Graphene nanosheets for enhanced lithium storage

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Graphene-nanosized silicon composites for lithium battery anodes with improved cycling stability

Graphene-nanosized silicon composites for lithium battery anodes with improved cycling stability

Graphene/nanosized silicon composites for lithium battery anodes with improved cycling stabilityHongfa Xiang a ,Kai Zhang a ,Ge Ji b ,Jim Yang Lee b ,Changji Zou c ,Xiaodong Chen c ,Jishan Wu a ,*aDepartment of Chemistry,National University of Singapore,3Science Drive 3,Singapore 117543,SingaporebDepartment of Chemical and Biomolecular Engineering,National University of Singapore,4Engineering Drive 4,Singapore 117576,Singapore cSchool of Material Science and Engineering,Nanyang Technological University,50Nanyang Avenue,Singapore 639798,SingaporeA R T I C L E I N F O Article history:Received 21June 2010Accepted 4January 2011Available online 9January 2011A B S T R A C TGraphene/nanosized silicon composites were prepared and used for lithium battery anodes.T wo types of graphene samples were used and their composites with nanosized sil-icon were prepared in different ways.In the first method,graphene oxide (GO)and nano-sized silicon particles were homogeneously mixed in aqueous solution and then the dry samples were annealed at 500°C to give thermally reduced GO and nanosized silicon com-posites.In the second method,the graphene sample was prepared by fast heat treatment of expandable graphite at 1050°C and the graphene/nanosized silicon composites were then prepared by mechanical blending.In both cases,homogeneous composites were formed and the presence of graphene in the composites has been proved to effectively enhance the cycling stability of silicon anode in the lithium-ion batteries.The significant enhance-ment on cycling stability could be ascribed to the high conductivity of the graphene mate-rials and absorption of volume changes of silicon by graphene sheets during the lithiation/delithiation process.In particular,the composites using thermally expanded graphite exhibited not only more excellent cycling performance,but also higher specific capacity of 2753mAh/g because the graphene sheets prepared by this method have fewer structural defects than thermally reduced GO.Ó2011Elsevier Ltd.All rights reserved.1.IntroductionTo meet requirement for electric vehicles and renewable sources of energy,the state-of-the-art energy storage and conversion devices should be endowed with higher energy density and power density,and longer lifespan [1].Lithium-ion batteries are now widely used as energy storage devices for portable electronic devices,and they are also very attrac-tive for power tools,electric vehicles and renewable sources of energy.Current dominant electrodes based on intercala-tion reactions have the limitations in the specific charge stor-age capacity,even though they have the advantages of small structure and volume changes and fast Li +transfer rate [2].Recently,Si has attracted much attention as a replacement of graphite (372mAh/g),due to its high theoretical specific capacity of about 4200mAh/g corresponding to the formation of Li 22Si 5alloy [3,4].The alloying process is accompanied with a huge volume expansion (about 400%)and significant struc-ture stress,which cause cracking and pulverization of the Si anode.As a result,electrical contact becomes worse and worse with cycling and eventual capacity fades dramatically.To fight against the volume change,many approaches have0008-6223/$-see front matter Ó2011Elsevier Ltd.All rights reserved.doi:10.1016/j.carbon.2011.01.002*Corresponding author:Fax:+6567791691.E-mail address:chmwuj@.sg (J.Wu).been considered,such as reducing the Si particle size to doz-ens of or even several nanometer[5–7],preparing Si/C com-posite by dispersing the Si particles into a carbon matrix [8,9],and improving the structure of the electrode by using special binder or abundant conductive additives[10,11].All ef-forts were made to buffer the volume change by introducing plenty of free spaces or enhancing the linkage of Si particles.Recently,graphene with superior electrical conductivities, high surface areas of over2600m2/g,excellent thermal prop-erty and mechanical property,has attracted much attention in thefield of materials science[12–15].Perfect graphene is one-atom-thick two-dimensional layers of sp2-hybridized car-bon.Graphene materials can be prepared in many ways.The most popular way is to prepare graphene oxide(GO)first and then obtain graphene sheets by chemical reduction or ther-mal reduction[16–18].Another economic way to get large-scale graphene-based materials is to thermally expand the expandable graphite at a very high heating rate to about 1000°C[19,20].Usually,the time for preparation must be short enough to avoid aggregation and graphitization under so high temperature.In addition,the graphene sheets also could be obtained by exfoliating graphite directly via mechan-ical or electrochemical routes[21,22],or via bottom-up routes, e.g.epitaxial growth[23–25],chemical vapor deposition and solvothermal method[26–28].The properties of graphene sheets usually depend on the route for their preparation.As a novel anode material for the lithium-ion batteries,graphene sheets mostly exhibit a higher reversible capacity than graph-ite[16,29,30].But the cycling performance is not as good as graphite when the graphene sheets are prepared by chemical reduction of GO,which is mainly due to facile stacking of graphene sheets and severe side reactions between graphene and the nonaqueous electrolyte arising from its high surface area and the existence of many defects.However,the graph-ene sheets prepared by thermal reduction of GO,exhibited higher specific capacity and improved cycling performance [31–33].Definitely,the superior electrical conductivity as well as high surface area makes it very promising to prepare some composite materials with excellent performance[34–37]. There are at least two advantages for the graphene-based composites.One is the improved electronic conductivity of the electrode system where graphene plays the role of a highly efficient conductive additive.The other is that the rest in the composite can effectively prevent graphene from stack-ing and also depress the side reactions between graphene and the electrolyte,which is promising to improve the cycling per-formance of the anode.Therefore,the graphene-based com-posites are welcome and very promising for the advanced lithium-ion batteries.Chou and his co-workers prepared graphene/nanosized Si composite by mixing nanosized Si particles with graphene synthesized via a solvothermal method in a mortar,and dem-onstrated that graphene/nanosized Si composite could accommodate large volume change of Si and maintain good electronic contact by graphene[38].But it is difficult to form a homogeneous composite just by mortar,which is believed as a key issue for a composite to exhibit good performances. Recently,Lee and his co-workers reported the graphene/ nanosized Si paper composite as anode for lithium-ion batter-ies[39].But from the X-ray diffraction(XRD)results,the sharp peak at26.4°indicated that there was a large amount of graphite in the composite paper,which could be a possible reason for the poor cycling performance.Since the properties of graphene materials prepared via different ways usually have distinct difference,the performance of the graphene-based composites should also strongly depend on the prepa-ration route of graphene.Here in our investigation,graphene/ nanosized Si composites were prepared via two facile meth-ods with different graphene structures.In thefirst method, stable GO suspension was used to prepare homogeneous graphene/nanosized Si composites,and the existence of–OH on the surface of Si particles is helpful to form the stable composite by chemical interactions with GO.The GO/nano-sized Si composites were then treated at500°C to give ther-mally reduced GO/nanosized Si composites.In the second method,the graphene sheets were obtained from thermal expansion of expandable graphite at1050°C.The expandable graphite is graphite intercalated compound along with slight oxidation,and the obtained graphene sheets areflat and smooth,not like that with many ripples derived from GO. Thus the graphene sheets from the expandable graphite are believed as more excellent conductive components for the graphene/nanosized Si composites which can be prepared by simple mechanical blending.The effect of the graphene sheets with different structures on the cell performance of graphene/nanosized Si in the lithium-ion batteries was investigated.2.Experimental section2.1.Preparation of grapheneIn this investigation,graphene was prepared by two different methods.One is thermal reduction of GO at the temperature of500°C.Firstly,GO was synthesized by a modified Hum-mers’method,just as described in our previous study[40]. Graphite(5g)and NaNO3(2.5g)were mixed with120mL of H2SO4(95%)in a500mLflask within an ice bath.While main-taining vigorous stirring and the ice bath,KMnO4(15g)was added to the suspension in batches.Then the reaction pro-ceeded overnight with stirring at room temperature.After two days,150mL of deionized H2O was slowly added to the pasty with vigorous agitation.Then the reaction had contin-ued at98°C with stirring for24h,before50mL of H2O2 (30%)was added to the mixture.For purification,the mixture was washed by rinsing and centrifugation with5%HCl solu-tion and then deionized H2O for several times.In most cases, the graphene oxide suspension after centrifugation was stored for use with the concentration of about10mg/mL.To prepare graphene for comparison,gray GO powder wasfil-tered from the suspension and dried in vacuum for6h,and then heated at500°C for1h under argon atmosphere.The other method is to quickly heat-treat the expandable graphite(Qingdao Yanxin Graphite Products Co.,Ltd.)at a high temperature of1050°C,according to the literature[20]. Firstly,expandable graphite(200mg)is placed into a1.2m long quartz tube(A3mm)that was sealed at one end.The other end of the quartz tube was closed using a rubber stop-per.A pinhead was inserted through the rubber stopper for1788C A R B O N49(2011)1787–1796gas exchange as follows:evacuate to vacuum followed by venting into argon,which is repeated three times to make the tubefilled with argon.Then the quartz tube was quickly inserted into a tube furnace preheated to1050°C and held in the furnace for30s.After the quartz tube was drawn out from the furnace and cooled to room temperature,the ob-tained expanded graphite was dispersed in ethanol,and then graphene sheets were obtained after ultrasonication for5h.2.2.Preparation of graphene/nanosized Si compositeIn thefirst method,graphene/nanosized Si composites were prepared by putting the nanosized Si powder(50nm,Sig-ma–Aldrich)into the GO suspension(10mg/mL)with stirring for2h,followed by drying at110°C and sintering at500°C for 1h in argon.This kind of graphene/nanosized Si composite was labeled as SG1,SG2and SG3,with the weight ratios of Si particles to GO as1:1,1:2and1:3,respectively.In the sec-ond method,the graphene/nanosized Si composite was pre-pared by mechanically blending the graphene sheets prepared from high temperature(1050°C)thermal expansion with nanosized Si particles under vigorous agitation at the weight ratio of1:2.This composite is denoted as SGE.2.3.General characterizationScanning electron microscope(SEM)measurements were car-ried out on afield emission scanning electron microscope (JEOL-6300F)at5kV.Transmission electron microscope (TEM)measurements were conducted on A JEOL2010FEG microscope at200keV.The TEM samples were prepared by dispensing a small amount of dry powder in ethanol with ultrasonication for1h.Then,one drop of the suspension was dropped on300mesh copper TEM grids covered with thin amorphous carbonfilms.XRD patterns of the composites were measured on a Bruker-AXS D8DISCOVER with GADDS Powder X-ray diffractometer.Thermogravimetric analysis (TGA)was carried out on a TA Instruments2960at a heating rate of10°C/min in air,from which the contents of Si in the composites were determined.2.4.Electrochemical measurementsElectrochemical properties of the products were measured using coin cells.The working electrodes were prepared by casting the slurry consisting of80%active material,10%so-dium carboxymethyl cellulose(CMC),and10%acetylene black onto a copper foil.A Celgard2400microporous polypro-pylene membrane was used as separator.The electrolyte con-sisted of a solution of1M LiPF6in ethylene carbonate(EC)/ diethyl carbonate(DEC)(1:1v/v).Lithium foil was used as counter electrodes.These cells were assembled in an argon-filled glovebox(MBraun Unilab)and galvanostatically cycled between5mV and1.2V on a multi-channel battery cycler (Neware BTS2300,Shenzhen).The ac impedance was also measured at an Autolab electrochemical workstation (PGSTAT302N),with the frequency range and voltage ampli-tude set as100kHz to0.01Hz and10mV,respectively.3.Results and discussion3.1.Morphology and structure of grapheneIn literatures,many methods have been reported for the prep-aration of graphene from GO,which include chemical reduc-tion[16–18],thermal reduction[19,20,31–33],irradiation reduction and hydrothermal reduction[33,41–43].In the chemical reduction of GO,usually some strong reductants such as hydrazine and NaBH4are used.It is an effective route to prepare surface functionalized graphene but the reductant hydrazine is extremely toxic and corrosive.Also,more exactly the obtained graphene should be named as reduced GO,since plenty of functional groups are still residual.When used as anode for lithium-ion batteries,the reduced GO usually exhibited poor cycling performance.But the graphene sheets prepared by thermal reduction shows much higher specific capacity and better cycling performance,mainly because of sufficient removal of oxygen-containing functional groups on the surface of graphene sheets[33].Above all,it is a very facile route for preparing graphene from GO,not like irradia-tion reduction and hydrothermal reduction which need some special apparatus or rigorous conditions.Therefore,the ther-mal reduction of GO is adopted in this investigation.TGA curve of GO(Fig.S1in Supporting information(SI))shows that about50%weight loss appears at500°C in nitrogenflow, which suggests that there is a high content of oxygen in the GO sample and many defects could be left after heating.So the graphene from GO is wrinkle-like as shown in Fig.1c,just similar to the original GO(Fig.1a).Energy dispersive X-ray spectroscopy(EDS)analysis suggests there is still about10% oxygen left in the obtained graphene(Fig.1d).However,when expandable graphite,so-called graphite intercalation com-pounds(GICs),were heated at a certain temperature,the decomposition of the intercalating proponent leads to a dra-matic increase in the dimension perpendicular to the graph-ene plane.This kind of graphene sheets were usuallyflat and smooth,and believed to have few defects.Fig.2shows the SEM(a–c)and TEM(d)images of the graphene sheets from the expandable graphite.The obtained graphene materials have a clear micrometer-sized porous structure with the wall made up of graphene sheets with relativelyflat and smooth surface(Fig.2a and b),which is significantly different from that prepared from GO.The thickness of graphene sheets is estimated to be about10nm or less(Fig.2c).The TEM image (Fig.2d)also shows that this kind of graphene sheets are very flat and thin and the oxygen content in these graphene sheets is about3%based on EDS analysis(Fig.S2in SI).The lower content of oxygen in these graphene sheets than that of ther-mally reduced GO(10%)means that fewer sp2-hydridized car-bon atoms are converted into sp3-hydridized state,which indicates that the two-dimensional carbon structure is less distorted.Therefore,this kind of graphene sheets are not so wrinkle-like as the graphene sheets prepared from GO.All the results above indicate that the graphene sheets derived from expandable graphite could have more intact two-dimen-sional all-sp2-hybridized carbon structure with fewer defects.Fig.3shows the XRD patterns of GO,graphene prepared by thermal reduction of GO and by thermal expansion fromC A R B O N49(2011)1787–17961789expandable graphite,and expandable graphite.The obtained GO just has a broad peak at about9–17°.After thermal reduc-tion,the peak at about10°basically disappears,and another broader and weaker peak at24.6°is detected,which indicates the successful convention from GO to amorphous graphene [40].Compared with GO,expandable graphite has not only a peak at 10°,but also a typically strong peak at26.5°similar to graphite.After thermal expansion at1050°C,the peak at 10°completely disappears,and the peak at26.5°signifi-cantly becomes weak.But this peak(at26.5°)is obviously much stronger than that of the graphene prepared by thermal reduction of GO,which indicates that nano-meter thick few-layer graphene instead of single layer graphene with relatively higher crystallization was obtained after thermal expansion.3.2.Preparation and characterization of graphene/ nanosized Si compositesAs we know,graphene is apt to stack and agglomerate,and also is hydrophobic and indiscerptible in most solvents, which make it difficult to prepare the graphene-based com-posite.However,the hydrophilic GO can be dispersed in waterto form very stable suspension,which can keep stable for sev-eral months.Therefore,using the GO suspension is a conve-nient route to prepare the homogeneous graphene-basedtion in ethanol for above 1h.That is to say,the higher content of graphene sheets is favorable to form stable compos-ite,by restricting the Si particles in the graphene matrix or link-ing more particles on the larger surface of graphene.Fig.6The crystalline structures of composites were investigated by XRD as shown in Fig.7.It is clear that all the composites contain a crystalline Si phase and an amorphous graphene phase,and the content of the amorphous phase increases from SG1to SG3due to the increased amount of graphene in the composites.The sharp peaks at28.5°and47.4°are cor-related to the Si crystalline phase.The peaks at 10°corre-sponding to GO can not be detected in the three composites,which indicates that GO has been completely converted to graphene(broad peak at26.5°).In addition,the broad character of the peak at26.5°also proves that the amor-phous graphene is homogeneously distributed in the compos-ites without stacking or agglomeration.To determine the content of Si in the three composites, TGA measurements were performed in air,where at certain temperature the graphene begins to react with oxygen in air to generate CO2and only Si and negligible SiO x are left alone. As shown in Fig.8,the graphene sheets obtained from the thermal reduction of GO has an onset reaction temperature of about500°C,and the oxidation reaction for graphene with oxygen in air is completed at600°C.Since the oxidation of Si powder in air is not significant at600°C,it is reasonable to determine the content of Si in the composites from the larg-est weight loss in the TGA curves.The weight percentages of Si in the three composites are calculated to be55%for SG1,45%for SG2and40%for SG3.In addition,all the com-posites have higher complete reaction temperature than the pure graphene from GO,which strongly suggests the occurrence of interactions between the graphene sheets and nanosized Si particles.The electrochemical performances of graphene/nanosized Si composites as anode for lithium-ion batteries were evaluated in the coin cell.Fig.9shows the initial charge–discharge volt-age profiles of the cells with SG1,SG2and SG3composites as well as the Si anode.The Si anode exhibits the highest revers-ible capacity of3170mAh/g and coulombic efficiency of75%. For all of the three composites,both the reversible capacity and coulombic efficiency drop with the increasing content of graphene.The main reason for the high irreversible capac-ity is the furious reaction between the graphene with high surface area and the electrolyte.Fig.10displays the cycling performances of the pristine Si and composite anodes.It is obvious that the capacity of Si anode drops rapidly to about 434mAh/g after30cycles,just13%of the initial capacity,con-firming the poor cycling performance of the Si anode,even though the CMC binder was used to improve the perfor-mance.For the composite SG1,the cycling performance is just slightly improved,which could be attributed to the insta-ble structure of this composite.For the stable composites SG2 and SG3,the cycling stabilities have been enhanced signifi-cantly,even though the specific capacities decrease as the re-sult of the introduction of plenty of graphene sheets.After30 cycles,SG2and SG3have the excellent capacity retention of 800mAh/g( 70%of the initial capacity)and730mAh/g(78%of the initial capacity),respectively.It can be seen that capacity retention of the graphene/nanosized Si compos-ites represent a significant improvement over that of the Fig.10–Cycling performance of SG1,SG2and SG3composite anodes.The capacity is calculated on the weight composite (a)and Si (b),respectively.The current density 300mA/g.Fig.11–The initial three charge–discharge voltage profiles the cells with SGE composite anode compared with the anode.The current density is 300mA/g.alloying process becomes tolerable.When the coin cells were disassembled after30cycles,we found that the SGE electrode kept intact,but the pure Si electrode was brittle.This fact could be also helpful to conclude the buffer effect indirectly. Finally and the most importantly,excellent electronic contact is provided by the graphene sheets with high conductivity, especially for those prepared from expandable graphite with fewer defects.Based on the SEM and TEM studies,the nano-sized Si particles are adsorbed on the graphene sheets whichexhibits more excellent enhanced effect on the cycling stabil-ity of Si anode.The graphene sheets can not only alleviate the large volume changes of the lithiation/delithiation of Si,but also improve the conductivity of Si anode,especially for the graphene sheets prepared from expandable graphite.Further studies by using different silicon nanostructures to further improve the performance are underway in our laboratories.AcknowledgmentThis work wasfinancially supported by A*Star SERC Thematic Strategic Research Programme–Sustainable Materials:Com-posites&Lightweights(R-143-000-401-305).Appendix A.Supplementary dataSupplementary data associated with this article can be found, in the online version,at doi:10.1016/j.carbon.2011.01.002.R E F E R E N C E S[1]Tarascon JM,Armand M.Issues and challenges facingrechargeable lithium batteries.Nature2001;414:359–67. 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石墨烯的制备及表征

石墨烯的制备及表征

石墨烯的制备及表征李亮;胡军;班兴明;陈郁勃【摘要】为了得到高性能的石墨烯材料,采用水合肼、茶多酚与抗坏血酸3种不同的还原剂将氧化石墨烯还原制备得到石墨烯.通过红外光谱、X射线衍射、接触角对产物的结构进行表征,采用四探针法测试电导率,循环伏安法和计时电位法测试电化学性能.水合肼、茶多酚与抗坏血酸这3种还原剂都能有效地将氧化石墨烯结构中的亲水基团去除,得到疏水的石墨烯.通过比较3种还原剂制备的石墨烯的电化学性能,发现通过茶多酚还原得到的石墨烯的导电性能最好,当电流密度为3 A/g时,茶多酚还原得到的石墨烯电容性能达到609 F/g,保持率达到87.71%.这表明由茶多酚还原得到的石墨烯具有更为优良的电化学性能.【期刊名称】《武汉工程大学学报》【年(卷),期】2014(036)008【总页数】5页(P46-50)【关键词】石墨烯;茶多酚;电化学性能【作者】李亮;胡军;班兴明;陈郁勃【作者单位】武汉工程大学材料科学与工程学院,湖北武汉430074;武汉工程大学材料科学与工程学院,湖北武汉430074;武汉工程大学材料科学与工程学院,湖北武汉430074;武汉工程大学材料科学与工程学院,湖北武汉430074【正文语种】中文【中图分类】O633石墨烯因其优异的电学﹑光学和机械性能被科学界称作奇迹材料[1-2],吸引了众多科学家和大量科研资金的投入,石墨烯的发现更是获颁 2010年度诺贝尔物理学奖[3-5].石墨烯最常用的制备方法是氧化还原法,步骤是先将石墨氧化成氧化石墨,再将氧化石墨剥离成氧化石墨烯,最后将氧化石墨烯还原成石墨烯.过程中常用到的氧化剂为高锰酸钾,高氯酸等,常用的还原剂为水合肼,联氨等.本文分别采用传统的水合肼,茶多酚,抗坏血酸作为还原剂,将氧化石墨烯还原成石墨烯,并将不同还原剂还原得到的石墨烯产物的电化学性能进行对比研究.1 实验部分1.1 石墨烯的制备方法a.水合肼作为还原剂:取一定量氧化石墨烯放入30 mL蒸馏水中,超声分散30 min后加水稀释至100 mL.用25%的氨水调节pH=10.向氧化石墨烯悬浮液中加入2 mL水合肼,使其混合均匀.加热至90 ℃,搅拌5 h.将所得产物过滤,用蒸馏水洗涤,真空60 ℃干燥24 h.密封保存,备用.b.茶多酚作为还原剂:取2 g绿茶粉加入到100 mL蒸馏水中,煮沸.过滤掉剩余茶叶粉末,绿茶水备用.取一定量氧化石墨烯加入到上述绿茶水中,加热至90 ℃,搅拌10 h.将产物过滤,用蒸馏水洗涤,真空60 ℃干燥24 h.密封保存,备用.c.抗坏血酸作为还原剂:取一定量氧化石墨烯放入30 mL蒸馏水中,超声分散30 min后加水稀释至100 mL.取一定量维生素C片研磨成粉末,加入氧化石墨烯悬浮液中,搅拌使其混合均匀.加热至90 ℃,搅拌24 h.将所得产物过滤,用蒸馏水洗涤,真空60 ℃干燥24 h.密封保存,备用.1.2 石墨烯的表征红外光谱(FT-IR)测试采用TJ270红外光谱仪,X射线衍射(XRD)测试采用BrukerD8 X射线粉末衍射仪.电化学性能测试是以1 moL/L KCl溶液为电解液,将产物固定在铂盘电极上作为工作电极,铂丝为对电极,Ag/AgCl电极为参比电极的三电极体系中进行.2 结果讨论与分析2.1 红外光谱分析(FT-IR)图1为采用不同还原剂还原氧化石墨制备的石墨烯的红外光谱图.从图中可以看出不同还原剂制备的石墨烯光谱图均在3 450 cm-1和1 632 cm-1处出现吸收峰,这与石墨原料的红外光谱图基本一致[6],而未出现氧化石墨中一些极性基团的吸收峰,说明在还原剂的作用下,石墨烯中的含氧官能团大大减少,还原效果较好. 注:(a)水合肼,(b)茶多酚,(c)抗坏血酸图1 采用不同还原剂制备的石墨烯的红外光谱图 Fig.1 FTIR spectrum of graphene2.2 X-射线衍射分析(XRD)图2为产物的X射线衍射谱图,图中在2θ角为22.4°和7.2°出现了衍射峰,22.4°处的衍射峰对应石墨的(002)晶面,说明部分氧化石墨中的含氧官能团被除去了,同时说明石墨烯微晶排列较为无序或者存在较大的晶格缺陷,无法回到有序排列的状态.7.2°可能对应未氧化完全的氧化石墨(001)晶面的衍射峰.注:(a)水合肼,(b)茶多酚,(c)抗坏血酸图2 采用不同还原剂制备的石墨烯的XRD图 Fig.2 XRD patterns of graphene2.3 电导率表1为3种不同还原剂制备的石墨烯的电阻率和电导率数据.石墨在强氧化剂的作用下,其结构中的sp2结构和共轭π键被破坏,形成羟基,羧基及环氧基等极性官能团,形成sp3杂化的氧化石墨.结构层中的共轭π键被破坏,导致氧化石墨是绝缘体.氧化石墨经过还原剂还原后,其结构中的极性官能团被除去,恢复表面共轭结构,从而恢复期导电性.图中数据也说明了这一点,石墨烯(茶多酚)的电导率为2.604 S/cm,其导电性最好.表1 3种不同还原剂制备的石墨烯的电导率数据Tabel 1 Conductivities of graphene prepared by three different reducing agents样品电阻率/(Ω/cm)电导率/(S/cm)石墨烯(水合肼)0.5961.678石墨烯(茶多酚)0.3842.604石墨烯(抗坏血酸)0.472.1282.4 接触角从表2中可以看出,3种还原剂制备的石墨烯的接触角都大于90°,说明产物是完全疏水的,氧化石墨烯GO层状结构中含有大量的极性基团,例如羟基,羧基,羰基以及环氧基等,大大增强了GO的亲水性能,所以GO是完全溶于水的,可见还原过程GO结构中极性基团还原了,得到了疏水的层状石墨烯.表2 3种不同还原剂制备的石墨烯的接触角数据Tabel 2 Water contact angles of graphene prepared by three different reducing agents样品接触角/(°)石墨烯(水合肼)123.87石墨烯(茶多酚)92.62石墨烯(抗坏血酸)101.992.5 电化学性能测试石墨烯是由碳原子紧密堆积成的准二维层状结构物质,具有优异的电学性质,光学性质以及力学性质等.其结构中未成键的电子可以在晶格中自由移动,使其具有很好的导电性和电容性质,本文通过循环伏安法和恒电流充放电法对石墨烯的电容性质进行研究.图3为通过不同还原剂(分别为水合肼,茶多酚和抗坏血酸)还原氧化石墨制备石墨烯的循环伏安图,扫描速率分别为a:0.01 V/s,b:0.02 V/s,c:0.05 V/s,d:0.1 V/s.石墨烯(水合肼)的循环伏安曲线没有明显的氧化还原峰,并且曲线呈现近似的矩形形状,石墨烯(茶多酚)的循环伏安曲线有微弱的氧化还原峰,但是曲线整体也呈现矩形形状,对于石墨烯(抗坏血酸)曲线呈现规则的矩形,没有明显的氧化还原峰,说明3种还原剂制备的石墨烯材料都具有很好的电容性质.从图3(Ⅳ)中可以看出,石墨烯(水合肼)的循环伏安图面积最小,说明其电容最小,其次电容较小的是石墨烯(抗坏血酸),循环伏安面积最大的是石墨烯(茶多酚),说明其比电容最大,电化学性能最好.(Ⅰ)水合肼(Ⅱ)茶多酚(Ⅲ)抗坏血酸(Ⅳ)3种还原剂图3 不同还原剂合成石墨烯的循环伏安图Fig.3 Cyclic voltammograms of graphene reduced由图4(Ⅰ)、(Ⅱ)、(Ⅲ)中可以看出,3种石墨烯材料的充放电曲线呈现良好的线性关系,并且对称性良好,说明这3种石墨烯材料的充放电可逆性良好,具有良好的电容特性.当电流密度为3 A/g时,根据计算石墨烯(茶多酚)的电容性能最好,其比容量最大,值为609 F/g,石墨烯(抗坏血酸)最大比容量为237.15 F/g,石墨烯(水合肼)的最大比容量为82.5 F/g,这也与循环伏安图计算的结果相一致.说明石墨烯(茶多酚)最适合做超级电容器电极材料.(Ⅰ)水合肼(Ⅱ)茶多酚(Ⅲ)抗坏血酸图4 不同还原剂合成石墨烯的充放电图Fig.4 Constant current charge/discharge curves图5为根据充放电图计算的石墨烯比电容与电流密度关系图.从图5可以看出随着电流密度的增大,比容量值逐渐减小.主要是因为在电流较小的情况下,石墨烯内部较深的孔洞都能发挥双电层电容的性质,使整个电路中的阻抗较小;当电流升高时,由于受扩散控制,石墨烯内部较深的孔不能被完全利用,电路中的阻抗增加,导致比电容下降.图5 根据充放电图计算的石墨烯比电容Fig.5 Constant currentcharge/discharge curves of graphene图6为石墨烯(水合肼)(a)石墨烯(抗坏血酸)(b)和石墨烯(茶多酚)(c)的循环次数图,从图中可以看出3种还原剂制备的石墨烯材料的循环性能很好.石墨烯(茶多酚)的初次放电容量为480.25 F/g,前200圈的比容量有相对较大幅度的损耗,损耗率约为4.14%,循环1 000圈后的放电比容量为451.33 F/g,总容量损耗率为6.02%,说明制备的石墨烯(茶多酚)的稳定性很好,具有很好的循环性能.而石墨烯(抗坏血酸)的初次放电容量为130.7 F/g,循环1 000圈后,放电比容量为114.63 F/g,总容量损耗为12.29%,石墨烯(水合肼)的初次放电比容量为80.4 F/g,循环1 000圈后,放电比容量为70.125 F/g,总容量损耗为12.77%.说明制备的石墨烯材料的电化学性能很好,稳定性良好,具有较好的循环性能.注:(a)水合肼,(b)抗坏血酸,(c)茶多酚图6 还原的石墨烯的循环圈数-电容保持率曲线比较图Fig.6 Comparison of cycle number and retention rate of capacitance of graphene3 结语分别用水合肼,抗坏血酸和茶多酚还原得到石墨烯,并分别测试了它们的性能,茶多酚还原得到石墨烯的导电性能最好,电容性能也最好.石墨烯具有很好的导电性,化学稳定性及热力学稳定性,有望被用于电子器件构造.致谢此研究受到国家自然科学基金委员会资助和武汉工程大学资金资助,特表感谢!参考文献:[1] LI D,MULLERr M B,GILJE S.Processable aqueous dispersions of graphene nanosheets[J].Nat Nano,2008,3:101-105.[2] JUNG I,DIKIN D A,PINER R D.Tunable electrical conductivity ofindividual graphene oxide sheets reduced at low temperatures[J].Nano Lett,2008,8:4283-4287.[3] GUO S J,DONG S J,WANG E K.Polyaniline/Pt hybrid nanofibers:high-efficiency nanoelectrocatalysts for electrochemicaldevices[J].Small,2009,5:1869-1876.[4] WANG H L,ROBINSON J T,LI X L.Solvothermal reduction of chemically exfoliated graphene sheets[J].J Am Chem Soc,2009,131:9910.[5] CHEN G H,WENIG W G,WU D.PMMA/graphite nanosheets and its conducting properties[J].Eur Polym J,2003,39:2329-2335.[6] CHANDRA S,BAG S,BHAR R,et al.Sonochemical synthesis and application of rhodium-graphene nanocomposite[J].J Nanoparticle Res,2011,13,2769-2777.。

石墨烯增强铝基纳米复合材料(Graphene reinforced alumina nanocomposites)

石墨烯增强铝基纳米复合材料(Graphene reinforced alumina nanocomposites)

石墨烯增强铝基纳米复合材料(Graphene reinforced aluminananocomposites)Graphene nanometers are two-dimensional materials of the thickness of a single atomic layer made up of sp2 hybrid carbon atoms, showing a series of unusual physical properties. In 2004, Novoselov and other [1] used tape stripping method to prepare graphene nano-chip samples and characterize their microstructure and physical properties. Graphene nano piece because of its special two-dimensional structure, caused the academic circles study physics, chemistry and materials the great interest of scholars, the basic research and engineering application research on graphene become a research hotspot in recent years [2].Graphene is the most tenacious, conductive and heat-conducting material found to date. To make graphene meet engineering application state as soon as possible, the European Union in 2012 to start the graphene flagship technology project [3], the United States also vigorously inputs, and in the application of graphene as a super capacitor and has made breakthrough progress [3]. The wet chemical reduction method is easy to realize the bulk preparation of graphene nanoparticles, and the obtained graphene has better hydrophilic and single dispersibility, which is the ideal composite materialnano-filler [4].Due to the high strength of graphene, its tensile strength can reach up to 1060GPa and how to use it to improve the strength of composite materials becomes a research hotspot. There have been reports of graphene nanoparticles enhanced with [5] andthe ceramic material, [6]. The tensile strength of the graphene nano-chip with 0.7 % quality fraction in polyvinyl alcohol increased by 76%. The bending strength of Al2O3 ceramic matrix with 0.78% of the volume fraction was increased by 30.75% while the fracture strength increased by 27.20% [6]. But no reports of graphene-enhanced metal matrix composites have been reported.Aluminum alloy has low density, high strength and good ductility. It has been widely used in aviation, aerospace and other fields. As a structural material, how to improve the strength of aluminum alloy has been the main direction of its researchers. Now, use change alloy smelting method, control components, adjustment methods such as heat treatment and the deformation process in further improving of aluminium alloy performance is difficult to have a breakthrough, aluminum matrix composites arises at the historic moment. In the aluminum alloy with graphite, silicon carbide, boron carbide and carbon nano-controlled preparation of aluminum matrix composite materials to improve the strength of alloy becomes the research direction of the scholars. However, the enhancement effect was not satisfactory, and the plasticity of the material decreased significantly [7-10]. Graphene nano has high strength, large specific surface area and good elongation, add it to the aluminum alloy aluminum matrix composites, which was formed in May is a good choice for improve the strength of aluminum alloy problems.This work adopts the ball mill mixing powder, hot isostatic pressing (HIP) and hot extrusion, the method of preparation of aluminum alloy material, the microstructure of aluminummaterial alloy structure and mechanical properties were characterized and analyzed graphene nano enhanced toughening mechanism.Experiment materials and methods1.1 preparation of aluminum alloy powderAluminum alloy powders (al-mg-cu) were prepared by tightly coupled aerosol, and the content of magnesium and copper was 1.5% and 3.9% respectively. Atomization medium for nitrogen (99.99%), atomizing chamber pressure is 800 pa, the temperature is 800 ℃.1.2 preparation of graphene nanoparticlesGraphene nanoparticles were prepared from natural graphite with a purity of 99.9%.With the improved Hummers method preparation of graphene oxide nano powder, with hydrazine hydrate reduction of 24 h under 95 ℃, get a few pieces of graphene nano atomic layer thickness, preparation method and the literature [11].1.3 preparation process of aluminum alloy and aluminum base alloy(1) dispersing 3g graphene nanometer fragments into 3L anhydrous ethanol, the ultrasonic oscillation 1h was obtained with a homogeneous black graphene solution; (2) will be 1 kg Al - Mg - Cu alloy powder were added to the 3 l graphene solutioncontaining 0.3% (preparation of graphene aluminium matrix composites) and 3 l (compared to aluminum alloy) preparation of anhydrous ethanol, encapsulated in ball mill pot ball mill for 24 h; (3) the ball mill of the pulp into a beaker, moved to 80 ℃ water bath pot, dry processing under the mechanical agitation to paste to dry state, moved to the vacuum drying box thoroughly dry processing; (4) the dry the powder into cylindrical aluminum coating, vacuum pressure and vacuum to 1 x 10-2 pa, after heating to 300 ~ 400 ℃, the heat preservation 2 h, after cooling to room temperature welding sealing; (5) will seal good aluminum coating on 480 ℃ / 150 mpa / 2 h hot isostatic pressing process; (6) after hot isostatic pressing block in 400 ~ 480 ℃ in hot extrusion, extrusion ratio of 10:1, extrusion rate of 3 mm/s, extrusion pressure is 300 kn; (7) to the bar for 30 min solid solution treatment + 495 ℃ / 96 h natural aging.1.4 microstructure characterization and mechanical property testingThe microstructure of materials was observed by optical microscope (Leica), field emission scanning electron microscope (FESEM, JEOL jsm-7001) and transmission electron microscope (TEM, FEI Tecnai G2 F20). The crystal structure of the material was characterized by X-ray diffractometer (XRD). Test the tensile properties on the universal stretching machine, the test temperature is room temperature, the loading direction is in line with the direction of hot extrusion, and the size of the tensile sample workspace is phi 5mm x 2.5mm.2 results and discussion2.1 structure of micronano powderThe aluminum alloy powder is a spherical or ellipsoidal particle with a diameter of d < 40 mu m. Graphene nanoparticles are feathery, translucent and thin, and radial dimensions are micrometers, with typical corrugated structure characteristics. The aluminum alloy powder is the surface core cubic crystal structure, and no impurities like Al4N3 or Al2O3 have been seen, indicating that the aluminum alloy has not reacted with O and N elements in the process of atomization. Graphene nano piece of XRD spectrum has a wide of the near 26 ° diffraction peak, that graphene nano powder is very small, the reports and literature [12] the high quality of graphene nano results are same. Ball mill, aluminum alloy by spherical particles into flake structure, chip is not more than 100 microns in diameter, the thickness of a few microns, graphene sheet attached to the aluminum alloy nanoparticles surface, make the aluminum alloy particles with graphene nano piece has great interface, and fold structure of graphene nano piece be well preserved.2.2 microstructure of alkylene alloyAfter the heat treatment of aluminum alloy, the microstructure of the microstructure was uniform and fine, the metallurgical quality was good, and the defects of metallurgy were not obvious. The aluminum alloy has a lamellar structure, and the thickness of the laminar is about 3 ~ 8 micrometers. The diameter of the laminar is about 20 ~ 40 microns.HIP + hot extrusion process does not destroy the flaky structure of aluminum alloy powder. The axial microstructure retains the characteristics of extrusion deformation. The tissue is elongated to over 100 mu m in the direction of deformation, and the thickness is a few microns. The authors first observed the morphology of graphene nanoparticles in graphene reinforced metal nanocomposites in TEM. Graphene nano malleable aluminum alloy substrate with the good, the two had a great combination of interface, clearly see the graphene nano 2 d thin film shape and fold structure characteristics, observed area of graphene nano size than 2 microns, that graphene nano piece without rupture in the aluminum alloy material alloy substrate. The ball mill, hot isostatic pressing, hot extrusion and after solution heat treatment and so on a series of crafts, graphene nano retains the original organizational structure characteristics, presumably it still maintained the original high tensile strength.The mechanical properties of aluminum alloy and aluminum alloyAdd graphene nano piece can improve the aluminum material yield strength and tensile strength of alloy, and the elongation is improved, the increase in the second phase in the study of metal matrix composites is found for the first time. The tensile strength of graphene nanoparticles increased from 364MPa to 455MPa and increased by 25%. At the same time, the yield strength of the alloy is increased sharply, from 204 mpa to 322 mpa, increase up to 58%, the increase of the amplitude is superior to other materials reinforced aluminum matrix composites enhanced effect [13]. At the same time, it can be seen in graphene nano film, not like SiC [7, 8] or [10] carbonnanotubes reinforced aluminum matrix composites plasticity declined significantly, aluminum alloy elongation did not decline, also slightly increases, increased to 11.80% from 11.03% alloy. Add graphene nano piece of little effects on the elastic modulus of the aluminum alloy, compared with the experimental data for particles or carbon fiber reinforced, graphene nano piece of the action mechanism of the metal substrate are different from ordinary carbon fiber or particles.2.4 analysis of toughening mechanism of graphene nano-chipThe microstructure of the tensile fracture of the aluminum base alloy rod is typical of the ductile fracture, the toughness and tearing edges are even and small, the surface of the ridges can be clearly observed with graphene nanoparticles. Compared with other reinforcing materials, graphene nanoparticles have different toughening mechanisms for aluminum alloy matrix. First of all, by TEM observation shows graphene nano piece and the combination of the aluminum alloy matrix formed a good interface, and graphene nano has * * specific surface area, which effectively prevents the heat treatment process of aluminum alloy grain grew up, at the same time the graphene nano/aluminum alloy combined interface can effectively prevent the dislocation movement in the process of deformation and crack propagation. Second, the thickness of the graphene are only a few nanometers, the spacing between aluminum alloy grain size is very small, it is more advantageous to the external force from the aluminum substrate is transferred to the graphene nano film, so the ultra-high strength of graphene nano piece could be directly used, so as to realize the high strengthof materials. Finally, because the graphene nano large specific surface area, easy to form a great combination of excellent performance of aluminum alloy matrix interface, and graphene nano piece of fold structure, make the aluminum alloy in the process of stress,Graphene nanoparticles have a process of flattening and refracture, and the graphene nanometer itself has good plasticity, so the plasticity of the material is very good. This gives a wide application prospect for the alkylene alloy material. However, the structure of graphene folds determines the good plasticity of alkylene alloy. Although graphene nano reinforced aluminum alloy, the mechanical properties of nanocomposite increase significantly, but there are many unknown need further exploration, then we will further expand the graphene nano enhanced toughening mechanism of in-depth study.3 conclusion(1) the new aluminum base alloy material was successfully prepared by means of the static pressure + extrusion of ball grinding powder + heat. The introduction of graphene nanoparticles did not affect the metallurgical forming of aluminum alloy.(2) the graphene nanoparticles are evenly distributed in the aluminum alloy matrix and formed a good interface with the aluminum alloy matrix. The graphene nanoparticles in alkylene alloy materials retain a good original structure.(3) the addition of 0.3 % of graphene nanoparticles significantly improved the strength of aluminum alloy. The yield strength increased from 204 MPa to 322 MPa, up to 58%. The tensile strength increased from 364 MPa to 455 MPa, an increase of 25%, while the shaping was not reduced.(4) based on the two-dimensional graphene nano, the fold structure and a good combination with the aluminum alloy matrix interface characteristics, and puts forward the fine-grain strengthening, * * interface strengthening and shear stress transfer strengthening way.(5) these results indicate that graphene nanoparticles are the ideal metal matrix composite nanoparticles.。

南京先丰纳米材料科技有限公司南京...

南京先丰纳米材料科技有限公司南京...

先丰客户发表文章Publications Featuring XFNANO Graphene, Carbon Nanotubes and Others.此统计数据日期截至2014年02月22日,由于文章较多,此处仅统计先丰客户英文文章且直接引用先丰公司英文名称”Nanjing XFNANO Materials Tech Co.,Ltd”,截至到现在已经有超过500篇文章(包括英文/中文/专利)署名先丰纳米,我司现整理出242篇高质量英文文章,总影响因子超过1000,平均影响因子3.993。

其中2014年前两个月客户已经发表高质量英文文章50篇;2013年客户发表200多篇高质量的英文文章,其中有JACS,AM,AFM,CC,JPCC,JMC 等等,值得骄傲的是这些材料都是实验的主体材料,在国际上宣传了”XFNANO”,为先丰带来了声誉和很多国际客户,这也说明了国外杂志对我司的认可,也为后来客户发表文章直接引用我司提供了很多方便和印证。

先丰纳米公司从09年发展至今,一直专注于提供高质量的石墨烯产品。

我司现摘录部分英文文章如下,一是为宣传我司;二是也是为广大客户更信任我司产品,启迪客户科研思路,用好我司提供的材料;三是推动我司继续前进,履行“先进纳米材料制造商以及技术服务商”的宗旨。

另外我司代理的产品,国内客户发表文章的也有上百篇,由于署名不是我司,较难查找,我司以后会摘录几篇影响因子较高的客户文章,同时也欢迎客户反馈文章发表信息。

反馈一篇我司此列表中未摘录的英文文章包括会议论文奖励一百元,作者亲自反馈的除奖金外,购买我司产品一律享受VIP待遇。

以下为影响因子和文章概述,经我司计算,客户以我司名义发表SCI文章影响因子平均高达:3.993影响因子(Impact Factor)概述:大于等于10:期刊:Advanced Materials 2013 影响因子:14.829文章Vertically Oriented Graphene Bridging Active-Layer/Current-Collector Interface for Ultrahigh Rate Supercapacitors期刊:Advanced Functional Materials 2012 影响因子:10.179文章: Layered H2Ti6O13-Nanowires: A New Promising Pseudocapacitive Material in Non-Aqueous Electrolyte南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China大于等于6:期刊:Nanoscale 2014 影响因子:6.233文章:Vertical junction photodetectors based on reduced graphene oxide/silicon Schottky diodes.期刊:Biomaterials 影响因子:7.604文章:Inhibitory effect of silver nanomaterials on transmissible virus-induced host cell infections.期刊:Biosensors and Bioelectronics 2014 影响因子: 5.437文章A general strategy to prepare homogeneous and reagentless GO/lucigenin&enzyme biosensors for detection of small biomolecules期刊:Biosensors and Bioelectronics 2014 影响因子: 5.437文章Simultaneous electrochemical detection of cervical cancer markers using reduced graphene oxide-tetraethylene pentamine as electrode materials and distinguishable redox probes as labels期刊:Biosensors and Bioelectronics 2014 影响因子: 5.437文章Electrochemical determination of cefotaxime based on a three-dimensional molecularly imprinted film sensor期刊:Biosensors and Bioelectronics 2014 影响因子: 5.437文章Femtomole level photoelectrochemical aptasensing for mercury ions using quercetin–copper(II) complex as the DNA intercalator期刊:analytical chemistry 2014 影响因子: 5.695文章 A Homogeneous Signal-On Strategy for the Detection of rpoB Genes of Mycobacterium tuberculosis Based on Electrochemiluminescent Graphene Oxide and Ferrocene Quenching期刊:Biosensors and Bioelectronics 2014影响因子: 5.437文章Investigation of the effect of phytohormone on the expression of microRNA-159a in Arabidopsis thaliana seedlings based on mimic enzyme catalysis systematic electrochemical biosensor期刊:Biosensors and Bioelectronics 2014 影响因子: 5.437文章Target-induced electronic switch for ultrasensitive detection of Pb2+ based on three dimensionally ordered macroporous Au–Pd bimetallic electrode期刊:Biosensors and Bioelectronics 2014 影响因子: 5.437文章Electrochemical immunoassay for procalcitonin antigen detection based on signal amplification strategy of multiple nanocomposites期刊:Carbon 2014 影响因子: 5.868文章Enhanced nonlinear optical and optical limiting properties of graphene/ZnO hybrid organic glasses期刊:Carbon 2014 影响因子: 5.868文章Reductive dechlorination of hexachloroethane by sulfide in aqueous solutions mediated by graphene oxide and carbon nanotubes文章Facile and novel electrochemical preparation of a graphene–transition metal oxide nanocomposite for ultrasensitive electrochemical sensing of acetaminophen and phenacetin期刊:Biomaterials 2014 影响因子:7.604文章Graphene oxide doped conducting polymer nanocomposite film for electrode-tissue interface 期刊:Nanoscale 2014 影响因子:6.233南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China文章Fabrication and application of flexible graphene silk composite film electrodes decorated with spiky Pt nanospheres期刊:Journal of Materials Chemistry A 2014 影响因子: 6.101文章Binder-free phenyl sulfonated graphene/sulfur electrodes with excellent cyclability for lithium sulfur batteries期刊:Journal of Materials Chemistry A 2014 影响因子: 6.101文章A 3D hierarchical porous α-Ni(OH)2/graphite nanosheet composite as an electrode material for supercapacitors期刊:Chemical Communications 2012 影响因子:6.169文章: Graphene electrochemical supercapacitors: the influence of oxygen functional groups期刊:Advanced Functional Materials 2013 影响因子:9.765文章Highly Electron Transparent Graphene for Field Emission Triode Gates期刊:Biomaterials 2013 影响因子:7.604文章Nanodiamonds-mediated doxorubicin nuclear delivery to inhibit lung metastasis of breast cancer期刊:Nanoscale 2013 影响因子:6.233期刊:Nanoscale 2013 影响因子: 6.233文章Using ruthenium polypyridyl functionalized ZnO mesocrystals and gold nanoparticle dotted graphene composite for biological recognition and electrochemiluminescence biosensing期刊:Nanoscale 2013 影响因子: 6.233文章One-pot, water-based and high-yield synthesis of tetrahedral palladium nanocrystal decorated graphene期刊:Journal of Materials Chemistry A 2013影响因子:6.101文章Graphene-wrapped silver/porous silicon composite with enhanced electrochemical performance for lithium-ion batteries期刊:Biomaterials 2013 影响因子:7.604文章:Protein-assisted fabrication of nano-reduced graphene oxide for combined in vivo photoacoustic imaging and photothermal therapy大于等于5:期刊:Biosensors and Bioelectronics 2014 影响因子:5.437文章:Mild and Novel Electrochemical Preparation of β-Cyclodextrin/Graphene Nanocomposite Film for Super-Sensitive Sensing of Quercetin期刊:Anal. Chem. 2014 影响因子:5.695文章:In Situ Growth of Porous Platinum Nanoparticles on Graphene Oxide for Colorimetric Detection of Cancer Cells期刊:Journal of Materials Chemistry A 2013 影响因子:5.968文章: Highly loaded CoO/graphene nanocomposites as lithium-ion anodes with superior reversible capacity期刊:Journal of Materials Chemistry 2012 影响因子:5.968文章: Graphene/porous cobalt nanocomposite and its noticeable electrochemical hydrogen storage ability at room temperature南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China期刊:Journal of Materials Chemistry 2012 影响因子:5.968文章: Graphene/polyaniline nanorod arrays: synthesis and excellent electromagnetic absorption properties期刊:Journal of Materials Chemistry 2012 影响因子:5.968文章: A novel Fe3O4–graphene–Au multifunctional nanocomposite: green synthesis and catalytic application期刊:Journal of Materials Chemistry 2013 影响因子:5.968文章: Enhanced photovoltaic performance of dye-sensitized solar cells based on TiO2 nanosheets/graphene composite films期刊:Journal of Materials Chemistry A 2013 影响因子:5.968文章: Stabilization of NaZn(BH4)3via nanoconfinement in SBA-15 towards enhanced hydrogen release期刊:Applied Catalysis B: Environmental 2012 影响因子:5.625文章: Enhanced photocatalytic activity of hierarchical macro/mesoporous TiO2–graphene composites for photodegradation of acetone in air期刊:Biosensors and Bioelectronics 2012 影响因子:5.602文章: Acetylcholinesterase biosensor based on chitosan/prussian blue/multiwall carbon nanotubes/hollow gold nanospheres nanocomposite film by one-step electrodeposition期刊:Biosensors and Bioelectronics 2012 影响因子:5.602文章: Label-free colorimetric sensor for ultrasensitive detection of heparin based on color quenching of gold nanorods by graphene oxide期刊:Biosensors and Bioelectronics 2012 影响因子:5.602文章: Direct electron transfer glucose biosensor based on glucose oxidase self-assembled on electrochemically reduced carboxyl graphene期刊:Biosensors and Bioelectronics 2012 影响因子:5.602文章: DNA electrochemical biosensor based on thionine-graphene nanocomposite期刊:Carbon 2012 影响因子:5.378文章: Synthesis of electrochemiluminescent graphene oxide functionalized with a ruthenium(II) complex and its use in the detection of tripropylamine期刊:Carbon 2013 影响因子: 5.868文章Preparation and tribological properties of TiAl matrix composites reinforced by multilayer graphene期刊:Biosensors and Bioelectronics 2013 影响因子: 5.437文章Simple Approach for Ultrasensitive Electrochemical Immunoassay of Clostridium difficile toxin B Detection期刊:Biosensors and Bioelectronics 2013 影响因子: 5.437文章Target-induced Electronic Switch for Ultrasensitive Detection of Pb2+ Based on Three Dimensionally Ordered Macroporous Au-Pd Bimetallic Electrode期刊:Biosensors and Bioelectronics 2014 影响因子: 5.437文章Direct electron transfer of glucose oxidase and biosensing for glucose based on PDDA-capped gold nanoparticle modified graphene/multi-walled carbon nanotubes electrode南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China期刊:Analytical chemistry 2013 影响因子: 5.695文章Graphene Oxide–Peptide Nanocomplex as a Versatile Fluorescence Probe of Protein Kinase Activity Based on Phosphorylation Protection against Carboxypeptidase Digestion期刊:Lab on a Chip 2013 影响因子: 5.697文章On-chip selective capture of cancer cells and ultrasensitive fluorescence detection of survivin mRNA in a single living cell期刊:Environmental Science & Technology 2013 影响因子:5.257文章Graphene and g-C3N4 Nanosheets Cowrapped Elemental α-Sulfur As a Novel Metal-Free Heterojunction Photocatalyst for Bacterial Inactivation under Visible-Light期刊:Biosensors and Bioelectronics 2014 影响因子:5.437文章A highly sensitive and wide-ranged electrochemical zinc(II) aptasensor fabricated on core–shell SiO2-Pt@meso-SiO2期刊:Analytical chemistry 2013 影响因子:5.695文章Electrochemiluminescent Quenching of Quantum Dots for Ultrasensitive Immunoassay through Oxygen Reduction Catalyzed by Nitrogen-Doped Graphene-Supported Hemin期刊:Biosensors and Bioelectronics 2013 影响因子:5.437文章A novel ionic liquid stabilized molecularly imprinted optosensing material based on quantum dots and graphene oxide for specific recognition of vitamin E期刊:APPLIED MATERIALS & INTERFACES 2013 影响因子:5.008文章Dye-Sensitization-Induced Visible-Light Reduction of Graphene Oxide for the Enhanced TiO2 Photocatalytic Performance期刊:Biosensors and Bioelectronics 2014 影响因子:5.437文章Graphene oxide as nanogold carrier for ultrasensitive electrochemical immunoassay of Shewanella oneidensis with silver enhancement strategy期刊:ACS APPLIED MATERIALS & INTERFACES 2013 影响因子:5.008文章Graphene-Wrapped CoS Nanoparticles for High-Capacity Lithium-Ion Storage期刊:Biosensors and Bioelectronics 2013 影响因子:5.437文章Combination of cascade chemical reactions with graphene–DNA interaction to develop new strategy for biosensor fabrication期刊:Biosensors and Bioelectronics 2013 影响因子:5.437文章 A graphene oxide-based FRET sensor for rapid and sensitive detection of matrix metalloproteinase 2 in human serum sample期刊:Biosensors and Bioelectronics 2014 影响因子:5.437文章Ultrasensitive photoelectrochemical immunoassay of indole-3-acetic acid based on the MPA modified CdS/RGO nanocomposites decorated ITO electrode期刊:Environ. Sci. Technol 2013 影响因子:5.228文章:Graphene Oxide-Facilitated Reduction of Nitrobenzene in Sulfide-Containing Aqueous Solutions期刊:Journal of Materials Chemistry A 2013 影响因子:5.968文章:Nitrogen-doped mesoporous carbons originated from ionic liquids as electrode materials for supercapacitors南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China期刊:Nanoscale 2013 影响因子:5.914文章:Label-free Electrochemical Impedance Genosensor Based on 1-Aminopyrene/Graphene Hybrids 期刊:Chemistry - A European Journal 2013 影响因子:5.925文章:Three-Dimensional Hierarchical Architectures Constructed by Graphene/MoS2 Nanoflake Arrays and Their Rapid Charging/Discharging Properties as Lithium-Ion Battery Anodes期刊:Chemistry - A European Journal 2013 影响因子:5.925文章:Structural Engineering for High Energy and Voltage Output Supercapacitors期刊:Chemistry - A European Journal 2013 影响因子:5.925文章: Label-Free Detection of MicroRNA: Two-Step Signal Enhancement with a Hairpin-Probe-Based Graphene Fluorescence Switch and Isothermal Amplification大于等于4:期刊:Analytica Chimica Acta 2014 影响因子:4.378文章:In situ synthesis of ceria nanoparticles in the ordered mesoporous carbon as a novel electrochemical sensor for the determination of hydrazine.期刊:Journal of Power Sources 2014 影响因子:4.675文章:Three-dimensional macroporous anodes based on stainless steel fiber felt for high-performance microbial fuel cells.期刊:Journal of Power Sources 2014 影响因子:4.675文章:Sulfonated poly(ether ether ketone)/mesoporous silica hybrid membrane for high performance vanadium redox flow battery期刊:Journal of Power Sources 2012 影响因子:4.951文章: Carbon felt supported carbon nanotubes catalysts composite electrode for vanadium redox flow battery application期刊:Journal of Power Sources 2012 影响因子:4.951文章: A new method for fabrication of graphene/polyaniline nanocomplex modified microbial fuel cell anodes期刊:J. Phys. Chem. C 2012 影响因子:4.805文章: Alignment of Single-Walled Carbon Nanotubes with Ferroelectric Liquid Crystal期刊:Analytica Chimica Acta 2012 影响因子:4.555文章: Highly sensitive luminol electrochemiluminescence immunosensor based on ZnO nanoparticles and glucose oxidase decorated graphene for cancer biomarker detection期刊:Journal of Chromatography A 2012 影响因子:4.531文章: Simultaneous determination of 10 β2-agonists in swine urine using liquid chromatography–tandem mass spectrometry and multi-walled carbon nanotubes as a reversed dispersive solid phase extraction sorbent期刊:ACS Applied Materials & Interfaces 2012 影响因子:4.525文章: “Turn-on”Fluorescence Detection of Lead Ions Based on Accelerated Leaching of Gold Nanoparticles on the Surface of Graphene期刊:Chemistry-An Asian Journal 2012 影响因子:4.5南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China文章: Dispersion of Reduced Graphene Oxide in Multiple Solvents with an Imidazolium-Modified Hexa-peri-hexabenzocoronene期刊:Analyst 2012 影响因子:4.23文章: Glucose sensor based on an electrochemical reduced graphene oxide-poly(L-lysine) composite film modified GC electrode期刊:Analyst 2012 影响因子:4.23文章: A functional graphene oxide-ionic liquid composites/gold nanoparticles sensing platform for ultrasensitive electrochemical detection of Hg2+期刊:Analyst 2012 影响因子:4.23文章: Ultrasensitive colorimetric detection of heparin based on self-assembly of gold nanoparticles on graphene oxide期刊:PLOS ONE 2012 影响因子:4.092文章: Obstruction of Photoinduced Electron Transfer from Excited Porphyrin to Graphene Oxide: A Fluorescence Turn-On Sensing Platform for Iron (III) Ions期刊:Pharmaceutical Research 2012 影响因子:4.093文章: PEGylated Multi-Walled Carbon Nanotubes for Encapsulation and Sustained Release of Oxaliplatin期刊:Electrochemistry Communications 2014 影响因子: 4.425文章A Novel Electrochemical Immunosensor for Golgi Protein 73 Assay期刊:Journal of Power Sources 2014 影响因子: 4.675文章Mesoporous Li3V2(PO4)3@CMK-3 nanocomposite cathode material for lithium ion batteries期刊:Analytica Chimica Acta 2014 影响因子: 4.387文章Sensitive and selective electrochemical determination of quinoxaline-2-carboxylic acid based on bilayer of novel poly(pyrrole) functional composite using one-step electro-polymerization and molecularly imprinted poly(o-phenylenediamine)期刊:Journal of Membrane Science 2014 影响因子:4.093文章Poly(vinyl alcohol)–graphene oxide nanohybrid “pore-filling” membrane for pervaporation of toluene/n-heptane mixtures期刊:Journal of Power Sources 2014 影响因子: 4.675文章Non-aqueous hybrid supercapacitors fabricated with mesoporous TiO2 microspheres and activated carbon electrodes with superior performance期刊:Journal of Power Sources 2014 影响因子: 4.675文章Preparation of three-dimensional hybrid nanostructure-encapsulated sulfur cathode for high-rate lithium sulfur batteries期刊:Bioresource Technology 2013 影响因子: 4.75文章Selective production of chemicals from biomass pyrolysis over metal chlorides supported on zeolite期刊:Journal of Chromatography A 2013 影响因子: 4.612文章Simultaneous determination of six resorcylic acid lactones in feed using liquid chromatography–tandem mass spectrometry and multi-walled carbon nanotubes as a dispersive solid phase extraction sorbent南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China期刊:Journal of Power Sources 2013 影响因子: 4.675文章Reduced graphene oxide film as a shuttle-inhibiting interlayer in a lithium–sulfur battery期刊:The Journal of Physical Chemistry C 2013 影响因子: 4.814文章Electromagnetic Wave Absorption Properties of Reduced Graphene Oxide Modified by Maghemite Colloidal Nanoparticle Clusters期刊:Journal of Power Sources 2013 影响因子: 4.675文章Improving the performance of lithium–sulfur batteries by graphene coating期刊:Journal of Chromatography A 2013 影响因子:4.612文章Application of graphene as the stationary phase for open-tubular capillary electrochromatography 期刊:Journal of Power Sources 2013 影响因子:4.675文章Design, hydrothermal synthesis and electrochemical properties of porous birnessite-type manganese dioxide nanosheets on graphene as a hybrid material for supercapacitors期刊:Appl. Mater. Interfaces 2013 影响因子:4.525文章:One-Pot Environmentally Friendly Approach toward Highly Catalytically Active Bimetal-Nanoparticle-Graphene Hybrids期刊:Electrochemistry Communications 2013 影响因子:4.859文章:Fabrication of streptavidin functionalized silver nanoparticle decorated graphene and its application in disposable electrochemical sensor for immunoglobulin E期刊:ACS Appl. Mater. Interfaces 2013 影响因子:4.525文章:Facile Fabrication and Enhanced Photocatalytic Performance of Ag/AgCl/rGO Heterostructure Photocatalyst期刊:Analyst 2013 影响因子:4.23文章:One-pot green synthesis of graphene oxide/gold nanocomposites as SERS substrates for malachite green detection大于等于3:期刊:Sensors and Actuators B: Chemical影响因子:3.535文章:Facile preparation of highly water-stable and flexible PEDOT:PSS organic/inorganic composite materials and their application in electrochemical sensors.期刊:Electrochimica Acta影响因子:3.777文章:Inhibitory effect of silver nanomaterials on transmissible virus-induced host cell infections期刊:Microchimica Acta 2014 影响因子:3.434文章:Graphene oxide functionalized magnetic nanoparticles as adsorbents for removal of phthalate esters.期刊:Nanotechnology 2013 影响因子:3.979文章: Facile and straightforward synthesis of superparamagnetic reduced graphene oxide–Fe3O4 hybrid composite by a solvothermal reaction期刊:Sensors and Actuators B: Chemical 2012 影响因子:3.898文章: Sensitive DNA biosensor improved by 1,10-phenanthroline cobalt complex as indicator based on the electrode modified by gold nanoparticles and graphene期刊:Electrochimica Acta 2013 影响因子:3.832南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China文章: Electrochemical biosensor based on reduced graphene oxide modified electrode with Prussian blue and poly(toluidine blue O) coating期刊:Electrochimica Acta 2012 影响因子:3.832文章: High sensitive determination of theophylline based on gold nanoparticles/l-cysteine/Graphene/Nafion modified electrode期刊:Electrochimica Acta 2013 影响因子:3.832文章: Graphene oxide/nickel oxide modified glassy carbon electrode for supercapacitor and nonenzymatic glucose sensor期刊:Electrochimica Acta 2012 影响因子:3.832文章: Graphene oxide nanoribbon and polyhedral oligomeric silsesquioxane assembled composite frameworks for pre-concentrating and electrochemical sensing of 1-hydroxypyrene期刊:Bioelectrochemistry 2012 影响因子:3.759文章: Nonenzymatic amperometric determination of glucose by CuO nanocubes–graphene nanocomposite modified electrode期刊:Chemical Engineering Journal 2012 影响因子:3.461文章: Self-assembly of graphene oxide and polyelectrolyte complex nanohybrid membranes for nanofiltration and pervaporation期刊:Fuel 2012 影响因子:3.248文章: Experimental study on bio-oil upgrading over catalyst in supercritical ethanol期刊:RSC Advances 2013 2011年创刊预计影响因子:大于3.0文章: Sandwich nanocomposites of polyaniline embedded between graphene layers and multi-walled carbon nanotubes for cycle-stable electrode materials of organic supercapacitors期刊:RSC Advances 2012 2011年新刊,预计影响因子:大于3.0文章: Electrochemically-driven and dynamic enhancement of drug metabolism via cytochrome P450 microsomes on colloidal gold/graphene nanocomposites期刊:Electrochimica Acta 2014 影响因子: 3.777文章(4-Ferrocenylethyne) Phenylamine Functionalized Graphene Oxide Modified Electrode for Sensitive Nitrite Sensing期刊:Sensors and Actuators B: Chemical 2014 影响因子: 3.535文章Simultaneous determination of dihydroxybenzene isomers based on graphene-graphene oxide nanocomposite modified glassy carbon electrode期刊:Sensors and Actuators B: Chemical 2014 影响因子: 3.535文章Sensitive electrochemiluminescence sensor based on ordered mesoporous carbon composite film for dopamine期刊:Talanta 2014 影响因子: 3.498文章Square wave anodic stripping voltammetric determination of Cd2+ and Pb2+ at bismuth-film electrode modified with electroreduced graphene oxide-supported thiolated thionine期刊:Sensors and Actuators B: Chemical 2014 影响因子: 3.535文章A multiple-promoted silver enhancement strategy in electrochemical detection of target virus期刊:Nanotechnology 2014 影响因子: 3.842南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China文章Ag–graphene hybrid conductive ink for writing electronics期刊:Analyst 2014 影响因子: 3.969文章Capillary electrophoresis-based immobilized enzyme reactor using graphene oxide as support via layer by layer electrostatic assembly期刊:Microchimica Acta 2014 影响因子: 3.434文章Fluorescent aptasensor for the determination of Salmonella typhimurium based on a graphene oxide platform期刊:Talanta 2014 影响因子:3.498文章Tannic acid functionalized N-doped graphene modified glassy carbon electrode for the determination of bisphenol A in food package期刊:Composites Science and Technology 2013 影响因子: 3.328文章Fabrication of graphene/polylactide nanocomposites with improved properties期刊:Microporous and Mesoporous Materials 2014 影响因子: 3.365文章Synthesis, characterization and CO2 capture of mesoporous SBA-15 adsorbents functionalized with melamine-based and acrylate-based amine dendrimers期刊:Analyst 2013 影响因子: 3.969文章Graphene based electrochemical biosensor for label-free measuring the activity and inhibition of protein tyrosine kinase期刊:Electrochimica Acta 2013 影响因子: 3.777文章Preparation and charaterization of Pt/functionalized graphene and its electrocatalysis for methanol oxidation期刊:Plos One 2013 影响因子: 3.73文章Synergistic Removal of Pb(II), Cd(II) and Humic Acid by Fe3O4@Mesoporous Silica-Graphene Oxide Composites期刊:Electrochimica Acta 2013 影响因子: 3.777文章Electrocatalytic oxidation and detection of N-acetylcysteine based on magnetite/reduced graphene oxide composite-modified glassy carbon electrode期刊:Catalysis Science & Technology 2013 影响因子: 3.753文章The role of reducing agent in perylene tetracarboxylic acid coating on graphene sheets enhances Pd nanoparticles-electrocalytic ethanol oxidation期刊:Acta Materialia 2013 影响因子: 3.941文章Nanoconfinement significantly improves the thermodynamics and kinetics of co-infiltrated 2LiBH4–LiAlH4 composites: Stable reversibility of hydrogen absorption/resorption期刊:Microchimica Acta 2013 影响因子:3.434文章Highly sensitive and selective voltammetric detection of mercury(II) using an ITO electrode modified with 5-methyl-2-thiouracil, graphene oxide and gold nanoparticles期刊:Composites Science and Technology 2013 影响因子:3.328文章Porous graphene sandwich/poly(vinylidene fluoride) composites with high dielectric properties 期刊:Electrochimica Acta 2013 影响因子: 3.777文章Cu2O/NiOx/graphene oxide modified glassy carbon electrode for the enhanced electrochemical oxidation of reduced glutathione and nonenzyme glucose sensor南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China期刊:Electrochimica Acta 2013 影响因子: 3.777文章Direct electrodeposion of reduced graphene oxide and dendritic copper nanoclusters on glassy carbon electrode for electrochemical detection of nitrite期刊:Analyst 2013 影响因子: 3.969文章Realization of on-tissue protein identification by highly efficient in situ digestion with graphene-immobilized trypsin for MALDI imaging analysis期刊:Food Chemistry 2014 影响因子:3.334文章Electrochemical determination of toxic ractopamine at an ordered mesoporous carbon modified electrode期刊:Talanta 2013 影响因子:3.498文章Simultaneous Determination of Dopamine and Uric Acid Using Layer-by-Layer Graphene and Chitosan Assembled Multilayer Films期刊:Electrochimica Acta 2013 影响因子:3.777文章Electrochemically Cathodic Exfoliation of Graphene Sheets in Room Temperature Ionic Liquids N-Butyl, methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide and Their Electrochemical Properties 期刊:Journal of Applied Physics 2013 影响因子:2.21文章An experimental investigation on fluidic behaviors in a two-dimensional nanoenvironment期刊:Journal of Molecular Catalysis A: Chemical 2013 影响因子:3.187文章Enhancing the photocatalytic activity of lead molybdate by modifying with fullerene期刊:Physical Chemistry Chemical Physics 2013 影响因子:3.829文章Improving the antifouling property of polysulfone ultrafiltration membrane by incorporation of isocyanate-treated graphene oxide期刊:Sensors and Actuators B: Chemical 2013 影响因子:3.535文章Electrochemical modification of graphene oxide bearing different types of oxygen functional species for the electro-catalytic oxidation of reduced glutathione期刊:Sensors and Actuators B: Chemical 2013 影响因子:3.535文章A novel graphene oxide-based fluorescence assay for RNA endonuclease activity of mammalian Argonaute2 protein期刊:Sensors and Actuators B: Chemical 2013 影响因子:3.535文章Enhanced room temperature sensing of Co3O4-intercalated reduced graphene oxide based gas sensors期刊:Talanta 2013 影响因子:3.498文章Graphene matrix for signal enhancement in ambient plasma assisted laser desorption ionization mass spectrometry期刊:Sensors and Actuators B: Chemical 2013影响因子:3.535文章Electrodeposition of electroreduced graphene oxide-Au nanoparticles composite film at glassy carbon electrode for anodic stripping voltammetric analysis of trace arsenic(III)期刊:Physical Chemistry Chemical Physics 2013 影响因子:3.829文章Enhanced reverse saturable absorption in graphene/Ag2S organic glasses期刊:Electrochimica Acta 2013 影响因子:3.777南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China文章Electrochemical immunoassay platform for high sensitivity detection of indole-3-acetic acid期刊:Analyst 2013 影响因子:3.969文章Aptamer-linked biosensor for thrombin based on AuNPs/Thionine-graphene nanocomposite期刊:Journal of Colloid and Interface Science 2013 影响因子:3.172文章Green Synthesis and Photo-catalytic Performances for ZnO-Reduced Graphene Oxide Nanocomposites期刊:Electrochimica Acta 2013 影响因子:3.832文章: Insight into effects of graphene in Li4Ti5O12/carbon composite with high rate capability as anode materials for lithium ion batteries期刊:Dalton Transactions 2013 影响因子:3.838文章:Remarkable improvements in the stability and thermal conductivity of graphite/ethylene glycol nanofluids caused by a graphene oxide percolation structure期刊:Talanta 2013 影响因子:3.794文章:Selective and sensitive determination of uric acid in the presence of ascorbic acid and dopamine by PDDA functionalized graphene/graphite composite electrode期刊:ELECTROPHORESIS 2013 影响因子:3.303文章:Graphene oxide and reduced graphene oxide as novel stationary phases via electrostatic assembly for open-tubular capillary electrochromatography期刊:Sensors and Actuators B 2013 影响因子:3.898文章:A reduced graphene oxide based biosensor for high-sensitive detection of phenols in water samples期刊:Sensors and Actuators B: Chemical 2013 影响因子:3.898文章:Amperometric biosensor for NADH and ethanol based on electroreduced graphene oxide–polythionine nanocomposite film南京先丰纳米材料科技有限公司Nanjing XFNANO Materials Tech Co.,Ltd 地址:南京市鼓楼区南京大学国家大学科技园Add:Nanjing Jiangsu Province China。

石墨烯衍生物在口服给药和口腔生物学的研究进展

石墨烯衍生物在口服给药和口腔生物学的研究进展

石墨烯衍生物在口服给药和口腔生物学的研究进展周瑞静;廖敏;陈昭西;毛茜潆;聂敏【摘要】石墨烯及其衍生物是目前各领域研究最热门的碳材料之一.这种碳材料虽然研究的历史很短,但由于其非凡的物理化学性能以及生物相容性,已成为生物医学应用的潜力材料.本文概述了石墨烯的性质和制备,重点介绍了石墨烯衍生物在口腔生物学方面的最新进展.%Graphene and its derivatives have been attracting considerable interest worldwide due to its remarkable physical and chem?ical properties as well as alluring biocompatibility. As a new kind of carbon material,graphene has a number of potential medical appli?cations in many fields. In this review,efforts are made to expect in elucidating the synthesis and characterization of graphene deriva?tives,with emphasis on their latest developments in oral biology.【期刊名称】《口腔医学》【年(卷),期】2017(037)010【总页数】3页(P954-956)【关键词】石墨烯衍生物;生物检测;光热治疗;抑菌;药物传递系统【作者】周瑞静;廖敏;陈昭西;毛茜潆;聂敏【作者单位】武汉大学口腔医院牙体牙髓科一科,湖北武汉430079;武汉大学口腔医院牙体牙髓科一科,湖北武汉430079;武汉大学口腔医院牙体牙髓科一科,湖北武汉430079;武汉大学口腔医院牙体牙髓科一科,湖北武汉430079;武汉大学口腔医院牙体牙髓科一科,湖北武汉430079【正文语种】中文【中图分类】R78;R393石墨烯(graphene),作为碳的一种同素异形体,在2004年首次被Geim和Novoselov等通过一种极为简单的胶带纸剥离方法成功制备[1],因此获得了2010年诺贝尔物理学奖。

锂离子电池存储之间的石墨

锂离子电池存储之间的石墨
Chan and Hill Nanoscale Research Letters 2011, 6:203 /content/6/1/203
NANO EXPRESS
Open Accesseen graphenes
Chan and Hill Nanoscale Research Letters 2011, 6:203 /content/6/1/203
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The present authors have investigated the minimum molecular spacing between two parallel graphene sheets for stable atom/ion storage, and we have determined the diffusion time for atom/ion leaving the graphene sheet of a given size under different temperatures [19]. Here, we investigate lithium ion storage between two parallel graphene sheets. The continuous approach is employed to approximate the van der Waals interaction between a single lithium ion and the graphene sheets, so that the equilibrium positions of the lithium ion between the graphene sheets h can be determined for a given separation D (see Figure 1), from which, we can deduce the number of possible ion layers that might be formed between two graphenes. Three distinct ion layers, namely single, double and triple layers for D = 5, 7.7, and 8.3 Å are predicted. While the double and triple ion layers are found to provide storage capacities exceeding that of conventional graphitic carbon materials [1,8], the single ion layer is found to provide the most stable option for ion batteries operating under extreme temperatures. Wherever possible, we compare our theoretical results with those obtained by Suzuki et al. [8] using semiempirical molecular orbital calculations.

柔性锂氧电池的发展现状

柔性锂氧电池的发展现状

柔性锂氧电池的发展现状陈建中;舒朝著;龙剑平;候志前【摘要】With the rapid development of flexible electronic devices, more and more requirements for rechargeable batteries are put forward. Flexible lithium oxygen battery with high energy density theory, have becomea hot field of battery. To develop efficient stable and high mechanical strength flexible lithium oxygen battery, flexible anode and cathode is the keyatpresent. In this paper, the development and design of flexible cathode material and lithium anode are briefly introduced, and the field is summarized and prospected.%柔性电子设备的飞速发展对可充式二次电池提出了越来越高的要求.柔性锂氧电池凭借着超高的理论能量密度,成为目前电池领域的研究热点,开发出高效、稳定、高机械强度及柔性的电池正极和负极是目前研究的关键.本文主要对柔性正极材料、锂负极的开发与设计进行简要介绍,并对该领域进行总结、展望.【期刊名称】《电子元件与材料》【年(卷),期】2018(037)001【总页数】6页(P1-6)【关键词】锂氧电池;柔性正极材料;综述;柔性锂负极;催化剂;二次电池【作者】陈建中;舒朝著;龙剑平;候志前【作者单位】成都理工大学材料与化学化工学院,四川成都 610059;成都理工大学材料与化学化工学院,四川成都 610059;成都理工大学材料与化学化工学院,四川成都 610059;成都理工大学材料与化学化工学院,四川成都 610059【正文语种】中文【中图分类】TM911.4随着现代科技的持续进步,可穿戴式电子设备越来越多地出现在人们的日常生活中,为人们带来更多的便利,如智能手表、智能运动鞋、智能衣服以及电子皮肤和可折叠可弯曲的智能手机等[1]。

菠萝皮生物炭负载纳米零价铁去除水中的铬

菠萝皮生物炭负载纳米零价铁去除水中的铬

菠萝皮生物炭负载纳米零价铁去除水中的铬宋宏娇;季斌;杨雨婷;刘扬;龚喜平;王家乐;舒垚荣;孙梦侠【摘要】以菠萝皮制成的生物炭为载体负载纳米零价铁(nZVI)合成功能性生物炭(nZVI/BC),采用X射线衍射(XRD)、扫描电镜(SEM)和X射线光电子能谱(XPS)等方法对材料进行表征,考察了pH和初始Cr(Ⅵ)浓度对Cr(Ⅵ)的去除率的影响,并对其机理进行研究.结果表明:nZVI/BC对Cr(Ⅵ)的去除效率在pH =3时达到峰值90.3%,而在pH =9时去除效率最低.吸附动力学实验数据符合准二级动力学(PSO)模型;当Cr(Ⅵ)的初始浓度由10 mg/L增加到30 mg/L时,速率常数由0.466 0 min-1减小到0.237 1 min-1,说明反应速率随着溶液Cr(Ⅵ)初始浓度的增大而减小.SEM图像显示nZVI与生物炭的表面结合良好.反应前后的XRD和XPS分析表明,在反应过程中,nZVI和Cr(Ⅵ)发生吸附,还原和共沉淀.因此,菠萝皮生物炭负载nZVI可作为水中Cr(Ⅵ)去除的有效复合材料.【期刊名称】《科学技术与工程》【年(卷),期】2019(019)013【总页数】6页(P342-347)【关键词】菠萝皮;生物炭;纳米零价铁;铬;准二级动力学模型【作者】宋宏娇;季斌;杨雨婷;刘扬;龚喜平;王家乐;舒垚荣;孙梦侠【作者单位】武汉科技大学城市建设学院,武汉430065;武汉科技大学城市建设学院,武汉430065;冶金矿产资源高效利用与造块湖北省重点实验室,武汉430081;武汉科技大学城市建设学院,武汉430065;武汉科技大学城市建设学院,武汉430065;武汉科技大学城市建设学院,武汉430065;武汉科技大学城市建设学院,武汉430065;武汉科技大学城市建设学院,武汉430065;武汉科技大学城市建设学院,武汉430065【正文语种】中文【中图分类】X703铬及其化合物已被广泛应用于现代工业,如耐火材料、电池和纺织工业[1]。

锂离子电池负极材料的研究进展

锂离子电池负极材料的研究进展

锂离子电池负极材料的研究进展摘要:锂离子电池作为一种电源应用很广泛,但是在应用中存在一些不足,选取电化学性能良好的正负极材料是提高和改善锂离子电池电化学性能最重要的因素。

简单介绍锂离子电池的电化学反应原理和从新型碳材料、硅基负极材料、锡基负极材料三方面锂离子电池的研究状况,并展望了锂离子电池负极材料的发展趋势。

关键词:锂离子电池;负极材料;研究现状0 引言目前全球最具潜力的可充电电池是锂离子电池。

用碳负极材料的商品化的锂离子电池可逆比容量已达350 mA∙h/g,快接近理论比容量372mA∙h/g[1]。

随着全球化的加快,科技日新月异,电子产品日益普及,发展中的电动汽车等对电池能源提出了更高的要求,其中主要包括能量密度、使用寿命等[2]。

开发新型、廉价的负极材料是锂离子电池研究的热点课题之一。

就目前而言,主要有新型碳材料、锡基材料、硅基材料等,本文研究了这些新型负极材料的研究现状及未来的发展方向。

1锂离子电池的电化学反应原理锂离子电池是指用锂离子嵌入化合物作为正负极的二次电池.锂离子电池的正极材料必须有能够接纳锂离子的位置和扩散路径,目前应用性能较好的正极材料是具有高插入电位的层状结构的过渡金属氧化物和锂的化合物,如LixCoO2,LixNiO2以及尖晶石结构的LiMn2O4等,这些正极材料的插锂电位都可以达到 4 V以上(vs.Li+/Li)[3].负极材料一般用锂碳层间化合物Li x C6,其电解质一般采用溶解有锂盐LiPF6、LiAsF6等的有机溶液。

锂离子电池实际上是一个锂离子浓差电池,正负电极由两种不同的锂离子嵌入化合物构成.充电时,Li+从正极脱嵌经过电解质嵌入负极,此时负极处于富锂态,正极处于贫锂态;放电时则相反,Li+从负极脱嵌,经过电解质嵌入正极,正极处于富锂态,负极处于贫锂态.锂离子电池的工作电压与构成电极的锂离子嵌入化合物本身及锂离子的浓度有关[3]。

2新型碳材料在新型碳负极方面,未来的发展将主要集中在高功率石墨类负极及非石墨类高容量碳负极,以满足未来动力和高能电池的需求。

石墨烯/纳米银复合材料的制备及应用研究进展

石墨烯/纳米银复合材料的制备及应用研究进展

石墨烯/纳米银复合材料的制备及应用研究进展综述了石墨烯/纳米银复合材料的制备方法及应用,讨论了其在导电、导热和生物医学等方面的应用,展望了石墨烯/纳米银复合材料的研究方向和发展前景。

标签:石墨烯;复合材料;纳米银;制备及应用石墨烯作为一种由单层单质原子组成的六边形结晶碳材料,其特殊性能的应用一直是近几年研究的重点。

但是石墨烯的生产效率低,需经常将其进行改性,达到以较少的添加量获得更好性能的目的。

其中,纳米银的出现在一定程度上扩大了石墨烯在导电[1],导热方面的应用。

而且纳米银的生产效率高,很好地解决了石墨烯/纳米银的生产问题,为石墨烯在诸多技术领域的应用拓展了空间[2]。

金属粒子由于含有自由移动的电子和极大的比表面积,在导电性和导热性方面有着出色的表现。

而纳米银颗粒,纳米银棒,纳米银线则可以在复合基体中形成网络通路,提高材料的导电性和导热性。

1 石墨烯/纳米银复合材料的制备方法目前,石墨烯掺杂纳米银复合材料可以根据纳米银的形貌特征分为石墨烯/纳米银颗粒复合材料和石墨烯/纳米银线复合材料。

纳米银的加入使得石墨烯复合材料的导电性和导热性以及石墨烯的表面硬度均得到了提高[3]。

1.1 机械共混法机械共混法可分为搅拌法和熔融共混法。

刘孔华[4]利用搅拌法制备得到石墨烯/纳米银线杂化物,在50 ℃下搅拌,升温至210 ℃,最后降至常温得到石墨烯/纳米银线杂化物。

熔融共混法是利用密炼机或者挤出机的高温和剪切作用力下将石墨烯、纳米银和基材熔融后,共混得到石墨烯/纳米复合材料。

该方法用途广泛,适用于极性和非极性聚合物和填料的共混。

并且纳米银的烧结温度在180 ℃,对于纳米银颗粒可以烧结形成一定规模的网络结构。

此方法制备的复合材料所需时间短,且纳米银线是单独制备,所以可以单独控制纳米银线的长度和长径比。

但是由于是机械共混,纳米银在石墨烯材料中的分散性不是很好,且容易发生团聚,达不到形成大量网络结构的目的。

1.2 化学还原法化学还原法是目前比较常见的将金属纳米粒子附着在石墨烯表面的方法。

石墨烯及其复合材料在锂离子电池中的应用

石墨烯及其复合材料在锂离子电池中的应用

石墨烯及其复合材料在锂离子电池中的应用俞会根;赵亮;盛军【摘要】介绍了石墨烯的物理化学性质,在锂离子电池中的应用及产业化的情况.石墨烯因其特殊的二维结构,具有与石墨负极不同的电化学性能.对石墨烯作为锂离子电池负极材料的电化学性能及其影响因素、制备方法、储锂机理等做了介绍.从石墨烯用于锂离子电池的两个方面材料,即负极及复合电极材料,对石墨烯电极国内外的研究状况做了介绍.与石墨负极相比,石墨烯电极具有高容量、高功率密度的优点,但也存在首周库仑效率低、充放电过程极化较大等缺点.目前石墨烯还未实现产业化,石墨烯电池的研发也多处于概念阶段.【期刊名称】《电源技术》【年(卷),期】2014(038)006【总页数】4页(P1155-1158)【关键词】锂离子电池;石墨烯;负极材料;石墨烯复合电极【作者】俞会根;赵亮;盛军【作者单位】北京新能源汽车股份有限公司,北京102606;北京新能源汽车股份有限公司,北京102606;北京新能源汽车股份有限公司,北京102606【正文语种】中文【中图分类】TM912.9石墨烯指单层石墨,是目前所知道的最薄的材料。

虽然科学家们从1947年开始就对石墨烯的物理性质进行了一系列的理论研究,但直到2004年,美国曼彻斯特大学Geim小组才用最简单的机械剥离法从高定向裂解石墨上剥离下了大片的石墨烯,进一步表征了石墨烯的各种性质,并因此获得了2010年诺贝尔物理学奖。

石墨烯是碳原子堆积成的六边形网格平面,具有理想的二维晶体结构,C-C原子键长是0.142 nm,面密度为0.77mg/m2。

类似于石墨的电子结构,石墨烯中的碳原子也是sp2杂化,每个碳原子贡献出一个未成键电子,所以石墨烯具有良好的导电性,电导率可达106 S/m。

另外,石墨烯层有很好的韧性来适应外力,所以其结构十分稳定。

石墨烯的室温热导率约为5×103W/mK,是室温下铜的热导率的10倍多[1],表1中列出了石墨烯、石墨、金属铜的一些物理性质。

天津工业大学在高分离性能纳滤膜制备方面取得新进展

天津工业大学在高分离性能纳滤膜制备方面取得新进展

第2期李雪燕等:B1-S11O2/GO电催化膜的制备及其性能研究・59・[5(刘志猛,朱孟府"邓橙"等.Sb-SnO2/炭膜对水中四环素电催化降解性能研究[(•水处理技术"2016,(12):69—72.[6(李娇,王虹,李建新,等.钛基电催化膜电化学合成制备丙酸及膜反应器优化设计[(•膜科学与技术"2013,33(6):64—70.[7(高晓红"张登松,施利毅"等.碳纳米管/S11O2复合电极的制备及其电催化性能研究[(•化学学报,2007,65(7)$589—594[8(Liu Z,Zhu M,Wang Z,et al Effective degradation of aqueoustetracyclineusinganano-TiO2/carbonelectro-catalytic membrane[J(.Mater,2016,9(5):364—368. [9(YongY A,Yang S Y,ChoiC,et&l Electrocatalytic activitiesofSb-SnO2andBi-TiO2anodesforwatertreat-ment$Efectsofelectrocatalystcompositionandelectro-lyte[J(.Catal Today,2016,282(6):62—67.[10(Chad D,Mary H S,Md S R.Electrochemical multi-waledcarbonnanotubefilterforviralandbacterialre-moval andinactivation[J(.Environ Sci Technol,2011,45(9):3672—3679[ll(Rahaman M D,Chad D V.Electrochemical carbon-nanotubefilterperformancetowardvirusremovalandinactivationinthepresenceofnaturalorganic mater[J(.Environ Sci Technol,2012,46(12):1556—1564.[12(Novoselov K S,Geim A K,Morozov S V,etal.Elec-tricfieldinatomicalythincarbonfilms[J(Science"2004306(5696):666—669[13(刘欣欣,王小平,王丽军,等.石墨烯的研究进展[(•材料导报,2011,25(23):92—97.[14(高振华,张建伟,王海滨,等.石墨烯的应用研究进展[(•化工科技,2012,20(4):64—67.[15(Li D,Muller M B,GiljeS,etal.Processable aqueous dispersionsofgraphenenanosheets[J(Nat Nano-technol,2008,3(2):101—105.[16(芦瑛,张林,李明,等.氧化石墨烯基水处理膜研究进展科技导报,2015,33(14):32—35.[17(Wang P,Deng Y,Hao L,et al.Continuous efficient removal and inactivation mechanism of E.coli by Bi—SnO2/Celectrocatalytic membrane[J(Environ SciPollut Res,2019,26(11):11399—11409.[18(张佳,夏明芳,王国祥,等.DSA电极电催化氧化降解四环素废水工艺优化[(•精细化工,2014,31(2):234—239[19(Liu H,Vajpayee A,Vecitis C D.Bismuth-doped tin oxide-coatedcarbonnanotubenetwork:Improvedan-ode stability and ef iciency for flow-through organicelectrooxidation[J(.ACS Appl Mater Interf,2013,5(20):10054—10066.[20(张,,邓,PTFE/Bi-SnO2-CNT 电催化膜的结构及性能表征[(•膜科学与技术,2019,39(1):34—40.[21(Liu Z,Zhu M,Zhao L,et al Aqueous tetracycline degradationbycoal-basedcarbonelectrocatalyticfiltra-tionmembrane$Efectofnanoantimony-dopedtindi-oxide coating[J(.Chem Eng J,2017,314(40):59_68[22(LiH,LiuJ,QianJ,et&l PreparationofBi-doped TiO2nanoparticles and their visible light photocatalyticperformance[(.Chin J Catal,2014,35(9):1578—1589.[23(NiranjanaE,SwamyBEK,NaikRR,et&l Electro-chemicalinvestigationsofpotassium ferricyanideanddopamine by sodium dodecyl sulphate modified carbonpasteelectrode$A cyclicvoltammetricstudy[J(J Electroanalyt Chem,2009,631(1):l—9.[24(Zhao H,GaoJ,ZhaoG,et&l Fabricationofnovel SnO2-Sb/carbonaerogelelectrodeforultrasonicelec-trochemical oxidation of perfluorooctanoate with highcatalytic efficiency[J(.Appl Catal B:Environ,2013,136(22):278—286.(下转第66页)天津工业大学在高分离性能纳滤膜制备方面取得新进展近日,天津工业大学分离膜与膜过程国家重点实验室何本桥教授课题组成功制得超薄且致密PA分离层,为高渗透选择性纳滤膜的制备提供了简易可行的新途径.课题组通过向常规界面聚合的小分子水相单体溶液中添加可溶性壳聚糖大分子,利用水相溶液中各组分之间黏度差异和扩散速度差异,促使原位形成中间层并调控界面聚合过程,成功制得超薄(约20nm)且致密PA分离层.该膜纯水通量达到226.l L/(m2-h),是对照组PIP/TMC纳滤膜和商业纳滤膜通量的5倍,而截留率都在99.3%以上(NaSOQ.研究工作将有利于推动纳滤膜在海水淡化、水质净化、小分子药物分离与纯化等领域的应用.(《膜科学与技术》编辑部供稿)。

层间共价增强石墨烯材料的构筑、性能与应用

层间共价增强石墨烯材料的构筑、性能与应用

物 理 化 学 学 报Acta Phys. -Chim. Sin. 2022, 38 (1), 2011059 (1 of 16)Received: November 23, 2020; Revised: December 11, 2020; Accepted: December 14, 2020; Published online: December 21, 2020.*Corresponding author. Email: wangb@. © Editorial office of Acta Physico-Chimica Sinica[Review] doi: 10.3866/PKU.WHXB202011059 Interlayer Covalently Enhanced Graphene Materials: Construction, Properties, and ApplicationsTao Liang, Bin Wang *CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China.Abstract: The development of large-scale and controlled grapheneproduction lays the foundation for macroscopic assembly. Among the diverseassembly strategies, modulating the interlayer interaction of graphenenanosheets is of vital importance because it determines the mechanical,electrical, thermal, and permeation properties of the macroscopic objects.Depending on the nature and strength of the interlayer interaction, covalent andnoncovalent bondings, such as hydrogen bonding, ionic interaction, π–πinteraction, and van der Waals force, are classified as two main types ofinterlayer connection methods, which solely or synergistically link the individualgraphene nanosheets for practical macroscopic materials. Among them, thecovalent bonding within the interlayer space renders graphene assemblyadjusted interlayer distance, strong interlayer interaction, a rich diversity of functionalities, and potential atomic configuration reconstruction, which has attracted considerable research attention. Compared with other noncovalent assembly methods, covalent connections are stronger and thus more stable; however, there are some issues that remain. First, the covalent modification of the graphene surface depends on the defects and/or functional groups, which becomes difficult for graphene films free of surface imperfections. Second, the covalent connection partly alters the sp 2 hybrid carbon atoms to sp 3, resulting in a deteriorated electrical conductivity. Thus, the electrical properties of the macroscopic assembly are far inferior to those of the constituent nanosheets, thereby restricting their applications. Lastly, covalent bonding is naturally rigid, rendering high modulus and strength to the graphene assembly while impairing the toughness. As in certain applications, both high strength and toughness are required; thus, a balanced covalent and noncovalent interaction is required. In this review, we discuss the recent progress in the construction method, properties, and applications of the interlayer covalently connected graphene materials. In the construction method, graphene is classified according to the synthesis method as oxidation-reduction and chemical vapor deposition method, wherein the latter represents graphene without abundant surface bonding sites and is hard to be covalently connected. For the former graphene produced by the oxidation-reduction method, the paper and fiber assembly forms are discussed. Then, the influence of covalent bonding on the mechanical and electrical properties is studied. Note that both the enhancement and potential impairments caused by covalent bonding are addressed. Finally, the applications in electrical devices, energy storage, and ion separation are summarized. The interlayer covalently connected macroscopic graphene material unifies the exceptional properties of graphene and the advantages of assembly strategy and will find applications in related fields. Moreover, it will also inspire the assembly of other graphene-like two-dimensional materials for a richer diversity of applications.Key Words: Graphene; Covalent bond; Diamane; Assembly; Mechanical property. All Rights Reserved.层间共价增强石墨烯材料的构筑、性能与应用梁涛,王斌*中国科学院纳米系统与多级次制造重点实验室,中国科学院纳米科学卓越创新中心,国家纳米科学中心,北京 100190摘要:大批量石墨烯可控制备技术的逐渐成熟为实现其宏观组装和应用提供了基础。

氮化碳复合石墨烯提高光生载流子利用率增强光催化性能

氮化碳复合石墨烯提高光生载流子利用率增强光催化性能

氮化碳复合石墨烯提高光生载流子利用率增强光催化性能张鹏;张新欣;冯可心;王宇;董晓丽【摘要】以尿素和氧化石墨烯为原料,采用简便易行的煅烧方法合成氮化碳与石墨烯的复合物.采用X射线衍射、扫描电子显微镜、荧光光谱、光电流密度等方法对样品进行表征,并研究其在可见光照射下降解罗丹明B的光催化性能.通过改变前驱体的不同复合比例,确定其最佳反应条件,并说明氨气氛围对煅烧过程的影响.结果表明,在550℃煅烧3 h,氧化石墨烯与尿素前驱体的复合比为4×10-6时其光催化效果最佳,90 min后染料降解率可达90%,是纯相氮化碳的1.4倍.与未复合石墨烯的氮化碳样品相比,复合物在抑制光生电子空穴复合率、加快光生载流子传输方面表现出优异性质.【期刊名称】《大连工业大学学报》【年(卷),期】2019(038)002【总页数】4页(P101-104)【关键词】氮化碳;石墨烯;光催化【作者】张鹏;张新欣;冯可心;王宇;董晓丽【作者单位】大连工业大学轻工与化学工程学院 ,辽宁大连 116034;大连工业大学轻工与化学工程学院 ,辽宁大连 116034;大连工业大学轻工与化学工程学院 ,辽宁大连 116034;大连工业大学轻工与化学工程学院 ,辽宁大连 116034;大连工业大学轻工与化学工程学院 ,辽宁大连 116034【正文语种】中文【中图分类】X703.50 引言石墨相氮化碳作为一种稳定性好、无毒、成本低廉的光催化剂,日益受到关注,并且被广泛应用于降解污染物、水裂解产氢、二氧化碳还原等诸多方面,在治理环境污染和解决能源危机方面具有潜在的利用价值[1-3]。

为进一步增强氮化碳的光催化活性,提高其光催化降解速率,人们已采取多种方法对氮化碳进行改性,如对其进行二次煅烧[2]、超声剥离[3]、通过模板调控形貌[4]等。

然而单一的氮化碳仍然存在很多不足之处,尤其是光生电子空穴的复合率较高,限制了其进一步的应用[5-7]。

石墨烯在锂离子电池电极材料中的应用

石墨烯在锂离子电池电极材料中的应用

石墨烯在锂离子电池电极材料中的应用沈文卓;郭守武【摘要】随着电子产品的普及,对锂离子电池的可逆容量、倍率充放电能力和循环稳定性提出了更高的要求.石墨烯由于其独特的电子共轭态和单一的原子层结构,具有优越的电子迁移性、大的表面积和良好的热和化学稳定性.因此,众多研究者致力于借助石墨烯的独有特性来改善锂离子电池正极和负极材料的综合电化学性能.本文对石墨烯在锂离子电池正负极材料中的应用情况以及面临的主要问题做了简要综述.%It is challenging to develop lithium ion batteries (LIBs) possessing simultaneously large reversible capacity,high rate capability,and good cycling stability.Graphene sheets,owing to the unique electronic conjugate state within the basal plane and also the single atomic layered morphology,have superior electronic mobility,large surface area,and decent thermal and chemical stability.Hence,many works have been devoted to the improvements of the cathode and anode materials with graphene.In the work,the achievements and the main problem in the area are overviewed.【期刊名称】《电子元件与材料》【年(卷),期】2017(036)009【总页数】4页(P79-82)【关键词】石墨烯;正极材料;综述;负极材料;电化学性能;锂离子电池【作者】沈文卓;郭守武【作者单位】上海交通大学电子信息与电气工程学院,上海200240;上海交通大学电子信息与电气工程学院,上海200240【正文语种】中文【中图分类】O613.71与其他种类的二次电池相比,锂离子电池具有高能量密度、高电压、无记忆效应、低自放电率等优点[1-2],在日用电子产品(如手机、手提电脑、摄像机、电玩)、电动汽车(EV/PHEV/HEV)以及储能电站等领域得到普遍应用。

石墨相氮化碳纳米片负载的钯纳米片催化4-硝基苯酚还原

石墨相氮化碳纳米片负载的钯纳米片催化4-硝基苯酚还原

石墨相氮化碳纳米片负载的钯纳米片催化4-硝基苯酚还原段兆磊【摘要】将Pd纳米片(Pd NSs)负载到石墨相氮化碳纳米片(CNNSs)表面,制备了Pd NSs/CNNSs催化剂,并采用透射电镜、X射线衍射、红外光谱和X射线光电子能谱对催化剂进行表征.结果表明,Pd NSs和CNNSs通过面面接触,形成紧密接触界面.负载后,Pd NSs具有较高分散性,没有发生明显团聚.将Pd NSs/CNNSs用于催化4-硝基苯酚还原生成4-氨基苯酚.结果表明,Pd NSs/CNNSs能够高效催化4-硝基苯酚还原.室温下,在Pd NSs/CNNSs催化剂、4-硝基苯酚和NaBH4浓度分别为2.1mg·L-1、0.14mmol·L-1和20mmol·L-1的条件下,反应速率常数达0.154min-1,是以Pd NSs为催化剂时的1.77倍.【期刊名称】《工业催化》【年(卷),期】2018(026)008【总页数】5页(P61-65)【关键词】催化剂工程;二维纳米材料;贵金属催化剂;钯纳米片;石墨相氮化碳;4-硝基苯酚还原【作者】段兆磊【作者单位】中国石油天然气股份有限公司大庆石化公司,黑龙江大庆163714【正文语种】中文【中图分类】TQ426.6;O643.36以石墨烯为代表的二维纳米片具有特殊的物化和电子性能,被广泛应用于催化领域[1]。

然而石墨烯对大多数化学反应没有催化活性。

受石墨烯的启发,贵金属纳米片引起广泛关注[2]。

贵金属纳米片表面原子含量高,表面原子处于配位不饱和态。

在催化反应中这些原子的催化活性远高于体相结构中的原子[3]。

因此,与传统催化剂相比,贵金属纳米片具有更为优异的催化性能。

近年来开发了多种制备贵金属纳米片的方法[4]。

然而高昂的价格和较差的稳定性限制了贵金属纳米片在催化中的应用。

以CO限域生长法制备的钯纳米片(Pd NNs)为例,当Pd NNs置于空气中时会被氧化,并降解为纳米颗粒[5]。

利用STM研究苝四羧酸分子间的作用机制

利用STM研究苝四羧酸分子间的作用机制

利用STM研究苝四羧酸分子间的作用机制刘春华;李亿保;谢云志;李勋;范小林【摘要】通过对苝-3,4,9,10-四羧酸二酐(PTCDA)酸化,合成了苝-3,4,9,10-四羧酸(PTCA),采用红外、氢谱等方法对目标产物进行了表征.并且采用荧光光谱研究了产物的光学性质,结果表明:酸化后的PTCA表现出很强的荧光特性.为了进一步揭示分子作用机制,以高定向热解石墨HOPG(Highly Oriented Pyrolytic Graphite)为基底,利用扫描隧道显微镜(STM)研究了PTCA分子在固-液界面的二维(2D)自组装行为,实验结果表明了分子间的作用力来源于分子间的氢键和π-π堆积相互作用力.【期刊名称】《赣南师范学院学报》【年(卷),期】2013(034)006【总页数】4页(P32-35)【关键词】苝-3,4,9,10-四羧酸;分子间作用力;扫描隧道显微镜(STM)【作者】刘春华;李亿保;谢云志;李勋;范小林【作者单位】赣南师范学院化学化工学院,江西赣州341000;赣南师范学院化学化工学院,江西赣州341000;赣南师范学院化学化工学院,江西赣州341000;赣南师范学院化学化工学院,江西赣州341000;赣南师范学院化学化工学院,江西赣州341000【正文语种】中文【中图分类】TB306自从Ijima在1991年发现了碳纳米管(CNTs)[1],研究者们开始对有机半导体产生极大的兴趣,在相当大的科学领域中,如多相催化[2],燃料分子[3-4],纳米器件等,都成为科学家们热衷于研究的课题.其中以苝-3,4,9,10-四羧酸酐(PTCDA)的应用最为广泛,因为这种酸酐具有高度有序的平面结构,强导电性,突出的化学稳定性等.这些性质使得其在科学和技术领域中具有潜在的应用价值,有待研究者们去发现,如传感器、纳米电子学、电池、纳米复合材料等[5].文献报道表明利用自组装的方式可以成功构筑功能纳米结构[6].人们采用“自下而上”的组装技术,已经制备了各种纳米结构.自组装是指基本结构单元通过分子间的非共价键作用,自发地形成有序聚集体的过程.该过程的特点是不受外力影响,一旦开始,将自动进行到某个终点[7].其驱动力来源于分子间弱相互作用力的协同作用,如氢键[8]、金属配位[9-10]、范德华[11]和偶极-偶极相互作用力[12].根据要求选择具有特殊功能的作用基团并以之为起点在合适的基底材料上进行设计组装,构筑具有特定形状和特殊功能的纳米结构或纳米阵列,进而实现结构的功能化.目前,对于如何构筑具有高稳定性、大小可控、特殊功能的自组装结构仍然是个挑战性的课题.在这些弱的相互作用中,氢键具有高度有序的方向性和选择性特点,从而被广泛用于作为构建二维或三维纳米结构的驱动力.扫描隧道显微镜具有超高的分辨率和各种工作环境的优势包括固-液界面[13-14]和超高真空条件[15-16],已被证明是分子水平上研究有机和生物体系的重要方法.最近,扫描隧道显微镜用来观察许多有机结构比如杯[8]芳烃[17]、环[12]噻吩[18]、金属超分子化合物[19]和咔唑大环[20].这些研究表明STM 也适合多酸衍生物的研究.大量文献已经报道了 PTCDA分子在超高真空条件下,可以在不同的基底表面如Au(111)[21]、Ag(111)[22]和HOPG[23]基底上形成高度有序的二维自组装结构,但常温下的二维组装结构未见报道.在常温下,PTCDA二维组装结构不够稳定,可能是PTCDA分子与底作用力不够强.若酸化后,引入-COOH间的氢键将有助于形成二维组装结构.因此,本文将PTCDA分子酸化后生成具有4个-COOH的共轭化合物PTCA,再借助STM研究PTCA分子在高定向热解石墨HOPG基底上的二维(2D)自组装行为,从而揭示了PTCA分子形成有序的二维组装结构的作用机制.1 实验部分1.1 仪器与试剂AVATAR傅里叶变换红外光谱仪,Bruker Avance400型核磁共振仪,Multi Mode扫描隧道显微镜.苝-3,4,9,10-四羧酸酐购于Alfa Aesar公司,稀硫酸和氢氧化钾均购于天津科密欧化学试剂开发中心,其它试剂均为分析纯.1.2 苝-3,4,9,10-四羧酸产物的合成与表征1.2.1 合成路线图1 苝-3,4,9,10-四羧酸的合成1.2.2 合成步骤与表征50 mL的圆底烧瓶中加入0.79 g苝-3,4,9,10-四羧酸二酐和0.11 g氢氧化钾,用水作为溶剂,加热回流6 h[24].反应完全后用稀硫酸酸化,抽滤,再用蒸馏水洗至中性,自然风干得到红棕色固体0.81 g,产率约为95%.IR(KBr)1 593 cm-1(C=C),1692,1 770 cm-1(C=O),3 386 cm-1(O - H);1HNMR(DMSO,400 MHz,ppm)13.09 -13.05(s,4H),8.63 -8.61(d,4H),8.04 -8.02(d,4H).1.2.3 PTCA和PTCDA荧光光谱性质研究配制原始浓度均为1.0×10-3mol/L的PTCA和PTCDA的无水乙醇溶液,然后分别稀释100倍,最终浓度均为1.0×10-5mol/L.以无水乙醇作为空白校正基线,在同样的环境及温度条件下检测其荧光光谱.1.2.4 STM研究PTCA的二维自组装行为STM实验是通过使用Nanoscope IIIa(Bruker,Germany)在室温条件下进行的.使用人工剪的Pt/Ir(80/20)针尖在恒流模式下进行实验,无水乙醇作为溶剂,配制样品的浓度为1.0×10-5mol/L用于接下来的实验.首先用移液枪吸取0.4 μL的样品滴到新鲜解离的高定向热解石墨HOPG表面,待溶剂挥发后,将样品装入仪器中,调试好针尖,然后再滴0.4 μL的辛基苯到被测样品表面,几min后进行STM实验.2 结果与讨论图2为目标化合物PTCA和原料PTCDA在无水乙醇溶液中的荧光发射光谱图,根据图谱分析得出,PTCA在490 nm和512 nm处有两个发射峰.而原料PTCDA则400 nm到700 nm之间都没有发射峰,发现PTCDA几乎不发荧光.说明原料原来不发荧光,经过酸化后,生成的目标产物为末端带有四个羧基,并且表现出强的荧光特性.为了进一步揭示分子间的作用机制,通过STM实验在HOPG基底表面来探索PTCA分子的2D自组装行为.首先将PTCA分子滴到HOPG基底表面,通过自组装方式形成有序的2D单分子结构,如图3a和图3b所示.从图3a中可以看出PTCA分子组装成很大范围稳定的2D单分子结构,说明它能够很稳定地吸附在石墨表面,其驱动力来源于它与石墨存在较强的π-π堆积作用力.从图3b的高分辨图可以看出每个分子类似一个“8”字型,而且有两排不同的取向,这说明PTCA分子中的羧基间发生了氢键作用,使其有不同方向的组装.基于这些观察结果可知,图3b中所量得的一个单元中,6个分子组成一个重复单元.分子间连接的间隙可以看到是比较暗的,这主要是由于芳环的电子云密度要比末端羧基高,“8”字型亮点是由于苝核的存在,周围亮度减少是由于羧基的电子云密度更低的原因.测得的晶胞参数为a=1.1±0.2 nm,b=2.2±0.2 nm 和α=100±1.0°.结合实验所得到的STM图,我们给出了可能的分子模型(图3c),模型中的单胞参数与实验值相符合. 图2 PTCA和PTCDA在无水乙醇溶液中荧光光谱图图3 PTCA分子在HOPG表面的自组装STM像:(a)(37.2 × 37.2 nm2,Iset=409.5 pA,Vbias=679.3 mV)揭示 PTCA 分子的大范围 STM 像.(b)(11.0 × 11.0 nm2,Iset=409.5 pA,Vbias=679.3 mV)揭示PTCA分子小范围的高分辨率STM像.(c)PTCA分子可能的二维堆积模型.以上STM实验结果表明,PTCA分子可以吸附在固-液界面上并组装成有序的2D结构.该实验结果揭示了PTCA分子间的作用力主要来源于氢键和π-π堆积作用力.分子间的氢键作用可能是导致形成强荧光特性的缘由.3 结论本文合成和表征了化合物PTCA,并做了相应的荧光光谱实验,结果表明酸化后产物PTCA产生的荧光强度增强.并且利用STM研究了它的2D自组装行为,实验结果揭示了PTCA所形成2D自组装结构来源于PTCA分子末端羧基间的氢键和分子核间的π-π堆积相互作用.为了证实PTCA的作用机制,对照实验表明PTCDA不能在HOPG表面组装出有序的2D结构,只有释放出羧基才能组装出有序的2D 结构,进一步揭示了末端羧基间氢键作用力的重要性.【相关文献】[1] Iijima S.Helical microtubules of graphitic carbon[J].Nature,1991,354:56 -58. 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Graphene nanosheets for enhanced lithium storage in lithium ion batteriesGuoxiu Wang *,Xiaoping Shen,Jane Yao,Jinsoo ParkInstitute for Superconducting and Electronic Materials,School of Mechanical,Materials and Mechatronic Engineering,University of Wollongong,NSW 2522,AustraliaA R T I C L E I N F O Article history:Received 8March 2009Accepted 24March 2009Available online 1April 2009A B S T R A C TGraphene nanosheets were synthesized in large quantities using a chemical approach.Field emission electron microscope observation revealed that loose graphene nanosheets agglomerated and crumpled naturally into shapes resembling flower-petals.High resolu-tion transmission electron microscope analysis,Raman spectroscopy and ultraviolet–visi-ble spectroscopy measurements confirmed the graphitic crystalline structure of the graphene nanosheets.The nanosheets exhibited an enhanced lithium storage capacity as anodes in lithium-ion cells and good cyclic performance.Ó2009Elsevier Ltd.All rights reserved.1.IntroductionLithium-ion batteries currently are ubiquitous power sources for portable electronics,using the chemistry of lithium cobalt oxide (LiCoO 2)cathode and graphite anode [1–3].The energy density and performance of lithium-ion batteries largely de-pend on the physical and chemical properties of the cathode and anode materials.The possibilities for the improvement of cathode materials are quite limited due to the stringent requirements such as high potential,structural stability,and inclusion of lithium in the structure [4,5].Nevertheless,there is considerable room for exploring new anode materials,ow-ing to many materials having reversible lithium storage capability.Recently,graphene,a single layer of carbon (carbon atoms in a two-dimensional (2D)honeycomb lattice),was found to exist as a free-standing form and exhibits many unusual and intriguing physical,chemical and mechanical properties [6,7].Due to the high quality of the sp 2carbon lattice,elec-trons were found to move ballistically in graphene layer even at ambient temperature [8,9].Graphene powders have been successfully applied in polymers to produce highly conduc-tive plastics [10].Despite the optimistic expectation on graph-ene-based electronics,it is unlikely that this will appear in next two decades.Current research mainly focuses on funda-mental research.In the meantime,one of exciting possibility is the use of bulk graphene powders as anode materials for reversible lithium storage in lithium-ion batteries [11].The maximum specific lithium insertion capacity for graphite (3D network of graphene)is 372mAh/g,correspond-ing to the formation of LiC 6–a first stage graphite intercala-tion compounds (GIC).During the intercalation process,lithium transfers its 2s electrons to the carbon host and is sit-uated between the carbon sheets.High capacity carbon mate-rials have also been reported.This could be mainly ascribed to (i)lithium insertion within the ‘‘cavities’’in the material [12],(ii)lithium absorbed on each side of the carbon sheet [13],(iii)lithium binding on the so called ‘‘covalent’’site [14],and (iv)lithium binding on hydrogen terminated edges of graphene fragments in carbon materials [15].Owing to its large sur-face-to-volume ratio and highly conductive nature,graphene may have properties that make it suitable for reversible lith-ium storage in lithium-ion batteries.This is because lithium ions could be bound not only on both sides of graphene sheets,but also on the edges and covalent sites of the graph-ene nanoplatelets.Therefore,it is expected that graphene0008-6223/$-see front matter Ó2009Elsevier Ltd.All rights reserved.doi:10.1016/j.carbon.2009.03.053*Corresponding author:Fax:+61242215731.E-mail address:gwang@.au (G.Wang).C A R B O N47(2009)2049–2053a v a i l ab l e a t w w w.sc i e n c ed i re c t.c o mj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a te /c a r b o ncould overtake its3D counterpart(graphite)for enhanced lithium storage in lithium-ion batteries.Herein,we report the chemical synthesis of graphene nanosheets and their electrochemical performance as anodes in lithium-ion cells.2.Experimental2.1.Chemical synthesis of graphene nanosheetsIn a typical synthesis process,natural graphite powders(SP-1, Bay Carbon,MI,USA)were oxidized to graphite oxide using a modified Hummers method[16].One gram graphite powder and0.5g sodium nitrate were poured into70ml concentrated H2SO4(under ice bath).Then3g KMnO4was gradually added. The mixture was stirred for2h and then diluted with de-ion-ised(DI)water.After that,5%H2O2was added into the solu-tion until the colour of the mixture changed to brilliant yellow.The as-obtained graphite oxide was re-dispersed in DI water and then exfoliated to generate graphene oxide nanosheets by ultrasonication using a Brandson Digital Sonif-er(S450D,40%amplitude).The brown graphene oxide nano-sheet dispersion was poured into a round-bottomedflask,to which hydrazine monohydrate(as reducing agent)was added.The mixed solution was then refluxed at100°C for 2h,over which the colour of the solution gradually changed to dark black as the graphene nanosheet dispersion was formed.The dispersion was further centrifuged for15min at3000rpm to remove a small amount of precipitate.The supernatant of the graphene nanosheet dispersion was di-rectly dried in a vacuum oven to obtain the bulk of graphene nanosheet powders.2.2.Nanostructural and physical characterisation of graphene nanosheetsThe structure of the pristine graphene nanosheets were analysed by X-ray diffraction(XRD,Philips1730X-ray diffrac-tometer),field emission electron microscope(FESEM,JEOL 7001F),and transmission electron microscopy(TEM)using a JEOL2011TEM facility.Graphene nanosheets were also char-acterised by Raman spectroscopy using a Jobin Yvon HR800 confocal Raman spectrometer with632.8nm diode laser exci-tation on1800-line grating.UV–Vis spectroscopy measure-ments were performed on a graphene nanosheet aqueous dispersion,using a Shimadzu UV1700UV–Vis spectrometer.2.3.Electrochemical testing of graphene nanosheets as anodes in lithium-ion cellsGraphene nanosheets obtained from chemical reduction contains A H and A OH groups.Therefore,we heat treated the as-prepared graphene nanosheets at500°C in argon atmosphere to remove A H and A OH groups.Then,graphene nanosheet powders were mixed with a binder poly(vinylidene fluoride)(PVdF)at weight ratios of90:10in N-methyl-2-pyrrol-idone(NMP)solvent to form a slurry.Then,the resultant slur-ries were uniformly pasted on Cu foil with a blade.These prepared electrode sheets were dried at120°C in a vacuum oven for12h and pressed under a pressure of approximately 200kg/cm2.CR2032-type coin cells were assembled in a glove box for electrochemical characterisation.The electrolyte was 1M LiPF6in a1:1mixture of ethylene carbonate and dimethyl carbonate.Li metal foil was used as the counter and reference electrode.The cells were galvanostatically charged and dis-charged at a current density of1C within the range of0.01–3.0V.Cyclic voltammetry(CV)curves were measured at 0.1mV/s within the range of0.01–3.0V using an electrochem-istry working station(CHI660C).3.Results and discussionFig.1a shows a FEG-SEM image of bulk graphene nanosheets at low magnification.The loose graphene nanosheets tend to stick together to formfluffy agglomerates with aflower-like appearance.A magnified view of one such agglomerate is shown in Fig.1b,from which we can clearly see the nano-sheets formingflower petal-like shape.Multilayer graphene nanosheets stick together if there is no perturbation by an external force.Graphene nanosheet petals are naturally crumpled and curved,which is visible in the micrometer domain.TEM and HRTEM analysis were performed on the as-pre-pared graphene nanosheets to determine their featuresinFig.1–(a)Low magnification FEG-SEM image of loose graphene nanosheet powders.(b)High magnification FEG-SEM view of graphene nanosheet petals.2050C A R B O N47(2009)2049–2053nanometer domain.Fig.2a shows a low magnification TEM im-age of the bulk of graphene nanosheets.Giant graphene nano-sheets (a few tens of square micrometers in area)were observed to form a covering on the top of the copper grid,like transparent silk.Graphene nanosheets are scrolled and entan-gled with each other.Corrugation and scrolling are part of the intrinsic nature of graphene nanosheets,which result from the fact that the 2D membrane structure becomes thermodynam-ically stable via bending [17,18].Through FEG-SEM and TEM analysis,we found that both multilayer graphene nanosheet petals and individual single graphene nanosheets tend to scroll.Therefore,nanovoids and nanocavities would exist in the scrolled graphene nanosheets.Fig.2b shows a high magni-fication TEM image of the basal planes of graphene nano-sheets,which are featureless.Due to scrolling and folding of graphene nanosheets,we would be able to observe the cross section view of stacked graphene nanosheets.Fig.2c shows a HRTEM image of stacked graphene layers,in which it is clearly visible that graphene nanosheets are scrolled to a tubular structure.In general,only 2–3layers of graphene sheets were observed,indicating excellent dispersing of graphene nano-sheets.Fig.2d exhibits another HRTEM image of the cross sec-tion view of stacked graphene layers.The interplanar distance was measured to be 0.37nm corresponding to the spacing of the (002)planes,which is larger than that of graphite (d 002=0.34nm).A selected area electron diffraction pattern (SAED)of the featureless region was recorded along the [001]zone axis (perpendicular to the basal plane)and is shown as the inset in Fig.2d.The diffraction dots were fully indexed to the hexagonal graphite crystal structure,unambiguously con-firming the graphitic crystalline nature of the graphene nanosheets.Raman spectroscopy is a non-destructive approach to char-acterise graphitic materials,in particular to determine ordered and disordered crystal structures of graphene nanosheets.Fig.3shows Raman spectrum of as-prepared graphene nano-sheets.As a comparison,Raman spectrum of high crystalline graphite powders is also presented as the inset in Fig.3.Raman peaks D line and G line can be well distinguished.Graphene nanosheets exhibit a strong D line at 1350cm À1,correspond-ing to a breathing mode or j -point photons of A 1g symmetry,and a relatively weak G line at 1580cm À1,which should be as-signed to the in-plane bond-stretching motion of pairs of C sp 2atoms (the first order scattering of the E 2g photons).The D mode is forbidden in perfect graphite (therefore,very weak as shown in the inset in Fig.3for graphite powders)and only becomes active in the presence of disorder [19].The significant increase of D/G intensity ratio,comparing to the well crystal-line graphite,indicated the decrease of the size of the in-plane sp 2domains and partially disordered crystal structure of graphene nanosheets [20,21].The optical properties of graph-ene nanosheet dispersion was measured by ultraviolet–visible (UV–Vis)spectroscopy (as shown in Fig.4).The spectra show an absorption peak at 265nm,indicating that graphene nano-sheets have a graphite structure.The absorption at 265nm (4.675eV)is generally regarded as the excitation of p -plasmon of graphitic structure [22].The electrochemical properties of graphene nanosheets as anodes in lithium-ion cells were evaluated via constant cur-rent charge/discharge cycling in the potential rangefromFig.2–(a)Low magnification TEM image of giant graphene nanosheets,resembling wavy silk under the TEM beam.(b)High magnification TEM image of the basal plane of graphene nanosheets.(c)HRTEM image of stacked graphene nanosheets,in which the lattice planes correspond to (002)planes with an interlayer distance of 0.37nm.The inset is the SAED pattern recorded on the basal plane of graphene nanosheet.C A R B O N47(2009)2049–205320510.02to 3.0V at1C rate.The charge/discharge profiles of graphene anode in thefirst cycle and the100th cycle are shown in Fig.5.Graphene anode delivered a specific capacity of945mAh/g in the initial discharging and a reversible capac-ity of650mAh/g in thefirst charging.The irreversible capac-ity could be associated with the formation of the SEI layer in thefirst cycle.The shape of the discharge and charge curves is typical of nanosize carbonaceous materials.In the discharge process(lithium insertion),the slope of the curve starts from 3.0V,and the largest part of the specific capacity(>70%)falls in the region below0.5V.During the charge process(lithium extraction),an appreciable potential hystersis exists,in which the inserted lithium ions were removed in a wide voltage range of0.05–3.0V.This observed unique electrochemical behaviour matches well with the micro-and nano-structure of graphene nanosheets.As indicated by FEG-SEM and HRTEM analysis,graphene agglomerates consists of inter-locked multilayer graphene nanosheets.The capacity below 0.5V could correspond to the lithium binding on the basal plane of graphene nanosheets.While,the capacity above 0.5V could be ascribed to the faradic capacitance on the sur-face or on the edge sites of graphene nanosheets[23].It has been proposed that lithium ions can be adsorbed on both sides of the graphene sheet that arranged like a‘‘house of cards’’in hard carbons,leading to two layers of lithium for each graphene sheet,with a theoretical capacity of 744mAh/g through the formation of Li2C6[13,15].On the other hand,nano-cavities between graphene nanosheets due to scrolling and crumpling could also contribute to the lithium storage.According to the micropore mechanism,the extraction of lithium from the nano-cavities has to go through the‘way’of graphene crystallites.The interaction be-tween lithium atoms and nanopores results in an appreciable voltage hysteresis during the charging process[24].Therefore, graphene nanosheet electrode exhibited lithium storage behaviour that was typical of both soft graphitized carbon and hard carbon.The cyclic voltammograms(CV)of graphene anode are shown as the inset in Fig.5.The shape of the CV2052C A R B O N47(2009)2049–2053curves matches well with the charge/discharge profiles (Fig.5).The cyclability of graphene nanosheet electrode was examined under long-term cycling over100cycles,which demonstrated a good cyclic performance and reversibility (as shown in Fig.6).After100cycles,the graphene anode still maintained a specific capacity of460mAh/g,which repre-sents a much enhanced performance than that of graphite anodes.Further improvements are expected by tuning the size of individual graphene nanosheets and graphitic struc-ture of graphene nanosheets through synthesis process and heat treatment.4.ConclusionsIn summary,we have prepared graphene nanosheets in large quantity by a soft-chemistry approach.FEG-SEM observation revealed that loose graphene nanosheets agglomerated and crumpled naturally into shapes resemblingflower-petals. 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