 따라 물리적 거름막으로 작용할 수 있으며, 또한 표면의 기능기 및 삽입된 물질과 거르는 물질 간의 상호작용을 제어함에 따라 다양한 물질의 선택적 분리가 가능하다. 본 총설에서는 산화그래핀의 나노여과막 응용분야에 관하여 중점적으로 다루고자 한다. 본고에서는, 다양한 용매 내에서 산화그래핀 박막의 분리 기작 및 성능에 영향을 미치는 핵심 요소들에 대해 요약하였으며, 그 외 산화그래핀 기반 분리막의 실질적인 상용화에 필요한 핵심 기술요소 및 개발 동향에 대하여 논하고자 한다.

본 연구에서는 탄소 나노재료 중 환원된 그래핀 옥사이드와 전도성 고분자중 폴리아닐린을 복합화 하여 슈퍼커패시터용 전극을 제조하였으며, 각각의 전극 재료가 가지는 단점을 서로 보완하고 장점을 극대화시킴으로써 전극의 전기화학적 특성을 크게 향상 시킬 수 있었다. 전극 물질에 사용된 폴리아닐린은 아닐린 단량체를 화학 중합법으로 제조하였고, 환원된 그래핀 옥사이드는 별도의 전 처리 과정 없이 사용 하였으며, DMF(N,N-dimethyl formamide)를 용매로 도입하여 분산용액을 제조하였다. 분산용액은 금이 코팅된PET(Polyethylene terephthalate) 기판위에 산업적 스케일로 적용이 가능한 스프레이 코팅 방법을 이용하여 전극으로 제조하였다. 환원된 그래핀 옥사이드/폴리아닐린 복합재료를 기반으로 제조된 전극의 전기화학적 특성을 비교하기 위하여 환원된 그래핀 옥사이드와 폴리아닐린 단일 전극을 제조하였으며, 동일 한 조건하에서 순환전압전류법, 임피던스 분광법, 정전류 충·방전법을 통하여 각각의 전극이 나타내는 전기 화학적 특성을 비교·분석 하였다. 그 결과로, 환원된 그래핀 옥사이드/폴리아닐린 복합재료를 기반으로 제조된 전극은 폴리아닐린, 환원된 그래핀 옥사 단일 전극에 비하여 전기 용량 값이 높게 나타났으며, 전해질 계면과의 내부 저항은 폴리아닐린, 환원된 그래핀 옥사이드 단일 전극에 비하여 각각 24 %, 58 % 감소하는 결과를 나타내었다. 이러한 결과로 미루어보아 본 연구를 통하여 제조된 환원된 그래핀 옥사이드/폴리 아닐린 복합재료 기반의 전극은 유연성 에너지 저장 매체나 웨어러블 전자기기에 적용이 가능할 것으로 판단된다.

Graphene oxide (GO) laminate is a new promising material for water purification system, which has extraordinary permeability only for water molecule. It consists of numerous nano-channels, in which water molecules could be nano-confined, resulting in slip of the molecules for very fast transportation speed. In this study, water penetration rate via different thickness of GO membrane according to driven pressures are measured experimentally, so that speed of water molecules and permeability are evaluated. Generally, water penetration rate via a membrane with macroscopic-sized channel increases linearly with pressure difference between up and bottom side of the membrane, but that via GO membrane approaches asymptotic value (i.e. saturation) as like a log function. Moreover, the permeability of GO membrane was observed in inverse proportion to its thickness. Based on the experimental observations, a correlation for volume flux via GO membrane was suggested with respect to its thickness and external pressure difference.

본 연구에서는 고분자인 polyacrylonitrile (PAN) 고분자에 산화 그래핀(Graphene Oxide, GO)을 첨가하여 전기방사법을 통해 나노섬유 복합막(GO-PAN)을 제조하였으며, 과량의 GO를 첨가하기 위해 표면개질 전략을 사용하였다. 계면활성제를 사용하여 GO의 표면을 간단히 변형하면 GO의 안정성 및 분산도 증가로 인해 최종적으로 분리막에 필러의 함량을 3wt%까지 증가시켰다. 이렇게 변형된 GO(mGO)의 PAN 나노섬유막으로의 도입은 원래의 PAN 나노섬유막과 GO-PAN 막에 비해 향상된 친수성과 기계적 강도를 가진다. 따라서 나노필러의 표면 개질은 최종 복합막의 성능에 영향을 미치며 이는 GO의 분산도와 상관관계가 있는 것으로 보인다.

3D프린팅 기술은 산업적 응용을 넘어서 기계 설비 및 각종 장비의 부품생산뿐만 아니라 의료, 식품, 패션에 이르기까지 많은 시제품들의 개발 및 연구가 진행되고 있다. 3D 프린팅 기반 기술의 적용사례를 볼 때 정밀도와 제작 속도 측면에서도 다른 산업에 충분이 활용될 수 있는 기술의 개발이 보고되고 있으나, 아직까지는 시제품 위주로 이용되고 있으며, 향후 3D 프린팅 기술은 4차산업혁명과 관련하여 광범위한 분야에서 응용될 수 있는 완성품이나 부품제작에 이용될 것으로 예상된다. 본 연구에서는 탄소나노 재료중 대표적으로 많이 이용되는 환원그래핀 [rGO(reduced graphene oxide)]과 전도성 고분자중 생체 친화적인 특성을 갖는 폴리피롤[Ppy(Polypyrrole)]의 복합체를 생분해성 고분자인 폴리카프로락톤 [PCL(polycaprolactone)]과 혼합하여 3D 프린팅용 전도성 레진을 개발하고자 하였다. 결과로, 폴리피롤과 환원그래핀 각각 5 wt%, 0.75 wt% 에서 최적의 전기적 특성을 나타내었으며, 환원그래핀의 농도에 따른 표면분석에서도 이와 부합하는 결과를 확인 할 수 있었다. 본 연구를 통하여 제조된 전도성 레진은 3D 프린팅 뿐만 아니라, 다른 산업분야의 전자재료에도 적용이 가능할 것으로 사료된다.

The present study aimed to prepare a novel efficient flame retardant additive for polypropylene. The new flame retardant was prepared by chemical grafting of melamine to graphene oxide with the aid of thionyl chloride. Fourier-transform infrared spectroscopy and thermogravimetric analysis proved that melamine had been successfully grafted to the graphene oxide. The modified graphene oxide was incorporated into polypropylene via solution mixing followed by anti-solvent precipitatio. Homogeneous distribution as well as exfoliation of the nanoplatelets in the polymer matrix was observed using transmission electron microscopy. Thermogravimetric analysis showed a significant improvement in the thermo-oxidative stability of the polymer after incorporating 2 wt% of the modified graphene oxide. The modified graphene oxide also enhanced the limiting oxygen index of the polymer. However, the amount of improvement was not enough for the polymer to be ranked as a self-extinguishing material. Cone calorimetry showed that incorporating 2 wt% of the modified graphene oxide lowered total heat release and the average production rate of carbon monoxide during burning of the polymer by as much as 40 and 35%, respectively. Hence, it was concluded that the new flame retardant can retard burning of the polymer efficiently and profoundly reduce suffocation risk of exposure to burning polymer byproducts.

An imprinted potentiometric sensor was developed for direct and selective determination of gabapentin. Sensor is based on carbon paste electrode adapted by graphene oxide that is decorated with silver nanoparticles and mixed with molecularly imprinted polymers nanoparticles using gabapentin as a template molecule. The synthesized nanoparticles were characterized by Fourier transmission infrared spectroscopy, transmission electron microscopy and X-ray diffraction. Under optimal experimental conditions, the studied sensor exhibited high selectivity and sensitivity with LOD of 4.8×10–11 mol L–1. It provided a wide linearity range from 1×10–10 to 1×10–3 mol L–1and high stability for more than 3 mo. The sensor was effectively used for the determination of gabapentin in pharmaceutical tablets and spiked plasma samples.

A citric acid functionalized graphene oxide nanocomposite was successfully synthesized and the structure and morphology of the nanocatalyst were comprehensively characterized by Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis, X-ray diffraction patterns, atomic force microscopy images, scanning electron microscopy images, transmission electron microscopy images, and thermogravimetric analysis. The application of this nanocatalyst was exemplified in an important condensation reaction to give imidazole derivatives in high yields and short reaction times at room temperature. The catalyst shows high catalytic activity and could be reused after simple work up and easy purification for at least six cycles without significant loss of activity, which indicates efficient immobilizing of citrate groups on the surface of graphene oxide sheets.