Graphene, or single-layered graphite, with its high crystallinity and interesting semimetal electronic properties, has emerged as an exciting two-dimensional material showing great promise for the fabrication of nanoscale devices [1][2][3] . Thin, elongated strips of graphene that possess straight edges, termed graphene ribbons, gradually transform from semiconductors to semimetals as their width increases 4-7 , and represent a particularly versatile variety of graphene. Several lithographic 7,8 , chemical 9-11 and synthetic 12 procedures are known to produce microscopic samples of graphene nanoribbons, and one chemical vapour deposition process 13 has successfully produced macroscopic quantities of nanoribbons at 950 6C. Here we describe a simple solution-based oxidative process for producing a nearly 100% yield of nanoribbon structures by lengthwise cutting and unravelling of multiwalled carbon nanotube (MWCNT) side walls. Although oxidative shortening of MWCNTs has previously been achieved 14 , lengthwise cutting is hitherto unreported. Ribbon structures with high water solubility are obtained. Subsequent chemical reduction of the nanoribbons from MWCNTs results in restoration of electrical conductivity. These early results affording nanoribbons could eventually lead to applications in fields of electronics and composite materials where bulk quantities of nanoribbons are required [15][16][17] .We obtained oxidized nanoribbons by suspending MWCNTs in concentrated sulphuric acid followed by treatment with 500 wt% KMnO 4 for 1 h at room temperature (22 uC) and 1 h at 55-70 uC (Methods). After isolation, the resulting nanoribbons were highly soluble in water (12 mg ml 21 ), ethanol and other polar organic solvents. The opening of the nanotubes appears to occur along a line, similar to the 'unzipping' of graphite oxide 18,19 , affording straightedged ribbons. This could occur in a linear longitudinal cut (Fig. 1a) or in a spiralling manner, depending upon the initial site of attack and the chiral angle of the nanotube. Although depicted in Fig. 1a as occurring on the mid-section of the nanotube rather than at one end, the location of the initial attack is not known.The mechanism of opening is based on previous work on the oxidation of alkenes by permanganate in acid. The proposed first step in the process is manganate ester formation (2, Fig. 1b) as the ratedetermining step, and further oxidation is possible to afford the dione (3, Fig. 1b) in the dehydrating medium 20 . Juxtaposition of the buttressing ketones distorts the b,c-alkenes (red in 3), making them more prone to the next attack by permanganate. As the process continues, the buttressing-induced strain on the b,c-alkenes lessens because there is more space for carbonyl projection; however, the bond-angle strain induced by the enlarging hole (or tear if originating from the end of the nanotube) would make the b,c-alkenes (4, Fig. 1b) increasingly reactive. Hence, once an opening has been initiated, its further opening is enhanced relative to an unopened ...

An improved method is described for the production of graphene oxide nanoribbons (GONRs) via longitudinal unzipping of multiwalled carbon nanotubes. The method produces GONRs with fewer defects and/or holes on the basal plane, maintains narrow ribbons <100 nm wide, and maximizes the high aspect ratio. Changes in the reaction conditions such as acid content, time, and temperature were investigated. The new, optimized method which introduces a second, weaker acid into the system, improves the selectivity of the oxidative unzipping presumably by in situ protection of the vicinal diols formed on the basal plane of graphene during the oxidation, and thereby prevents their overoxidation and subsequent hole generation. The optimized GONRs exhibit increased electrical conductivity over those chemically reduced nanoribbons produced by previously reported procedures.

Graphene combines unique electronic properties and surprising quantum effects with outstanding thermal and mechanical properties. Many potential applications, including electronics and nanocomposites, require that graphene be dispersed and processed in a fluid phase. Here, we show that graphite spontaneously exfoliates into single-layer graphene in chlorosulphonic acid, and dissolves at isotropic concentrations as high as approximately 2 mg ml(-1), which is an order of magnitude higher than previously reported values. This occurs without the need for covalent functionalization, surfactant stabilization, or sonication, which can compromise the properties of graphene or reduce flake size. We also report spontaneous formation of liquid-crystalline phases at high concentrations ( approximately 20-30 mg ml(-1)). Transparent, conducting films are produced from these dispersions at 1,000 Omega square(-1) and approximately 80% transparency. High-concentration solutions, both isotropic and liquid crystalline, could be particularly useful for making flexible electronics as well as multifunctional fibres.

Graphite oxide (GO) polymer nanocomposites were developed at 1, 5, and 10 wt % GO with polycarbonate (PC), acrylonitrile butadiene styrene, and high-impact polystyrene for the purpose of evaluating the flammability reduction and material properties of the resulting systems. The overall morphology and dispersion of GO within the polymer nanocomposites were studied by scanning electron microscopy and optical microscopy; GO was found to be well-dispersed throughout the matrix without the formation of large aggregates. Mechanical testing was performed using dynamic mechanical analysis to measure the storage modulus, which increased for all polymer systems with increased GO loading. Microscale oxygen consumption calorimetry revealed that the addition of GO reduced the total heat release and peak heat release rates in all systems, and GO-PC composites demonstrated very fast self-extinguishing times in vertical open flame tests, which are important to some regulatory fire safety applications.