红外光谱法氧化石墨烯表面氧化度的测定

氧化石墨烯是由sp2和sp3两种杂化碳原子构成的单原子层二维网络结构,富含羟基、环氧基和羧基多种含氧基团,是众多功能化石墨衍生物的前驱体;其中,羟基和环氧基主要分布在氧化石墨烯片层表面,羧基主要位于片层结构的边缘,利用氧化石墨烯表面的羟基或环氧基可以得到垂直于表面的有序结构材料,利用边缘的羧基可得到多种悬垂结构的功能复合材料。利用不同氧化方法和同种氧化剂不同用量进行氧化得到石墨烯的氧化度不同,从而功能化后的石墨烯性能有很大差异。氧化石墨烯的氧化度测定是对其进行改性的基础。科学家们通过XRD,XPS,FTIR,Zeta,拉曼光谱法等研究石墨烯中不同杂化的碳原子和氧原子比例,但是几乎没有报道可以直接测量氧化石墨烯上含氧官能团的量。主要通过苯酚作为标准利用傅里叶变换红外光谱建立一种氧化石墨烯片层间羟基含量的测定方法。采用化学氧化-还原法制备薄层氧化石墨烯(GO),由于苯酚和GO具有相似骨架结构,以苯酚的红外光谱谱图可以作为标准图谱,苯酚红外光谱在1597,1500和1474 cm^-1为其苯环结构的伸缩振动吸收峰;在1374 cm^-1处为苯环C-H面内弯曲振动吸收峰;而在1234 cm^-1处为酚类C-OH伸缩振动吸收峰。氧化石墨烯的红外谱图中1630 cm^-1出现类苯环骨架CC的伸缩振动吸收峰,在1400 cm^-1出现氧化石墨烯片层上C-O(H)的伸缩振动吸收峰。利用测试苯酚中苯环和羟基C-OH吸收峰面积的比值,与氧化石墨烯上类苯环结构CC和片层上羟基C-O(H)吸收峰面积的比值,可以得到片层上羟基含量的值。同时利用场发射扫描电镜,透射电镜,原子力显微镜,紫外可见分光光度计和激光拉曼光谱仪对计算结果进行验证,结果表明类比红外光谱法,可以作为测定氧化石墨烯片层上羟基含量的一种有效方法。

Determination of the Oxidizability on the Surface of the Graphene Oxide Layer by Infrared Spectroscopy

Graphene oxide is composed of sp2 and sp3 hybrid carbon atoms and contains a plurality of oxygen-containing groups of hydroxyl,epoxy and carboxyl groups,and which is the precursor of many functionalized graphenes.The hydroxyl group is mainly on the surface of the graphite sheet,and the carboxyl group is mainly located at the edge of the sheet structure.An ordered composite material perpendicular to the surface,and a functional composite of various overhanging structures can be obtained by the hydroxycarboxyl group of graphene oxide.The performance of functional graphene varies greatly depending on the degree of oxidation.According to the literature,scientists have studied the ratio of different carbon atoms and oxygen atoms in graphene by XRD,XPS,FT-IR,Zeta,Raman spectroscopy,etc.,but almost no reports can directly measure the oxygen-containing functional groups on graphene oxide.A method for measuring hydroxyl content of graphene oxide by infrared spectroscopy was set up by using phenol as standard substance,Graphene oxide(GO)was prepared by the method of a chemical oxidation-reduction reaction,then using phenol as standard substance measured the hydroxyl content since phenol and GO have similar skeletal structure.The spectrum of phenol illustrated the peaks of a benzene ring frame vibration(1597,1500 and 1474 cm^-1),the benzene ring C-H in-plane bending vibration absorption peak(1692 cm^-1),and the C-OH stretching vibration absorption peak of phenols(1234 cm^-1),while the spectrum of GO illustrated the peaks of C=C stretching vibration(1630 cm^-1)and C-OH stretching vibration(1400 cm^-1).Thus,with the ratio of peak area of a benzene ring or C-OH of both phenol and GO,hydroxyl content of graphene oxide sheets was calculated by structural analogy analysis and correlation formula.The analogy infrared spectroscopy method could be applied to estimate the oxygen or hydroxyl content on the surface of graphene oxide sheets.Field emission scanning electron microscopy,Transmission electron microscopy,Atomic force microscopy,UV-visible spectrophotometer and Laser Raman spectroscopy were used to further verify the rationality of the above method.