PEG接枝氧化石墨烯的制备与细胞成像

通过酯化反应将不同分子量的聚乙二醇(PEG)接枝到氧化石墨烯(GO)表面,得到系列GO-PEG。利用傅里叶变换红外光谱(FTIR)、拉曼光谱(Raman)、扫描电子显微镜(SEM)对GO-PEG的结构和形貌进行了表征,用热重分析(TGA)测定了GO-PEG中PEG的接枝量。SEM结果表明GO-PEG的剥离程度高于GO。GO-PEG在磷酸盐缓冲溶液中具有良好的分散稳定性,稳定性与接枝量呈正相关。GO-PEG通过非共价键合作用对荧光素(Flu)的负载量可达1.75 mg·mg-1,且负载量受接枝量影响;另外,GO-PEG对Flu的释放行为具有pH值触发药物释放性能。将接枝PEG的端羟基与Flu共价键合,所得GO-PEG6000-Flu荧光探针实现了对HepG2细胞的成像。     

PEG接枝氧化石墨烯的制备与细胞成像

通过酯化反应将不同分子量的聚乙二醇（PEG）接枝到氧化石墨烯（GO）表面,得到系列GO-PEG。利用傅里叶变换红外光谱（FTIR）、拉曼光谱（Raman）、扫描电子显微镜（SEM）对GO-PEG的结构和形貌进行了表征,用热重分析（TGA）测定了GO-PEG中PEG的接枝量。SEM结果表明GO-PEG的剥离程度高于GO。GO-PEG在磷酸盐缓冲溶液中具有良好的分散稳定性,稳定性与接枝量呈正相关。GO-PEG通过非共价键合作用对荧光素（Flu）的负载量可达1.75mg·mg^-1,且负载量受接枝量影响;另外,GO-PEG对Flu的释放行为具有pH值触发药物释放性能。将接枝PEG的端羟基与Flu共价键合,所得GO-PEG₆₀₀₀-Flu荧光探针实现了对HepG₂细胞的成像。     

石墨烯的氧化还原法制备及结构表征

采用改进的Hummers法对天然鳞片石墨进行氧化处理制备氧化石墨,经超声分散,然后在水合肼的作用下加热还原制备了在水相条件下稳定分散的石墨烯。用红外光谱、拉曼光谱、扫描探针显微镜和ζ电位仪对样品进行了结构、谱学、形貌和ζ电位分析。结果表明,石墨被氧化后形成以C=O、C-OH、-COOH和C-O-C等官能团形式的共价键型石墨层间化合物;还原氧化石墨后形成的石墨烯表面的官能团与石墨的相似;氧化石墨烯和石墨烯在碱性条件下可形成稳定的悬浮液;氧化石墨烯和石墨烯薄片厚度为1.0nm左右。考察并讨论了还原过程中水合肼用量,体系反应温度、反应时间和pH值对石墨烯还原程度和稳定性的影响,水合肼用量和反应时间是影响石墨烯还原程度的主要因素;pH值对石墨烯稳定性影响较大。     

氧化石墨烯增强卡拉胶复合膜的制备与性能

在Hummers法基础上制得了氧化石墨烯(GO), 采用流延法制备了氧化石墨烯/κ-卡拉胶(GO/κ-Car)复合膜材料. 结合红外光谱、 扫描电子显微镜及热重分析对其结构进行表征. 探讨了不同条件所得膜的成膜性、 溶解性、 透气性和力学性能, 得到性质稳定GO/κ-Car复合膜的制备条件为15.0 g 3%的κ-Car溶液、0.040 g GO粉末及5.0 g 8%的PVA溶液于75 ℃搅拌混合5 h后, 流延铺平, 于30 ℃烘干6.5 h. GO质量分数为5%的GO/κ-Car复合膜的最大负荷、 拉伸强度及杨氏模量分别是对照组κ-Car膜的1.5倍、 1.5倍和1.6倍. 同时, GO/κ-Car复合膜具有较强的透气性能, 且保留了κ-Car清除羟基自由基的生物性能.     

氧化石墨烯的制备及低温还原研究

用化学氧化法制备氧化石墨烯,并用一种新型的低温化学还原方法将其还原。用红外光谱、拉曼光谱、X射线衍射、X射线光电子能谱、扫描电镜、原子力显微镜等多种手段表征氧化石墨烯和还原氧化石墨烯的结构与形貌。结果表明,即使在低温条件下,壳聚糖依然可以还原氧化石墨烯,从而预示,在低温条件下,能够在同一环境下实现氧化石墨烯的还原和石墨烯的应用。     

氧化石墨烯的可控还原及结构表征

采用氧化还原法, 通过控制还原时间制备了不同还原程度的石墨烯; 用红外光谱、 紫外光谱、 拉曼光谱、 X射线衍射、 热重分析、 电导率测量等多种手段系统研究了不同还原程度石墨烯的结构与性能; 采用透射电子显微镜、 扫描电子显微镜和原子力显微镜比较了氧化石墨烯和石墨烯的形貌. 结果表明, 随着还原程度的增加, 石墨烯中含氧基团减少, 紫外吸收峰逐渐红移, D带与G带的强度比增加, 热稳定性和导电性提高. 微观结构表征说明石墨烯比氧化石墨烯片的厚度增加, 褶皱增多.     

石墨烯薄膜的光化学还原制备与表征

采用光化学还原方法制备了图案化的石墨烯薄膜.研究了光还原氧化石墨烯薄膜(PRGO)的热稳定性和发光性质.热重分析(TGA)结果表明,光化学还原主要引起氧化石墨烯(GO)氧化基团的减少,而对GO内水含量影响较小;发光(PL)测试结果表明,不同激发条件下,PRGO的发光与GO相比表现出了不同的变化规律:在波长514 nm的光激发下,PRGO的发光强度比GO明显降低,同时伴随着发光峰峰位红移;而在波长830 nm的光激发下,PRGO的发光强度比GO略有增强,并且发光峰峰位无明显变化,此结果表明不同尺寸的碳团簇局域态(sp2C团簇)的光还原反应活性不同,这与GO特殊的能带结构密切相关.     

氧化石墨烯-海藻酸钠-壳聚糖复合支架的制备及表征

通过冷冻干燥技术,将不同量的氧化石墨烯与海藻酸钠和壳聚糖复合,构建复合支架材料.研究了不同的氧化石墨烯含量(质量分数0, 0.3%, 0.5%, 0.7%, 1%)对支架材料微观结构、孔隙率、溶胀比、体外降解性能、机械性能及生物相容性的影响,以确定复合支架中最佳氧化石墨烯含量.研究结果表明,复合材料呈固态海绵状结构,具有一定的形态可塑性;扫描电子显微镜观察发现,各组支架均为三维网状结构,随着氧化石墨烯含量的增加,孔隙尺寸逐渐降低,孔壁厚度增加,孔隙尺寸在140～240μm之间;随氧化石墨烯含量的增加,复合支架溶胀比和体外降解速率逐渐降低,而机械强度明显增强;体外细胞毒性显示,当氧化石墨烯质量分数为0.3%时,细胞存活率最高,而当氧化石墨烯含量增高时,细胞活性会被明显抑制,造成细胞死亡.因此,氧化石墨烯在复合支架中最佳含量为0.3%.     

石墨烯薄膜的制备和结构表征

采用氧化还原法制备了石墨烯胶状悬浮液, 通过真空抽滤获得了石墨烯薄膜. 利用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、拉曼(Raman)光谱、粒度分析和扫描探针显微镜(SPM)等研究了石墨烯薄膜制备过程中各阶段产物的晶体结构、粒度及分子光谱特征变化. FTIR分析结果表明, 石墨在氧化过程中结构层键合大量含氧官能团, 还原后结构层表面仍残存有部分稳定的含氧官能团. XRD结果表明, 石墨氧化后衍射峰向小角度偏移、宽化, 原有石墨峰消失. 在成膜过程中氧化石墨烯形成凝聚体,而石墨烯形成絮凝体. 粒度分析和SPM测试分析结果表明, 氧化石墨烯在水中粒径分布呈拖尾峰形, 分布范围较宽. 石墨烯在水中的粒径成单峰分布, 分布范围较窄、对称性较好且平均粒径较小. Raman测试结果表明, 石墨在氧化和还原过程中, D、G峰逐渐宽化, I_D/I_G逐渐增强, 样品无序度增加. 在以上分析的基础上对石墨烯制备过程的结构特征进行了归纳总结.     

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。     

Microwave‐Assisted Synthesis and Physicochemical Characterization of Tetrafuranylporphyrin‐Grafted Reduced‐Graphene Oxide

This work describes the design of a modified porphyrin that bears four furan rings linked by 1,2‐bis‐(2‐aminoethoxy)ethane spacers. This unit is a well‐suited scaffold for a Diels–Alder reaction with commercial reduced‐graphene oxide, which is also described in this paper. A new hybrid material is obtained, thanks to efficient grafting under microwave irradiation, and fully characterized in terms of structure (UV, TGA, Raman) and morphology (HR‐TEM and AFM). Potential applications in photo‐ and sonodynamic therapy are envisaged.     

In Situ Synthesis and Characterization of Poly(aryleneethynylene)‐Grafted Reduced Graphene Oxide

Using highly soluble bromo‐functionalized reduced graphene oxide (RGBr) as a key graphene template for surface‐directing Sonogashira–Hagihara polymerization, a novel soluble poly(arylene‐ethynylene)‐grafted reduced graphene oxide, hereafter abbreviated as PAE‐g‐RGO, was prepared in situ. The entirely different electron distribution of LUMO and HOMO of PAE‐g‐RGO suggested the existence of a charge‐transfer (CT) state (PAE^.?–RGO^.+). The negative ΔG_CS value (?2.57 eV) indicates that the occurrence of the charge separation via ¹RGO* in o‐DCB is exothermic and favorable. Upon irradiation with 365 nm light, the light‐induced electron paramagnetic resonance (LEPR) spectrum of PAE‐g‐RGO showed a decrease in the spin‐state density owing to photoinduced intramolecular electron transfer events in this system. A sandwich‐type Al/PAE‐g‐RGO/ITO device showed representative bistable electrical switching behavior. The nonvolatile memory performance was attributed to the CT‐induced conductance changes, which was supported by molecular computation results and conductive atomic force microscopy (C‐AFM) images.     

Preparation and Characterization of Carbon Fibers from Lyocell Precursors Grafted with Polyacrylamide via Electron-Beam Irradiation

Carbon fibers, which act as reinforcements in many applications, are often obtained from polyacrylonitrile (PAN). However, their production is expensive and results in waste problems. Therefore, we focused on producing carbon fibers from lyocell, a cellulose-based material, and analyzed the effects of the process parameters on their mechanical properties and carbon yields. Lyocell was initially grafted with polyacrylamide (PAM) via electron-beam irradiation (EBI) and was subsequently stabilized and carbonized. Thermal analysis showed that PAM grafting increased the carbon yields to 20% at 1000 °C when compared to that of raw lyocell, which degraded completely at about 600 °C. Stabilization further increased this yield to 55%. The morphology of the produced carbon fibers was highly dependent on PAM concentration, with fibers obtained at concentrations ≤0.5 wt.% exhibiting clear, rigid, and round cross-sections with smooth surfaces, whereas fibers obtained from 2 and 4 wt.% showed peeling surfaces and attachment between individual fibers due to high viscosity of PAM. These features affected the mechanical properties of the fibers. In this study, carbon fibers of the highest tensile strength (1.39 GPa) were produced with 0.5 wt.% PAM, thereby establishing the feasibility of using EBI-induced PAM grafting on lyocell fabrics to produce high-performance carbon fibers with good yields.     

KH-570功能化石墨烯的制备与表征

采用Hummers法对天然石墨进行氧化处理制备了氧化石墨烯,通过γ-甲基丙烯酰氧丙基三甲氧基硅烷与氧化石墨烯反应得到功能化氧化石墨烯,然后在水合肼的作用下制备了功能化石墨烯。未烘干的功能化石墨烯在超声处理下,能稳定分散在体积比为9∶1(V/V)的乙醇/水、丙酮/水或N,N-二甲基甲酰胺/水的混合溶剂中。用傅立叶变换红外光谱、原子力显微镜、X射线光电子能谱及X射线衍射对样品结构、形貌进行了分析。结果表明,KH-570上的硅氧烷与氧化石墨烯上的羟基发生了反应,经水合肼还原后,功能化石墨烯的无序度增加,层间距也比功能化氧化石墨烯的缩小了。功能化石墨烯在DMF/水中呈高度剥离状态,片层厚度为1.1～2.3 nm。     

氧化石墨烯水热还原前后的发光光谱

分别采用改进Hummers方法和水热还原法制备了氧化石墨烯(GO)和还原氧化石墨烯(RGO)。 GO和RGO经透射电子显微镜(TEM)、紫外-可见吸收光谱(UV-Vis)、红外光谱(IR)、荧光发射和激发光谱(PL、PLE)等技术手段进行了表征。 荧光发射光谱显示,氧化石墨烯(GO)在可见光的激发下可以得到波长在600~800 nm范围内的宽谱近红外荧光。 通过比较氧化石墨烯水热还原前后的光谱变化,发现氧化石墨烯近红外荧光起源于氧化石墨烯的表面含氧基团,如C=O、COOH。 近红外荧光穿透性好、对生物组织损坏小,非常适合于生物成像,预示着氧化石墨烯在生物成像方面的应用潜力。     

Investigation of the Thermal Stability of the Carbon Framework of Graphene Oxide

In this study, we use our recently prepared graphene oxide (GO) with an almost intact σ‐framework of carbon atoms (ai‐GO) to probe the thermal stability of the carbon framework for the first time. Ai‐GO exhibits few defects because CO₂ formation is prevented during synthesis. Ai‐GO was thermally treated before chemical reduction and the resulting defect density in graphene was subsequently determined by statistical Raman microscopy. Surprisingly, the carbon framework of ai‐GO is stable in thin films up to 100 °C. Furthermore, we find evidence for an increase in the quality of ai‐GO upon annealing at 50 °C before reduction. The carbon framework of GO prepared according to the popular Hummers’ method (GO‐c) appears to be less stable and decomposition starts at 50 °C, which is qualitatively indicated by CO₂‐trapping experiments in μm‐thin films. Information about the stability of GO is important for storing, processing, and using GO in many applications.