Graphene Oxide Support Research Articles

Resolving the Nanoscale Morphology and Crystallographic Structure of Molecular Thin Films: F16CuPc on Graphene Oxide

Electron microscopy and diffraction are used to examine the nanoscale structure and molecular orientation in molecular films down to nominally monolayer thickness. The films studied consist of the planar n-type molecular semiconductor copper hexadecafluorophthalocyanine (F16CuPc) directly deposited onto graphene oxide (GO) membranes by organic molecular beam deposition. The graphene oxide support crucially provides the strength and low background required to analyze the crystal structure and morphology of even nominally monolayer thick films and is of relevance for molecular electronic applications. The crystal structure of the F16CuPc polymorph is solved by X-ray diffraction of single crystals and used to analyze the electron diffraction patterns from the thin-films, revealing that the F16CuPc molecules assemble with their molecular plane oriented perpendicular to the GO. There is no evidence for changes in the unit cell with film thickness, although the thinnest films show the greatest disorder in molec...

Highly Efficient Electron Field Emission from Graphene Oxide Sheets Supported by Nickel Nanotip Arrays

Electron field emission is a quantum tunneling phenomenon whereby electrons are emitted from a solid surface due to a strong electric field. Graphene and its derivatives are expected to be efficient field emitters due to their unique geometry and electrical properties. So far, electron field emission has only been achieved from the edges of graphene and graphene oxide sheets. We have supported graphene oxide sheets on nickel nanotip arrays to produce a high density of sharp protrusions within the sheets and then applied electric fields perpendicular to the sheets. Highly efficient and stable field emission with low turn-on fields was observed for these graphene oxide sheets, because the protrusions appear to locally enhance the electric field and dramatically increase field emission. Our simple and robust approach provides prospects for the development of practical electron sources and advanced devices based on graphene and graphene oxide field emitters.

Nitrogen-doped graphene stabilized gold nanoparticles for aerobic selective oxidation of benzylic alcohols

Increasing efforts have been made to fabricate Au/graphene composites due to the fascinating properties of both graphene and gold. Some Au nanoparticles with an average size of tens of nanometers were directly deposited on reduced graphene oxide (RGO), utilizing the residual oxy-functional groups as the “hitching post” of the nanoparticles. Some functional groups, such as amino and thiol, were attached to the surface of the graphene in order to stabilize gold nanoparticles with a smaller particle size (<5 nm in general). Unfortunately, most of these strategies result in Au particles with limited exposed atoms, which is certainly a disadvantage for their application, such as catalysis. Introduction of nitrogen heteroatoms into the framework of graphene can not only modulate the electronic structure, but also change the surface properties of the graphene. In this work, naked Au nanoparticles with an average size of about 2–4 nm were fabricated on nitrogen-doped graphene nanosheets (NG) via the direct simple reduction method. The Au/NG nanocomposites were characterized by XRD, XPS, TEM, AFM and Raman. It was revealed that the nitrogen atoms doped in NG, rather than defects or oxygen moieties, play an essential role in stabilizing Au NPs. It was also found that the initial reaction rate of benzyl alcohol oxidation over the Au/NG catalyst is about ten fold higher than that over Au/graphene catalysts. Our findings may provide a clue of nitrogen incorporation to stabilize uncapped noble metal nanoparticles on graphene or other inorganic oxide supports, such as TiO2.

A simple approach to characterizing block copolymer assemblies: graphene oxide supports for high contrast multi-technique imaging.

Block copolymers are well-known to self-assemble into a range of 3-dimensional morphologies. However, due to their nanoscale dimensions, resolving their exact structure can be a challenge. Transmission electron microscopy (TEM) is a powerful technique for achieving this, but for polymeric assemblies chemical fixing/staining techniques are usually required to increase image contrast and protect specimens from electron beam damage. Graphene oxide (GO) is a robust, water-dispersable, and nearly electron transparent membrane: an ideal support for TEM. We show that when using GO supports no stains are required to acquire high contrast TEM images and that the specimens remain stable under the electron beam for long periods, allowing sample analysis by a range of electron microscopy techniques. GO supports are also used for further characterization of assemblies by atomic force microscopy. The simplicity of sample preparation and analysis, as well as the potential for significantly increased contrast background, make GO supports an attractive alternative for the analysis of block copolymer assemblies.

Influences of graphene oxide support on the electrochemical performances of graphene oxide-MnO2 nanocomposites

MnO2 supported on graphene oxide (GO) made from different graphite materials has been synthesized and further investigated as electrode materials for supercapacitors. The structure and morphology of MnO2-GO nanocomposites are characterized by X-ray diffraction, X-ray photoemission spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and Nitrogen adsorption-desorption. As demonstrated, the GO fabricated from commercial expanded graphite (denoted as GO(1)) possesses more functional groups and larger interplane gap compared to the GO from commercial graphite powder (denoted as GO(2)). The surface area and functionalities of GO have significant effects on the morphology and electrochemical activity of MnO2, which lead to the fact that the loading amount of MnO2 on GO(1) is much higher than that on GO(2). Elemental analysis performed via inductively coupled plasma optical emission spectroscopy confirmed higher amounts of MnO2 loading on GO(1). As the electrode of supercapacitor, MnO2-GO(1) nanocomposites show larger capacitance (307.7 F g-1) and better electrochemical activity than MnO2-GO(2) possibly due to the high loading, good uniformity, and homogeneous distribution of MnO2 on GO(1) support.

SnO2 nanosheets grown on graphene sheets with enhanced lithium storage properties

We demonstrate a new hydrothermal method to directly grow SnO(2) nanosheets on a graphene oxide support that is subsequently reduced to graphene. This unique SnO(2)/graphene hybrid structure exhibits enhanced lithium storage properties with high reversible capacities and good cycling performance.