【作者】 郭焕焕；

【导师】 张锐； 范冰冰；

【作者基本信息】 郑州大学 ， 材料工程（专业学位）， 2013， 硕士

【摘要】 氧化石墨烯(GO)作为合成化学改性石墨烯及石墨烯复合材料的前驱体材料,具有成本低、可实现批量生产的特点,受到人们的广泛关注。本文采用改进的Hummers法,在充足氧化剂用量下,分别改变低温(0℃)、中温(35℃)、高温(95℃)三个独立阶段的氧化时间,制备得到不同氧化程度的GO样品。结合XRD、FTIR、Raman、SEM等测试手段,对不同GO样品的晶体结构、含氧官能团类型、无序度及形貌特征进行表征,揭示Hummers法制备GO的动力学过程。以GO与硝酸银为前驱体,在NaOH溶液作用下,一步绿色合成银/石墨烯(Ag/rGO)纳米复合材料,研究银离子浓度、合成温度、反应时间等工艺参数对Ag/rGO复合材料性能的影响,分析银粒子在GO表面的析晶过程。最后,探索了Ag/rGO纳米复合材料在光疗、热疗治疗人体乳腺癌MCF-7细胞的应用价值。研究结果表明：采用改进的Hummers法,在充足氧化剂用量下,低温短时间氧化反应可以完全改变鳞片石墨的原始晶体结构,实现羟基、环氧基官能团在GO片层底面大量衍生,层间距明显提高,且随低温氧化时间的延长,GO的氧化度逐渐提高；中温阶段氧化反应对GO氧化度的提高影响不大,属于Hummers法中低温反应向高温反应的一个过渡阶段；高温氧化半小时内,GO无序度明显上升,羧基、羰基、烷氧基官能团大量衍生,随机分布于GO片层边缘处,并导致GO碳膜破裂、缺陷及孔洞的产生,高温氧化时间过长,碳结构缺陷加剧,但部分结合不牢固的官能团发生脱离,导致GO无序度下降。在氢氧化钠作用下,一步绿色合成了Ag/rGO纳米复合材料,银颗粒平均尺寸为11nm左右,且均匀牢固分布在rGO片层上,Ag/rGO纳米复合材料在水中有着优异的分散性；在合成过程中,NaOH脱除Ag/rGO表面的羧基、羰基、环氧基等基团,体系内仅保留少量的羟基官能团；Ag+将GO表面烷氧基脱除,并在还原过程中消耗一定量的羟基,Ag+的加入,促进了rGO向石墨烯sp2共轭结构转化,生成的银纳米颗粒与rGO表面残余羟基具有一定结合作用。前驱体硝酸银溶液浓度增加,可提高石墨烯表面银颗粒负载率,但对银颗粒尺寸影响不大；随着合成温度的提高,Ag2O衍射峰消失,当反应温度为70℃时,可制备得到纯净的Ag/rGO纳米复合材料；反应在6min内即可合成Ag/rGO复合结构,反应时间的延长,对复合结构中银颗粒影响不大,但促进复合材料中rGO向石墨烯sp2共轭结构转变。通过Ag/rGO纳米复合材料对人体乳腺癌(MCF-7)细胞的光疗、热疗作用测试,结果发现：在无光照作用下,该复合体系对MCF-7细胞毒性很小,Ag/rGO药物安全性高；当在532nm激光作用下,细胞内产生活性氧(ROS),药物通过光疗效应杀死MCF-7细胞；在近红外光(808nm)作用下,利用热疗作用损伤MCF-7细胞。因此,本课题绿色合成的Ag/rGO纳米复合材料有望用于光疗或热疗治疗肿瘤领域。更多还原

【Abstract】 Graphene oxide (GO) has re-emerged as an intense research interest to its role as a precursor for the cost-effective and mass production of chemically converted graphene (CCG) and graphene-based materials. In this thesis, GO samples with different oxidation degree were synthetized through modified Hummers method by changing their reaction time, respectively. The structure, composition, and disorder parameter of GO were confirmed by means of XRD, FTIR, Raman, and SEM. An one-pot and green synthesis approach had been employed to prepare silver/reduced graphene oxide (Ag/rGO) nanocomposite in the presence of sodium hydroxide at70℃. Parameters in the preparation process, such as reaction temperture and reaction time, were discussed and the potential application of Ag/rGO nanocomposite in cancer photodynamic therapy and photothermal therapy was explored at the same time.Results show that:the structure of origin graphite was damaged completely within oxidation time of1hour at0℃, with the derivation of hydroxyl and epoxy groups on the basal of GO sheets. The degree of oxidation of GO increased over time at0℃, while it changed little at35℃. Within30min at95℃, it showed a significant increase of the degree of oxidation of GO. And carboxyl, carbonyl and alkoxy groups appeared in larger numbers at the edge of GO sheets, which lead to defects and holes on the GO surface. The disorder degree of GO may decrease if the reaction time at95℃was so long, due to the removal of some unstable goups on GO sheets.The Ag/rGO nanocomposite was prepared in an one-pot and green approach in alikaline solution using silver nitrate as precursor and graphene oxide as substrate.Within11min, the small-sized (av.11nm) and highly dispersed silver nanoparticles were supported on reduced graphene oxide sheets. The FTIR and XRD results demonstrates that NaOH accelerated the removal of carboxyl groups on the surface of GO, and Ag+attributed to recover the C=C sp2structure of rGO. Strong interaction may exist between silver nanopaticles and the remaining surface hydroxyl groups in Ag/rGO nanocomposite. The silver crystal growth was influenced by temperature and alkali concentration, rather than the reaction time. While long reaction time attributed to the recover of C=C sp2structure of rGO.In this work, for the first time we studied the behaviors of Ag/rGO nanocomposite in photodynamic therapy under532nm laser and photothermal therapy under NIR light (808nm) to kill MCF-7human breast cancer cell. Ag/rGO nanocomposite has cytotoxicity under irradiation and can be used as cancer therapeutic photosensitizer. The as-obtained Ag/rGO nanocomposite presented effective ability of cancer photodynamic therapy and photothermal therapy.更多还原