乙二胺和己二胺氨基功能化氧化石墨烯(英文)

采用了一种通过采用乙二胺和己二胺接枝改性制备氨基功能化石墨烯的高效、经济的方法。结果表明,该方法可对氧化石墨烯进行有效的氨基化,且官能化程度较高,每9～10个碳原子中就有一个参与氨基化反应;随着二元胺烷基链长度的增长,氨基功能化氧化石墨烯的的热稳定性得到明显提高,但在N,N-二甲基甲酰胺溶剂中的分散性却会变差。     

Intrinsic structure and friction properties of graphene and graphene oxide nanosheets studied by scanning probe microscopy

In this paper, atomic structure of single-layered graphene oxide (GO) and chemically reduced graphene oxide (CRGO) nanosheets was investigated using atomic force microscopy and scanning tunneling microscopy (AFM and STM). Furthermore, friction properties of the graphene and GO nanosheets were studied by frictional force microscopy (FFM). STM imaging provided direct evidence and the morphology was influenced by oxygen-containing groups and defects. The atomic scale structural disorder in a hexagonal two-dimensional network of carbon atoms changes the surface condition, which also caused the frictional property variations of the samples.     

Improved dispersion of attapulgite nanorods in polymer with graphene oxide nanosheets

To improve the dispersion stability of rod-like attapulgite (ATT) in polymers, a small amount of graphene oxide (GO) nanosheets were employed as a supporter to fix ATT before introducing into polymer. The ATT nanorods were found attached tightly and dispersed uniformly on the GO nanosheets from TEM images of GO-ATT hybrids. The dispersion stability of ATT in water was also improved after being attached on GO nanosheets due to the abundant hydrophilic groups of GO, which was paramount for introducing them into polymers through water blending method. Poly(vinyl alcohol) (PVA) was then chosen to be reinforced by these GO-supported ATT via water blending method. Compared to the heavy aggregation of neat ATT in PVA, a homogeneous distribution of ATT nanorods in the matrix was achieved by introducing them in the form of GO-ATT, indicating a favorable assisted dispersion effect of GO nanosheets for ATT. Furthermore, PVA/GO-ATT nanocomposites containing only 2 wt% GO-ATT exhibited a significantly increase of 41.4 and 83.6 % in tensile strength and storage modulus, respectively.     

Polyelectrolyte-assisted one-step hydrothermal synthesis of Ag-reduced graphene oxide composite and its antibacterial properties

We demonstrate an effective one-pot hydrothermal route for the synthesis of Poly (diallyldimethylammonium chloride) (PDDA)-protected reduced graphene oxide (RGO) sheets-silver (Ag) nanocomposite in the absence of any seeds and surfactants. In this method, PDDA, an ordinary and water-soluble polyelectrolyte, acts as both a reducing and a stabilizing agent. More importantly, the incorporation of PDDA as a “glue” molecule successfully turns RGO into general platforms for in situ growth of Ag. Small Ag nanoparticles with average height of 4 nm are distributed on the surface of RGO sheets. It is also found that the antibacterial activity of Ag nanoparticles is retained in the composite, suggesting that it can be used as RGO-based biomaterial.     

A low-cost method for preliminary separation of reduced graphene oxide nanosheets

Reduced graphene oxide (RGO) nanosheets were produced by chemical reduction of exfoliated graphite oxide. Atomic force microscopy (AFM) images show that the obtained RGO nanosheets vary greatly in lateral-dimensional sizes, ranging from less than 100  100 nm to more than 2000  2000 nm. In order to separate these nanosheets, one simple and low-cost method mainly based on magnetic-stirring and centrifugation treatments was proposed. Preliminary statistical analysis of RGO nanosheets, based on AFM images, shows that the dot-like RGO nanosheets (with lateral dimensions less than 100  100 nm) and leaf-like RGO nanosheets (with lateral dimensions more than 500  500 nm) were effectively separated by this simple method.     

Functionalized gold nanoparticles self-assemblies with efficient nonlinear optical properties

Satellite-patterns aggregate structures of gold nanoparticles were fabricated by the inducing pi-pi stacking interactions. The self-assembly process of satellite-patterns was tuned by the controlling ligand exchange on the surface of spherical gold nanoparticles, which provide a novel concept and an efficient method for controlling self-assembly of gold nanoparticles. With increasing the porphyrin alkanethiol ratio (r) of gold nanoparticles, the self-assembly induces to form the larger satellite-structures. The study indicates that exchange process of tetra-n-octylammonium bromide molecules and porphyrin alkanethiol molecules results in the formation of satellite-pattern structures with topological features. Nonlinear optical properties of porphyrin alkanethiol capped gold nanoparticles of toluene solution were measured using the Z-scan technique, and its third-order nonlinear optical susceptibility (chi(3)) is calculated as 0.9 x 10(-13) esu, presented the third-order nonlinear optical properties. The well-ordered assembly of gold nanoparticles exhibits controlled the third-order nonlinear optical properties, which can be enhanced with the increasing of the porphyrin alkanethiol ratio in systems.     

Size distribution-controlled preparation of graphene oxide nanosheets with different C/O ratios

A convenient and efficient preparation method for separation graphene oxide with well-defined size distribution is developed using a centrifugation technique. The graded profile of graphene oxide nanosheets with narrow size distribution is effectively controlled by varying the centrifugation speed. The results show that the oxygen content of graphene oxide is highly dependent on their size distribution. Graphene oxide nanosheet with large size shows a red-shift in UV–vis absorption spectra, compared to graphene oxide with small size. This phenomenon is interpretation by a density functional theory calculation. The present work will provide a simple method to prepare graphene oxide nanosheets with controllable size distribution and C/O ratio, which will be valuable for the functionalization of graphene-based hybrids and the fabrication of graphene nano-devices.     

Ultrathin Co3O4 nanosheets highly dispersed on reduced graphene oxide: An efficient bi-functional catalyst for Li-O2 battery

Ultrathin Co₃O₄ nanosheets grown on the reduced graphene oxide (Co₃O₄/rGO) was synthesized by a simple hydrothermal method and was investigated as a cathode in a Li-O₂ battery. Benefited from the synergistic effect between Co₃O₄ and rGO, the hybrid exhibits a high initial capacity of 10,528 mAh g^?1 along with a high coulombic efficiency (84.4%) at 100 mA g^?1. In addition, the batteries show an enhanced cycling stability and after 113 cycles, the cut-off discharge voltage remains above 2.5 V. The outstanding performance is intimately related to the high surface area of rGO, which not only provide carbon skeleton for the uniform distribution of Co₃O₄ nanosheets but also facilitate the reversible formation and decomposition of insoluble Li₂O₂. The results of electrochemical tests confirm that the Co₃O₄/rGO hybrid is a promising candidate for the Li-O₂ batteries.     

Effect of graphene oxide nanosheets on the physico-mechanical properties of chitosan/bacterial cellulose nanofibrous composites

In this work, novel chitosan/bacterial cellulose (CS/BC) nanofibrous composites reinforced with graphene oxide (GO) nanosheets are introduced. As cell attachment and permeability of nanofibrous membranes highly depend on their fiber diameter, the working window for successful electrospinning to attain sound nanofibrous composites with a minimum fiber diameter was determined by using the response surface methodology. It is shown that the addition of GO nanosheets to CS/BC significantly reduces the average size of the polymeric fibers. Their mechanical properties are also influenced and can be tailored by the concentration of GO. Fourier transform infrared spectroscopy reveals hydrogen bonding between the GO nanosheets and the polymer matrix. A decrease in the hydrophilicity of the electrospun nanofibers and their water vapor permeability with the addition of GO are also reported. The prepared nanofibrous composites are potentially suitable candidates for biomedical applications such as skin tissue engineering and wound dressing.     

Synthesis of erbium oxide nanosheets and up-conversion properties

A novel erbium-based compound as well as Er(2)O(3) nanosheets have been synthesized through a simple hydrothermal route. The nanosheets are of 200 nm width and 10-15 nm thickness. It is suggested that this erbium-based compound has a possible formula of Er(2)O(5)H(4) with a primitive tetragonal structure (cell parameters: a = 8.465(1) and c = 15.117(2) ?). Face-centered cubic and body-centered cubic structured Er(2)O(3) nanosheets were obtained after calcination of this compound at 623 and 973 K, respectively, both having a paramagnetic behavior. Er(2)O(5)H(4) and Er(2)O(3) nanosheets have similar up-conversion properties with strong blue emission, which is rarely reported in the literature. The existence of absorbed surface contaminations in nanosheets might be the origin for the blue emission enhancement.     

石墨烯纳米片/环氧树脂复合材料的制备与介电性能研究

以天然鳞片石墨为原料,通过Hummers法制备氧化石墨,微波热解剥离制备出少层数的石墨烯纳米片。以硅烷偶联剂KH-560为改性剂,超声共混制备石墨烯纳米片/环氧树脂复合材料。采用FT-IR和SEM分析样品的微观结构和形貌,测试其介电性能。结果表明,随着石墨烯纳米片添加量的增加,复合材料介电常数呈现先增大后减小的趋势,当石墨烯纳米片含量为0.3%(质量分数)时,介电常数达到最大;石墨烯纳米片对复合材料介电损耗的影响与之相反;偶联改性使复合材料的介电常数增大,介电损耗减小。     

Reduced graphene oxide supersonically sprayed on wearable fabric and decorated with iron oxide for supercapacitor applications

We demonstrate the fabrication of wearable supercapacitor electrodes.The electrodes were applied to wearable fabric by supersonically spraying the fabric with reduced graphene oxide(rGO)followed by decoration with iron oxide(Fe2O3)nanoparticles via a hydrothermal process.The integration of iron oxide with rGO flakes on wearable fabric demonstrates immense potential for applications in high-energy-storage devices.The synergetic impact of the intermingled rGO flakes and Fe2O3 nanoparticles enhances the charge transport within the composite electrode,ultimately improving the overall electrochemical performance.Taking advantage of the porous nature of the fabric,electrolyte diffusion into the active rGO and Fe2O3 materials was significantly enhanced and subsequently increased the electrochemical interfacial activities.The effect of the Fe2O3 concentration on the overall electrochemical performance was investigated.The optimal composition yields a specific capacitance of 360 F g-1 at a current density of 1A g-1 with a capacitance retention rate of 89％after 8500 galvanostatic cycles,confirming the long-term stability of the Fe2O3/rGO fabric electrode.     

Coupling of short DNAs with reduced graphene oxide for electronic and sensing applications

Abstract

In this article, we described an approach for coupling of short DNAs with reduced graphene oxide and thus formation of transducer layer for biological sensors. We investigated the dependence of coupling ratio on the graphene oxide reduction level. We found optimal reduction parameters and showed successful conjugation of aptamers with reduced graphene oxide. We have revealed a trend to increase aptamer conjugation efficiency with a decrease of graphene oxide reduction rate. Finally, we made biosensor structures with Π-shaped reduction pattern and showed excellent sensitivity of the sensor during thrombin exposure. These results are important for the development of flexible low-cost biosensors of a new generation.     

Tribological properties of copper matrix composites reinforced with homogeneously dispersed graphene nanosheets

Graphene reinforced copper matrix composites (Gr/Cu) were fabricated by electrostatic self-assembly and powder metallurgy. The morphology and structure of graphene oxide, graphene oxide-Cu powders and Gr/Cu composites were characterized by scanning electronic microscopy, transmission electronic microscopy, X-ray diffraction and Raman spectroscopy, respectively. The effects of graphene contents, applied loads and sliding speeds on the tribological behavior of the composites were investigated. The results indicate that the coefficient of friction of the composites decreases first and then increases with increasing the graphene content. The lowest friction coefficient is achieved in 0.3?wt% Gr/Cu composite, which decreases by 65% compared to that of pure copper. The coefficient of friction of the composite does not have significant change with increasing the applied load, however, it increases with increasing the sliding speed. The tribological mechanisms of the composite under different conditions were also investigated.     

Three-dimensional graphene oxide nanostructure for fast and efficient water-soluble dye removal

In this study, we demonstrated the potential of graphene nanomaterials as environmental pollutant adsorbents by utilizing the characteristics of ultralarge surface area and strong π-π interaction on the surface. We generated a three-dimensional (3D) graphene oxide sponge (GO sponge) from a GO suspension through a simple centrifugal vacuum evaporation method, and used them to remove both the methylene blue (MB) and methyl violet (MV) dyes which are main contaminants from the dye manufacturing and textile finishing. The efficiency and speed of dye adsorption on a GO sponge was investigated under various parameters such as contact time, stirring speed, temperature, and pH. The adsorption process shows that 99.1% of MB and 98.8% of MV have been removed and the equilibrium status has been reached in 2 min. The 3D GO sponge displays adsorption capacity as high as 397 and 467 mg g(-1) for MB and MV dye, respectively, and the kinetic data reveal that the adsorption process of MB and MV dyes is well-matched with the pseudo second-order model. The MB and MV adsorption on the 3D GO sponge involved in endothermic chemical adsorption through the strong π-π stacking and anion-cation interaction with the activation energy of 50.3 and 70.9 kJ mol(-1), respectively. The 3D GO sponge has demonstrated its high capability as an organic dye scavenger with high speed and efficiency.     

Transparent, luminescent, antibacterial and patternable film forming composites of graphene oxide/reduced graphene oxide

Multifunctional graphene oxide/reduced graphene oxide (GO/RGO) composites were prepared through electrostatic interaction using biocompatible ingredients. Different functionalities were added to GO/RGO by anchoring materials such as native lactoferrin (NLf), NLf protected Au clusters (designated as Au@NLf), chitosan (Ch) and combinations thereof. Anchoring of Ch and NLf enhances the antibacterial property of RGO/GO. The addition of Ch to RGO/GO not only helped in forming stable dispersions but also helped in fabricating large (cm(2)) area films through a simple solvent evaporation technique. Functionalities such as photoluminescence were added to Ch-RGO/GO composites by anchoring Au@NLf on it. The composites thus formed showed stable luminescence in presence of various metal ions in the solid state. The composite showed reasonable stability against pH and temperature variations as well. The as-prepared films were transparent and the transparency could be modulated by controlling the concentration of RGO/GO in the composite. The antibacterial property and ability to form stable thin films may provide an opportunity to use such composites for medical and environmental remediation applications as well. Erasable patterns were fabricated on the film by stamping required patterns under compressive pressure. Luminescent patterns can be inscribed on the film and can be erased by simply wetting it. Such films with erasable information may be useful for security applications.     

氧化石墨烯纳米片层对水泥基复合材料的增韧效果及作用机制

通过氧化和超声波分散制备了氧化石墨烯（GO）纳米片层分散体系,研究了GO纳米片层对水泥基复合材料的增韧效果及作用机制。用EDS、FTIR、XRD、SEM和AFM对GO纳米片层的结构进行了表征。研究结果表明：所得GO含氧量为32.3wt%,GO纳米片层的厚度为6 nm左右,在GO片层表面含有羟基、羧基和磺酸基等活性基团。水泥基复合材料的SEM形貌及力学性能测定结果表明：当GO掺量为0.03wt%时,GO能够使水泥水化产物形成花朵状晶体,并使水泥基复合材料的拉伸强度、抗折强度和压缩强度比对照样品分别提高了65.5%、60.7%和38.9%。提出了GO纳米片层对水泥水化产物的模板调控机制,揭示了花状晶体的形成过程。     

CuS nanoplatelets arrays grown on graphene nanosheets as advanced electrode materials for supercapacitor applications

CuS nanoplatelets arrays grown on graphene nanosheets are successfully synthesized via a facile low-temperature solvothermal reaction with graphene oxide (GO), CH₃CSNH₂ and Cu(CH₃COO)₂·H₂O as the reactants. CH₃CSNH₂ plays an important role in being the reducing agent for GO and the sulfur source of CuS. Supercapacitive performance of the graphene/CuS nanocomposite as active electrode materials has been evaluated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy measurements. The results indicate that graphene/CuS electrode delivers a high capacitance of 497.8 F g^–1 at a current density of 0.2 A g^–1, which outperforms bare CuS electrode. This excellent performance is ascribed to the short diffusion path and large surface area of the unique hierarchical nanostructure with nanoflakes building blocks for bulk accessibility of faradaic reaction.