산화그래핀 층수에 따른 폴리스타이렌 표면 코팅 특성

이지훈,박재범,박단비,허증수,임정옥,Lee, Jihoon,Park, Jaebum,Park, Danbi,Huh, Jeung Soo,Lim, Jeong Ok 한국재료학회 2021 한국재료학회지 Vol.31 No.7

Graphene, a new material with various advantageous properties, has been actively used in various fields in recent years. Applications of graphene oxide are increasing in combination with other materials due to the different properties of graphene oxide, depending on the number of single and multiple layers of graphene. In this study, single-layer graphene oxide and multi-layer graphene oxide are spray coated on polystyrene, and the physicochemical properties of the coated surfaces are characterized using SEM, Raman spectroscopy, AFM, UV-Vis spectrophotometry, and contact angle measurements. In single-layer graphene oxide, particles of 20 ㎛ are observed, whereas a 2D peak is less often observed, and the difference in surface height increases according to the amount of graphene oxide. Adhesion increases with an increase in graphene oxide up to 0.375 mg, but decreases at 0.75 mg. In multi-layer graphene oxide, particles of 5 ㎛ are observed, as well as a 2D peak. According to the amount of graphene oxide, the height difference of the surface increases and the adhesive strength decreases. Both materials are hydrophilic, but single-layer graphene oxide has a hydrophilicity higher than that of multi-layer graphene oxide. We believe that multi-layer graphene oxide and single-layer graphene oxide can be implemented based on the characteristics that make them suitable for application.

Fabrication and Characterization of Graphene Oxide-Coated Plate for Efficient Culture of Stem Cells

박단비,박재범,이지훈,Shim Chang Jae,김민성,이태용,임정옥 한국조직공학과 재생의학회 2021 조직공학과 재생의학 Vol.18 No.5

Background: For stem cell applications in regenerative medicine, it is very important to produce high-quality stem cells in large quantities in a short time period. Recently, many studies have shown big potential of graphene oxide as a biocompatible substance to enhance cell growth. We investigated if graphene oxide-coated culture plate can promote production efficiency of stem cells. Methods: Three types of graphene oxide were used for this study. They are highly concentrated graphene oxide solution, single-layer graphene oxide solution, and ultra-highly concentrated single-layer graphene oxide solution with different single-layer ratios, and coated on cell culture plates using a spray coating method. Physiochemical and biological properties of graphene oxide-coated surface were analyzed by atomic force microscope (AFM), scanning electron microscope (SEM), cell counting kit, a live/dead assay kit, and confocal imaging. Results: Graphene oxide was evenly coated on cell culture plates with a roughness of 6.4 ~ 38.2 nm, as measured by SEM and AFM. Young’s Modulus value was up to 115.1 GPa, confirming that graphene oxide was strongly glued to the surface. The ex vivo stem cell expansion efficiency was enhanced as bone marrow-derived stem cell doubling time on the graphene oxide decreased compared to the control (no graphene oxide coating), from 64 to 58 h, and the growth rate increased up to 145%. We also observed faster attachment and higher affinity of stem cells to the graphene oxide compared to control by confocal microscope. Conclusion: This study demonstrated that graphene oxide dramatically enhanced the ex vivo expansion efficiency of stem cells. Spray coating enabled an ultra-thin coating of graphene oxide on cell culture plates. The results supported that utilization of graphene oxide on culture plates can be a promising mean for mass production of stem cells for commercial applications. Background: For stem cell applications in regenerative medicine, it is very important to produce high-quality stem cells in large quantities in a short time period. Recently, many studies have shown big potential of graphene oxide as a biocompatible substance to enhance cell growth. We investigated if graphene oxide-coated culture plate can promote production efficiency of stem cells. Methods: Three types of graphene oxide were used for this study. They are highly concentrated graphene oxide solution, single-layer graphene oxide solution, and ultra-highly concentrated single-layer graphene oxide solution with different single-layer ratios, and coated on cell culture plates using a spray coating method. Physiochemical and biological properties of graphene oxide-coated surface were analyzed by atomic force microscope (AFM), scanning electron microscope (SEM), cell counting kit, a live/dead assay kit, and confocal imaging. Results: Graphene oxide was evenly coated on cell culture plates with a roughness of 6.4 ~ 38.2 nm, as measured by SEM and AFM. Young’s Modulus value was up to 115.1 GPa, confirming that graphene oxide was strongly glued to the surface. The ex vivo stem cell expansion efficiency was enhanced as bone marrow-derived stem cell doubling time on the graphene oxide decreased compared to the control (no graphene oxide coating), from 64 to 58 h, and the growth rate increased up to 145%. We also observed faster attachment and higher affinity of stem cells to the graphene oxide compared to control by confocal microscope. Conclusion: This study demonstrated that graphene oxide dramatically enhanced the ex vivo expansion efficiency of stem cells. Spray coating enabled an ultra-thin coating of graphene oxide on cell culture plates. The results supported that utilization of graphene oxide on culture plates can be a promising mean for mass production of stem cells for commercial applications.

The effect of diverse metal oxides in graphene composites on the adsorption isotherm of gaseous benzene

Khan, Azmatullah,Szulejko, Jan E.,Samaddar, Pallabi,Kim, Ki-Hyun,Eom, Wonsik,Ambade, Swapnil B.,Han, Tae Hee Elsevier 2019 Environmental research Vol.172 No.-

<P><B>Abstract</B></P> <P>The effective removal technique is necessary for the real world treatment of a hazardous pollutant (e.g., gaseous benzene). In an effort to develop such technique, the adsorption efficiency of benzene in a nitrogen stream (5 Pa (50 ppm) at 50 mL atm min<SUP>−1</SUP> flow rate and 298 K) was assessed against 10 different metal oxide/GO composite materials (i.e., 1: graphene oxide Co (GO-Co (OH)<SUB>2</SUB>), 2: graphene oxide Cu (GO-Cu(OH)<SUB>2</SUB>), 3: graphene oxide Mn (GO-MnO), 4: graphene oxide Ni (GO-Ni(OH)<SUB>2</SUB>), 5: graphene oxide Sn (GO-SnO<SUB>2</SUB>), 6: reduced graphene oxide Co (rGO-Co(OH)<SUB>2</SUB>), 7: reduced graphene oxide Cu (rGO-Cu(OH)<SUB>2</SUB>), 8: reduced graphene oxide Mn (rGO-MnO), 9: reduced graphene oxide Ni (rGO-Ni(OH)<SUB>2</SUB>), and 10: reduced graphene oxide Sn (rGO-SnO<SUB>2</SUB>)) in reference to their pristine forms of graphene oxide (GO) and reduced graphene oxide (rGO). The highest adsorption capacities (at 100% breakthrough) were observed as ~23 mg g<SUP>−1</SUP> for both GO-Ni(OH)<SUB>2</SUB> and rGO-SnO<SUB>2</SUB>, followed by GO (~19.1 mg g<SUP>−1</SUP>) and GO-Co(OH)<SUB>2</SUB> (~18.8 mg g<SUP>−1</SUP>). Therefore, the GO-Ni(OH)<SUB>2</SUB> and rGO-SnO<SUB>2</SUB> composites exhibited considerably high capacities to treat streams containing >5 Pa of benzene. However, the lowest adsorption capacity was found for GO-MnO (0.05 mg g<SUP>−1</SUP>). Alternately, if expressed in terms of the 10% breakthrough volume (BTV), the five aforementioned materials showed values of 0.50, 0.46, 0.40, 0.44, and 0.39 L g<SUP>−1</SUP>, respectively. The experimental data of target sorbents were fitted to linearized Langmuir, Freundlich, Elovich, and Dubinin-Radushkevich isotherm models. Accordingly, the non-linear Langmuir isotherm model revealed the presence of two or more distinct sorption profiles for several of the tested sorbents. Most of the sorbents showed type-III isotherm profiles where the sorption capacity proportional to the loaded volume.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The diverse forms of graphene-based composite with metal oxides were synthesized. </LI> <LI> The adsorption performance of these composites has been evaluated against benzene. </LI> <LI> Empirical isotherm models were employed to interpret the role of metal oxides in the adsorption. </LI> <LI> The possible mechanisms were explained by performance metrics over varying pressure regions. </LI> </UL> </P>

Graphene/graphene oxide: A new material for electrorheological and magnetorheological applications

Zhang, Wen Ling,Choi, Hyoung Jin Sage Science Press (UK) 2015 Journal of intelligent material systems and struct Vol. No.

<P>The presence of functional groups provides graphene oxide sheets amphiphilic abilities with lower electrical conductivity and relatively high polarizability, which is appropriate for its electrorheological effect. In addition, because the graphene oxide sheets possess high surface area and relatively low particle density, graphene-/graphene oxide–supported materials have also attracted significant interest for fascinating magnetorheological applications. In this article, we briefly review the fabrication mechanisms and electrorheological characteristics of graphene-/graphene oxide–based electrorheological systems, such as pure graphene oxide sheets and various graphene-/graphene oxide–based polymer composites and nanocomposites of graphene/graphene oxide sheets with inorganic particles. As for the magnetorheological fluid application, the fabrication of graphene oxide sheets coated on the surface of carbonyl iron particles and graphene oxide/iron oxide composites are covered regarding improved dispersibility of the magnetorheological suspensions.</P>

Synthesis and Electrochemical Characterization of Reduced Graphene Oxide-Manganese Oxide Nanocomposites

Lee, Yu-Ri,Song, Min-Sun,Lee, Kyung-Min,Kim, In-Young,Hwang, Seong-Ju The Korean Electrochemical Society 2011 Journal of electrochemical science and technology Vol.2 No.1

Nanocomposites of reduced graphene oxide and manganese (II,III) oxide can be synthesized by the freeze-drying process of the mixed colloidal suspension of graphene oxide and manganese oxide, and the subsequent heat-treatment. The calcined reduced graphene oxide-manganese (II,III) oxide nanocomposites are X-ray amorphous, suggesting the formation of homogeneous and disordered mixture without any phase separation. The reduction of graphene oxide to reduced graphene oxide upon the heat-treatment is evidenced by Fourier-transformed infrared spectroscopy. Field emission-scanning electronic microscopy and energy dispersive spectrometry clearly demonstrate the formation of porous structure by the house-of-cards type stacking of reduced graphene oxide nanosheets and the homogeneous distribution of manganese ions in the nanocomposites. According to Mn K-edge X-ray absorption spectroscopy, manganese ions in the calcined nanocomposites are stabilized in octahedral symmetry with mixed Mn oxidation state of Mn(II)/Mn(III). The present reduced graphene oxide-manganese oxide nanocomposites show characteristic pseudocapacitance behavior superior to the pristine manganese oxide, suggesting their applicability as electrode material for supercapacitors.

Electroplating of reduced-graphene oxide on austenitic stainless steel to prevent hydrogen embrittlement

Kim, Yong-Sang,Kim, Jung-Gu Pergamon Press 2017 International journal of hydrogen energy Vol.42 No.44

<P><B>Abstract</B></P> <P>In this study, reduced graphene oxide was deposited on stainless steel by an electroplating method and investigated for application as a protective barrier against hydrogen embrittlement. After electroplating, the reduced graphene oxide on stainless steel was evaluated via scanning electron microscopy and infrared spectroscopy. A thick and rough reduced graphene oxide layer was formed on the substrate, and removal of the oxidation product from the graphene oxide was confirmed by infrared spectroscopy. Electrochemical methods (i.e., potentiodynamic polarization tests and electrochemical impedance spectroscopy) and slow strain rate tests were performed to analyze the hydrogen embrittlement resistance. The hydrogen reduction reaction was decreased and a durable protective layer was formed after formation of the reduced graphene oxide. The decreased stress and strain under hydrogen conditions were ameliorated under hydrogen reduction conditions by the formation of reduced graphene oxide; this was caused by the formation of hydro-generated graphene and the increased hydrogen diffusion length.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thick rough reduced graphene oxide layer was formed by an electroplating method. </LI> <LI> Reduced graphene oxide layer decrease the hydrogen reduction reaction on the surface. </LI> <LI> Reduced graphene oxide layer increases the hydrogen embrittlement resistance. </LI> <LI> Main protection mechanism is formation of hydro-generated graphene. </LI> <LI> Main protection mechanism is the increase of hydrogen diffusion length. </LI> </UL> </P>

Fabrication of diverse graphene-conducting polymer composites (graphene-polythiophene, graphene-polyaniline, and graphene-polypyrrole) by facilitating graphene oxide as broad initiator

김민규,장정식 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

Diverse graphene-conducting polymer (CP) composites (graphene-poly-thiophene, graphene-polyaniline, and graphene-polypyrrole) have been simply and rapidly prepared by facilitating graphene oxide as broad initiator. The UV-vis, SEM, and TEM analysis showed that the graphene-CP composites have successfully been produced. In addition with these, the series of FT-IR analysis were also conducted to investigate how the graphene oxide initiated the polymerizations. Given IR results, plausible polymerization mechanisms were proposed.

그래핀 기반 광촉매 담지 세라믹필터에서 질소산화물(NO_x)의 제거

김용석 ( Yong-seok Kim ),김영호 ( Young-ho Kim ) 한국공업화학회 2022 공업화학 Vol.33 No.6

V₂O₅-WO₃-TiO₂ 촉매를 담지하여 그래핀(graphene) 기반 세라믹필터를 제조하였으며, 이를 활용하여 질소산화물(NO_x)의 제거실험을 수행하였다. 산화그래핀(graphene oxide, GO)은 흑연(graphite)을 이용하여 Hummer`s method에 의해 제조하였고 환원제로 히드라진(N₂H₄)을 통해 환원 산화그래핀(reduced graphene oxide, rGO)을 제조하였다. 제조된 그래핀을 세라믹필터 표면에 유-무기 하이브리드 원리를 이용하여 코팅하였으며, 여기에 광촉매물질을 담지하였다. 광촉매물질은 바나듐(V), 텅스텐(W), 티타늄(Ti)를 사용하여 sol-gel법에 의해 코팅 후 350 °C 소성 공정을 통하여 광촉매담지 세라믹필터를 제조하였다. UV광을 제조된 필터에 조사하여 NO_x의 제거 실험을 수행하였으며, NO_x의 제거 효율은 기존의 세라믹필터보다 GO 및 rGO가 코팅된 경우가 우수하였다. 이는 코팅된 그래핀에 의한 흡착성의 향상 때문으로 판단되며, 그래핀의 농도가 증가함에 따라 보다 높은 NO_x의 제거효율을 확인하였다. In this study, nitrogen oxide (NO_x) removal experiments were performed using a graphene based ceramic filter coated with a V₂O₅-WO₃-TiO₂ catalyst. Graphene oxide (GO) was prepared by Hummer's method using graphite, and the reduced graphene oxide was produced by reducing with hydrazine (N₂H₄). Vanadium (V), Tungsten (W), and Titanium (Ti) were coated by the sol-gel method, and then a metal oxide-supported filter was prepared through a calcination process at 350 °C. A NO_x removal efficiency test was performed for the catalytic ceramic filters with UV light in a humid condition. When graphene oxide (GO) and reduced graphene oxide (rGO) were present on the filter, the NO_x removal efficiency was superior to that of the conventional ceramic filter. Most likely, this is due to an improvement in the adsorption properties of NO_x molecules on graphene coated surfaces. As the concentration of graphene increased, higher NO_x removal efficiency was confirmed.

Fast and controllable reduction of graphene oxide by low-cost CO₂ laser for supercapacitor application

Bhattacharjya, Dhrubajyoti,Kim, Chang-Hyeon,Kim, Jae-Hyun,You, In-Kyu,In, Jung Bin,Lee, Seung-Mo Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.462 No.-

<P><B>Abstract</B></P> <P>Direct reduction of graphene oxide has been regarded as the economically viable route for large-scale synthesis of graphene. However, the currently known methods suffer from either poor reduction efficiency or involve multi-step and energy-intensive reduction processes. Here, we demonstrate a remarkably fast, single step as well as highly efficient reduction technique to produce high-quality multilayer graphene film using a compact and low-cost CO<SUB>2</SUB> laser pyrolysis. Thanks to the intrinsically high absorptivity of graphene oxide in the near- and mid-infrared regions, the irradiation of CO<SUB>2</SUB> laser generates instantaneous and strong localized heating on it and thus burst apart the oxygen functional groups from the graphene oxide layers. The extent of reduction in the synthesized multilayer graphene films can be fruitfully controlled by variation of laser processing parameters such as laser intensity, scanning speed and shifting pitch. To prove the worth of this method, the graphene films were used as the binder-free and self-standing electrode for symmetric supercapacitor cell. The electrochemical performance data shows that specific capacitance and cyclic stability has a contrasting relation with the reduction efficiency. We believe that this CO<SUB>2</SUB> laser-based reduction method could guarantee a high outturn of multilayer graphene and its composites for innumerable applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Instantaneous reduction of graphene oxide is achieved by using inexpensive CO<SUB>2</SUB> laser. </LI> <LI> The extent of reduction is controlled by changing the laser processing parameters. </LI> <LI> Very high carbon to hetero atom ratio is achieved in the synthesized graphene in this method. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Low-cost CO<SUB>2</SUB> laser allows incomparably fast and efficient reduction of graphene oxide film to produce high quality multilayer graphene.</P> <P>[DISPLAY OMISSION]</P>

Maximizing volumetric energy density of all-graphene-oxide-supercapacitors and their potential applications for energy harvest

Kim, Hyuk Joon,Lee, Seul-Yi,Sinh, Le Hoang,Yeo, Chang Su,Son, Yeong Rae,Cho, Kang Rae,Song, YoonKyu,Ju, Sanghyun,Shin, Min Kyoon,Park, Soo-Jin,Park, SangYoon Elsevier 2017 Journal of Power Sources Vol.346 No.-

<P><B>Abstract</B></P> <P>Graphene has attracted widespread attention for supercapacitor applications thank to their excellent conductivity, mechanical flexibility, chemical stability and extremely high specific surface area. Here, all-graphene-oxide-supercapacitors were developed from two reduced graphene oxide (rGO) films as electrodes and one graphene oxide (GO) film as separator. The supercapacitors were then treated with 4M sulfuric acid at temperatures around 80 °C. By this treatment, the sulfuric acid molecules were physically intercalated into both rGO and GO films, which were confirmed by significant decrease intensity of characteristic peaks of sulfuric acid in Raman spectra. These sulfuric-acid-intercalated GO films can function as both quasi-solid-state electrolytes and separators. The average capacitance values measured at 100 mV s<SUP>−1</SUP> of the thermally wetted supercapacitor at 84 °C is improved 93.7 times higher than that of the as-prepared all-graphene-oxide-supercapacitor. The maximum capacitance of 266 F cm<SUP>−3</SUP> is obtained at scan rate 10 mV s<SUP>−1</SUP> for the thermally wetted supercapacitor at 84 °C. To the best of our knowledge, this is the highest specific capacitance that has ever been reported for a graphene oxide-based supercapacitor. Importantly, being in a quasi-solid-state, the energy storage performance of supercapacitors are persistent over several thousand cycles, making it very much unlike other carbon-based supercapacitors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Quasi-solid-state all-graphene-oxide-supercapacitors were developed for the first time. </LI> <LI> Thermal wetting of the supercapacitors with H<SUB>2</SUB>SO<SUB>4</SUB> around 80 °C produces quasi-solid-state. </LI> <LI> A large volumetric capacitance of 266 F cm<SUP>−3</SUP> at a scan rate of 10 mV s<SUP>−1</SUP>. </LI> <LI> Energy storage performances of the supercapacitors are persistent over several thousand cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>