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layout: post title: 氧化石墨烯的结构与建模 categories:

科 tags:
gmx
js chem: true

2020-04-05 23:39:40 感谢裴铁柱整理翻译

氧化石墨烯具有与石墨烯相似的结构, 但由于合成条件的等不确定因素, 其精确的化学结构仍无法确定. 通常认为, 其含氧官能团有环氧桥(-O-)、羟基(-OH)、羧基(-COOH)和羰基(=O), 其中羧基和羰基通常出现在石墨烯边缘C原子上. 由于在表面及边缘上大量含氧基团的引入, 可在水溶液以及极性溶剂中稳定存在.

作为石墨烯基材料一类重要的衍生物, 尽管氧化过程破坏了石墨烯高度共轭结构, 但是仍保持着特殊的表面性能与层状结构. 含氧基团的引入不仅使得氧化石墨烯具有化学稳定性, 而且为合成石墨烯基/氧化石墨烯基材料提供表面修饰活性位置和较大的比表面积. 并且由于石墨烯片层骨架的基面和边缘上有多种含氧官能团共存的结构, 使得氧化石墨烯可以通过调控所含含氧官能团的种类及数量, 来调制其导电性和带隙.

Wiki条目

结构说明

以下翻译自 Luo, Haining. "A theoretical study of graphene oxide chemical structure." (2017). Chapter2 section 2.2

目前已提出了至少6种经典的GO结构模型[25, 33, 40-43]. 第一个模型由Hofmann和Holst于1939年提出, 在该模型中环氧基随机分布在平坦的碳骨架平面上, C/O比为2. 1946年, Ruess课题组提出了第二种模型[44]. 不同于Hofmann的类苯环碳平面结构, 该模型中晶格碳由环己烷组成, 并引入了羟基和1,3-醚氧基. 第三种Scholz-Boehm模型[43]用羟基全部取代环氧基. 碳底面由规律褶皱的环己烷及相连的喹诺酮组成. 1994年提出的Nakajima-Matsuo模型[45]是第四种GO模型, 其碳骨架类似聚(C2F)n形成的stage2石墨烯插层化合物. 不过, 由于固态核磁分析技术(SSNMR)在GO结构表征中的应用, 最近基于SSNMR提出的两种模型受到越来越多的认可. SSNMR技术明显提高了GO中官能团检测的准确度. Lerf-Klinowski模型40中, 叔醇基和1,2-醚是GO表面的主要官能团. LK模型放弃了周期性晶体结构, 并且含氧基团随机取代. 他们还认为GO边缘的C=C倾向于以芳香或共轭或羰基酮的形式存在. 随后, Décány提出了第六种模型[33], 以Scholz-Boehm模型为基础在环己烷上引入了1,3-醚氧基团[42].

Rouff课题组利用13C标记的SSNMR分析了GO结构, 并将从头算得到的化学位移与实验数据对比, 结果发现以上模型中只有LK模型与实验结果符合最好[44]. 但由于计算的复杂性, 用于计算的LK模型被简化并且尺寸受到限制. 因此, 官能团的准确分布及边缘的结构仍不明确.

除了实验结果, 理论计算表征还可以为探索GO结构的细节提供新视角. Lahaye等使用密度泛函理论(DFT)计算了带羟基和环氧的 2×2 GO单元体系[46], 发现1,3-醚由于结合能而不太可能存在, 并且单一的环氧和羟基倾向出现在相近位置. Boukhvalov和Katsnelson提出了一种链状结构, 并发现其带隙随着氧覆盖率的增加而增加[47]. 他们还发现, 由于单个氢原子存在产生化学吸附会导致石墨烯片发生半径约5 Å的变形, 因此石墨烯具有很高的柔韧性[48]. 至于两个氢原子的化学吸附, 能量上的有利构型是两个氢分别从石墨烯两侧与相邻的碳键合[4]. 完全加氢可以使石墨烯片的总能量最小化. Yan和Chou使用MD(分子动力学)模拟从理论上也证实了这一结果[49], 并揭示了在热退火过程中羟基和环氧基向羰基的转化. Paci等人通过蒙特卡洛模拟发现了氢键的重要性[50]. 另外, 在通过氢键稳定过程或通过可移动的环氧基与相邻官能团之间的氢转移催化反应的过程中观察到环氧基在基面上的迁移行为. Li等发现在氧化石墨烯平面上成直线排列的环氧基对儿可能形成羰基对, 进一步导致GO片"解压缩"[51]. 该结果表明通过受控的氧化过程可以获得光滑的GO边缘.

[4] X. Huang, X. Qi, F. Boey, and H. Zhang, "Graphene-based composites," Chemical Society Reviews, vol. 41, pp. 666-686, 2012 2012.
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[33] T. Szabo, O. Berkesi, and I. Dekany, "DRIFT study of deuterium-exchanged graphite oxide," Carbon, vol. 43, pp. 3186-3189, Dec 2005.
[40] A. Lerf, H. Y. He, M. Forster, and J. Klinowski, "Structure of graphite oxide revisited," Journal of Physical Chemistry B, vol. 102, pp. 4477-4482, Jun 4 1998.
[41] K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, et al., "Two-dimensional atomic crystals," Proceedings of the National Academy of Sciences of the United States of America, vol. 102, pp. 10451-10453, Jul 26 2005.
[42] T. Szabo, O. Berkesi, P. Forgo, K. Josepovits, Y. Sanakis, D. Petridis, et al., "Evolution of surface functional groups in a series of progressively oxidized graphite oxides," Chemistry of Materials, vol. 18, pp. 2740-2749, May 30 2006.
[43] W. Scholz and H. P. Boehm, "Graphite Oxide .6. Structure of Graphtite Oxide," Zeitschrift Fur Anorganische Und Allgemeine Chemie, vol. 369, pp. 327-&, 1969 1969.
[44] D. R. Dreyer, A. D. Todd, and C. W. Bielawski, "Harnessing the chemistry of graphene oxide," Chemical Society Reviews, vol. 43, pp. 5288-5301, Aug 7 2014.
[45] T. Nakajima and Y. Matsuo, "FORMATION PROCESS AND STRUCTURE OF GRAPHITE OXIDE," Carbon, vol. 32, pp. 469-475, 1994 1994.
[46] R. J. W. E. Lahaye, H. K. Jeong, C. Y. Park, and Y. H. Lee, "Density functional theory study of graphite oxide for different oxidation levels," Physical Review B, vol. 79, p. 125435, 03/27/ 2009.
[47] D. W. Boukhvalov and M. I. Katsnelson, "Modeling of graphite oxide," Journal of the American Chemical Society, vol. 130, pp. 10697-10701, Aug 2008.
[48] D. W. Boukhvalov and M. I. Katsnelson, "Enhancement of chemical activity in corrugated graphene," The Journal of Physical Chemistry C, vol. 113, pp. 14176-14178, 2009.
[49] J.-A. Yan and M. Y. Chou, "Oxidation functional groups on graphene: Structural and electronic properties," Physical Review B, vol. 82, p. 125403, 09/02/ 2010.
[50] J. T. Paci, T. Belytschko, and G. C. Schatz, "Computational studies of the structure, behavior upon heating, and mechanical properties of graphite oxide," Journal of Physical Chemistry C, vol. 111, pp. 18099-18111, Dec 2007.
[51] Z. Y. Li, W. H. Zhang, Y. Luo, J. L. Yang, and J. G. Hou, "How Graphene Is Cut upon Oxidation?," Journal of the American Chemical Society, vol. 131, pp. 6320-+, May 2009.

结构模型

下面是一个使用xtb方法优化的氧化石墨烯结构, 一些参数用于后面的建模工具.

<figure><script>var Mol1=new ChemDoodle.TransformCanvas3D('Mol-1',502,376.5);Mol1.specs.shapes_color='#fff';Mol1.specs.backgroundColor='black';Mol1.specs.set3DRepresentation('Ball and Stick');Mol1.specs.projectionPerspective_3D=false;Mol1.specs.compass_display=true; /*//Mol1.specs.atoms_resolution_3D=15; //Mol1.specs.bonds_resolution_3D=15; //Mol1.specs.crystals_unitCellLineWidth=1.5;*/ Mol1.nextFrame=function(delta){var matrix=[];ChemDoodle.lib.mat4.identity(matrix);var change=delta*Math.PI/15000;ChemDoodle.lib.mat4.rotate(matrix,change,[1,0,0]);ChemDoodle.lib.mat4.rotate(matrix,change,[0,1,0]);ChemDoodle.lib.mat4.rotate(matrix,change,[0,0,1]);ChemDoodle.lib.mat4.multiply(this.rotationMatrix, matrix)}; Mol1.startAnimation=ChemDoodle._AnimatorCanvas.prototype.startAnimation;Mol1.stopAnimation=ChemDoodle._AnimatorCanvas.prototype.stopAnimation;Mol1.isRunning=ChemDoodle._AnimatorCanvas.prototype.isRunning;Mol1.dblclick=ChemDoodle.RotatorCanvas.prototype.dblclick;Mol1.timeout=5;Mol1.handle=null; var Fmol='225\nenergy: -429.150502701623 gnorm: 0.000294406473 xtb: 6.3.0 (preview)\nC 0.069995 -0.006239 0.251714\nC -1.123160 0.668449 0.172231\nC -1.148469 2.047225 0.015156\nC 0.031592 2.800024 -0.092331\nC 2.510526 0.037787 0.265258\nC 1.288190 0.703507 0.190446\nC 1.269069 2.121043 0.032081\nC 2.486505 2.838887 -0.006075\nC 4.948767 0.051878 0.266013\nC 3.726415 0.725821 0.204689\nC 3.713643 2.149568 0.081649\nC 4.933848 2.856052 0.039765\nC 7.387055 0.053657 0.248704\nC 6.166969 0.733780 0.207830\nC 6.160395 2.161273 0.095653\nC 7.383329 2.865438 0.037219\nC 9.826003 0.048482 0.224982\nC 8.608136 0.731482 0.196063\nC 8.610586 2.160838 0.102674\nC 9.831975 2.856555 0.076039\nC 12.266270 0.034984 0.185777\nC 11.048676 0.722551 0.178463\nC 11.056066 2.152372 0.121038\nC 12.281457 2.848349 0.102538\nC 14.704187 0.017353 0.139509\nC 13.487139 0.707372 0.144774\nC 13.496729 2.140129 0.113321\nC 14.729296 2.832079 0.097751\nC 17.134456 -0.008118 0.091682\nC 15.929865 0.685007 0.112287\nC 15.942808 2.124353 0.096471\nC 17.173375 2.808484 0.089708\nC 19.526939 -0.124442 -0.008462\nC 18.395099 0.633856 0.064778\nC 18.405301 2.096390 0.104634\nC 19.578419 2.821578 0.183165\nC 0.023222 4.216725 -0.289366\nC -1.224095 4.923527 -0.566586\nC -1.153710 6.351142 -0.511349\nC 0.006049 7.063800 -0.330364\nC 2.469766 4.253628 -0.118658\nC 1.231796 4.942295 -0.226470\nC 1.245978 6.365607 -0.267122\nC 2.459850 7.081079 -0.248076\nC 4.921299 4.269677 -0.073540\nC 3.693651 4.968410 -0.145239\nC 3.692206 6.383110 -0.235538\nC 4.917973 7.090432 -0.326019\nC 7.381379 4.273406 -0.093027\nC 6.144827 4.975144 -0.151984\nC 6.120559 6.367096 -0.338537\nC 7.376773 7.050022 -0.631662\nC 9.838071 4.276599 -0.021704\nC 8.612053 4.975609 -0.134700\nC 8.634777 6.370542 -0.325533\nC 9.829417 7.090871 -0.283996\nC 12.290944 4.276473 0.061665\nC 11.055807 4.981584 -0.032732\nC 11.058066 6.392582 -0.130902\nC 12.279505 7.099853 -0.081486\nC 14.739039 4.256985 0.138644\nC 13.500094 4.970385 0.108892\nC 13.507304 6.399462 0.056814\nC 14.703948 7.110470 0.127188\nC 17.173412 4.231535 0.114747\nC 15.955111 4.928791 0.192379\nC 15.966570 6.394314 0.494111\nC 17.218642 7.101949 0.051059\nC 19.581271 4.210335 0.156186\nC 18.408136 4.934357 0.077627\nC 18.397916 6.380245 -0.086089\nC 19.561802 7.081956 -0.440183\nC 0.008500 8.505011 -0.234751\nC -1.183252 9.229586 -0.135070\nC -1.187645 10.596649 -0.073911\nC 0.003445 11.333224 -0.103977\nC 2.462111 8.504051 -0.240483\nC 1.228468 9.211865 -0.207453\nC 1.223874 10.629107 -0.141060\nC 2.456306 11.340980 -0.087802\nC 4.913635 8.521268 -0.314047\nC 3.679954 9.213398 -0.223205\nC 3.677285 10.632711 -0.116107\nC 4.897144 11.338588 0.017800\nC 7.372987 8.575612 -0.616838\nC 6.115128 9.256371 -0.301868\nC 6.135779 10.629386 -0.062262\nC 7.375306 11.342834 -0.008617\nC 9.830258 8.525176 -0.290156\nC 8.631517 9.249645 -0.316921\nC 8.610036 10.638645 -0.122355\nC 9.833625 11.339753 -0.048706\nC 12.282805 8.513119 -0.109466\nC 11.055233 9.221460 -0.163531\nC 11.058199 10.632001 -0.095040\nC 12.282697 11.338784 -0.057933\nC 14.727267 8.507336 0.023753\nC 13.503921 9.217448 -0.062402\nC 13.510047 10.634134 -0.067275\nC 14.732672 11.337804 -0.065621\nC 17.193527 8.502089 -0.087790\nC 15.958730 9.221557 -0.021135\nC 15.958636 10.622022 -0.092139\nC 17.188267 11.339308 -0.185420\nC 19.565079 8.445737 -0.530068\nC 18.399388 9.197108 -0.320814\nC 18.402033 10.634957 -0.314827\nC 19.592153 11.370570 -0.401853\nC 0.006556 12.771687 -0.075890\nC -1.179060 13.513387 -0.126345\nC -1.171044 14.881322 -0.076824\nC 0.021264 15.605172 0.029145\nC 2.457285 12.750772 0.003012\nC 1.229664 13.472236 -0.006328\nC 1.234807 14.890177 0.051984\nC 2.482471 15.586141 0.115165\nC 4.881775 12.728319 0.180560\nC 3.684409 13.444923 0.127376\nC 3.684379 14.881200 0.170325\nC 4.929483 15.581850 0.188983\nC 7.398738 12.722385 0.177177\nC 6.142814 13.431619 0.597015\nC 6.145809 14.895720 0.256494\nC 7.363765 15.576079 0.193489\nC 9.831297 12.748777 0.037289\nC 8.598931 13.441374 0.142006\nC 8.602187 14.867280 0.184200\nC 9.812955 15.567674 0.132558\nC 12.281284 12.751464 -0.011454\nC 11.053907 13.455196 0.038216\nC 11.051346 14.869416 0.082797\nC 12.269751 15.573767 0.061256\nC 14.734459 12.755864 -0.055680\nC 13.505850 13.458569 -0.014560\nC 13.501205 14.873703 0.015885\nC 14.723971 15.581228 -0.001156\nC 17.186913 12.758744 -0.161440\nC 15.955264 13.468046 -0.082528\nC 15.951356 14.883820 -0.054613\nC 17.178478 15.604621 -0.076770\nC 19.593366 12.736585 -0.347771\nC 18.405381 13.468770 -0.220325\nC 18.404719 14.907332 -0.150120\nC 19.588998 15.651216 -0.145988\nC 0.022331 17.052971 0.090856\nC -1.148193 17.802554 0.133955\nC -1.124477 19.194750 0.159611\nC 0.066256 19.869053 0.139065\nC 2.484983 17.015437 0.107644\nC 1.263662 17.732801 0.101311\nC 1.284487 19.158593 0.112630\nC 2.506920 19.830369 0.099123\nC 4.931134 17.002308 0.123540\nC 3.705651 17.708844 0.104947\nC 3.718761 19.141236 0.089609\nC 4.942767 19.818295 0.077542\nC 7.371574 16.996583 0.126908\nC 6.152779 17.700471 0.111581\nC 6.158798 19.135641 0.086131\nC 7.379686 19.812326 0.077228\nC 9.817335 16.994055 0.118896\nC 8.598535 17.696962 0.111425\nC 8.599661 19.129092 0.090345\nC 9.818369 19.808445 0.088763\nC 12.267922 16.996741 0.079416\nC 11.040827 17.695569 0.098870\nC 11.038848 19.126764 0.093677\nC 12.257326 19.809612 0.092191\nC 14.718666 17.004334 0.029242\nC 13.486104 17.700669 0.064611\nC 13.478646 19.132066 0.081202\nC 14.694951 19.818741 0.081193\nC 17.171983 17.025781 -0.026387\nC 15.931510 17.712060 0.021210\nC 15.919637 19.145903 0.055530\nC 17.124040 19.843245 0.059825\nC 19.580154 17.023626 -0.083934\nC 18.390700 17.744971 -0.028311\nC 18.382445 19.203468 0.026861\nC 19.516806 19.967089 0.047224\nH 0.097628 -1.079380 0.372961\nH -2.056389 0.128794 0.239671\nH -2.094907 2.560310 -0.032788\nH 2.520411 -1.038883 0.363494\nH 4.952606 -1.024946 0.357791\nH 7.386324 -1.024328 0.320550\nH 9.822252 -1.030493 0.281790\nH 12.259759 -1.044925 0.222344\nH 14.694155 -1.063135 0.155916\nH 17.112391 -1.088576 0.084637\nH 20.515970 0.289224 -0.057082\nH 19.457306 -1.197684 -0.032048\nH 20.527465 2.314661 0.253454\nH -2.103295 6.842415 -0.651065\nH 20.533368 4.714684 0.204307\nH 20.474648 6.544907 -0.639341\nH -2.126468 8.711112 -0.091650\nH -2.137433 11.097864 0.012163\nH 20.491129 8.938213 -0.777095\nH 20.538736 10.864182 -0.494663\nH -2.129846 13.015135 -0.217582\nH -2.116144 15.396027 -0.130363\nH 20.541596 13.244309 -0.410070\nH 20.545013 15.155857 -0.185520\nH -2.110334 17.317760 0.152615\nH -2.057914 19.737476 0.191507\nH 0.094027 20.948657 0.148454\nH 2.514911 20.911063 0.099867\nH 4.944222 20.898804 0.064029\nH 7.382434 20.892762 0.060408\nH 9.819800 20.888982 0.081505\nH 12.255424 20.890128 0.096557\nH 14.689395 20.899104 0.099355\nH 17.098490 20.923084 0.091379\nH 20.525834 17.541005 -0.081965\nH 19.441945 21.039463 0.087524\nH 20.509509 19.560600 0.028174\nO 6.198181 13.349640 2.051636\nH 5.410854 13.777894 2.408221\nO 7.371167 7.825089 -1.808002\nC 16.107094 6.577393 2.037787\nO 15.769421 7.562206 2.630163\nO 16.701173 5.538860 2.619634\nH 16.827065 5.708179 3.567502\nO -2.303414 4.367241 -0.826962\n'; Mol1.loadMolecule(ChemDoodle.readXYZ(Fmol));Mol1.startAnimation();Mol1.stopAnimation();function setProj1(yesPers){Mol1.specs.projectionPerspective_3D=yesPers;Mol1.setupScene();Mol1.repaint()}function setModel1(model){Mol1.specs.set3DRepresentation(model);Mol1.setupScene();Mol1.repaint()}function setSpeed1(){Mol1.timeout=500-document.getElementById('spd1').value;Mol1.loadMolecule(ChemDoodle.readXYZ(Fmol));Mol1.startAnimation()}</script><br><span class='meta'>视图: <input type='radio' name='group2' onclick='setProj1(true)'>投影 <input type='radio' name='group2' onclick='setProj1(false)' checked=''>正交速度: <input type='range' id='spd1' min='1' max='500' onchange='setSpeed1()'/><br>模型: <input type='radio' name='model' onclick='setModel1('Ball and Stick')' checked=''>球棍 <input type='radio' name='model' onclick='setModel1('van der Waals Spheres')'>范德华球 <input type='radio' name='model' onclick='setModel1('Stick')'>棍状 <input type='radio' name='model' onclick='setModel1('Wireframe')'>线框 <input type='radio' name='model' onclick='setModel1('Line')'>线型 <input type='checkbox' onclick='Mol1.specs.atoms_displayLabels_3D=this.checked;Mol1.repaint()'>名称<br>左键: 转动滚轮: 缩放双击: 自动旋转开关 Alt+左键: 移动</span><br><figurecaption>Fig.1</figurecaption></figure>

建模工具

在线工具网址

在以前石墨烯建模工具的基础之上增加添加-O-, -OH, -COOH基团的功能, 其结构参数和取向参考了上面的结构.

-O-的覆盖度以C-C键数目计, 其他两种基团的覆盖度以C原子计.
添加时随机选择C-C键或C原子.
如果一个C原子被选择添加, 其与其直接相连的周围C原子不会再被选择添加. 因此最大覆盖度不可能100%.