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>

환원된 그래핀 옥사이드/폴리아닐린 복합재료 기반의 슈퍼커패시터용 전극 제조

김세현,안원준,최재용,박현영,김창현,김용렬,정현택 한국응용과학기술학회 2018 한국응용과학기술학회지 Vol.35 No.4

In this study, reduced graphene oxide/polyaniline composite was fabricated tomaximize their advantages with electrochemical performances and use as a electrodematerial for supercapcaitor. Polyaniline as an electrode material was synthesized bychemical polymerization of aniline monomer and reduced graphene oxide wasintroduced to prepare composite with polyaniline without any pre-treatment. Thereduced graphene oxide, polyaniline and their composite electrodes were fabricatedon gold coated PET(polyethylene terephthalate) substrate through spray coatingmethod which can also apply to industrial scale. we have also prepared reducedgraphene oxide and polyaniline single material electrode to compare theirelectrochemical properties with reduced graphene oxide/polyaniline composite electrode. We have analyzed and compared electrochemical properties of eachelectrodes by using cyclic voltammetry(CV), galvanostaticcharge-discharge(GCD) and electrochemical impedancespectroscopy(EIS) at same condition. As a result, reduced graphene oxide /polyaniline composite electrode showed higher capacitance value more thanpolyaniline and reduced graphene oxide electrode, respectively. Internal resistanceof reduce graphene oxide/polyaniline composite electrode was 24% and 58% lessthan polaniline and reduced graphene oxide electrode respectively. These resultsconsidered that reduced graphene oxide/polyaniline composite electrode has potential ability and enable to apply flexible energy storage and wearable devices. 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, 동일한 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.

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.

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.

Optical properties of reduced graphene oxide nanodots prepared by laser ablation

Seliverstova Evgeniya,Ibrayev Niyazbek,Alikhaidarova Elmira,Menshova Evgeniya 한국탄소학회 2022 Carbon Letters Vol.32 No.6

The effect of the laser ablation duration of reduced graphene oxide sheets on their optical properties was studied. After 30 min of ablation, the average lateral size of reduced graphene oxide sheets decreases from 347.4 ± 86.5 nm to 98.8 ± 36.0. The sizes of almost all particles are in the range up to 100 nm, which was confirmed by transmission electron microscopy and dynamic light scattering data. The FTIR spectroscopy data showed that after ablation the intensity of the bands associated with O–H, C–OH and C=O vibrations were noticeably decreased. The optical density and the fluorescence intensity of reduced graphene oxide also depend on the ablation time. After ablation, the reduced graphene oxide fluorescence intensity increased 2–3 times. The fluorescence lifetime decreases both for the first (from 1.36 ns to 0.71 ns) and second (from 6.03 to 3.66 ns) components. A broad band was recorded in the long-lived luminescence spectrum. The long-lived luminescence intensity is higher on 80% for the samples after 30 min of ablation compared to the unablated sample. It was assumed that during laser ablation of reduced graphene oxide a change in the ratio between oxidized and sp2-hybridized carbon occurs. This opens up possibilities for controlling the optical properties of reduced graphene oxide.

Synthesis of heteroatoms doped reduced graphene oxide for the electrochemical determination of uric acid in commercial milk

Fatma Besbes,Zouhour Hsine,Rym Mlika 한국탄소학회 2023 Carbon Letters Vol.33 No.7

A simple and one-pot synthetic procedure using two different sources has been demonstrated to prepare heteroatoms doped reduced graphene oxide such as nitrogen-doped reduced graphene oxide (N-RGO) and sulfur-doped reduced graphene oxide (S-RGO). The N-RGO has been hydrothermally synthesized using urea as nitrogen precursor, wherein the S-RGO has been synthesized using dimethyl sulfoxide (DMSO) as sulfur precursor. The successful N-doping, S-doping and other physicochemical properties of N-RGO and S-RGO have been confirmed with different spectroscopic and electrochemical techniques. The results indicated that doping into the graphene structure exhibits a high conductivity and a better transfer of charge. Moreover, heteroatoms doped graphene (N-RGO and S-RGO) and graphene-related materials (RGO) have been applied for the individual detection of uric acid (UA). Interestingly, the N-RGO exhibited a lower limit of detection (LOD, S/N = 3) of 2.7 10– 5 M for UA (10–1000 μM) compared with undoped RGO and S-RGO. Furthermore, the simultaneous detection of UA in the presence of Xanthine (XA) has been demonstrated a wide linear range of detection for UA: 10–1000 μM, with unchanged concentration of XA to be 200 μM, and exhibited a low limit of detection of 8.7 10? 5 M ( S?N = 3) for UA. This modified sensor based on N-RGO has revealed a high selectivity and reproducibility thanks to its large surface area, high catalytic properties, and chemical structure. Indeed, the practical applicability of the proposed sensor has been evaluated in milk samples even in the presence of high concentrations of UA with satisfactory results.

Enhanced capacitance properties of nitrogen doped reduced graphene oxide obtained by simultaneous reduction and nitrogen doping

Bharathidasan, P.,Idris, Mustapha Balarabe,Kim, Dong-Won,Sivakkumar, S.R.,Devaraj, S. Elsevier 2018 Flatchem Vol.11 No.-

<P><B>Abstract</B></P> <P>One of the strategies employed to improve the capacitance of reduced graphene oxide is nitrogen doping. Herein, we report the effectiveness of hydrazine hydrate as a nitrogen dopant cum reducing agent. Graphene oxide synthesized by modified Hummer’s method is reduced hydrothermally in the presence and in the absence of hydrazine hydrate and are labeled as NRGO-H and RGO-H, respectively. Hydrothermal reduction of graphene oxide in the presence of a small amount of (6 µL) hydrazine hydrate results in doping of 1.66 atomic weight % of nitrogen as inferred from X-ray photoelectron spectroscopic studies. The effect of nitrogen doping on the morphology and textural properties of reduced graphene oxide is systematically studied using Raman spectroscopy, transmission electron microscope and nitrogen sorption studies. The protruding dopant prevents restacking of graphene layers, resulting in comparatively less number of graphene layers in NRGO-H than in RGO-H. Nitrogen doping also increases number of mesopores and thereby surface area. Owing to Faradaic reaction of the dopant, NRGO-H delivers higher specific capacitance (332 F g<SUP>−1</SUP>) than RGO-H (149 F g<SUP>−1</SUP>) in aqueous electrolyte (0.25 M H<SUB>2</SUB>SO<SUB>4</SUB>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> NRGO is synthesised by simultaneous reduction and nitrogen doping of RGO. </LI> <LI> The protruding dopant prevents restacking and increases number of mesopores. </LI> <LI> NRGO outperforms pristine reduced graphene oxide. </LI> <LI> Doped pyridinic nitrogen contributes to the overall capacitance via Faradaic reaction. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

An in vitro evaluation of graphene oxide reduced by <i>Ganoderma</i> spp. in human breast cancer cells (MDA-MB-231)

Gurunathan, Sangiliyandi,Han, JaeWoong,Park, Jung Hyun,Kim, Jin Hoi Dove Medical Press 2014 INTERNATIONAL JOURNAL OF NANOMEDICINE Vol.9 No.-

<P><B>Background</B></P><P>Recently, graphene and graphene-related materials have attracted much attention due their unique properties, such as their physical, chemical, and biocompatibility properties. This study aimed to determine the cytotoxic effects of graphene oxide (GO) that is reduced biologically using <I>Ganoderma</I> spp. mushroom extracts in MDA-MB-231 human breast cancer cells.</P><P><B>Methods</B></P><P>Herein, we describe a facile and green method for the reduction of GO using extracts of <I>Ganoderma</I> spp. as a reducing agent. GO was reduced without any hazardous chemicals in an aqueous solution, and the reduced GO was characterized using a range of analytical procedures. The <I>Ganoderma</I> extract (GE)-reduced GO (GE-rGO) was characterized by ultraviolet-visible absorption spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, dynamic light scattering, scanning electron microscopy, Raman spectroscopy, and atomic force microscopy. Furthermore, the toxicity of GE-rGO was evaluated using a sequence of assays such as cell viability, lactate dehydrogenase leakage, and reactive oxygen species generation in human breast cancer cells (MDA-MB-231).</P><P><B>Results</B></P><P>The preliminary characterization of reduction of GO was confirmed by the red-shifting of the absorption peak for GE-rGO to 265 nm from 230 nm. The size of GO and GE-rGO was found to be 1,880 and 3,200 nm, respectively. X-ray diffraction results confirmed that reduction processes of GO and the processes of removing intercalated water molecules and the oxide groups. The surface functionalities and chemical natures of GO and GE-rGO were confirmed using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface morphologies of the synthesized graphene were analyzed using high-resolution scanning electron microscopy. Raman spectroscopy revealed single- and multilayer properties of GE-rGO. Atomic force microscopy images provided evidence for the formation of graphene. Furthermore, the effect of GO and GE-rGO was examined using a series of assays, such as cell viability, membrane integrity, and reactive oxygen species generation, which are key molecules involved in apoptosis. The results obtained from cell viability and lactate dehydrogenase assay suggest that GO and GE-rGO cause dose-dependent toxicity in the cells. Interestingly, it was found that biologically derived GE-rGO is more toxic to cancer cells than GO.</P><P><B>Conclusion</B></P><P>We describe a simple, green, nontoxic, and cost-effective approach to producing graphene using mushroom extract as a reducing and stabilizing agent. The proposed method could enable synthesis of graphene with potential biological and biomedical applications such as in cancer and angiogenic disorders. To our knowledge, this is the first report using mushroom extract as a reducing agent for the synthesis of graphene. Mushroom extract can be used as a biocatalyst for the production of graphene.</P>

Reduction of graphene oxide by resveratrol: a novel and simple biological method for the synthesis of an effective anticancer nanotherapeutic molecule

Gurunathan, Sangiliyandi,Han, Jae Woong,Kim, Eun Su,Park, Jung Hyun,Kim, Jin-Hoi Dove Medical Press 2015 INTERNATIONAL JOURNAL OF NANOMEDICINE Vol.10 No.-

<P><B>Objective</B></P><P>Graphene represents a monolayer or a few layers of sp2-bonded carbon atoms with a honeycomb lattice structure. Unique physical, chemical, and biological properties of graphene have attracted great interest in various fields including electronics, energy, material industry, and medicine, where it is used for tissue engineering and scaffolding, drug delivery, and as an antibacterial and anticancer agent. However, graphene cytotoxicity for ovarian cancer cells is still not fully investigated. The objective of this study was to synthesize graphene using a natural polyphenol compound resveratrol and to investigate its toxicity for ovarian cancer cells.</P><P><B>Methods</B></P><P>The successful reduction of graphene oxide (GO) to graphene was confirmed by UV-vis and Fourier transform infrared spectroscopy. Dynamic light scattering and scanning electron microscopy were employed to evaluate particle size and surface morphology of GO and resveratrol-reduced GO (RES-rGO). Raman spectroscopy was used to determine the removal of oxygen-containing functional groups from GO surface and to ensure the formation of graphene. We also performed a comprehensive analysis of GO and RES-rGO cytotoxicity by examining the morphology, viability, membrane integrity, activation of caspase-3, apoptosis, and alkaline phosphatase activity of ovarian cancer cells.</P><P><B>Results</B></P><P>The results also show that resveratrol effectively reduced GO to graphene and the properties of RES-rGO nanosheets were comparable to those of chemically reduced graphene. Biological experiments showed that GO and RES-rGO caused a dose-dependent membrane leakage and oxidative stress in cancer cells, and reduced their viability via apoptosis confirmed by the upregulation of apoptosis executioner caspase-3.</P><P><B>Conclusion</B></P><P>Our data demonstrate a single, simple green approach for the synthesis of highly water-dispersible functionalized graphene nanosheets, suggesting a possibility of replacing toxic hydrazine by a natural and safe phenolic compound resveratrol, which has similar efficacy in the reduction of GO to rGO. Resveratrol-based GO reduction would facilitate large-scale production of graphene-based materials for the emerging graphene-based technologies and biomedical applications.</P>

Mechanical properties of thin films of graphene materials: A study on their structural quality and functionalities

Velram Balaji Mohan,Hamid Souri,Krishnan Jayaraman,Debes Bhattacharyya 한국물리학회 2018 Current Applied Physics Vol.18 No.8

Several studies have been done on physiochemical properties of thin films of graphene materials, but less on their mechanical properties. The mechanical properties such as tensile and storage modulus of films of graphene oxide (GO), different reduced graphene oxides (rGO), functionalised reduced graphene oxide (frGO) and a few layers graphene (graphene) were analysed in this study. During syntheses processes, a range of variations occurs due to different reducing agents and functionalising components used; this affects or changes the mechanical properties of the materials. In addition, it has become vital to comprehend the mechanical properties of these films as the potential applications such as sensor and electrodes demand extended life cycles or lifetime. It has been found that the ultimate tensile strength (UTS), tensile modulus, and storage modulus vary across all the samples that highly depend on nature/efficiency of reducing agent used, amount of impurities such as oxygen functional groups and defect density such as discrepancies/holes in the aromatic structure. The highest UTS and modulus have been identified with a few layers graphene and with hydroiodic acid reduced GO among the rGOs. The frGO shows almost similar properties to that of graphene.