Surface Of Graphene Oxide Sheets Research Articles

Coating graphene oxide sheets with luminescent rare-earth complexes

Rare-earth (RE) complexes can be easily adsorbed on the surface of graphene oxide sheets (GOSs) by a simple noncovalent approach. The resulting nanocomposite materials, RE complexes functionalized GOSs, have been comprehensively characterized via transmission electron microscopy, X-ray photoelectron spectroscopy, FT-IR spectra, X-ray diffraction, and thermogravimetric analysis. The luminescence properties of GOSs-RE were also investigated. Under the excitation of UV light, these samples display the characteristic emissions of Eu3+ ions. The photophysical investigations revealed that the presence of GOSs do not quench the lanthanide-centered luminescence stemming from the characteristic electronic transitions within the 4f shell of the Eu3+ ions. The GOSs–RE complex hybrids and their dispersion can emit bright red luminescence. Moreover, the presence of GOSs can elongate the fluorescence lifetime of the RE complexes to 983 μs. These properties make them useful in many practical fields, such as in the lighting and biological labeling.

Electrodeposition of graphene oxide doped poly(3,4-ethylenedioxythiophene) film and its electrochemical sensing of catechol and hydroquinone

A novel poly(3,4-ethylenedioxy-thiophene) (PEDOT)/graphene oxide (GO) hybrid film was directly electrodeposited on a glassy carbon electrode. The SEM and TEM images of the as-obtained film revealed that PEDOT grew well on the surface of GO sheets with high affinity. The chemical structure of the composite was characterized by FT-IR, and the result conformed the formation of PEDOT doped by GO, leading to the enhanced electrochemical performance of the modified electrode. The composite modified electrode was utilized as an electrochemical sensor for the simultaneous detection of hydroquinone (HQ) and catechol (CT). It showed well electrocatalytic activity toward the redox of HQ and CT. Under the optimized condition, the response peak currents of the modified electrodes were linear over ranges from 2.5 to 200μM for HQ and from 2 to 400μM for CT. The sensor also exhibited good sensitivity with the detection limit of 1.6μM for both HQ and CT, and good stability. This study provides a new kind of composite modified electrode for electrochemical sensors.

MnO/reduced graphene oxide sheet hybrid as an anode for Li-ion batteries with enhanced lithium storage performance

Relatively small hysteresis in voltage, appropriate electromotive force and low average delithiation voltage make MnO, among many transition metal oxides. MnO/reduced graphene oxide sheet (MnO/RGOS) hybrid is synthesized by a two-step electrode design consisting of liquid phase deposition of MnCO3 nanoparticles on the surface of graphene oxide sheets followed by heat treatment in flowing nitrogen. As an anode for Li-ion batteries, the MnO/RGOS hybrid electrode shows a reversible capacity of 665.5 mA h g−1 after 50 cycles at a current density of 100 mA g−1 and delivers 454.2 mA h g−1 at a rate of 400 mA g−1, which is obviously better than that of bare MnO electrode. Those reasons for such enhanced electrochemical properties are investigated by galvanostatic intermittent titration technique (GITT) as well as electrochemical impedance spectroscopy (EIS). The probable origins, in the term of thermodynamic and kinetic factors, for the marked hysteresis in voltage observed between charge and discharge are also discussed.

Well-defined graphene/polyaniline flake composites for high performance supercapacitors

The simultaneous reduction of the graphene oxide/polyaniline (GO/PANI) flake composites prepared by coating polyaniline (PANI) onto graphene oxide (GO) sheets was developed to prepare the novel electrode materials for the high performance supercapacitors. Firstly, the GO/PANI composites were prepared by the chemical oxidation polymerization of aniline in the aqueous dispersion of GO. Secondly, the reduced graphene oxide/polyaniline (R(GO/PANI)) flake composites were obtained by the chemical reduction of the GO/PANI composites with hydrazine hydrate as the reducing agent. Transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and cyclic voltommetry (CV) were employed to investigate the morphology, thermal property, and electrochemical activity of the samples. TEM results revealed that PANI was polymerized on the surface of GO sheets and there was still thin PANI coating on RGO sheets after being reduced. The results of TGA and CV indicated that both the thermal stability and the electroactivity of the R(GO/PANI) flake composites were distinctly enhanced than those of the GO/PANI composites. In the R(GO-PANI) flakes, RGO played the dual roles: as electron acceptor and also as a counterion to stabilize an atypical intermediate oxidation state of PANI, which resulted in the high electroactivity of the R(GO/PANI) flakes.

Praparation, characterizations, and its potential applications of PANi/ graphene oxide nanocomposite

Graphene oxide (GO), nano/micro-structured polyaniline (PANi) are some typical important functional materials, which have many applications in lithium ion battery with high energy, supercapacitor, catalysts, solar cells, nanodevices, chemical sensors, biosensors and biomedical fields. In this paper, GO was obtained by using chemical oxidation method at room temperature, and nano/micro-structured GO/PANi composite was prepared with in-situ polymerization of aniline in the presence of GO suspension. A series of characterizations were examined by TEM (transmission electron microscopy), SEM (scanning electron microscope), XRD (X-ray diffraction), the Fourier-Transform Infrared (FTIR) spectra, UV-Vis, et al. The results indicated that most of the surface of GO sheets was covered with a smooth thin layer of polyaniline, and some domains of the surface of GO sheets were clearly observed polyaniline nanowires anchored. To examine the surface and interface properties of GO/PANi nanocomposite, chemical prototype sensors were constructed based on GO/PANi nanocomposite and a QCM (quartz crystal microbalance) device. The response behaviors of the sensor to some typical volatile compounds operating at room temperature were investigated. The adsorption features to some typical volatile compounds were discussed. Some key issues and modification ideas were suggested for further investigation.

Graphene oxide strongly inhibits amyloid beta fibrillation

Since amyloid beta fibrillation (AβF) plays an important role in the development of neurodegenerative diseases, we investigated the effect of graphene oxide (GO) and their protein-coated surfaces on the kinetics of Aβ fibrillation in the aqueous solution. We showed that GO and their protein-covered surfaces delay the AβF process via adsorption of amyloid monomers. Also, the large available surface of GO sheets can delay the AβF process by adsorption of amyloid monomers. The inhibitory effect of the GO sheet was increased when we increase the concentration from 10% (in vitro; stimulated media) to 100% (in vivo; stimulated media). our results revealed that GO and their surface proteins inhibit AβF by decreasing the kinetic reaction.

Functionalization of graphene oxide towards thermo‐sensitive nanocomposites via moderate in situ SET‐LRP

AbstractA mild and efficient strategy is presented for growing thermo‐sensitive polymers directly from the surface of exfoliated graphene oxide (GO). This method involves the covalent attachment of Br‐containing initiating groups onto the surface of GO sheets followed by in situ growing poly[poly(ethylene glycol) ethyl ether methacrylate] (PPEGEEMA) via single‐electron‐transfer living radical polymerization (SET‐LRP). Considering the lack of reactive functional groups on the surface of GO, exfoliated GO sheets were subjected to an epoxide ring opening reaction with tris(hydroxymethyl) aminomethane (TRIS) at room temperature. The initiating groups were grafted onto TRIS‐GO sheets by treating hydroxyls with 2‐bromo‐2‐methylpropionyl bromide at room temperature. PPEGEEMA chains were synthesized by in situ SET‐LRP using CuBr/Me6TREN as catalytic system at 40 °C in H2O/THF. The resulting materials were characterized using a range of testing techniques and it was proved that polymer chains were successfully introduced to the surface of GO sheets. After grafting with PPEGEEMA, the modified GO sheets still maintained the separated single layers and the dispersibility was significantly improved. This TRIS‐GO‐PPEGEEMA hybrid material shows reversible self‐assembly and deassembly in water by switching temperature at about 34 °C. Such smart graphene‐based materials promise important potential applications in thermally responsive nanodevices and microfluidic switches. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Coupled fluorescein isothiocyanate on graphene oxide

In this study, we presented a simple and direct approach for the decoration of graphene oxide (GO) by fluorescent material. In this protocol, the GO functionalized with COCl groups was first prepared by treating with SOCl 2. Fluorescein isothiocyanate (FITC), which is a popular fluorescence probe, was then chemically bonded to the surface of GO sheets, resulting in the formation of FITC-coupled GO hybrid. Fluorescence spectrophotometer, Raman spectroscopy, X-ray photoelectron spectrometer, and Fourier transform infrared spectra were used to demonstrate the successful attachment of FITC to the surface of GO sheets. In addition, the method could be extended to further development of graphene-based nanoelectronics.

A simple approach for immobilization of gold nanoparticles on graphene oxide sheets by covalent bonding

Amino—functionalized gold nanoparticles with a diameter of around 5nm were immobilized onto the surface of graphene oxide sheets (GOS) by covalent bonding through a simple amidation reaction. Pristine graphite was firstly oxidized and exfoliated to obtain GOS, which further were acylated with thionyl chloride to give acyl chloride bound GOS. Gold nanoparticles (AuNPs) were functionalized using 4-aminothiophenol in a single-phase system to introduce amino groups on their surface through the well-developed Au–S chemistry. Subsequently, amino groups of AuNPs were reacted with acyl chloride groups of GOS to form a novel hybrid material containing GOS and AuNPs. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy were used to study the changes in surface functionalities and demonstrate the successful immobilization of AuNPs on GOS surface. High resolution transmission electron microscopy (HR-TEM), field emission scanning electronic microscopy (FE-SEM), and atomic force microscopy (AFM) were employed to investigate the morphologies of prepared AuNPs and their distribution onto the GOS surface. Thermogravimetric analysis (TGA) was used to characterize the thermal stability of the samples on heating.

Depositing ZnO nanoparticles onto graphene in a polyol system

In this work, graphene-ZnO nanocomposites were prepared through a one-step solvothermal approach, using ethylene glycol as the solvent and reducing agent. ZnO particles can attach on the surfaces and edges of graphene oxide sheets. The in situ formed ZnO nanoparticles were randomly decorated on the surfaces of graphene oxide sheets, which were simultaneously reduced directly capable of forming the graphene sheets by the ethylene glycol. In addition, photoluminescence spectra of graphene-ZnO nanocomposites display the fluorescence quenching property.