Our top-down approaches [1,2] inspired physicists to study individual layers of graphite obtained by micromechanical exfoliation, and one of our current approaches has been to convert graphite to graphite oxide (GO), generate aqueous colloidal suspensions containing individual layers of GO (we call them ‘graphene oxide’), and to use these ‘graphene oxide sheets’ in a variety of ways. For example, we have embedded individual and reduced graphene oxide sheets in polymers such as polystyrene and evaluated their dispersion, morphology, and the electrical percolation and thus conductivity of the resulting composites. In parallel paths, we have: (i) undertaken studies of individual graphene oxide and reduced graphene oxide sheets, to elucidate their chemical, optical, and electrical properties, (ii) embedded graphene oxide sheets in glass by a sol-gel route and made electrically conductive and transparent glass coatings, and (iii) produced 'graphene oxide paper', a material with intriguing mechanical properties (iv) produced reduced graphene oxide powder with moderately high surface area and used this to study electrochemical double layer capacitance (v) made carbon-13 labeled graphite and thus carbon-13 labeled graphite oxide, and studied its detailed chemical structure with SS NMR. Finally, (vi) I will talk about recent work in our group on growing and characterizing graphene and few layer graphene films on metal substrates, and their transfer to other substrates for device fabrication and characterization. This survey talk about graphene and its chemical derivatives will present an overview of these various results. Support of our work by the NSF, ONR/NRL, NASA, and DARPA is appreciated. 1. Lu XK, Yu MF, Huang H, and Ruoff RS, Tailoring graphite with the goal of achieving single sheets, Nanotechnology, 10, 269-272 (1999).2. Lu XK, Huang H, Nemchuk N, and Ruoff RS, Patterning of highly oriented pyrolytic graphite by oxygen plasma etching, Applied Physics Letters, 75, 193-195 (1999).See also papers on http://bucky-central.me.utexas.edu/publications.htm such as #139,146, 150,155, 160, 164, 166, 168, 169, 174, 179, 180, 181, 182, etc.

Current interest in graphene oxide (GO) sheets has been sparkled by the recent discovery of graphene. Graphene oxide is the most promising precursor for bulk production of graphene. Graphene oxide sheets are heavily oxidised layers, which contain a large number of oxygen groups within the graphene structure. These oxygen functional groups can be partially removed by deoxidation either thermally or by chemical reduction, yielding a partially reduced structure, which is of interest as a filler to polymer composites; as transparent conducting films for low cost photovoltaics and energy –storage materials, liquid crystal devices as well as a potential component for biosensing and nanoelectronics devices. Although graphene derived from graphene oxide holds significant technological promise the evolution of its fundamental electronic structure at different reduction steps remains largely unexplored. There is also controversy in the literature which groups are dominant in graphene oxide or after its conversion to graphene. To address these points, we have studied the progressive loss of oxygen functional groups and the electronic structure of graphene oxide at various stages of ultra high vacuum thermal annealing process by in situ high resolution X ray photoelectron spectroscopy, XPS (conducted at the NCESS facility in Daresbury, UK). In particular temperature dependent XPS and valence band studies revealed that the majority of oxygen species in thermally deoxidized GO consist of hydroxyl C-OH groups; followed by contributions from carbonyl and carboxylic C=O, COOH groups, whereas the epoxy/ether C-O-C groups are the least thermally stable. Annealing up to 1000C is able to remove oxygen content from 32 at% to 3at% (C:O ratio 11.3). The valence band spectrum of the de-oxygenated film via heating to 1000 C resembles significantly that of graphite. After thermal treatment to 1000 C the intensity ratio of D to G Raman peaks slightly decreased and both peaks exhibited a reduction in FWHM suggesting improvement in the graphitization. The thermal treatment process can increase the sp2 bonding fraction up to ~70% and functionalize the surface to meet application demands. Our study shows that the graphene oxygen functional groups can be decreased in a controllable manner using high temperature annealing. Our findings provide useful information, critical to graphene device engineering and fabrication.

Single sheets of graphite oxide are emerging as starting materials providing alternative path to graphene. The exfoliation of graphite oxide in aqueous solution allows deposition of single sheets, referred to as graphene oxide (GO), or multilayer films on virtually any substrate. The stoichiometry, atomic and electronic structures of GO are largely unknown. GO is an insulator but controlled reduction provides tunability of the electronic properties, allowing the possibility of accessing zero-band gap graphene. We present a detailed description of opto-electronic properties, chemical state [1] and structure [2] of single and few-layered of GO at different stages of reduction. Particular attention has been given to understanding the atomic structure of pristine GO before investigating its transformation upon annealing. The sp²/sp³ fraction for single and multilayered pristine GO have been elucidated using comparative X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) measurements of the fine structure of C and O K-edges. The distortion of carbon basal plane induced by sp³ C-O bonds in pristine GO has been observed by annular dark filed imaging [2].We found that the electrical characteristics of reduced GO do not approach those of intrinsic graphene obtained by mechanical cleaving because the materials remains significantly oxidized. In fully reduced GO, the carbon-carbon sp² bonding fraction is ~ 0.80 while the residual oxygen still forms sp³ bonds with carbon atoms in the basal plane. The oxygen disrupts the transport of carriers delocalized in the sp² network, limiting the mobility and conductivity of reduced GO thin films. Our analysis reveals that removal of oxygen to achieve sp² carbon fraction of > 0.95 in GO should lead to properties that are comparable to graphene.[1] C. Mattevi et al.“Evolution of electrical, chemical, and structural properties of transparent and conducting chemically derived graphene thin films” Adv. Funct. Mater. Vol 19, (2009) p.1.[2] K. A. Mkhoyan et al.” Atomic and electronic structure of graphene oxide” Nano Lett. vol.9, (2009), p 1058.

Exposing nanostructured graphene oxide (GO) to a camera flash results in a photothermally activated reaction. This process is accompanied by a pronounced photoacoustic effect along with a rapid temperature increase, which initiates a deoxygenation reaction to yield graphitic carbon. SEM images of the product reveal that an expanded graphite with an accordion type structure forms. Nitrogen absorption measurements (BET), carried out b