氧化环境和比例对改性Hummers法制备GO的影响

以鳞片石墨(GR)为原料,采用改性Hummers法液相氧化方法制备氧化石墨,通过超声剥离的方法剥离出片状的氧化石墨烯(GO),探讨了H₂SO₄环境与H₂SO₄+H₃PO₄混酸环境和KMnO₄与GR的比例对GO制备的影响。采用FTIR、UV、TG、XRD、SEM和XPS等分析手段对制备的GO进行分析。结果表明：GO外貌是呈褶皱片状,在片层上主要有C=O、C-OH、-COOH和C-O-C等官能团,以共价键形式存在石墨层间;通过TG与XPS数据分析表明在H₂SO₄ H₃PO₄混酸环境下制备的GO含氧官能团较多,并且(KMnO₄)与鳞片石墨的最佳比例是1:4。     

超声辅助Hummers法制备氧化石墨烯

采用超声辅助Hummers法制备氧化石墨烯,单片层厚～1 nm。本法首先在Hummers法的低温、中温反应阶段加入超声振荡,以此来分别提高石墨的插层效率和氧化程度,然后在高温反应开始时,采用把含有残留浓硫酸的混合液缓慢滴入低温去离子水中再加热的方式,以此减少硫酸分子等插入物因为局部温度过高从石墨层间脱出,最后通过低速离心得到氧化石墨。使用超声辅助Hummers法制备氧化石墨烯既方便快捷,又能有效地增大氧化石墨的层间距,且随着超声功率的提高,所得氧化石墨的层间距呈扩大趋势。     

十六烷基三甲基溴化铵改进Hummers法制备石墨烯的研究

将阳离子表面活性剂（十六烷基三甲基溴化铵,CTAB）作为絮凝剂,利用其与氧化石墨烯（GO）产生静电吸引的原理,实现中间产物CTAB-GO复合物的快速分离和纯化,并利用水合肼还原制得还原氧化石墨烯（RGO）。采用UV-Vis、 SEM、 TEM、 AAS和XPS对石墨烯的形貌、纯度、制备过程及机理进行了分析表征。结果显示,CTAB能通过静电力吸附在GO表面,形成CTAB-GO复合物的絮凝沉淀。当CTAB和GO的质量比为1:2时,可以达到最佳的絮凝效果。该絮凝沉淀仅通过低压过滤或低速离心（3 000 rpm, 3 min）便能实现快速分离和纯化,得到CTAB-GO复合物。AAS和XPS证实CTAB-GO复合物中不存在杂质离子。此外,CTAB-GO复合物经过水合肼还原后,CTAB能快速完全脱除,从而得到高纯度RGO。     

石墨烯和氧化石墨烯的表面功能化改性

石墨烯和氧化石墨烯由于特殊的电子、光学、力学性能已成为当今科学研究的热点.重点综述了近年来石墨烯和氧化石墨烯的表面功能化改性研究进展.首先介绍了石墨烯、氧化石墨烯的基本结构与性质.然后将表面功能化分为非共价键结合改性、共价键结合改性和元素掺杂改性.非共价键结合的功能化改性分为四类：π-π键相互作用、氢键作用、离子键作用以及静电作用.共价键结合的功能化改性分为四类：碳骨架功能化、羟基功能化、羧基功能化和环氧基功能化.元素掺杂改性分为N、B、P等不同元素的掺杂功能化.总结了石墨烯、氧化石墨烯基体与改性分子的相互作用和反应类型,以及改性产物的性能与应用.最后对石墨烯和氧化石墨烯在表面功能化改性方面的发展前景作了展望和预测.     

改性氧化石墨烯膜的制备及其性能研究

为了改善氧化石墨烯(GO)膜的低渗透性和不稳定性,本文采用过氧化氢对GO进行改性后抽滤成膜,并在不同温度下对膜进行热还原.采用超高性能全自动气体吸附仪、透射电镜、扫描电镜、拉曼光谱仪、接触角、X射线衍射等对材料进行结构和形貌表征.分析不同HGO(H2O2改性GO)负载量和不同温度热还原对膜水通量和截留率的影响.在优化条...     

球磨辅助氧化还原法制备石墨烯

本文利用天然石墨作为原材料,采用改进的Hummers法制备氧化石墨(GO)。首先将氧化石墨在低能球磨机中球磨10 h,然后超声剥离得到氧化石墨烯。最后利用水合肼作为还原剂,通过磁力搅拌回流反应得到石墨烯。利用SEM,AFM,XRD,Raman,FTIR,TEM对所制备的石墨烯的形貌和结构进行表征。同时将经低能球磨制备的石墨烯与未经低能球磨制备的石墨烯进行比较,分析了在不同工艺条件下制备的石墨烯的效果。结果表明低能球磨有利于减薄氧化石墨,促进氧化石墨的剥离。并且有利于氧化石墨的还原,从而缩短回流还原反应时间,提高了制备石墨烯的效率。     

两步法制备氧化石墨烯方法研究

以大鳞片石墨为原料在低温、高温反应两步氧化法制备了氧化石墨烯,得到大片氧化石墨烯。由于原料石墨鳞片大,制作出的氧化石墨烯片也较大,因此可以在160倍光学显微镜下清晰观察到其形态,通过160倍和640倍光学显微镜的观测,能够初步判断氧化石墨烯厚度,为后续检测提供参考,因而该方法是一种制备并观测氧化石墨烯的有效方法。     

季铵盐改性氧化石墨烯的制备及其性能研究

本论文采用改进的Hummers法制备了氧化石墨烯(GO),并将氧化石墨烯用十二烷基二甲基苄基氯化铵(1227)进行修饰,得到1227非共价改性的氧化石墨烯(GO-1227)。用拉曼光谱、漫反射红外光谱分析、X-射线光电子表面能谱技术表征了其化学结构;用X-射线衍射分析、扫描电子显微镜与透射电子显微镜观察了其剥离情况和微观形貌;分析了它们在不同溶剂中的分散性。结果表明,季铵盐改性后,1227阳离子通过静电作用插入到GO片层之间,使GO片层进一步剥离,且在极性较弱的有机溶剂中的溶解性增加。热失重分析表明,GO-1227的初始分解温度提高了约70℃。将GO-1227与聚甲基丙烯酸甲酯与苯乙烯的嵌段共聚物(PMMA-b-PS)凝胶聚电解质复合,制备了纳米复合凝胶聚合物电解质(NGPE),并用交流阻抗法测试其电性能,发现占聚电解质总质量2‰的GO-1227可以将其离子电导率提高8.6倍。     

通过“点击化学”对石墨烯和氧化石墨烯进行功能化改性

点击化学具有操作简单方便、灵活高效等特点,在石墨烯的功能化改性上具有极其重要的应用.本工作针对点击化学对石墨烯和氧化石墨烯功能化改性方面进行了综述.将石墨烯点击功能化改性方法分为两种情况:共价键结合的点击功能化改性和非共价键作用的点击功能化改性,其中共价键结合又可细分为边缘点击功能化改性和表面点击功能化改性.首先,本工作对石墨烯点击功能化改性的反应过程和反应条件及其研究方法作了详细的归类和系统的总结.一方面,在石墨烯点击功能化改性的分类上包括:氧化石墨烯边缘点击,氧化石墨烯表面点击,石墨烯表面点击,石墨烯表面经过Diels-Alder[4+2]的点击反应,以及通过非共价键作用的π-π堆积之后的点击反应;另一方面,在点击反应的合成路线上,详细列出了对石墨烯或者氧化石墨烯进行炔基化或者叠氮基化以及功能化分子进行相应地叠氮基化或者炔基化的连接方法和反应条件,通过点击反应将两部分连接起来,并指出石墨烯功能化复合物的功能特性和应用前景.对这部分工作进行列表总结,然后作图列出石墨烯和氧化石墨烯的点击功能化反应的具体分类和反应过程.另外,本工作列表总结了IR,Raman,UV,1H NMR,13C NMR,XPS,XRD,AFM,TEM,SEM,CV,TGA等对石墨烯和氧化石墨烯进行表征的常用方法,指出了常见的出峰位置以及表征结果和测试目的,并作了简要的分析和说明.最后,对点击化学在石墨烯和氧化石墨烯上的功能化应用作出了总结和展望.     

改性氧化石墨烯稳定Pickering乳液法制备高导热相变整体材料

采用表面引发原子转移自由基聚合法(SI-ATRP)改性氧化石墨烯(GO), 并用其稳定Pickering高内相乳液, 一步成型制得高导热氧化石墨烯/石蜡复合整体相变材料. 通过SI-ATRP方法, 在氧化石墨烯表面引入分子刷, 提高GO的分散性, 实现了低GO含量下优异的导热强化效果. 当GO添加量仅为相变复合材料整体的0.4%(质量分数)时, 其热导率(3.968 W?m^-1?K^-1)比纯石蜡的热导率(0.608 W?m^-1?K^-1)有较大提升. 通过测试发现, 在1000次循环后相变材料的泄漏率仅为1.1%~1.3%, 表现出良好的形状稳定性和热可靠性. 制备的新型形状稳定相变材料在温控、 储能应用中具有潜在的用途.     

Evaluation of Reduced Graphene Oxide Modified with Antimony and Copper Nanoparticles for Levofloxacin Oxidation

This work presents, for the first time, the oxidation mechanism of levofloxacin combining electrochemical experiments and molecular modelling techniques. Levofloxacin is one of the most widely used antibiotics in the world. The detection of this antibiotic is important, because it cannot be fully assimilated by the human organism, therefore levofloxacin is considerate a hazardous pollutant for environment. Sensors based on reduced graphene oxide (rGO) modified with antimony and copper nanoparticles (NPs) were synthesized, characterized and evaluated for the electrochemical detection of the levofloxacin. The morphological and electrochemical characterization of the composites confirmed that the rGO was modified with the metallic nanoparticles. Molecular modelling studies were performed applying Density Functional Theory (DFT) approach, which indicated that the mechanism of levofloxacin oxidation is given by the loss of two electrons: one from N14 atom and other from C13 atom of the levofloxacin molecule. The glassy carbon electrode (GCE) modified with the SbNPs/rGO and CuNPs/rGO composites were evaluated for the determination of levofloxacin using differential pulse voltammetry (DPV) and achieved detection limit of 4.1×10⁻⁸ mol L⁻¹ and 1.7×10⁻⁸ mol L⁻¹, respectively, presenting as alternative composites to be used in the analysis of antibiotics.     

石墨烯及氧化石墨烯对分离膜改性的方法、效能和作用机理

石墨烯及氧化石墨烯由于其独有的性质在分离膜领域引起广泛关注。本文综合分析了石墨烯及氧化石墨烯在分离膜改性方面的几种典型应用,即共混膜、多孔石墨烯膜和层状排列氧化石墨烯膜,并结合其制备方法、效能和作用机理进行阐述。结果表明,相转化法制备的共混膜可以提高膜通量和截留率、增加膜的亲水性并有效抑制膜污染,但是其并不能充分发挥氧化石墨烯独有的结构和性能优势,具有一定的局限性;层薄和机械性能强的完美结合使石墨烯可以通过打孔形成分离性能较好的多孔石墨烯膜,但是制备大片石墨烯的难度和不成熟的打孔技术限制了其进一步发展;而层状排列的氧化石墨烯膜可充分发挥氧化石墨烯材料的特性,以层间间距作为主要运输通道有利于充分发挥氧化石墨烯高输运速率的优点和高选择性的特性,为开创下一代高通量、高选择性、强抗污染性的高性能分离膜提供了重要思路。     

High Correlation between Oxidation Loci on Graphene Oxide

Recent experiments have shown the coexistence of both large unoxidized and oxidized regions on graphene oxide (GO), but the underlying mechanism for the formation of the GO atomic structure remains unknown. Now, using density functional calculations, 52 oxidation pathways for local pyrene structures on GO were identified, and a kinetic profile for graphene oxidation with a high correlation between oxidation loci was proposed, which is different from the conventional view, which entails a random distribution of oxidation loci. The high correlation is an essential nature of graphene oxidation processes and can be attributed to three crucial effects: 1) breaking of delocalized π bonds, 2) steric hindrance, and 3) hydrogen‐bond formation. This high correlation leads to the coexistence of both large unoxidized and oxidized regions on GO. Interestingly, even in oxidized regions on GO, some small areas of sp²‐hybridized domains, similar to “islands”, can persist because of steric effects.     

石墨烯的制备及石墨烯修饰电极对p-苯二酚的催化氧化

采用氨水还原氧化石墨烯(GO)制备石墨烯(GN), 并考察石墨烯修饰玻碳电极(GN/GCE)电催化氧化p-苯二酚(HQ)的性能. 利用傅里叶红外光谱(FTIR)、拉曼光谱(Raman)、X射线衍射(XRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)、比表面分析(BET)和电分析化学测试等技术对GN结构、表面形貌和电化学行为进行了表征. 采用循环伏安法(CV)和差分脉冲溶出伏安法(DPV)研究GN/GCE对HQ的电催化氧化性能. 结果表明, 与裸玻碳电极(GCE)相比, [Fe(CN)₆]^3-/4-在GN/GCE上电荷转移电阻为75.0 Ω·cm², 减小约9倍, 说明GN具有良好导电性; 同时HQ在GN/GCE上氧化峰电位负移, 还原峰电位正移, 峰电位差ΔE_p减小165 mV, 且氧化还原峰电流(I_pa和I_pc)均增大, HQ电化学氧化可逆性明显改善, 表明GN/GCE对HQ氧化具有显著电催化作用.     

Enhanced Thermal Oxidation Stability of Reduced Graphene Oxide by Nitrogen Doping

Nitrogen‐doped reduced graphene oxide (N‐doped RGO) samples with a high level of doping, up to 13 wt. %, have been prepared by annealing graphene oxide under a flow of pure ammonia. The presence of nitrogen within the structure of RGO induces a remarkable increase in the thermal stability against oxidation by air. The thermal stability is closely related with the temperature of synthesis and the nitrogen content. The combustion reaction of nitrogen in different coordination environments (pyridinic, pyrrolic, and graphitic) is analyzed against a graphene fragment (undoped) from a thermodynamic point of view. In agreement with the experimental observations, the combustion of undoped graphene turns out to be more spontaneous than when nitrogen atoms are present.     

Photocatalytic Oxidation Based on Modified Titanium Dioxide with Reduced Graphene Oxide and CdSe/CdS as Nanohybrid Materials

Photocatalytic activity of TiO₂ nanoparticles in the visible light region was enhanced. TiO₂–CdSe and TiO₂–CdSe/CdS nanohybrids were supported on the reduced graphene oxide. These nanohybrid materials were applied as photocatalyst toward oxidation of aromatic alcohols under a mild condition and the molecular oxygen as oxidant. A plausible mechanism for the photocatalytic oxidation was also proposed. Desired nanohybrids were obtained via in situ fixation of CdSe/CdS on the surface of nanosheets of reduced graphene oxide (rGO). Finally, it was modified by TiO₂ sol nanoparticles through a hydrothermal method. The obtained nanomaterials, were characterized by SEM, TEM imaging, XRD, EDAX, DRS and XPS analyses. The size of nanohybrids materials were distributed mostly in a narrow range of 50–65 and 60–75 nm for TiO₂–rGO–CdSe and TiO₂–rGO–CdSe/CdS, respectively. These photocatalysts showed high catalytic activity under visible light irradiation in a short reaction time and even higher selectivity rather than UV irradiation. The yield of catalytic oxidation increased at least 25–30% for TiO₂–CdSe/CdS on rGO, which could be related to its higher light sensitivity and lower energy band gap. The photocatalysts were recycled and reused 8 times without significant loss of their activities due to their stability under visible light.     

The Influence of Lateral Size and Oxidation of Graphene Oxide on Its Chemical Reduction and Electrical Conductivity of Reduced Graphene Oxide

The chemical reduction efficiencies of graphene oxide (GO) are critically important in achieving graphene-like properties in reduced graphene oxide (rGO). In this study, we assessed GO lateral size and its degree of oxidation effect on its chemical reduction efficiency in both suspension and film and the electrical conductivity of the corresponding rGO films. We show that while GO-reduction efficiency increases with the GO size of lower oxidation in suspension, the trend is opposite for film. FESEM, XRD, and Raman analyses reveal that the GO reduction efficiency in film is affected not only by GO size and degree of oxidation but also by its interlayer spacing (restacking) and the efficiency is tunable based on the use of mixed GO. Moreover, we show that the electrical conductivity of rGO films depends linearly on the C/O and Raman I_D/I_G ratio of rGO and not the lateral size of GO. In this study, an optimal chemical reduction was achieved using premixed large and small GO (L/SGO) at a ratio of 3:1 (w/w). Consequently, the highest electrical conductivity of 85,283 S/m was achieved out of all rGO films reported so far. We hope that our findings may help to pave the way for a simple and scalable method to fabricate tunable, electrically conductive rGO films for electronic applications.