Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to approximately 0.01 mg ml(-1), produced by dispersion and exfoliation of graphite in organic solvents such as N-methyl-pyrrolidone. This is possible because the energy required to exfoliate graphene is balanced by the solvent-graphene interaction for solvents whose surface energies match that of graphene. We confirm the presence of individual graphene sheets by Raman spectroscopy, transmission electron microscopy and electron diffraction. Our method results in a monolayer yield of approximately 1 wt%, which could potentially be improved to 7-12 wt% with further processing. The absence of defects or oxides is confirmed by X-ray photoelectron, infrared and Raman spectroscopies. We are able to produce semi-transparent conducting films and conducting composites. Solution processing of graphene opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry.
Tin dioxide (SnO2) used in various applications due to suitable band gap and tunable conductivity. It has excellent thermal, mechanical and chemical stability.
Photoelectron spectroscopy has been used to study the products resulting from high temperature phase transformation of nanodiamonds (ND). Depending on the temperature of annealing various particles with a diamond core covered by nanometer sized fullerene-like shells, and onionlike carbon (OLC) were formed. Analysis of the photoemission lines of the intermediates of ND transformation, prepared at temperatures of 1420 and 1600 K and then exposed to atmosphere, reveals the presence of oxygen-containing groups and both and carbon. The component for these samples has binding energies of (for the sample prepared at 1420 K) and (for the sample prepared at 1600 K). A difference of in the binding energy of the and components was observed. The component for OLC prepared at 1800, 1900, and 2140 K has a binding energy of . The shift towards higher binding energies of the component of the samples prepared at lower temperatures is explained by significant curvature of graphite layers formed in the initial stages of graphitization. The observed increase in density of states at the Fermi level for the samples prepared at 1600, 1800, and 1900 K is associated with an accumulation of different types of defects in the curved graphite layers during graphitization of diamond. The Lorentzian widths of photoemission lines from OLC are large compared with those of HOPG. The possible reasons for this broadening are discussed.
Recently, there have been enormous efforts to tailor the properties of graphene. These improved properties extend the prospect of graphene for a broad range of applications. Plasmas find applications in various fields including materials science and have been emerging in the field of nanotechnology. This review focuses on different plasma functionalization processes of graphene and its oxide counterpart. The review aims at the advantages of plasma functionalization over the conventional doping techniques. Selectivity and controllability of the plasma techniques opens up future pathways for large scale, rapid functionalization of graphene for advanced applications. We also emphasize on atmospheric pressure plasma jet as the future prospect of plasma based functionalization processes.
18 January 2016 in Journal of Materials Chemistry A
Vacuum hydrogen annealing of TiO2 leads to increased visible light absorption. The origin thereof was revealed by ab initio calculations and X-ray photoelectron spectroscopy.