Produce Graphene Oxide Research Articles

The effect of heat treatment on the electrical conductivity of highly conducting graphene films

Graphene oxide films were prepared by the modified Hummers method, which includes sonication, aggregation and self-assembly. The graphene films were obtained by vacuum heat treatment of the graphene oxide films. XRD, SEM, FTIR and Raman spectroscopy were used to investigate the microstructure evolution of the films during preparation. It is found that self-assembly is a simple method to produce graphene oxide films with controllable size and perfect stacks of graphene oxide layers. Heat treatment gives the graphene films high electrical conductivities. The electrical conductivity of the films increases up to 536 S/cm with increasing heat treatment temperature under vacuum.

Monitoring influence of chemical preparation procedure on the structure of graphene nanosheets

A comparison concerned about the three approaches (Hummers' method, improved method and Marcano–Tour's method, which all have been published and widely quoted in the field of producing graphene oxide) for the preparation of graphene oxide is discussed. The monitoring effect of preparation procedure is determined by investigating the influences of chemical reagents and reaction conditions on the structure of graphene nanosheets. The structure of graphene oxide and chemically reduced graphene is characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The exact mechanisms concerned about the effects of chemical reagents on the product structures are briefly described. The incorporation of H3PO4 and the addition of excessive H2SO4 and KMnO4 are proved to make a higher oxidation degree compared with the traditional methods. Ice in Marcano–Tour's method is also seen to be beneficial to the increase of the graphite oxide interlayer spacing. Surprisingly, the graphene, which is prepared by reducing the product of Marcano–Tour's method, shows less defects than the other two ones. In addition, the graphene oxide produced by improved method is found to confront with few difficulties during the reduction process.

Emerging methods for producing graphene oxide composites in coatings with multifunctional properties

The most common preparation method of graphene starts from the oxidation and exfoliation of graphite to graphene oxide (GO). Such graphitic planes, decorated with oxygen-containing groups, are hydrophilic and soluble in water. From an industrial point of view, wet-chemistry approaches are the most desirable methods for the large scale integration of GO based polymer nanocomposites. The critical issue remains in the aggregation of the GO sheets after the dispersant evaporation which is detrimental for the coating uniformity. We present several methods for the development of such functional coatings preserving the physical properties such as optical transparency and electrical conductivity.

Influence of pH condition on colloidal suspension of exfoliated graphene oxide by electrostatic repulsion

A facile chemical process is described to produce graphene oxide utilizing a zwitterions amino acid intermediate from graphite oxide sheets. 11-aminoundecanoic acid molecules were protonated to intercalate molecules into the graphite oxide sheets to achieve ion exchange, and the carboxyl groups were then ionized in a NaOH solution to exfoliate the graphite oxide sheets. In this way, the produced graphene oxide nanosheets were stably dispersed in water. The delaminated graphene nanosheets were confirmed by XRD, AFM, and TEM. XRD patterns indicated the d002-spacing of the graphite greatly increased from 0.380nm and 0.870nm. AFM and TEM images showed that the ordered graphite crystal structure of graphene nanosheets was effectively exfoliated by this method. The prepared graphene nanosheets films showed 87.1% transmittance and a sheet resistance of 2.1×103Ω/square.

Covalent synthesis of organophilic chemically functionalized graphene sheets

In this study, we report a scalable, fast, and easy method for preparation of organophilic chemically functionalized graphene (OCFG) sheets. The basic strategy involved the preparation of graphite oxide (GO) and the complete exfoliation of GO into graphene oxide sheets, followed by reacting with 1-bromobutane to obtain OCFG sheets. Thermogravimetric analysis, Raman spectroscopy, and Fourier transform infrared spectroscopy indicated the functionalization of GO. Transmission electron microscopy and atomic force microscopy were used to demonstrate the structure of produced graphene oxide and OCFG sheets. Ultraviolet–visible spectroscopy confirmed that OCFG sheets disperse well in organic solvents and the solutions obey Beer’s law. The resulting organic dispersions are homogeneous, exhibit long-term stability, and are made up of graphene sheets a few hundred nanometers large. The ability to prepare graphene dispersions in organic media facilitates their combination with polymers to yield homogeneous composites.

Fast and Facile Preparation of Graphene Oxide and Reduced Graphene Oxide Nanoplatelets

In this study, we report an inexpensive, massively scalable, fast, and facile method for preparation of graphene oxide and reduced graphene oxide nanoplatelets. The basic strategy involved the preparation of graphite oxide (GO) from graphite through reaction with benzoyl peroxide (BPO), complete exfoliation of GO into graphene oxide sheets, followed by their in situ reduction to reduced graphene oxide nanoplatelets. The mechanism of graphene oxide producing is mainly the generation of oxygen-containing groups on graphene sheets. In addition, inserted BPO and expansion of CO2 evolved during reaction will expand the distance between graphite layers, which are also main factors for exfoliation. Thermogravimetric analysis, Raman spectroscopy, and Fourier transform infrared spectroscopy indicated the successful preparation of GO. X-ray diffraction proved the mechanism of intercalation and exfoliation of graphite. Transmission electron microscopy and atomic force microscopy were used to demonstrate the structure of produced graphene oxide and reduced graphene oxide nanoplatelets.