水溶液体系中氧化石墨烯的γ射线辐射还原

石墨烯是一种碳原子以二维蜂窝状晶格结构构成的单片层材料,由于其具有优异的电传导性、力学性能和热传导性近年来受到广泛关注.本文采用γ射线辐射技术分别处理水溶液和对苯二胺(PPD)水溶液中的氧化石墨烯(GO),得到辐照还原氧化石墨烯(RGO)和胺基化修饰的还原氧化石墨烯(RGON).通过傅里叶变换红外(FTIR)光谱、X射线光电子能谱(XPS)、拉曼(Raman)光谱、X射线衍射(XRD)和热失重分析(TGA)等表征分析产物的化学结构和元素组成;通过四探针测试仪和接触角测量仪研究产物的导电性能和亲水性.实验结果表明,在水溶液及PPD水溶液中γ射线辐射均可高效还原GO,还原后得到的RGO和RGON电导率均显著增大.PPD的胺基在辐射还原过程中还可以修饰到石墨烯的表面,因此RGON的亲水性比RGO好,但胺基的存在会干扰石墨烯表面π电子的传导,导致其电导率下降.     

Functionalized reduced graphene oxide/epoxy composites with enhanced mechanical properties and thermal stability

One-pot hydrothermal reduction of graphene oxide (GO) in N-methyl-2-pyrrolidone (NMP) suspension was performed, wherein GO surface were functionalized by free radicals generated from NMP molecules. The NMP functionalized reduced GO (NMPG) nanosheets were then incorporated into epoxy matrix to prepare epoxy composites. The significant improvement of 100 and 240% in fracture toughness (critical intensity factor, K_IC) and fracture energy (critical strain energy release rate, G_IC) achieved from single edge notched bending (SENB) test revealed the excellent toughening ability of NMPG. The improved compatibility and interfacial interaction between the epoxy matrix and NMPG yielded∼28, 19 and 51% improvement in tensile strength, Young's and storage modulus, respectively. Thermal stability of pure epoxy and its composites was determined at 5, 10 and 50% weight loss, which showed 30, 27.5 and 29 °C improvement with 0.2 wt% NMPG loading. The work provides a simple method to prepare graphene-based epoxy composites with improved performance.     

Ornidazole-loaded graphene paper for combined antibacterial materials

Excellent antibacterial property of graphene oxide makes it an important antibacterial material. However, in some cases, a synergistic combination of materials with different antibacterial mechanisms is desired. In this work, we developed a simple two-step protocol to prepare ornidazole (ONZ), a nitroimidazole antiprotozoal drug, loaded graphene-based paper for combined antibacterial materials. Graphene oxide (GO) and reduced graphene oxide (rGO) were used as carriers in antibacterial materials. After mixed with ONZ directly in aqueous media and filtrated under vacuum, the freestanding GO/ONZ and rGO/ONZ were peeled off from the filtrate membrane. The ONZ loading contents in the paper was determined by UV/vis spectroscopy and the surface properties were investigated by measuring their contact angle, which will have an important impact on the antibacterial effects of the papers.     

Stabilization of Aqueous Graphene Oxide with Acetone under \begin{document}$\gamma$\end{document}-Ray/UV Irradiation

Graphene oxide (GO) is a kind of water soluble two-dimensional materials containing a large amount of oxygen-containing groups which infuse GO with water solubility, biocompatibility and functionality, etc. But GO can be easily reduced by losing oxygen-containing groups under some circumstances such as irradiation of \begin{document}$\gamma$\end{document}-ray or ultraviolet (UV). In this work, we found that acetone can significantly slow down the reduction process of GO under the irradiation of either \begin{document}$\gamma$\end{document}-ray or UV, which was supported by analysis results with UV-visible (UV-Vis) absorption spectra, X-ray photoelectron spectroscopy, etc. Acetone can capture and remove strongly reducible hydrated electrons generated under \begin{document}$\gamma$\end{document}-irradiation. GO reduction by UV also involves electron transfer process which can be affected by the presence of acetone. Hence, acetone can be used to stabilize, adjust the radiation reduction process of GO. This would be interesting not only in radiation and radiation protection, but also in understanding the redox properties of GO.     

Enhanced CO2-selective behavior of Pebax-1657: A comparative study between the influence of graphene-based fillers

Mixed matrix membranes (MMMs) containing graphene-based fillers have attracted considerable attention in the field of gas separation. In this study, two types of graphene derivatives (Graphene (G) and Graphene Oxide (GO)) were embedded into the poly-ether-block-amide (Pebax) based MMM to investigate and compare CO₂/N₂ separation at various filler loadings (0.3–1 wt%). The morphologies of the prepared neat Pebax and MMMs were characterized by SEM, XRD, FTIR and DSC. Compared with the neat Pebax, the permeability of all gases was increased by adding filler content in the MMMs due to the crystallinity decrement of the polyamide (PA) segment. The best separation performance of the Pebax/G MMMs occurred at 0.7 wt%, where the CO₂ permeability increased from 26.51 to 44.78 Barrer (~1.7 times). Also, for the Pebax/GO MMMs, the CO₂ permeability was increased up to 58.96 Barrer (~2.2 times) by adding 0.5 wt% filler. This further gas permeation increment for the Pebax/GO sample was attributed to the higher affinity of GO nanosheets to CO₂ sorption, which can facilitate CO₂ gas transition through the membrane matrix. Moreover, the CO₂/N₂ ideal selectivity increased from 74.26 for the neat Pebax to 111.95 (~1.5 times) and 120.72 (~1.62 times) by adding 0.7 wt% G (Pebax/G-0.7) and 1 wt% GO (Pebax/GO-1) into Pebax, respectively. As a consequence, graphene derivatives can be recognized as a promising developer of permselectivity (permeability and selectivity) of the MMMs.     

Preparation of Reinforced poly (BisGMA-UDMA) Graphene-Based Nanocomposites Via Moderate in Situ SET-LRP

In the present study, cross-linked poly (dimethacrylate- urethane dimethacrylate) [poly (BisGMA-UDMA)] functionalized-graphene oxide nanosheets were prepared via single-electron transfer living radical polymerization (SET-LRP) using the ‘grafting from’ strategy, under mild conditions. This method first involves the covalent attachment of Br-containing groups onto the surface of grapheme sheets to give the initiating-groups-containing graphene (G-Br). After that, the succeeding SET-LRP polymerization in DMSO in the presence of a Cu wire/Me₆TREN catalytic system at room temperature leads to the grafting of poly (BisGMA-UDMA) chains onto the graphene surface. The resulting graphene-poly (dimethacrylate- urethane dimethacrylate) (G-PDMA-UDMA) nanocomposites were characterized using FT-IR, XRD, DSC, AFM, FE-SEM, and TEM analysis techniques. It was proved that polymer chains were successfully introduced to the surface of the graphene planes. After grafting with poly (BisGMA-UDMA), the dispersibility of the modified GO sheets significantly improved. When compared to G-PDMA, the resulting G-PDMA-UDMA nanocomposite revealed around 75%, 97%, and 65%, increase in compressive strength, Young's modulus and toughness, respectively. Such smart graphene-based nanocomposites can be used as promising biomaterials in orthopaedic and dental applications with the desired mechanical properties.     

A facile synthesis of cellulose acetate reinforced graphene oxide nanosheets as proton exchange membranes for fuel cell applications

In this work, for the first time, a simple casting process is used to create an efficient and highly stable cellulose acetate (CA) based membrane with dispersive graphene oxide nanosheets (GO). The successful preparation of GO and its integration into the polymer matrix was verified by structural and morphological characterization using FTIR, TEM, SEM, and XRD. Furthermore, the impact of GO nanosheets and their content on the composite membranes' physicochemical properties is investigated. The water uptake increased up to 24% as the concentration of GO increased, while the ion exchange capacity increased threefold compared to the blank CA membrane. Additionally, increasing GO loading also enhanced the proton conductivity and the tensile strength of the developed membranes. The homogeneous CA/GO nanocomposite membranes with GO filler amounts ranging from 0.3 to 0.8 wt% were found to have excellent proton conductivity varying from 9.2 to 15.5 mS/cm compared to 6.94 mS/cm for Nafion 212. Further, as systematically studied and compared in membrane performance, the overall power density of the membrane electrode assembly (MEA) with GO content was increased up to 519 mW/cm² compared to 401 mW/cm² for Nafion 212 with significantly lower cost. The encouraging outcomes of this study pave the way for a simple, environmentally friendly, and cost-effective approach for developing nanocomposite membranes for application in PEMFCs.     

Graphene/inorganic nanocomposites: Evolving photocatalysts for solar energy conversion for environmental remediation

Current energy crisis and environmental issues, including depletion of fossil fuels, rapid industrialization, and undesired CO₂ emission resulting in global warming has created havoc for the global population and significantly affected the quality of life. In this scenario the environmental problems in the forefront of research priorities. Development of renewable energy resources particularly the efficient conversion of solar light to sustainable energy is crucial in addressing environmental problems. In this regard, the synthesis of semiconductors-based photocatalysts has emerged as an effective tool for different photocatalytic applications and environmental remediation. Among different photocatalyst options available, graphene and graphene derivatives such as, graphene oxide (GO), highly reduced graphene oxide (HRG), and doped graphene (N, S, P, B-HRG) have become rising stars on the horizon of semiconductors-based photocatalytic applications. Graphene is a single layer of graphite consisting of a unique planar structure, high conductivity, greater electron mobility, and significantly very high specific surface area. Besides, the recent advancements in synthetic approaches have led to the cost-effective production of graphene-based materials on a large-scale. Therefore, graphene-based materials have gained considerable recognition for the production of semiconducting photocatalysts involving other semiconducting materials. The graphene-based semiconductors photocatalysts surpasses electron-holes pairs recombination rate and lowers the energy band gap by tailoring the valence band (VB) and conduction band (CB) leading to the enhanced photocatalytic performance of hybrid photocatalysts. Herein, we have summarized the latest developments in designing and fabrication of graphene-based semiconducting photocatalysts using a variety of commonly applied methods such as, post-deposition methods, in-situ binding methods, hydrothermal and/or solvothermal approaches. In addition, we will discuss the photocatalytic properties of the resulting graphene-based hybrid materials for various environmental remediation processes such as; (i) clean H₂ fuel production, photocatalytic (ii) pollutants degradation, (iii) photo-redox organic transformation and (iv) photo-induced CO₂ reduction. On the whole, by the inclusion of more than 300 references, this review possibly covered in detail the aspects of graphene-based semiconductor photocatalysts for environmental remediation processes. Finally, the review will conclude a short summary and discussion about future perspectives, challenges and new directions in these emerging areas of research.     

仿鲍鱼壳石墨烯多功能纳米复合材料

石墨烯具有力学性能高、电导率优异等特点,然而单层石墨烯纳米片在组装成为宏观纳米复合材料的过程中,往往会出现片层团聚、界面作用弱、无规取向等问题,导致宏观石墨烯纳米复合材料性能远低于单片石墨烯。因此,如何将微观石墨烯纳米片层的高性能在宏观纳米复合材料中体现出来,是目前研究的热点和难点。本专论结合目前石墨烯纳米复合材料的研究现状,简要讨论了受天然鲍鱼壳的“砖-泥”结构的启发,仿生构筑高性能石墨烯纳米复合材料的最新研究进展。并对本课题组在仿鲍鱼壳石墨烯多功能纳米复合材料领域近年来的工作进行介绍,包括石墨烯纤维、薄膜和块材等多种宏观石墨烯纳米复合材料,系统总结构筑仿鲍鱼壳结构和反鲍鱼壳结构两种策略,在一定程度上解决了石墨烯在组装过程中的科学问题。同时,详细阐述了仿鲍鱼壳石墨烯多功能纳米复合材料的增强增韧机制和功能化策略,分析了今后研究工作中可能遇到的问题,并展望了未来的发展趋势。     

Robust curcumin-mustard oil emulsions for pro to anti-oxidant modulation of graphene oxide

The compositional flexibility of emulsions, via surfactant and additive choice, has been the major reason for their recognition as tuneable delivery sources for a variety of drugs. In particular, the kinetically stable nanoemulsions (NE) are preferred to minimize the toxicity extents of several poorly hydrophobic drugs through variation in their delivered extents. Inspired by these specialties, we have optimized our curcumin (curc) loaded sodium dodecylsulpahte (SDS) and dodecyl trimethylammonium bromide (DTAB) stabilized mustard oil microemulsions (ME) which catalyzed the pro-oxidant (with ethanol only) to antioxidant graphene oxide (GO) structural expression. The GO was synthesized using wet chemical approach, using ubiquitous graphite flakes as raw material. GO was loaded into 1:1 mixtures of (separately made) SDS and DTAB curc loaded formulations (CLFs). Henceforth, the resultant formulation contained 60% (1:1 SDS and DTAB) CLF mixture and ethanol dispersed GO (@ 1 mg/mL) as the other component. Compared to an insignificant (~47%) free state (while being dispersed in ethanol) DPPH free radical scavenging, the GO dispersed in CLFs enabled (62.47–100.96)% increments in DPPH scavenging, with 94.45% as maximum neutralization extent. The (493.57–3154.95)% particle size increments and (40.64–92.70)% PDI decrements for GO supplemented formulation over SDS and DTAB CLF mixtures, have inferred a wider curc distribution, through the larger GO surface area (SA) and its augmented oxygen enhanced chemical controls. In support, the physicochemical variations, characterized by (1.77–21.23)% γ decrements, (63.56–98.08%) and (68.90–163.22)% η and σ increments, have complemented the dispersion enhancing GO activities. Considering the bioactive nature of curc, these observations predict a prevalence of native curc structure or its enhanced non-covalent interaction controls with GO. Edible nature of mustard oil alongwith frequent inclusion of SDS and DTAB in routine gadgets, propel our formulations as robust media for attaining desired structural activities of functionalized GO derivatives.     

Thermal,mechanical and water barrier properties of graphene oxide/polyvinyl alcohol/polyol composite films

The novel polymer composite of polyvinyl alcohol (PVA), polyol(PO) and graphene oxide (GO) was used to prepare the PVA/PO and GO/PVA/PO with different weight percents of GO (0.5 and 1% denoted as (0.5 wt%)GO/PVA/PO and (1 wt%)GO/PVA/PO, respectively) through solution casting blend technique. The structure–properties of all used films were confirmed by scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and mechanical properties. The SEM results exhibited the uniform and homogeneous dispersion of GO in the PVA/PO blend matrix. The TEM and XRD analysis confirmed the structure and exfoliation of GO nanosheets, respectively. Thermal stability suggested that (0.5 wt%)GO/PVA/PO and (1 wt%) GO/PVA/PO films are more stable than PVA/PO. The tensile strength of (0.5 wt%)GO/PVA/PO and (1 wt%)GO/PVA/PO films reached 270.5% and 1349.6%, respectively, which are higher than that of the PVA/PO film. The decrease in the water absorption (WA) of GO/PVA/PO was found from 110.5 to 38.4%. The physico-mechanical properties of used films suggested that the prepared GO/PVA/PO blend composite films can be applied in food packaging areas.     

Recent advancements in graphene adsorbents for wastewater treatment: Current status and challenges

From emerging pollutants to emerged threat, researchers are continuously looking for promising technologies for wastewater treatment. Adsorption has been identified as the most convenient approach for treating wastewater at low-cost and with high-efficiency. Recently, graphene and its derivatives have gained heightened attention as novel adsorbents because of their unique molecular structure and outstanding physicochemical properties. Heavy metals, dyes, polycyclic aromatic hydrocarbons (PAHs) and other pollutants, which are widely concerned recently, all show different adsorption behaviors. Numerous functional groups, resonating and delocalized π-electron system of graphene derivatives lead to the formation of various adsorptive interactions i.e., π-π interactions, electrostatic interactions, H-bonding, etc. with these venomous pollutants, and quarantine them in solution. The pristine form of graphene subsidiaries tends to exhibit low sorption efficiency due to high propensity of agglomeration, lack of selectivity, hydrophobicity and difficulty in phase separation after treatment. Therefore, designing of efficient graphene composites through the surface modification with numerous functional groups, polymers or nanoparticles is an ongoing challenge. Complex graphene composites are increasingly reported, but the fate of pollutants and adsorption mechanisms are still far to be fully clarified. This review summarizes the recent progresses in the application of graphene-based adsorbents for eliminating a wide range of organic and inorganic pollutants from wastewater. A critical explanation is provided on the synthesis of graphene adsorbents, systematic adsorption and desorption mechanisms along with their pollutant removal performances under different experimental conditions. A brief perspective on upcoming research needs and challenges involved in the designing of high-quality graphene-based adsorbents are highlighted.     

Mechanically Strong Janus Poly(N-isopropylacrylamide)/Graphene Oxide Hydrogels as Thermo-responsive Soft Robots

Simple preparation of stimuli-responsive hydrogels with good mechanical properties and mild stimuliresponsiveness is essential for their applications as smart soft robots.Mechanically strong Janus poly(Nisopropylacrylamide)/graphene oxide (PNIPAM/GO) nanocomposite hydrogels with stimuli-responsive bending behaviors are prepared through a simple one-step method by using molds made of a Teflon plate and a glass plate.Residual oxygen in the air bubbles on the Teflon plate surface affects the polymerization and hence the cross-linking density,leading to the different swelling/deswelling rates of the two sides of the gels.Therefore,the hydrogels exhibit bending/unbending behaviors upon heating/cooling in water.The incorporation of GO nanosheets dramatically enhances the mechanical properties of Janus hydrogels.Meanwhile,the photo-responsive property of the GO nanosheets also imparts the hydrogels with remotecontrollable deformation under IR irradiation.The application of the Janus PNIPAM/GO hydrogels as thermo-responsive grippers is demonstrated.     

Recent progress in applications of graphene oxide for gas sensing: A review

This paper is a review of the recent progress on gas sensors using graphene oxide (GO). GO is not a new material but its unique features have recently been of interest for gas sensing applications, and not just as an intermediate for reduced graphene oxide (RGO). Graphene and RGO have been well known gas-sensing materials, but GO is also an attractive sensing material that has been well studied these last few years. The functional groups on GO nanosheets play important roles in adsorbing gas molecules, and the electric or optical properties of GO materials change with exposure to certain gases. Addition of metal nanoparticles and metal oxide nanocomposites is an effective way to make GO materials selective and sensitive to analyte gases. In this paper, several applications of GO based sensors are summarized for detection of water vapor, NO₂, H₂, NH₃, H₂S, and organic vapors. Also binding energies of gas molecules onto graphene and the oxygenous functional groups are summarized, and problems and possible solutions are discussed for the GO-based gas sensors.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料,采用Hummers法液相氧化合成了氧化石墨(GO),然后用化学一步还原制得石墨烯负载钯催化剂.X射线衍射(XRD)、透射电镜(TEM)表征表明,Pd在石墨烯载体上有较好的分散度,粒径为3-5nm.电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明,与传统Pd/VulcanXC-72相比,Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.