PMo12-functionalized Graphene nanosheet-supported PtRu nanocatalysts for methanol electro-oxidation

Graphene nanosheets, synthesized by a modified Hummers method, have been functionalized by PMo₁₂, and used as the supports of the PtRu nanoparticles. The electrocatalytic properties of the resultant nanocatalysts (PtRu/PMo₁₂-Graphene) for methanol electro-oxidation have been evaluated by cyclic voltammetry and chronoamperometry. The micrograph and the elemental composition have also been investigated by transmission electron microscopy and energy dispersive X-ray spectroscopy. The results suggest that the addition of PMo₁₂ benefits the high dispersion of graphene nanosheets in the water and the uniform dispersion of the PtRu nanoparticles on the graphene nanosheets, and the PtRu/PMo₁₂-Graphene catalysts have higher electrocatalytic activity and better electrochemical stability for methanol oxidation compared to the PtRu/Graphene catalysts.     

Sandwich-type electrochemical immunosensor for sensitive determination of IgG based on the enhanced effects of poly-L-lysine functionalized reduced graphene oxide nanosheets and gold nanoparticles

Journal of Solid State Electrochemistry - Poly-L-lysine functionalized reduced graphene oxide nanosheets (PLL-rGO) were prepared and thoroughly characterized with transmission electron microscopy,...     

Covalent attaching protein to graphene oxide via diimide-activated amidation

In this paper, graphene oxide nanosheets (GOS) are functionalized by bovine serum albumin (BSA) via diimide-activated amidation under ambient conditions. The obtained GOS–BSA conjugate is highly water-soluble. Results of atomic force microscopy (AFM), Raman spectra and Fourier transform infrared spectroscopy analysis confirm that GOS–BSA conjugate contains both GOS and BSA protein. AFM image shows that GOS are fully exfoliated. Results of cyclic volatammograms show that the protein in the GOS–BSA conjugate retains its bioactivity. The present method may also provide a way to synthesize graphene-based composites with other biomolecules.     

Graphene nanosheets decorated with Pd,Pt,Au,and Ag nanoparticles:Synthesis,characterization,and catalysis applications

We report that noble metal nanopartcles (Pd,Pt,Au,and Ag) decorated-graphene nanosheets can be synthesized with the template of graphene oxide by a one-pot solution-based method.The resulting hybrid materials are characterized by transmission electronic microscopy,energy dispersive X-ray spectroscopy,scanning electronic microscopy,atomic force microscopy,X-ray diffraction,and Raman spectroscopy,which demonstrate that the metal nanoparticles have been uniformly deposited on the surfaces of graphene nanosheet...     

Graphene‐Functionalized 3D‐Carbon Fiber Electrodes – Preparation and Electrochemical Characterization

Graphene nanosheets were produced on the surface of carbon fibers by in situ electrochemical procedure including oxidative and reductive steps to yield first graphene oxide, later converted to graphene. The electrode material composed of graphene‐functionalized carbon fibers was characterized by scanning electron microscopy (SEM) and cyclic voltammery demonstrating superior electrochemical kinetics comparing with the original carbon paper. The interfacial electron transfer rate for the reversible redox process of [Fe(CN)₆]^3?/4? was found ca. 4.5‐fold higher after the electrode modification with the graphene nanosheets. The novel electrode material is suggested as a promising conducting interface for bioelectrocatalytic electrodes used in various electrochemical biosensors and biofuel cells, particularly operating in vivo.     

Electrochemical Sensor for Sensitive Determination of Capsaicin Using Pd Decorated Reduced Graphene Oxide

In this work, the reduced graphene oxide functionalized with poly dimethyl diallyl ammonium chloride (PDDA) modified palladium nanoparticles (PDDA‐rGO/Pd) had been facile synthesized and used as the sensing layer for sensitive determination of capsaicin. The prepared composite was characterized by transmission electron microscopy, UV‐visible absorption spectroscopy. The image demonstrated that Pd nanoparticles were uniformly distributed on the graphene surface. The electrochemical properties of the prepared sensor were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the nanocomposite exhibits attractive electrocatalytic activity towards the oxidation of capsaicin. This attributed to the synergistic action of the excellent properties of Pd nanoparticles and graphene nanosheets. Under optimized conditions, the electrochemical sensor possessed a dynamic linear range from 0.32 μM to 64 μM with a detection limit of 0.10 μM (S/N=3) for capsaicin detection. Moreover, the cost‐effective and simple fabrication procedure, good reproducibility and stability as well as acceptable accuracy for capsaicin determination in actual samples are also the main advantages of this method, which might have broad application in other amide alkaloid detection.     

Single‐Step Functionalization and Exfoliation of Graphene with Polymers under Mild Conditions

The simultaneous polymer functionalization and exfoliation of graphene sheets by using mild bath sonication and heat treatment at low temperature is described. In particular, free‐radical polymerization of three different vinyl monomers takes place in the presence of graphite flakes. The polymerization procedure leads to the exfoliation of graphene sheets and at the same time the growing polymer chains are attached onto the graphene lattice, which gives solubility and stability to the final graphene‐based hybrid material. The polymer‐functionalized graphene sheets possess fewer defects as compared with previously reported polymer‐functionalized graphene. The success of the covalent functionalization and exfoliation of graphene was confirmed by using a variety of complementary spectroscopic, thermal, and microscopy techniques, including Raman, IR and UV/Vis spectroscopy, thermogravimetric analysis, and transmission electron microscopy.     

Structural Characterization of Graphene Nanosheets for Miniaturization of Potentiometric Urea Lipid Film Based Biosensors

The present article describes a miniaturized potentiometric urea lipid film based biosensor on graphene nanosheets. Structural characterization of graphene nanosheets for miniaturization of potentiometric urea lipid film based biosensors have been studied through atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. UV‐Vis and Fourrier transform IR (FTIR) spectroscopy have been utilized to study the pre‐ and postconjugated surfaces of graphene nanosheets. The presented potentiometric urea biosensor exhibits good reproducibility, reusability, selectivity, rapid response times (～4 s), long shelf life and high sensitivity of ca. 70 mV/decade over the urea logarithmic concentration range from 1×10^?6 M to 1×10^?3 M.     

Water-soluble graphene dispersion functionalized by Diels–Alder cycloaddition reaction

Water-soluble graphene dispersions were fabricated by the exfoliation of graphite functionalized with furfuryl alcohol by Diels–Alder cycloaddition reaction. The pristine graphite was firstly heat-treated in N-methyl-2-pyrrolidone (NMP) before it was functionalized with furfuryl alcohol, and then, the increased interlayer spacing is propitious for furfuryl alcohol to enter into the lattice and react with graphite. High-resolution transmission electron microscopy and Raman spectroscopy indicate that the functional graphene is a high-quality product without any significant defects, and atomic force microscopy shows that the functional graphene consists of single to few layers graphene. Moreover, the grafting ratio onto graphene is up to 1.52 mmol/g. Therefore, the method provides a feasible route to produce functional graphene.     

Preparation of MoS2‐graphene Hybrid Nanosheets and Simultaneously Electrochemical Determination of Levodopa and Uric Acid

MoS₂ nanoflakes were prepared by exfoliating commercial MoS₂ powders with the assistance of ultrasound and graphene foam was synthesized by chemical vapor deposition using nickel foam as the template. MoS₂‐graphene hybrid nanosheets were developed through the combination of MoS₂ nanoflakes and graphene nanosheets by ultrasonic dispersion. The hybrid nanosheets were sprayed onto the ITO coated glass, which acts as an electrode for the simultaneously electrochemical determination of levodopa and uric acid. The MoS₂‐graphene hybrid nanosheets were characterized by scanning electron microscopy, X‐ray diffraction and Raman spectroscopy. The results show that the hybrid nanosheets are composed of MoS₂ and graphene with a sheet‐like morphology. The sensitivity of the electrode for levodopa and uric acid is 0.36 μA μM⁻¹ and 0.39 μA μM⁻¹, respectively. The electrode also shows low limit of detection, good selectivity, reproducibility and stability. And it is potential for use in clinical research.     

One-pot, solvothermal synthesis of TiO(2)-graphene composite nanosheets

In this article, we propose a facile one-pot solvothermal route for synthesizing TiO(2)-graphene composite nanosheets (TGCN). In the system, ethylene glycol not only as a reducing agent can convert graphene oxide to reduced graphene oxide nanosheets, but also is employed to control the hydrolysis and condensation rates of tetrabutoxytitanium. The obtained TGCN hybrid materials are characterized by atomic force microscopy, transmission electron microscopy, UV-vis spectroscopy, Raman spectroscopy, X-ray photo-electron spectroscopy, X-ray diffraction, and thermal gravimetric analysis. It is found that the quantity of H(2)O used in the reaction is the key to obtain high-quality product. The photocatalytic activities of the products are evaluated using the photocatalytic degradation of methylene blue (MB) as a probe reaction. The results showed that the obtained TGCN have an enhanced adsorption capacity and remarkable improvements in the photodegradation rate of MB under visible light compared to P25.     

Synthesis of Ferrosoferric Oxide‐graphene Oxide Nanocomposite by Isoelectric Point Method for the Detection of Catechol

Ferrosoferric oxide functionalized graphene oxide nanocomposite with layer by layer structure was synthesized by isoelectric point method in this work. The prepared material was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Then the material was used to modify a glassy carbon electrode to fabricate an electrochemical sensor for the detection of catechol. The electrochemical sensor exhibited excellent electrochemical performance towards the detection of catechol with a linear response in the range of 5–205 μM and a detection limit of 2.32 μM. Furthermore, the electrochemical sensor showed excellent selectivity, stability and repeatability. These results revealed ferrosoferric oxide functionalized graphene oxide nanocomposite has potential applications in the fabrication of electrochemical sensors.     

Assembly of Graphene Nanosheets and SiO2 Nanoparticles Towards Transparent,Antireflective, Conductive,and Superhydrophilic Multifunctional Hybrid Films

A new approach for the fabrication of transparent, antireflective, conductive and superhydrophilic multifunctional hybrid films through the layer‐by‐layer (LbL) assembly of reduced graphene oxide (RGO) nanosheets and SiO₂ nanoparticles is reported. The RGO nanosheets, SiO₂ nanoparticles and films were characterized by means of transmission electron microscopy, UV/Vis absorption spectrophotometry, Raman spectroscopy, atomic force microscopy, contact angle/interface system, and a four‐point probe. It was found that the graphene/SiO₂ hybrid films exhibited a significant increase in transmittance as compared with RGO films. The optical, electronic and wetting properties of hybrid films could be manipulated by rational design of the film structure and variation of the cycle number of the LbL assembly. The obtained transparent, conductive, and superhydrophilic graphene/SiO₂ hybrid films showed excellent antireflective, antistatic, and antifogging behaviors. The remarkable performance could be attributed to the combination of electrical conductivity of RGO nanosheets and superhydrophilic antireflective surface derived from SiO₂ nanoparticles.     

Preconcentration of U(VI) ions on few-layered graphene oxide nanosheets from aqueous solutions

Graphene oxide nanosheets have attracted multidisciplinary attention due to their unique physicochemical properties. Herein, few-layered graphene oxide nanosheets were synthesized from graphite using a modified Hummers method and were characterized by TEM, AFM, Raman spectroscopy, XPS, FTIR spectroscopy, TG-DTA and acid-base titrations. The prepared few-layered graphene oxide nanosheets were used as adsorbents for the preconcentration of U(VI) ions from large volumes of aqueous solutions as a function of pH, ionic strength and temperature. The sorption of U(VI) ions on the graphene oxide nanosheets was strongly dependent on pH and independent of the ionic strength, indicating that the sorption was mainly dominated by inner-sphere surface complexation rather than by outer-sphere surface complexation or ion exchange. The abundant oxygen-containing functional groups on the surfaces of the graphene oxide nanosheets played an important role in U(VI) sorption. The sorption of U(VI) on graphene oxide nanosheets increased with an increase in temperature and the thermodynamic parameters calculated from the temperature-dependent sorption isotherms suggested that the sorption of U(vi) on graphene oxide nanosheets was an endothermic and spontaneous process. The maximum sorption capacities (Q(max)) of U(VI) at pH 5.0 ± 0.1 and T = 20 °C was 97.5 mg g(-1), which was much higher than any of the currently reported nanomaterials. The graphene oxide nanosheets may be suitable materials for the removal and preconcentration of U(VI) ions from large volumes of aqueous solutions, for example, U(VI) polluted wastewater, if they can be synthesized in a cost-effective manner on a large scale in the future.     

Sensitive detection of biomolecules and DNA bases based on graphene nanosheets

High surface area electrode materials are of interest for the application of electrochemical sensors. Currently, chemical vapor deposition (CVD) graphene-sensing electrodes are scarce. Herein, for the first time, a graphene based on a Ta wire support was prepared using the CVD method to form a highly electroactive biosensing platform. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) were utilized to characterize the morphology and investigate the electrochemical properties of the CVD graphene electrodes. The resulting CVD graphene electrode exhibited good electrocatalytic activity and had a prominent response effect on dopamine, uric acid, guanine, and adenine. Standing graphene nanosheets have rich catalytic sites such as the edges, the defect levels of the plane, and porous network structures between the graphene nanosheets. These catalytic sites prompt the adsorption and resolution for the four species and the strong electron transport capability of the CVD graphene, which effectively improved the electrical signals for response to four species. Moreover, the graphene electrode is a promising candidate in electrochemical sensing and other electrochemical device applications.     

Stable aqueous dispersions of graphene prepared with hexamethylenetetramine as a reductant

Highly stable graphene aqueous dispersions were achieved by chemical reduction of graphene oxide with an environmentally friendly reagent of hexamethylenetetramine (HMTA). By this method, chemical reduction as well as dispersion of graphene can be carried out in one step without the need of organic stabilizers or pH control. The as-synthesized products were characterized by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy, scanning and transmission electron microscopy, and thermogravimetry and differential scanning calorimetry. It is revealed that the bulk of the oxygen-containing functional groups were removed from graphene oxide via HMTA reduction, and stable aqueous colloidal dispersions of graphene have a concentration up to ca. 0.65mg/mL. Moreover, it is found that the freshly precipitated graphene nanosheets can be re-dispersed in water with simple ultrasonic treatment. A mechanism for the formation of stable graphene colloidal dispersions is proposed. This simple and green approach should find practical applications in the preparation of graphene-based nanocomposites with a facile and low-cost solution processing technique.     

石墨烯纳米载药体系的制备及对人口腔鳞癌细胞杀伤效果

利用化学氧化还原法制备了氧化石墨烯,进一步超声破碎剥离,得到纳米氧化石墨烯,并对其进行聚乙二醇(PEG)的功能化修饰后载药顺铂。 采用扫描电子显微镜(SEM)、紫外-可见吸收光谱(UV-Vis)、傅立叶变换红外光谱(FTIR)对石墨烯纳米载药体系进行表征,细胞存活率实验(MTT)法检验石墨烯纳米载药体系对人口腔鳞癌(KB)细胞的杀伤作用。 结果表明,石墨烯纳米载药体系对顺铂的负载率为42.4%,聚乙二醇修饰后可以降低纳米氧化石墨烯的细胞毒性并提高生物相容性,对KB细胞具有双重的杀伤作用,为纳米氧化石墨烯在肿瘤治疗的临床应用提供了理论依据。     

Direct electrochemistry and electrocatalysis of hemoglobin based on poly(diallyldimethylammonium chloride) functionalized graphene sheets/room temperature ionic liquid composite film

The functionalized graphene nanosheets (PDDA-G) with poly(diallyldimethylammonium chloride) (PDDA) were synthesized and used to combine with room temperature ionic liquid (RTIL). The resulting RTIL/PDDA-G composite displayed an enhanced capability for the immobilization of hemoglobin to realize its direct electrochemistry. Moreover, the RTIL/PDDA-G based biosensor exhibited excellent electrocatalytic activity for the detection of nitrate with a wide linear range from 0.2 to 32.6 μM and a low detection limit of 0.04 μM at 3σ. This work opens a new way to functionalized graphene nanosheets with good biocompatibility and solubility in biosensors.     

Layer-by-layer stacked graphene nanocoatings by Marangoni self-assembly for corrosion protection of stainless steel

Graphene nanosheets are widely used in anti-corrosion polymeric coating as filler,owing to the excellent electrochemical inertness and barrier property.However,as the arrangement of graphene nanosheets is difficult to form a perfect layered structure,polymeric coating with graphene nanosheets usually needs micron-scale thickness to ensure the enhancement of corrosion protection.In this work,layer-by-layer stacked graphene nanocoatings were fabricated on stainless steel by self-assembly based on Marangoni effect.The anti-corrosion property of graphene coatings were studied through Tafel polarization curves,electrochemical impedance spectroscopy and accelerated corrosion test with extra applied voltage.The self corrosion current density of optimized three-layered graphene coated sample was one quarter of that of bare stainless steel.And the self corrosion potential of optimized sample is increased to-0.045 V.According to the results,graphene nanocoatings composed of layered nanosheets exhibits good anticorrosion property.Besides,the self-assembly method provide a promising approach to make layeredstructure coating for other researches about 2 D material nanosheets.     

KOH-activated nitrogen-doped graphene by means of thermal annealing for supercapacitor

KOH-activated nitrogen-doped graphene nanosheets (aNG) have been synthesized using thermal annealing method and applied in supercapacitor. The samples are characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and electrochemical techniques. Electrochemical results show that a capacitance of 132.4 F g^?1 at a charge/discharge current density of 0.1 A g^?1 is obtained for KOH-activated nitrogen-doped graphene which is nearly five times larger than that without KOH treatment. The present work demonstrates that KOH activation of thermally annealed nitrogen-doped graphene is a promising method for enhancing its application in energy storage system.