学生石墨烯文献翻译
石墨烯翻译2
石墨烯是一种原子薄的碳片，它拥有非凡的电子特性，所以在电子设备的制造方面得到一些应用，例如，半导体器件和透明电极。
由于这些应用要求高质量的石墨烯，一个高效率的生产，以及可扩展性，实际应用中的一个关键问题是方法。
各种生产方法中，化学气相沉积（CVD）是高效生产高品质的石墨烯薄膜的一种有效方法。
在一个典型的热CVD法合成步骤，在石英管式炉内，气相（例如，甲烷）碳源存在下催化金属基板上加热到1000度，然后在金属基板上分解并且再结晶形成石墨烯薄膜。
通过选择一个碳溶解度低的催化金属，如铜，这样就可以得到高品质，大面积，单层石墨烯。
为了高效的生产石墨烯，使用铜箔的锟对锟式薄膜沉积法合成一直是一个主要目标锟对锟式CVD工艺中，石墨烯连续在金属箔上合成就好像它穿了一双带有一些指南作用的溜冰鞋穿过了高温反应堆。
Hesjedal进行的常压CVD在一个25毫米直径的石英管式炉通过加热铜箔，它的温度达到1000℃。
虽然观察到在整个铜箔表面形成的是连续薄膜石墨烯，但是它被认为是多层的和有缺陷的，可能是因为它是生长在一个较高甲烷浓度的大气压力下。
Yamada等人已经报道的大规模和高流通量的锟对锟式CVD石墨烯合成是在297毫米宽的铜箔上以相对温度较低的400℃通过协助微波等离子体解离甲烷完成的。
然而，所得到的石墨烯薄膜片的电阻高于10千欧姆 /平方米，这在电子应用上是不够的。
因此，通过一种有效的卷对卷过程生产高质量的石墨烯薄膜仍然是一个挑战。
在以往的研究中，已经知道的是石墨烯的质量随着生长温度的增加而提高。
石墨烯的生长率也被认为是石墨烯薄膜的生产高效率效一个重要因素。
如果与类似质量的石墨烯薄膜的增长率相比，石墨烯可以在一个比大气压力低的数量级上的压力下生长。
在上述研究的基础上，我们进行了一个锟对锟式CVD法在高温和低压下环境下合成石墨烯，开发出一种不仅能够选择性地加热大铜箔的反应堆，而且还能够在真空中进行卷对卷处理的铜箔。
石墨烯
Selectivity in the Interaction of Electron Donor and Acceptor Molecules with Graphene and Single-Walled Carbon NanotubesNeenu Varghese,†Anupama Ghosh,†,‡Rakesh Voggu,†Sandeep Ghosh,†,‡and C.N.R.Rao*,†,‡Chemistry and Physics of Materials Unit,New Chemistry Unit and CSIR Centre of Excellence in Chemistry,Jawaharlal Nehru Centre for Ad V anced Scientific Research,Jakkur P.O.,Bangalore 560064,India,and Solid State and Structural Chemistry Unit,Indian Institute of Science,Bangalore 560012,India Recei V ed:August 5,2009;Re V ised Manuscript Recei V ed:August 29,2009Interaction of electron donor and acceptor molecules with graphene samples prepared by different methods as well as with single-walled carbon nanotubes (SWNTs)has been investigated by isothermal titration calorimetry (ITC).The ITC interaction energies of the graphene samples and SWNTs with electron acceptor molecules are higher than those with electron donor molecules.Thus,tetracyanoethylene (TCNE)shows the highest interaction energy with both graphene and SWNTs.The interaction energy with acceptor molecules varies with the electron affinity as well as with the charge-transfer transition energy for different aromatics.Metallic SWNTs interact reversibly with electron acceptor molecules,resulting in the opening of a gap.IntroductionRecent investigations of the interaction of electron donor and acceptor molecules with single-walled carbon nanotubes (SWNTs)have shown that molecular charge transfer affects the electronic structure of the nanotubes.1-4Thus,by the interaction of tetracyanoethylene (TCNE)and tetrathiafulvalene (TTF),it has been possible to introduce metallic to semiconducting transition and vice versa,but specificity of interaction with respect to the electronic nature of the SWNTs is not established.Interaction of electron donor and acceptor molecules with few-layer graphene has been investigated using Raman spectroscopy and other techniques.Molecular charge-transfer interaction between these molecules and graphene causes marked changes in the electronic structure of graphene.5First-principles calculations based on the DFT-GGA method suggest the interaction of graphene with donor and acceptor molecules to involve charge transfer,giving rise to the associated Raman band shifts.6We felt that it was important to carry out a comparative investigation of the interaction of donor and acceptor molecules with graphene and SWNTs in terms of the relative interaction energies.For this purpose,we have employed isothermal titration calorimetry (ITC)to measure the heats of interaction of a few electron donor and acceptor molecules with graphene and SWNTs.ITC is known to be a sensitive tool to study such binding interactions,as illustrated in the case of nucleobases.7,8ITC may not provide actual interaction energies but gives trends in interaction energies.Since SWNTs prepared by arc discharge and other methods constitute mixtures of semiconducting and metallic species,9we have investigated the interaction of pure metallic nanotubes,specially prepared by a new method,with donor and acceptor molecules,in order to examine the specificity of interaction.Besides showing that electron-withdrawing mol-ecules interact more strongly with graphene and SWNTs,the present study demonstrates that doping by charge transfer changes the Fermi level of SWNTs,to create a band gap in the initially metallic SWNTs.In the case of graphene also,a band gap is opened through charge transfer by electron acceptor molecules.Experimental SectionIsothermal titration calorimetric experiments were carried out with graphene samples prepared by three different methods,namely,thermal exfoliation of graphitic oxide (EG),10arc discharge of graphite in hydrogen (HG),11and conversion of nanodiamond (DG).12Dodecylamide derivatives of EG (EG-A)and DG (DG-A)were prepared by the literature procedure.13The graphene samples were characterized by atomic force microscopy (AFM),transmission electron microscopy (TEM),field-emission scanning electron microscopy (FESEM),and Raman spectroscopy.The EG,DG,and HG samples contained 3-4,5-6,and 2-3layers,respectively.The surface area of the HG sample is small (∼400m 2g -1)compared to DG (∼800m 2g -1)and EG (∼1100m 2g -1).EG-A ,DG-A,and HG dispersed in toluene were used in the experiments.ITC experiments were carried out with 1mg mL -1dispersions of graphene.The graphene dispersion was taken in the sample cell of the isothermal titration calorimeter and the reference cell filled with toluene.10mM solutions of tetracyanoethylene (TCNE),tetracyanoquinodimethane (TCNQ),2,4,7-trinitrofluo-renone (TNF),tetrathiafulvalene (TTF),and N ,N -dimethyl para-phenylenediamine (DMPD)were prepared in toluene.In each experiment,10µL of 10mM of each of these solutions taken in a syringe was added in equal intervals of 3min to the sample cell and the heat changes were measured after each addition.The experiments were carried out at a constant temperature of 26°C.Control experiments were performed by titrating the respective molecules against toluene under the same conditions,and the data so obtained were subtracted from the experimental data to eliminate the dilution effect.*To whom correspondence should be addressed.E-mail:cnrrao@jncasr.ac.in.Fax:+918022082760.†Jawaharlal Nehru Centre for Advanced Scientific Research.‡Indian Institute of Science.1685510.1021/jp9075355CCC:$40.752009American Chemical SocietyPublished on Web09/08/20092009,113,16855–16859SWNT samples were prepared by the arc discharge method and purified by successive acid and hydrogen treatment.14,15Metallic SWNTs were prepared by DC arc evaporation of a graphite rod containing the Ni +Y 2O 3catalyst,under a continuous flow of helium bubbled through Fe(CO)5.16The samples so obtained were nearly pure metallic SWNTs (around 95%).SWNT samples dispersed in o -dichlorobenzene (DCB)were sonicated for 1h to obtain 1mg mL -1solutions.Interaction of SWNTs with donor and acceptor molecules was studied in DCB solvent in the same manner as the graphene samples.In order to compare the results obtained with graphene and SWNTs,graphene samples (EG,EG-A,and HG)were also dispersed in DCB by sonication for 1h to obtain 1mg mL -1solutions.These solutions were used to study the interaction with TCNE.Results and DiscussionWe shall first discuss the results of ITC measurements on the interaction of graphenes with donor and acceptor molecules.Figure 1shows typical data obtained with 1.0mg mL -1solutions of EG-A in toluene with TCNE and TTF.Raw ITC data for the blank titration of 10mM TCNE and TTF against toluene are shown in Figure 1a and d.Figure 1b and e show the raw data for the titration of 10mM TCNE and TTF solutions against 1.0mg mL -1EG-A solution.The ITC response in the TCNE and TTF titrations against EG-A is exothermic,as shown in Figure 1b and e.In order to eliminate dilution effects,heats from the blank titration data were subtracted from the molecule -graphene titration data.Figure 1c and f show the integrated heat changes (enthalpy changes in kcal mol -1)aftereach injection of TCNE and TTF,respectively,after correcting for the heat of dilution.The exothermicity of the peaks reduces with progressive injection as the number of free sites for the binding of molecules available on the graphene decreases.The heat of reaction curve should ideally be sigmoidal in shape,but the limited solubility of graphene in toluene does not permit recording of the initial part of the sigmoidal curve.Absolute binding energies cannot therefore be obtained from the present data.The relative affinities of the different electron donor and acceptor molecules can,however,be estimated from the heat liberated in the initial injections,since all of the experiments were performed under similar conditions.The relative binding energies obtained from the initial points of the integrated heat plots in the case of EG-A and HG are listed in Table 1.The trend in the relative binding energies of electron acceptor molecules with EG-A obtained from ITC measurements isFigure 1.ITC data recorded for the interaction of TCNE and TTF with EG-A.ITC response for the blank titration with TCNE (a)and TTF (d).The raw ITC data for the titration of TCNE and TTF with 1.0mg mL -1of EG-A is shown in parts b and e.Parts c and f show the integrated heat of reaction at each injection of TCNE and TTF,respectively.TABLE 1:Energies of Interaction of Graphene and SWNTs with Electron Donor and Acceptor Molecules Obtained from ITC Measurements (in kcal mol -1)aEG-A bHG b SWNT c TCNE -5.88d -4.2-4.25TCNQ -0.24-0.32TNF -0.12-0.30-0.06DMPD -0.40-0.12-7.4e TTF-0.07-0.18aThe concentration of graphene and SWNTs was 1mg mL -1in all of the cases.b In toluene solvent.c In o -dichlorobenzene (DCB)solvent.d With DG-A,the value is -1.6.e This high value is due to interaction with the semiconducting SWNTs.16856J.Phys.Chem.C,Vol.113,No.39,2009LettersTCNE >TCNQ >TNF.Interaction energies of electron donor molecules with the graphene samples are considerably lower,the highest value being with N ,N -dimethyl para-phenylenedi-amine (DMPD).The interaction energy of TTF is lower than that of DMPD.In the case of the interaction of TCNE with the different graphene samples,the highest ITC interaction energy is found to be with EG-A (-5.9kcal mol -1)and the lowest with DG-A (-1.6kcal mol -1).It is noteworthy that the surface area of EG is highest among the graphene samples.17Interaction energies of graphene with different donor and acceptor molecules have been calculated by employing first-principles calculations using a linear combination of atomic orbital DFT methods implemented in the SIESTA package.6This study shows evidence for charge transfer between graphene and the donor and acceptor molecules.According to this study,the interaction energies of graphene with TCNE and TCNQ are greater than that with TTF.This is consistent with the results from our ITC studies.The calculations also show that a gap develops in the electronic structure of graphene on interaction with these molecules.We have obtained ITC interaction energies of SWNTs with donor and acceptor molecules by a procedure similar to that with graphene by using o -dichlorobenzene (DCB)as the solvent.Typical data obtained for 1.0mg mL -1solutions of SWNTs in DCB interacting with TCNE and TTF are given in Figure 2,the raw data for the blank titration of 10mM TCNE and TTF against DCB being shown in Figure 2a and d,respectively.Raw data for the titration of 10mM TCNE and TTF solutions against the 1.0mg mL -1SWNT solution are given in Figure 2b and e.The ITC response in the titrations is exothermic,as revealed by Figure 2b and e.The integrated heat changes after each injection of TCNE and TTF,respectively (after correcting for the heat of dilution),are shown in Figure 2c and f.Just as in the case of graphene,exothermicity of the peaks reduces with progressive injection.The energies of interaction calculated from the initial points of the integrated heat plots are listed in Table 1.It is interesting that,for electron acceptor molecules,the trend in the ITC interaction energies with SWNTs is the same as that with graphene (TCNE >TCNQ >TNF).Among the donor molecules,DMPD shows a higher interaction energy than TTF.Since the data for SWNTs were obtained in DCB solvent,we wanted to compare the data of graphenes in the same solvent.The relative interaction energies of TCNE in DCB solvent are -1.4,-0.7,and -0.6kcal mol -1with EG-A,EG,and HG,respectively,giving the trend EG-A >EG >HG.This trend parallels that of the surface area.The interaction energy of SWNTs (-4.3kcal mol -1)with TCNE is generally larger than that for the graphene samples.First-principles calculations of Pati in this laboratory (personal communication)has shown the interaction energy of SWNTs with TCNQ to be greater than that with TTF.SWNTs exhibit a higher interaction energy than graphene.Interaction energies of graphene as well as SWNTs with electron acceptor molecules increase progressively with the electron affinities of the acceptors,as can be seen in Figure 3a.18This result confirms that charge transfer between the acceptor molecules and graphene or SWNTs contributes sig-nificantly to the interaction energy.Indirect confirmation of this conclusion is also provided by the fact that the interaction energy varies systematically with the charge-transfer transition energy,Figure 2.ITC data recorded for the interaction of TCNE and TTF with SWNTs.ITC response for the blank titration with TCNE (a)and TTF (d).The raw ITC data for the titration of TCNE and TTF with 1.0mg mL -1of SWNT is shown in parts b and e.Parts c and f show the integrated heat of reaction at each injection for TCNE and TTF,respectively.Letters J.Phys.Chem.C,Vol.113,No.39,200916857hυCT,of the acceptors with an aromatic such as anthracene,19-21 as shown in Figure3b.SWNTs prepared by arc-discharge and other methods contain a mixture of metallic and semiconducting species,9the propor-tion of semiconducting nanotubes being around66%.The interaction energies that we have given in Table1correspond to the mixture of metallic and semiconducting SWNTs.It would be more instructive if one were able to determine the interaction energy between the donor and acceptor molecules with pure metallic or semiconducting nanotubes.ITC measurements on the interaction of metallic SWNTs with donor and acceptor molecules reveal the interaction energy to be high in the case of TCNE(-7.4kcal mol-1),the energy varying in the order TCNE>TNF>TCNQ in the case of the acceptor molecules (Table2).Interaction energies of acceptor molecules with metallic SWNTs are generally higher than those with the as-prepared SWNTs(containing the mixture of metallic and semiconducting species).The interaction energy of metallic nanotubes with a donor molecule such as TTF is negligible and could not be measured by ITC.This result shows that metallic nanotubes specifically interact with electron-withdrawing mol-ecules.In order to understand the nature of this interaction,we examined the effect of acceptor and donor molecules on the Raman spectrum of metallic SWNTs.In Figure4,we show the Raman G-band of metallic nanotubes before and after the interaction with TCNE(10mM).On interaction with TCNE, the feature around1540cm-1due to the metallic species1,22disappears completely and the band maximum shifts to1582 cm-1.This change in the Raman spectrum corresponds to the opening of a gap due to a change in the Fermi level of SWNTs, giving rise to an apparent metal-semiconductor transition. Electron-donating molecules have no effect on the Raman spectrum of metallic SWNTs.First-principles calculations also show that metallic(9,0)SWNTs develop a gap on interaction with TCNE.Electron-donating molecules,however,specifically interact with semiconducting nanotubes.Raman spectra show that semiconducting SWNTs exhibit an intense metallic feature in the1540cm-1region on interaction with TTF. ConclusionsIn conclusion,ITC provides a satisfactory means to investi-gate the interaction of graphene as well as SWNTs with electron donor and acceptor molecules.Although ITC does not provide absolute interaction energies,it gives trends in interaction energy which are of value.Interaction energies of electron acceptor molecules(TCNE,TCNQ,and TNF)with graphene samples are higher than those of electron donor molecules(TTF and DMPD).Among the different graphene samples,the function-alized graphene EG-A shows the highest interaction energy.The studies carried out by us are on few-layer graphenes,but it would be somewhat difficult to investigate single-layer graphenes in this manner owing to its agglomeration in solid state.Interaction energies of SWNTs obtained from ITC are generally higher than those with graphene samples.Here again,TCNE gives the highest interaction energy.Metallic SWNTs interact reversibly with electron acceptor molecules,such as TCNE,the interaction energy being higher than with as-prepared SWNTs(containing a mixture of metallic and semiconducting species).On interac-tion of metallic SWNTs with TCNE,the metallic feature in the Raman G-band disappears,due to the opening of a gap through molecular charge transfer.It would be worthwhile to study the interaction of pure semiconducting SWNTs with donor and acceptor molecules by a combined use of ITC Raman spectroscopy.Figure3.Variation of interaction energies of EG-A and SWNTs with electron acceptors(a)with the electron affinity of acceptors,E A,and (b)with the charge-transfer transition energy,hυCT,with anthracene (EG-A,squares;SWNTs,circles;metallic SWNTs,triangles).TABLE2:Energies of Interaction of SWNTs with Electron Donor and Acceptor Molecules Obtained from ITC Measurements(in kcal mol-1)aSWNT b metallic SWNT TCNE-4.25-7.4TCNQ-0.32-0.64TNF-0.06-0.80TTF-0.18+0.07a The concentration of SWNTs was1mg mL-1in DCB solvent in all of the cases.b Mixture containing66%semiconducting and 33%metallic SWNTs.Figure4.Raman G-band of(a)metallic SWNTs and(b)metallic SWNTs after interaction with TCNE(10mM).16858J.Phys.Chem.C,Vol.113,No.39,2009LettersAcknowledgment.We thank indaraj for help with the preparation of SWNTs.References and Notes(1)Voggu,R.;Rout,C.S.;Franklin,A.D.;Fisher,T.S.;Rao,C.N.R. 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石墨烯光学性质以及二维材料的纳米光子学性质浅析
使光集中用于等离子体共振，从而使局部电场得到显著增强。在量子效 率方面得到巨大提高。但也会导致可操作宽带的范围减少。
② 整合量子点和石墨烯
用胶体量子点覆盖石墨烯可以获得具有能够获得具有 108 电子/光子的的超高光电探测和 107AW-1 的光响应的光电探测器。但由于需要长时间产生增益， 它们的运算速度也很低。
石墨烯等离激元学
由于石墨烯同时具有高的载流子迁移率和高导电性，它也成为了一种极具前 景的太赫兹到中红外等离子体器件应用的候选材料。等离子体具有高局域场 强度，广泛用于包括光学天线，近场光学显微镜，化学和生物传感器和亚波 长光学器件等。和传统等离子材料相比具有以下优点： ① 可以通过化学掺杂和门电压调控。 ② 具有更强的局域性 ③ 低损耗和长寿命 ④ 结晶度
过渡金属二硫化物光子学
过渡金属二硫化物(TMDCs)是化学公式为MX2的材料，M代表Mo、W、Nb、Re 这一类元素，X是硫元素。
TMDCs的层间相互作用是弱范德华力，而平面成键是强共价键。因此TMDCs 可以被剥离到类似石墨烯的薄膜结构，显著地扩展了二维材料的材料库。一 些二维的TMDCs，如钼和钨的硫化物，在多层的形式中有间接带隙，而在它们 的单层形式中成为直接带隙半导体。他们相当大的和可调带隙，不仅仅能产 生强的光致发光，也能打开像光电探测器，能量收集器，电致发光等光电器 件的大门。而且不同于石墨烯基器件，他具有可操作的光谱范围。另外，在 一些二维的TMDCs中已经证明了的奇异光学性质，如谷相干和谷选择性的圆二 色性，使这些材料非常有希望发现新的物理现象。
① 光与石墨烯的相互作用从能带跃迁的角度主要有两种：带间跃迁和带内跃 迁。远红外和太赫兹光谱区为带内跃迁，近红外及可见光光谱区主要是带 间跃迁；
石墨烯外国文献翻译
石墨烯基础材料的光电特性Inhwa Jung在这研究报告中，石墨烯基础材料的光电性能被调查，特别是研究具有氧化石墨单层的石墨烯氧化物的物理和化学性质和它的化学简式与石墨的不同。
尽管氧化石墨在一百多年前就被Brodie（在1859年）合成，但直到现在特殊层还没被深入研究，与我们正在研究的石墨烯氧化物比较，物理学家在原始石墨烯(石墨的一个层)发现了卓越的物理输送特性同时也显示石墨烯在纳米电子方面的潜力;这提高我们对包括石墨烯氧化物在内的化学法改变石墨性质的兴趣。
从石墨烯的光学性质方面来看，为了识别和测量石墨烯基底的有效光学性质，由于由硅上的薄介电层组成的基底的作用，一个直截了当的方法被提出。
通过这个方法和优化介电层的厚度，获得石墨烯基底独特晶片和基底的的巨大差别。
选择合适的光学性能和介电层的厚度，氧化石墨的有效折射率和光学吸收系数可以减少氧化石墨，通过对比预测与实际测量的差别可以获得石墨烯。
椭圆光度法成像是一种为光学成像和表征超薄材料（1nm~）例如特殊化学法改变的石墨烯晶片和少层氧化石墨烯晶片保持电势的方法，单独使用椭圆光度法成像无论能否确定它的光学性质和厚度都是非常有趣的，传统的光谱椭圆光度法也可以应用到比特殊晶片宽数毫米的多层叠加的氧化石墨上。
利用两种成像方法得到的结果对比最大的区别在于光学性质的差异。
观察热处理过的单体和多层叠加，多层叠加和单层的区别类似氧化石墨（无论是特殊晶片还是多层叠加）的对比结果。
分别从轮廓仪和AFM得到厚度，解释厚度和光学性质在热处理时会改变的模型被提出。
电学特征是前面提及的异常原始石墨性能基本的技术领域，通过在真空中加热单层石墨氧化物(沉积于基体)对材料的电阻率进行了监测。
通过监测随时间和温度响应的电导率能够表明,导电率的变化可能与一个激活的化学过程有关, 并由此可以获得活化能(势垒高度)。
通过高达85 S/m的时间温度曝光可以知道单层的氧化石墨的导电率，其次在真空中加热并与气相肼发生化学还原可以成倍地得到更高的导电率，如原始石墨一样，氧化石墨导电率对电场方向很敏感，伏安测量还表明，氧化石墨的电气性能与石墨烯存在差别。
“Graphene”研究及翻译
“Graphene”研究及翻译摘要：查阅近5年我国SCI、EI期源刊有关石墨烯研究873篇，石墨烯研究的有关翻译存在很大差异。
从石墨烯的发现史及简介，谈石墨烯内涵及研究的相关翻译。
指出“石墨烯”有关术语翻译、英文题目、摘要撰写应注意的问题。
关键词：石墨烯；石墨烯术语；翻译石墨烯是目前发现的唯一存在的二维自由态原子晶体，它是构筑零维富勒烯、一维碳纳米管、三维体相石墨等sp2杂化碳的基本结构单元，具有很多奇异的电子及机械性能。
因而吸引了化学、材料等其他领域科学家的高度关注。
近5年我国SCI、EI期源刊研究论文873篇，论文质量良莠不齐，发表的论文有35.97%尚未被引用过，占国际论文被引的4.84%左右。
石墨烯研究的有关翻译也存在很大差异。
为了更好的进行国际学术交流，规范化专业术语。
本文就“graphene”的内涵及翻译谈以下看法。
l “Graphene”的发现史及简介1962年，Boehm等人在电镜上观察到了数层甚至单层石墨（氧化物）的存在，1975年van Bom-mel等人报道少层石墨片的外延生长研究，1999年德克萨斯大学奥斯汀分校的R Ruoff等人对用透明胶带从块体石墨剥离薄层石墨片的尝试进行相关报道。
2004年曼彻斯特大学的Novoselov和Geim小组以石墨为原料，通过微机械力剥离法得到一系列叫作二维原子晶体的新材料——石墨烯，并于10月22日在Sclence期刊上发表有关少层乃至单层石墨片的独特电学性质的文章，2010年Gelm和No-voselov获得了诺贝尔物理学奖。
石墨烯有着巨大的比表面积（2630 m2/g）、极高的杨氏模量（1.06 TPa）和断裂应力（～130GPa）、超高电导率（～106 S/cm）和热导率（5000W/m·K）。
石墨烯中的载流子迁移率远高于传统的硅材料，室温下载流子的本征迁移率高达200000 cm2/V.s），而典型的硅场效应晶体管的电子迁移率仅约1000 cm2/V.s。
毕业论文外文翻译-负载银的掺氮石墨烯概论
学号：10401604常州大学毕业设计（论文）外文翻译（2014届）外文题目Easy synthesis of nitrogen-doped graphene–silvernanoparticle hybrids by thermal treatment ofgraphiteoxide with glycine and silver nitrate 译文题目通过水热处理氧化石墨烯、甘氨酸和硝酸银简便地合成掺氮石墨烯-银纳米粒子复合物外文出处CARBON50(2012)5148–5155学生王冰学院石油化工学院专业班级化工106校内指导教师罗士平专业技术职务副教授校外指导老师专业技术职务二○一四年二月通过水热处理氧化石墨烯、甘氨酸和硝酸银简便地合成氮杂石墨烯-银纳米粒子杂合物Sundar Mayavan,Jun-Bo Sim,Sung-Min Choi摘要：氮杂石墨烯-银纳米粒子杂合物在500℃通过水热处理氧化石墨烯（GO）、甘氨酸和硝酸银制得。
甘氨酸用于还原硝酸根离子，甘氨酸和硝酸根混合物在大约200℃分解。
分解的产物可作为掺杂氮的来源。
水热处理GO、甘氨酸和硝酸银混合物在100℃可形成银纳米粒子，200℃时GO还原，300℃时产生吡咯型掺氮石墨烯，500℃时生成吡咯型掺氮石墨烯。
合成物质中氮原子所占百分比为13.5%.在合成各种纳米金属粒子修饰的氮杂石墨烯方面，该合成方法可能开辟了一个新的路径，其在能量储存和能量转换设备方面很有应用价值。
1.引言石墨烯是所有石墨材料的基本构件，其蜂窝状晶格由单层碳原子排列而成。
它表现出与结构有关的独特电子、机械和化学性质，具有较高的比表面积（2630-2965m2g-1）[1–3]。
化学掺杂杂原子石墨烯像掺杂氮原子，极大地引起了人们的兴趣，因其在传感器、燃料电池的催化剂和锂离子电池的电极等方面具有应用潜力[4–6]。
氮原子的掺杂改变了石墨烯的电子特性和结构特性，导致其电子移动性更强，产生更多的表面缺位。
Layer-by-Layer Assembly of Ultrathin Composite Films
Layer-by-Layer Assembly of Ultrathin Composite Films from Micron-Sized Graphite Oxide Sheets andPolycationsNina I.Kovtyukhova,*,†Patricia J.Ollivier,‡Benjamin R.Martin,‡Thomas E.Mallouk,*,‡Sergey A.Chizhik,§Eugenia V.Buzaneva,|andAlexandr D.Gorchinskiy|Institute of Surface Chemistry,National Academy of Sciences of Ukraine,31,Pr.Nauky, 252022Kyiv,Ukraine;Department of Chemistry,The Pennsylvania State University, University Park,Pennsylvania16802;Metal-Polymer Research Institute,32A Kirov Street, Gomel,246652,Belarus;and National T.Shevchenko University,64,Vladimirskaya Str.,252033Kyiv,UkraineReceived November24,1998.Revised Manuscript Received December28,1998Unilamellar colloids of graphite oxide(GO)were prepared from natural graphite and were grown as monolayer and multilayer thin films on cationic surfaces by electrostatic self-assembly.The multilayer films were grown by alternate adsorption of anionic GO sheets and cationic poly(allylamine hydrochloride)(PAH).The monolayer films consisted of11-14Åthick GO sheets,with lateral dimensions between150nm and9µm.Silicon substrates primed with amine monolayers gave partial GO monolayers,but surfaces primed with Al13O4-(OH)24(H2O)127+ions gave densely tiled films that covered approximately90%of the surface. When alkaline GO colloids were used,the monolayer assembly process selected the largest sheets(from900nm to9µm)from the suspension.In this case,many of the flexible sheets appeared folded in AFM images.Multilayer(GO/PAH)n films were invariably thicker than expected from the individual thicknesses of the sheets and the polymer monolayers,and this behavior is also attributed to folding of the sheets.Multilayer(GO/PAH)n and(GO/ polyaniline)n films grown between indium-tin oxide and Pt electrodes show diodelike behavior,and higher currents are observed with the conductive polyaniline-containing films. The resisitivity of these films is decreased,as expected,by partial reduction of GO to carbon.IntroductionThe assembly of composite thin films from lamellar inorganic particles and organic macromolecules is an inexpensive and versatile route to functional nanometer-scale structures.1These films are grown by a wet chemical,layer-by-layer adsorption method,which is similar to that developed earlier by Decher and co-workers for organic polyelectrolytes.2The addition of inorganic components offers the possibility of added optical,electronic,magnetic,mechanical,and thermal properties that may be difficult to achieve by using organic polymers alone.Additionally,the continuous inorganic sheets provide a barrier to interpenetration of sequentially deposited polymer or nanoparticle layers, a feature that can be important in thin films intended to act as current rectifiers,photodiodes,or Coulomb blockade devices.Several electronic and photonic ap-plications along these lines have established the utility of this method.3The layer-by-layer assembly method relies on the exfoliation of solids to produce colloids of sheets,which typically have nanometer thicknesses and lateral di-mensions of tens of nanometers to microns.Exfoliation procedures based on ion exchange and redox reactions have been developed for a variety of lamellar solids.4 Thus,multilayer inorganic/organic films have been grown from lamellar metal phosphates,titanates,nio-bates,5silicates,1b and metal chalcogenides,6compounds which in bulk form possess transport properties ranging from insulating to semimetallic.Recently,Fendler and co-workers have shown that such films can also be†National Academy of Sciences of Ukraine.‡The Pennsylvania State University.§Metal-Polymer Research Institute.|National T.Shevchenko University.(1)(a)Iler,R.K.J.Colloid Interface Sci.1966,21,569.(b)Kleinfeld,E.R.;Ferguson,G.S.Science1994,265,370.(c)Fendler,J.H.; Meldrum,F.Adv.Mater.1995,7,607.(d)Mallouk,T.E.;Kim,H.-N.; Ollivier,P.J.;Keller,S.W.In Comprehensive Supramolecular Chemistry;Alberti,G.,Bein,T.,Eds.;Elsevier Science;Oxford,UK, 1996;Vol.7,pp189-218.(2)Decher,G.Science1997,277,1232.(3)(a)Kaschak,D.M.;Mallouk,T.E.J.Am.Chem.Soc.1996,118, 4222.(b)Feldheim,D.L.;Grabar,K.C.;Natan,M.J.;Mallouk,T.E. J.Am.Chem.Soc.1996,118,7640.(c)Keller,S.W.;Johnson,S.A.; Yonemoto,E.H.;Brigham,E.S.;Mallouk,T.E.J.Am.Chem.Soc. 1995,117,12879.(d)Cassagneau,T.;Mallouk,T.E.;Fendler,J.H.J. Am.Chem.Soc.1998,120,7848.(4)(a)Jacobson,A.J.Mater.Sci.Forum1994,152-153,1.(b) Jacobson,A.J.In Comprehensive Supramolecular Chemistry;Alberti, G.,Bein,T.,Eds.;Elsevier Science;Oxford,UK,1996;Vol.7,pp315-335.(5)(a)Keller,S.W.;Kim,H.-N.;Mallouk,T.E.J.Am.Chem.Soc. 1994,116,8817.(b)Fang,M.,Kim,C.-H.;Saupe,G.B.;Kim,H.-N.; Waraksa,C.C.;Miwa,T.;Fujishima,A.;Mallouk,T.E.Submitted to Chem.Mater.(6)Ollivier,P.J.;Kovtyukhova,N.I.;Keller,S.W.;Mallouk,T.E. J.Chem.Soc.,mun.1998,1563.771Chem.Mater.1999,11,771-77810.1021/cm981085u CCC:$18.00©1999American Chemical SocietyPublished on Web01/28/1999grown from graphite oxide(GO),7which can subse-quently be reduced electrochemically to make electroni-cally conducting graphitic films.In their work,GO nanoparticles were prepared from synthetic graphite. They noted that the multilayer films consisted of incompletely exfoliated platelets that were tens of nanometers in their lateral dimensions.In this paper, we revisit the assembly of GO/polycation thin films, using GO prepared from natural crystals.We show that exfoliated GO derived from these crystals is a mechani-cally robust material that deposits conformally on cationic surfaces as micron-sized,nanometer-thick sheets. Graphite oxide is a pseudo-two-dimensional solid in bulk form,with strong covalent bonding within the layers.Weak interlayer contacts are made by hydrogen bonds between intercalated water molecules.8-11The carbon sheets in GO contain embedded hydroxyl and carbonyl groups,as well as carboxyl groups situated mainly at the edges of the sheets.8,9,12While there is no consensus as to the precise structure of GO layers, different structural models,9a,b,10which correspond to an ideal formula of C8O2(OH)2,have been advanced.A recent study of the structure of GO argues from13C and 1H NMR evidence for the presence of epoxy groups.13 Nakajima and co-workers have proposed that the carbon layers in GO are linked together in pairs by sp3C-C bonds perpendicular to the sheets.10According to Kli-nowski et al.,13the carbon layers in GO contain two kinds of domains,aromatic regions with unoxidized benzene rings and aliphatic regions with six-membered carbon rings.The relative size of the domains,which are randomly distributed,depends on the degree of oxidation.In both models,the hydroxyl groups project above and below the carbon grid.The phenolic hydroxyl groups are acidic and,together with the carboxyl groups, are responsible for the negative charge on the GO sheets in aqueous suspensions.9,13The surface charge density of colloidal GO particles(degree of oxidation85%)was measured by Fendler and co-workers as0.4per100Å2.7 The GO interlayer distance is not constant and depends strongly on the GO:H2O ratio.8-10,15In very dilute aqueous suspensions,the interlayer distance is large,so interaction between the layers is sufficiently weak that exfoliation occurs.8Our previous research showed that the number of layers in the GO colloidal particles can be controlled by the dilution of the suspen-sions.16,17The adsorption capacity for Cu(II)ions,which was for both aqueous suspensions16and thin films deposited from these suspensions on powder supports (ZnO,Al2O3,fumed SiO2),17increased with decreasing GO concentration in the starting suspension.For ex-ample,the adsorption capacity of GO films on SiO2 increased by a factor of2.4when the GO concentration in the starting suspension was decreased from1.0to 0.3g/L.This result shows that more complete exfoliation provides increased access to the GO functional groups. For samples prepared from the colloids with GO con-centrations of0.02-0.3g/L,the maximum adsorption capacity,22-24mmol/g,was obtained.This value is close to the total quantity of oxygen-containing groups in GO(25mmol/g9)and gives indirect evidence that dilute GO colloids are exfoliated as monolayers.We report here a detailed study of the preparation and characterization of GO/polycation films grown on planar Si and Al2O3/Al ing atomic force microscopy(AFM),ellipsometry,and electrical mea-surements,the following questions have been addressed: What does the first layer of the sheets adsorbed on a substrate look like microscopically?Can we affect the quality of mono-and multilayer films by varying the conditions of their deposition and the chemical composition of the substrate surface? What are the electronic properties of GO/polycation films,and how are they influenced by the nature of the polycation?Experimental SectionMaterials.GO was synthesized from natural graphite powder(325mesh,GAK-2,Ukraine)by the method of Hum-mers and Offeman.18It was found that,prior to the GO preparation according to ref18,an additional graphite oxida-tion procedure was needed.Otherwise,incompletely oxidized graphite-core/GO-shell particles were always observed in the final product.The graphite powder(20g)was put into an80°C solution of concentrated H2SO4(30mL),K2S2O8(10g),and P2O5(10g).The resultant dark blue mixture was thermally isolated and allowed to cool to room temperature over a period of6h.The mixture was then carefully diluted with distilled water,filtered,and washed on the filter until the rinse water pH became neutral.The product was dried in air at ambient temperature overnight.This preoxidized graphite was then subjected to oxidation by Hummers’method.The oxidized graphite powder(20g)was put into cold(0°C)concentrated H2SO4(460mL).KMnO4(60g)was added gradually with stirring and cooling,so that the temperature of the mixture was not allowed to reach20°C.The mixture was then stirred at35°C for2h,and distilled water(920mL)was added.In 15min,the reaction was terminated by the addition of a large amount of distilled water(2.8L)and30%H2O2solution(50 mL),after which the color of the mixture changed to bright yellow.The mixture was filtered and washed with1:10HCl solution(5L)in order to remove metal ions.The GO product was suspended in distilled water to give a viscous,brown,2% dispersion,which was subjected to dialysis to completely remove metal ions and acids.The resulting0.5%w/v GO dispersion,which is stable for a period of years,was used to prepare exfoliated GO.Exfoliation was achieved by dilution of the0.5%GO disper-sion(1mL)with deionized water(24mL),followed by15min sonication.The resulting homogeneous yellow-brown sol, which contained0.2g/L GO,was stable for a period of months and was used for film preparation.An aqueous solution(0.01M)of poly(allylamine hydrochlo-ride),PAH,(Aldrich,MW)50000-65000)was adjusted to pH7with NH3and was used for growth of polycation layers.(7)(a)Kotov,N.A.;Dekany,I.;Fendler,J.H.Adv.Mater.1996,8,637.(b)Cassagneau,T.;Fendler,J.H.Adv.Mater.1998,10,877.(8)(a)Thiele,H.Kolloid-Z1948,111,15.(b)Croft,R.C.Quart.Rev.1960,14,1.(9)(a)Scholz,W.;Boehm,H.P.Z.Anorg.Allg.Chem.1969,369,327.(b)Clauss,A.;Boehm,H.P.;Hofmann,U.Z.Anorg.Allg.Chem.1957,291,205.(10)Nakajima,T.;Mabuchi,A.;Hagiwara,R.Carbon1988,26,357.(11)Karpenko,G.;Turov,V.;Kovtyukhova,N.;Bakai,E.;Chuiko,A.Theor.Exp.Chem.(Russ.)1990,1,102.(12)Hadzi,D.;Novak,A.Trans.Faraday.Soc.1955,51,1614.(13)Lerf,A.;He,H.;Forster,M.;Klinowski,J.J.Phys.Chem.B1998,102,4477.(14)Hennig,Z.Progr.Inorg.Chem.1959,1,125.(15)Lagow,R.J.;Badachhape,R.B.;Wood,J.L.;Margrave,J.L.J.Chem.Soc.Dalton1974,1268.(16)Kovtjukhova,N.I.;Karpenko,G.A.Mater.Sci.Forum1992,91-93,219.(17)(a)Kovtyukhova,N.I.;Chuiko,A.A.Abstracts;Fall Meetingof the Materials Research Society,1994,Boston,C9.6.(b)Kovtyukhova,N.I.;Buzaneva,E.V.;Senkevich,A.Carbon1998,36,549.(18)Hummers,W.;Offeman,R.J.Am.Chem.Soc.1958,80,1339. 772Chem.Mater.,Vol.11,No.3,1999Kovtyukhova et al.An aqueous solution of doped polyaniline(PAN)was made from a saturated solution of the emeraldine base form in dimethylformamide.A3mL portion of this solution was slowly added with stirring to26mL of water,which had been acidified to pH3.5with aqueous HCl.The pH of the final PAN solution was then adjusted to2.5by addition of aqueous HCl.The alu-minum Keggin ion Al13O4(OH)24(H2O)127+was prepared trom Al13O4(OH)25(H2O)11(SO4)3‚x(H2O),which was available from a previous study.5Briefly,0.102g of the sulfate salt was added to a solution of0.042g of BaCl2in200mL of water and stirred overnight.The resulting0.3mM solution of the chloride salt of the aluminum Keggin ion was filtered using a0.2µm filter.Polished(100)Si wafers were sonicated in CCl4for15min and then rinsed with2-propanol and water.Their surface was then hydroxylated by30min sonication in“piranha”solution (4:1concentrated H2SO4:30%H2O2)(CAUTION:piranha solution reacts violently with organic compounds!)and was rinsed sequentially with water,methanol,and1:1methanol/ toluene before the surface derivitization steps began.Aluminum foil,Al-coated glass,both bearing a native oxide, and ITO glass were cleaned by washing with hexane for15 min prior to GO adsorption.Multilayer GO/PAH Film Growth.Hydroxylated silicon wafers were primed with one of three different types of cationic monolayers in order to initiate the growth of the GO films. This was achieved either by(1)reacting with4-((dimethyl-methoxy)silyl)butylamine(15h treatment with a5%toluene solution under dry Ar,over KOH at ambient temperature)or by(2)adsorbing a monolayer of aluminum Keggin ions(5min adsorption from aqueous solution of the chloride salt at80°C19) or by(3)adsorbing PAH(15min adsorption from a0.01M aqueous solution at pH7and ambient temperature).The primed Si substrates(1,2,and3)are designated hereafter as Si(NH2),Si(OH)/Al-Kg,and Si(OH)/PAH,respectively.The primed substrates were immersed in an aqueous(pH 5)or aqueous ammonia(pH9)GO sol(0.2g/L)for15min and then rinsed with deionized water and dried in flowing Ar.The samples were then immersed in aqueous PAH solutions for 15min,rinsed with deionized water,and dried in flowing Ar. Multilayer GO/PAH films were grown by repeating these adsorption cycles.Preliminary experiments had shown that the thickness of a deposited layer(estimated by ellipsometry) does not depend on the substrate/solution contact time in the range from2min to2h.For electronic measurements, multilayer(GO/PAH)14and(GO/PAN)30films were grown on ITO in similar adsorption cycles.For comparison purposes,a GO colloid film(ca.90nm thick)was prepared by dip-coating the ITO/glass in the GO colloidal dispersion.Characterization.Atomic force microscopy(AFM)images of the layers deposited on Si substrates were obtained with a Digital Instruments Nanoscope IIIa in tapping mode,using a 3045JVW piezo tube scanner.The125µm etched Si cantile-vers had a resonant frequency between250and325kHz,and the oscillation frequency for scanning was set to∼0.1-3kHz below resonance.Typical images were obtained with line scan rates of2Hz while256×256pixel samples were collected.Ellipsometric measurements were made with a Gaertner model L2W26D ellipsometer.An analyzing wavelength of632 nm was used,because GO absorbs minimally at this wave-length.The incident angle was70°and the polarizer was set at45°.Ellipsometric parameters were measured following each GO or PAH adsorption step.Si substrates were dried in an Ar stream before each measurement.The film thickness of the GO/PAH multilayers was calculated using the Si refractive indices,n s)3.875and k s)-0.018,determined from a blank sample.The refractive index of GO/PAH films was estimated as n f)1.540,k f)0.Transmission electron microscope(TEM)images were ob-tained with a JEOL1200EXII microscope at120kV ac-celerating voltage.Samples were prepared by immersing a copper grid in the GO sol and drying in air.The elemental composition of GO was determined by using a home-built mass spectrometer with laser probe(LMS).The diameter of the crater for single laser impulse was0.42-0.48 mm,and the depth was1µm.IR spectra were recorded using a Perkin-Elmer325instrument.XPS spectra were obtained using a Kratos Series800spectrometer with hν)1253.6eV and an analyzing window of4×6mm2.The accuracy of the measured core level binding energies(E b)was0.1eV.For LMS, IR,and XPS experiments,GO samples were prepared as films by drying a droplet of the sol in air at ambient temperature. X-ray powder diffraction(XRD)patterns were recorded with a DRON-1instrument using Cu K R radiation.Prior to the measurement,the GO sample was dried in a vacuum over P2O5 for24h.Electrical measurements of films deposited on ITO glass were carried out using top Pt electrode contacts that were10µm in diameter and mechanically pressed into the film,usinga home-built parametric analyzer.The sensitivity of current measurements was0.01nA.All measurements were carried out in air at ambient temperature.The turn-on potential for all thin film devices studied was taken as the potential at which a current of1.0nA was observed.In regions where current was more than3nA,every step of voltage increase (typically0.1mV in both the forward and reversed directions) was followed by repeating the measurement cycle to ensure the reproducibility of the current measured at the lower voltage.Measurements were considered irreversible(i.e.,a permanent change to a more conductive state occurred)when the current recorded the second time at the lower voltage was noticeably higher than that measured in the previous cycle.Results and Discussion Characterization of the GO Colloid.The XRD pattern of GO prepared by preoxidation with persulfate followed by oxidation with permanganate reveals a sharp002reflection at2θ)12.80°,which corresponds to a c-axis spacing of6.91ÅThis value falls within the range of6.3-7.7Åreported in the literature9a,10,20,21for GO prepared from natural graphite according to Hum-mers’method.18No002diffraction peak from unreacted graphite(d)3.35Å)is observable in the XRD pattern. The IR spectrum of GO prepared by this method is essentially identical to that reported in the litera-ture.9a,12,21A band at3420cm-1and a broad band centered around3220cm-1are attributed to O-H stretching vibrations of the C-OH groups and water, respectively;a band at1730cm-1is assigned to C d O stretching vibrations of the carbonyl and carboxyl groups.Bands at1365,1425,and1615cm-1are assigned to the O-H deformations of C-OH groups and water,respectively.A band at1080cm-1is due to C-O stretching vibrations.Deconvolution of the C1s peak in the XPS spectrum shows the presence of four types of carbon bonds:C-C (284.8eV),C-O(286.2eV),C d O(287.7eV),and O-C d O(288.5eV).By integrating the area of the deconvolu-tion peaks,the following approximate percentages were obtained:C-C,49.5;C-O,31.4;C d O,9.1;O-C d O, 2.9.The LMS spectrum of GO prepared by this method gave the following atomic composition(wt%):H,2.3; C,45.2;O,46.5;P,3.3;K,2.7;C:O ratio)1.3.The same or nearly the same C:O ratio has been found previously for GO samples prepared from natural graphite.21,22It is generally accepted that the conversion of graphite to(19)Schoenherr,S.;Goerz,G.;Mueller,D.;Gessner,W.Z.Anorg. Allg.Chem.1981,476,188.(20)Carr,K.E.Carbon1970,8,245.(21)Kyotani,T.;Suzuki,K.;Yamashita,H.;Tomita,A.Tanso1993, 160,255.(22)Slabaugh,W.H.;Seiler,B.C.J.Phys.Chem.1962,66,396.Assembly of Ultrathin Composite Films Chem.Mater.,Vol.11,No.3,1999773GO is complete when the C:O ratio becomes 2.0.The observed ratio C:O:H )4:3.1:2.5is richer in O and H than that calculated for C 8O 2(OH)2:4:2:1;this can be explained by the presence of intercalated/adsorbed water and carboxyl groups,as shown by IR and XPS.It should be noted that the ideal formulation does not take into account the presence of carboxyl groups,which are mainly situated on the edges of the sheets,8or interca-lated water,some amount of which is probably an integral part of the GO structure.3Allowing that 2.9%of the carbon atoms are present as carboxyl groups (from XPS)and assuming that the potassium ions are incor-porated by ion-exchange,we calculate a formula of C 3.77O 2.05H 0.92K 0.07‚0.73H 2O,or C 8O 2.25(OH)1.95(OK)0.15‚1.55H 2O,which gives a C:O:H ratio of 4:2.95:2.5.The remaining oxygen (2.05wt %)is most probably bound to phosphorus,an impurity introduced by the graphite preoxidation step.TEM images of the GO sol (Figure 1)reveal flexible,wrinkled sheets of different lateral sizes ranging from hundreds to thousands of nanometers.Flexible GO particles were also observed by Hennig and Carr.14,20No graphite particles are observed in these images.AFM Images of the First Adsorbed GO Layer.Si Substrates.AFM images (Figure 2a -c)of the GO films deposited in one adsorption cycle from aqueous solution show surface coverages of about 30%for Si(NH 2),85%for Si(OH)/PAH,and 90%for Si(OH)/Al-Kg substrates.The main features are 150-900-nm-wide islands,whose size is close to that determined by TEM for the GO sheets.In some cases,corrugations and the turned-in edges of the sheets are seen.For the PAH-primed Si substrate,the average roughness of the sheet-coveredpart of the surface is 4.5ÅBy comparison,the rough-ness of the Si(OH)/PAH substrate was 6.2-Å,indicating slight smoothing of the surface by the GO monolayer.The height of the islands on Si(NH 2)and Si(OH)/PAH,10.6-14.1Å,and the average roughness of their surface,3.9-4.5Å,are consistent with exposure of GO basal planes covered by adsorbed H 2O.8-10Ellipsometric measurements gave 11and 14Åthicknesses for GO monolayers on Si(NH 2)and Si(OH)/PAH.Considering that the thickess of the priming layer is about 7Å,and that the GO sheets cover only part of the surface,these results are in reasonable agreement with the island heights measured by AFM.According to Nakajima’s structural model,10the thick-ness of a GO monolayer depends on the content of hydroxyl groups on its basal planes and can reach 8.2Åfor the completely hydroxylated monolayer.Assuming the presence of completely hydroxylated GO carbon layers in very dilute colloids,one can take the thickness of a GO monolayer as 8.2Å.By comparing this value with the height of the islands in Figure 2,one can conclude that the islands consist of a single GO sheet covered by a layer of adsorbed water molecules.The thickness of doubled GO layers can be estimated from the thickness of two GO monolayers,2×8.2Å,plus the distance between the layers,which is determined by the thickness of the layer of weakly bound mobile water molecules.11,13This interlayer distance can be estimated at about 3Å,from the repeat distance along the c -axis of well-hydrated GO samples,I c )11Å,9,14minus the thickness of a GO monolayer,8.2Å.This means the thickness of doubled GO layers should be about 20Åor more,if water adsorbed onto the top basal plane is considered.This value is significantly greater than the height of adsorbed islands (10.6-14.1Å).The height,20.1Å,of the GO islands adsorbed onto the Al-Keggin-primed Si surface (Figure 2b)is roughly consis-tent with the thickness of the Al-Keggin anchoring layer (7Å23)and a monolayer of GO sheets covered by adsorbed H 2O (10.6-14.1Å).An AFM image of the first GO layer adsorbed from an aqueous ammonia suspension (pH 9)onto a Si(NH 2)substrate is shown in Figure 2d.In this case,the adsorption process selects much larger sheets (900-9000nm)which cover about 60-65%area of the surface.The dissociation of the GO hydroxyl groups (situated mainly on the basal planes)occurs around pH 9and significantly increases the negative charge density on the GO sheets.The increased attraction of the sheets for the cationic surface results in higher coverage than that observed at lower pH.This interaction is appar-ently more effective for the larger sheets,which can bridge over neutral regions of the incompletely primed surface.Previous studies have shown that the amine priming layer does not completely cover the surface,and that it is only partially protonated at pH 9.5The average roughness of the sheets on the surface is 4.4Å.The height of the sheets,which are corrugated and some-times have turned-in edges,is in the range of 19-23Å.The increased thickness may be due to a hydrated layer of charge-compensating NH 4+ions,which cover the basal plane surface.The adsorption of a bilayer of sheets(23)Johansson,G.;Lundgren,G.;Sillen,L.G.;Soderquist,R.Acta Chem.Scand.1960,14,769.Figure 1.Transmission electron micrograph of colloidal graphite oxide particles.774Chem.Mater.,Vol.11,No.3,1999Kovtyukhova et al.seems unlikely,since in basic media the exfoliation of GO occurs more readily.8Al 2O 3/Al Substrates.AFM images of the first GO layer grown on Al-coated glass (Figure 3a)and alumi-num foil (not shown)resemble those of the substrates,except that corrugations similar to those seen in the TEM image of GO and AFM images of the GO/Si have appeared.Because both Al 2O 3/Al substrates are very rough and because the flexible GO sheets conform to the surface,it is not possible to determine the lateral and vertical dimensions of the sheets.However,the average roughness of the brighter area in the image,which is presumed to have an adsorbed GO sheet,is 2.7nm.By comparison,the substrate roughness is 3.5-nm,again indicating a slight smoothing of the surface by the GO sheets.Characterization of GO/PAH Multilayers.Ellipsometry.Figure 4shows plots of film thickness,determined by ellipsometry,versus the number of adsorption cycles for GO/PAH multilayer films.The films were grown on Si(NH 2),Si(OH)/PAH,and Si(OH)/Al-Kg substrates.The linearity of the filmthicknessFigure 2.Tapping-mode AFM images of the first graphite oxide layer deposited from aqueous and aqueous ammonia sols on primed Si substrates:(a)Si(NH 2),GO sol pH 5,with the linescan showing the apparent height of sheet (14Å)above the background;(b)Si(OH)/Al-Kg,GO sol pH 5;(c)Si(OH)/PAH,GO sol pH 5;and (d)Si(NH 2),GO sol pH 9.Assembly of Ultrathin Composite Films Chem.Mater.,Vol.11,No.3,1999775plots indicates that on average the same amount of material is deposited in each adsorption cycle.However,for each the sample,the average increase in layer thickness per PAH/GO bilayer is different and ranges from 29to 50Å(Table 1).The lowest value,29Åper PAH/GO bilayer,is found for GO grown from aqueous ammonia solution (pH 9).The smaller layer pair thick-ness in this case may arise from partial deprotonation of the underlying PAH layer at this pH.Because thesurface charge density is lower,fewer anionic sheets are bound by the polymer per unit area.It should be noted that the measured thickness of the GO/PAH layer pair (40-50Å)is more than that expected from the thickness of monolayer GO sheets (10.6-14.1Å,as estimated by AFM for the first depos-ited GO layer,Figure 2a -c)and the thickness of single PAH layer (5Å24).This can be explained in part by folding of the flexible GO sheets,which is apparent in the AFM images of all GO monolayers except the low coverage layer grown on Si(NH 2).The multilayer ad-sorption model proposed by Kleinfeld and Ferguson for clay/polycation films 1b may also be operative for GO/PAH.In their model,each adsorption cycle deposits about two layers of polyelectrolyte,but they rearrange (possibly by folding in the present case)into alternating single sheet/polycation films.A plot of the thickness of a GO/PAH film grown from aqueous solution onto Si(NH 2)is linear only after the third cycle.The average increase in thickness per PAH/GO bilayer is 23Åin the first two adsorption cycles and 49Åin the following three adsorption cycles (Figure 4).This behavior is reminiscent of that observed by Kleinfeld and Ferguson for clay/polycation films,which nucleate in islands and completely cover the surface only after several adsorption cycles.25We conclude that the GO/PAH film coverage is relatively complete after adsorption of the second bilayer (the first adsorption cycle covers ∼30%of the surface;Figure 2a).In subse-quent adsorption cycles,the layer pair thickness is close to that found for GO/PAH multilayers on Si(OH)/PAH.In the latter case,the surface coverage is ∼85%after the first adsorption cycle,as shown in Figure 2c.AFM.AFM images of four or five bilayer GO/PAH films on all three substrates were similar and did not clearly resolve the sheet edges or the voids between sheets.From these images,one can only conclude that the multilayer films completely cover the surface.Figure 3b shows a typical image of a Si(OH)/Al-Kg /(GO/PAH)3GO film.The average roughness of this film is 20Å,which is consistent with a surface of loosely tiled and folded sheets.Multilayer film roughness and thick-ness parameters,determined by AFM and ellipsometry,respectively,are summarized in Table 1.For all the substrates under investigation (except for very rough aluminum foil),GO/PAH multilayers depos-ited from aqueous sols on Al(OH)x -terminated surfaces (Si(OH)/Al-Kg and Al/Al 2O 3)are smoother than those deposited on NH 2-terminated surfaces (Si(NH 2)and Si-(OH)/PAH)(Table 1).Comparing the surface morphol-ogies of the first GO layer and the multilayer films,one can see that the more densely tiled first layer (∼90%,Figure 2b),grown on the Keggin-primed surface,yields a smoother and more compact multilayer film,whereas the poorly tiled first layer (∼35%,Figure 2a)on Si(NH 2)yields the roughest multilayer surface.Again,this behavior is consistent with the model proposed by Kleinfeld and Ferguson for multilayer growth on is-lands,which eventually coalesce into smoother films.25(24)(a)Lvov,Yu.;Haas,H.;Decher,G.;Mohwald,H.;Kalachev,A.J.Phys.Chem.1993,97,12835.(b)Lvov,Yu.;Decher,G.;Mohwald,ngmuir 1993,9,481,(c)Decher,G.;Hong,J.;Schmitt,J.Thin Solid Films 1992,210/211.(25)Kleinfeld,E.R.;Ferguson,G.R.Chem.Mater.1996,8,1575.Figure 3.(a)Tapping-mode AFM image of the first graphite oxide layer deposited from the aqueous sol onto Al-coated glass and (b)image of a (GO/PAH)3GO film on Si(OH)/Al-Kg.Z range is 15nm in bothimages.Figure 4.Ellipsometric measurements of the thickness of multilayer GO/PAH films vs number of adsorption cycles:1,Si(OH)/PAH(GO/PAH)n GO;2,Si(OH)/Al-Kg(GO/PAH)n GO;3,Si(NH 2)(GO/PAH)n GO;4,Si(NH 2)(GO/PAH)n GO (pH 9).The thicknesses at an abscissa value of 0.5correspond to primer cationic layers;points on the plots refer to films terminated by a GO layer.776Chem.Mater.,Vol.11,No.3,1999Kovtyukhova et al.。
Graphene Corrosion--InhibitingCoating 简介及翻译
Graphene: Corrosion-InhibitingCoating石墨烯：防腐蚀涂层研究发表在美国化学学会（ACS）《纳米》（Nano）上石墨烯是一种从石墨材料中剥离出的单层碳原子面材料，是碳的二维结构，是一种“超级材料”，硬度超过钻石，同时又像橡胶一样可以伸展。
它的导电和导热性能超过任何铜线，重量几乎为零。
这种石墨晶体薄膜的厚度只有0.335纳米，把20万片薄膜叠加到一起，也只有一根头发丝那么厚。
Dhiraj Prasai,† Juan Carlos Tuberquia,§Robert R. Harl,§G. Kane Jennings,§and Kirill I. Bolotin‡,* Interdisciplinary Graduate Program（跨学科研究生课程）in Materials Science（材料科学）Department of Physics and Astronomy,物理和天文学Department of Chemical and Biomolecular Engineering,化学和生物分子工程学Vanderbilt University, Nashville, Tennessee 37235, United States范德比尔特大学（田纳西州州纳什维尔）37235美国范德比尔特大学是一所私立研究型大学，位于美国田纳西州纳什维尔。
学校成立于1873年，学校是以航运和铁路大亨“准将”科尼利厄斯范德比尔特的名字命名的，他提供范德比尔特一百万美元捐赠，尽管他从未到过南方，但希望他的捐赠能够帮助学校在抚平内战留下的创伤方面发挥更大的作用。
目前，范德比尔特大学包括4个本科学院和6个研究生学院，招收学生约12000多名，分别来自美国50个州和90多个国家。
在2009年的大学排名中，美国新闻与世界报道将范德比尔特排在国家大学的第18名，其中教育、法律、工程、医学、护理等几个学院在该国都跻身前20名。
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石墨烯/聚合物纳米复合材料摘要：石墨烯由于其特殊的电导性、机械性能和大的表面积而具有巨大的科研价值，当加入适当时，这些原子薄碳层可以显著提高主要高聚物的物理性能。
我们首先按照从上到下的战略回顾一下从氧化石墨到石墨烯的生产工艺过程，包括每种方法的优点和缺点。
然后按溶解和熔融的战略即分散化学和加热的方法讨论降低氧化石墨在聚合物中的含量。
对于微粒大小的性质、表面性质和在基体中的离散性的技术分析也有介绍。
我们总结石墨烯/聚合物纳米复合材料的导电性、导热性、机械性能和阻气性。
我们结合石墨烯复合材料的加工和可量测性总结这些观点列出最近的挑战和这些新的纳米复合材料的远景。
1介绍基于炭黑、碳纳米管和层状硅酸盐的聚合物纳米复合材料被用于增强聚合物的机械性能、导电性、导热性和阻气性。
石墨烯极其特殊的物理性能和能溶于多种基本聚合物的结合的发现创造了一类新的聚合物纳米复合材料。
石墨烯是由sp2杂化的碳原子按蜂窝状结构排列成的单层、二维片状结构。
它被誉为其他所有不同维数的石墨碳的同素体的基础材料，例如，石墨（三维碳的同素体）由石墨烯的薄碳片正面向上堆积在一起并且分开距离为3.37A组成。
0维同素体，富勒烯（足球烯），可以想象成单层石墨烯的一部分卷曲成的。
一维碳同素体，碳纳米管和碳纳米带可以分别由单层石墨烯旋转和剪切制成。
实际上，然而，这些碳的同素体，除了碳纳米带，都不是由石墨烯合成的。
石墨是一种天然生成的材料，它最早的记载于1555年在英国的Borrowdale，但是它最早的应用可向前追溯4000年。
在1985年发现富勒烯后于1991年第一次合成单壁碳纳米管。
尽管生产石墨烯纳米片的第一个方法报道可以追溯到1970年，但对存在的单层石墨烯在2004年第一次被生产出来，用微机械剥离的方法从石墨中分离出石墨烯。
杨氏模量为1TPa和极限强度为130GPa，单层石墨烯为测量出来的最强的材料。
它的导热系数为5000W/cm3*KJ,与报道的碳纳米束最高值的上限相一致。
而且，单层石墨烯有很高的电导率，高达6000 /cm，并且不像碳纳米管，手性特性不是影响电导率的因素。
这些特性加之极高的表面积（理论极限：2630m2/g）和不透过气体性，表明石墨烯对提高聚合物的机械性质、导电性、导热性和阻气性的巨大潜力。
由于石墨烯薄层的性质引起巨大兴趣并且发现了它们的生产方法，世界各地的科学家都有在研究石墨烯，研究石墨烯的研究机构的数目清楚地证明了这些兴趣。
一个简单的研究用石墨烯作为关键字从三个最常用的数据库搜索，例如IsI-wabvf Science, Science Direct and Sci Finder,如图2所示，表明出版论文从2005到2009近3000篇的速度增长。
用“石墨烯复合物“作为关键字的文献的数目的简单趋势也可见于图2.在这篇文章里，我们专注于石墨烯/石墨烯复合物高聚物来评论这项文化。
我们首先评论准备石墨烯薄层的不同方法，以这些方法适合高聚物复合应用为重点。
然后讨论表征石墨烯的方法包括层数、薄层厚度和化学改性。
石墨烯进入聚合物的分散途径和生成的聚合物/石墨烯复合物的性质也被评论。
我们总结了这令人兴奋的新的纳米复合材料的未来发展的挑战2．Bottom-Up石墨烯石墨烯通过多种方法合成，例如化学气相沉淀法、CVD和epitaxial growth经常用于生产少量厚的、无缺陷的石墨烯薄层。
它们在生产用于基础研究和导电应用的石墨烯薄片比机械剥离法更有吸引力。
但不是要求适于表面结构修改的大量石墨烯薄片的适合来源。
通过不同的bottom-up方法生产的石墨烯的自然性质、平均大小和厚度，并且每种方法的优点和缺点总结在表里。
3.Top—Down石墨烯在上—下过程，石墨烯或者改性的石墨烯薄片是通过分离或剥离石墨或石墨的衍生物（例如氧化石墨和石墨的氟化物）生产的。
总之，这些方法适用于要求聚合物复合应用的大规模产品。
从石墨或其衍生物开始比Bottom—up方法提供了明显的导电优点。
石墨是一种常见的材料，每年全球产量多于1.1百万吨且在2008年825美元每吨。
因此，Top—down 方法将讨论更多的细节。
图3所示的一组图表总结了石墨或氧化石墨生产石墨烯或改性后的石墨烯的不同路径汇报告。
石墨中添加碱金属或酸能够扩大加热处理来生产由2层碳原子组成的薄层被称作扩展石墨，它常用作聚合物复合材料的填料。
然而，扩展石墨依然维持石墨的层结构。
最近，通过氟化石墨夹层化合物的热扩散或微波放射酸分层的被用研磨或超声球状物得的粉状石墨得到一种更薄的形状（1~10nm）的扩展石墨被称作GNP。
因为石墨片的大的直径和刚度在加工中得到保存，即使不能完全剥离，在相当小的负荷比时石墨或EG可以提高在相当小的负荷时，比石墨或EG可以提高聚合物的导电性和力学性能。
GNP增强聚合物的性质在第六部分的比较会提到，但由于本次你讨论的重点是对单层或少数层的石墨烯材料，GNP将不会被进一步讨论。
3.1.机械玻璃石墨烯微机械剥离石墨烯产生了石墨烯的研究兴趣，它可以生产大规格、高品质的薄层，但数量有限，这使得它仅适合基础研究或电子应用。
然而，最近石墨也通过在吡咯烷酮或N-甲基吡咯烷酮中超声直接剥离得到单层或多层石墨烯，石墨的电化学性能协助离子液体，并通过在超强酸中分散。
直接超声的方法有可能扩大规模生产大量的单层和多层石墨稀或功能化石墨烯，可用于复合应用。
然而，从散装石墨中分离剥离的石墨烯薄层可能是一个挑战。
另一方面，在氯磺酸中分散石墨有大规模生产的潜力，the hydrosulfonic的危险性和去除的成本可能会限制这种潜力。
电化学剥离法产生的石墨烯薄层在能协助在非质子溶剂中分散的咪唑组中功能化。
3.2.氧化石墨目前，最有前途的大规模生产石墨烯的方法是基于氧化石墨的剥离和减少，GO是150多年前由Brodie首先发现的。
它也使用不同的方法生产如Staudenmaier或Hummers方法，石墨的氧化用强氧化剂例如在硝酸或与硫酸的混合物中的KMnO4,KClO3, 和NaNO2。
类似石墨，是由石墨烯薄片堆积组成的，GO是由氧化石墨烯薄片堆积成的，根据水的含量不同层间距在6到10A之间。
氧化石墨烯的结构一直是理论和实验研究的主题。
Lerf-Klinowski 模型被认为最可能是GO的结构说明，该模型描述GO为被含大量环氧基和羟基和双键的脂肪烃区域分开的原始的芳香烃“孤岛“，如图4所示。
近日，Gao et al.使用C NMR.研究GO的结构，他们猜测GO中除了含有环氧基和羟基还可能含酮、-membered lactol lrings,和叔醇（图4B）。
GO的C/O/Hatomic比例近似为2/1/0.8.。
在氧化石墨烯氧化薄层进行还原时造成比原来的鳞片状石墨大小有所减小。
对GO的更多详情，我们建议读者去查阅Dreyer et al.的关于GO的制备、结构和反应的广泛评论。
剥离GO来产生化学改性的石墨烯薄片提供了大规模生产功能化石墨烯薄片的不同路线。
虽然GO在化学改性后可以很好的分散在水和有机溶剂中，氧化石墨烯是绝缘和热不稳定的。
因此，至少部分还原后的氧化石墨烯恢复导电性是必要的。
目前存在一些不同的方法剥离和还原GO来产生化学改性的石墨烯。
选择术语“化学改性“是因为氧化石墨烯完整的还原为石墨烯还没有发现，在下面两节描述这些方法。
对这些方法的更多细节，我们提供Park and Ruoff’s的最近评论3.3.GO的化学还原在这些方法中，形成一个稳定的GO的胶体，然后化学还原剥离的氧化石墨烯薄层。
使用水、酒精和其他质子溶剂结合超声或长时间搅拌可以得到稳定的氧化石墨烯的稳定胶体。
另外，GO在极性非质子溶剂中与有机化合物如异氰酸酯和十八胺或治疗性表面活性剂反应可以被剥离。
尽管这些悬浮液可以用来生产GO /聚合物复合材料，氧化石墨烯的导电性低和稳定性差是明显的缺点。
氧化石墨烯胶体或有机处理的样品可以通过用肼、二甲肼、由肼生成的博罗氢钠肼、对苯二酚和紫外线照射二氧化钛化学还原的方法生产化学还原的石墨烯。
Stankovich et al.提出用肼还原氧化石墨的一下机制。
还原的氧化石墨烯恢复导电性。
然而，仍含大量的氧：C/O∼10/1.尽管化学还原氧化石墨烯为生产CRG提供了有效的途径，在还原中使用化学品的危险性和费用可能限制它的使用。
一种替换化学还原法的是在高温（120-200C）高压的水中对氧化石墨烯的羟基脱水。
在酸性条件下铝粉可以催化该过程。
3.4.热剥离和还原热还原氧化石墨烯可以通过在惰性气体和高温下快速加热干的GO来生产。
在惰性环境中1000C时加热GO30S导致GO还原和剥离，产生TRG薄层。
由于环氧树脂分解产生压力气体时发生剥离并且GO的羟基通过范德华力控制氧化石墨烯薄层在一起。
约30％的重量损失与含氧基团的分解和水分的蒸发有关。
由于剥离导致体积100-300倍的扩大产生非常低密度散装的TRG薄层（图5d）由于CO2损失所造成的结构缺陷，这些薄层是高度褶皱的如图5e所示。
80%的TRG薄层是单层的，与起始的GO薄层大小不同它的平均大小约500nm。
热机械法的优势是不需要在溶剂中分散就能产生化学改性的石墨烯薄层的能力。
相比GO的C/O比为2/1，TRG的约是10/1。
通过高温（1500C）或长时间热处理这一比例已上升为660/1。
TRG薄层有高的表面积，1700 m2/g以亚甲蓝作为标准，并且可以很好的分散在有机溶剂中例如N，N-二甲基甲酰胺（DMF）和四氢呋喃等。
报道压实密度为0.3 g/cm3的导电率介于10de到20 S/cm,，相比无缺陷的单层石墨烯薄层，热还原也导致导电率的恢复。
通过不同的自上而下的方法产生的石墨烯薄层的性质、平均大小、厚度和每种方法的优点和缺点总结在表2里。
正如上面和表中的讨论，准备聚合物纳米复合材料的石墨烯的最好路径是从GO开始。
因此，在这个角度的其余部分，我们将继续关注这些路线。
4.石墨烯的表征证明上述合成方法事实上能产生单层石墨烯非常重要。
此外，这些薄层的大小和附加功能对在聚合物中的扩散是重要的。
在本节中，我们简要回顾最适合表征石墨烯薄片的技术。
4.1.层的数量和大小使用X射线衍射证明石墨被插入，例如，最明显的反射在2θ = 26.3（铜雷克南辐射，X射线反射波长=0.154 nm）的石墨转变为14.1—14.9的氧化石墨。
然而，当GO薄片剥离成单层薄片时X-射线衍射消失。
虽然是间接的，表面面积已被用作剥离程度的指标。
由于理论上比表面积与圆盘状粒子（〜2/密度/厚度）的厚度成反比，剥离程度好的薄片有较高的比表面积。
表面积可由N2或亚甲蓝吸附来确定。
但是，Schniepp等指出N2吸附测量高度依赖TRG的可压缩性。