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Graphenes are attracting renewed interests owing to recent advances in micromechanical exfoliation and epitaxial growth methods that make macroscopic 2D sheets of sp 2 -carbon atoms available.[1] A variety of simple yet elegant physics relating to its zero-gap semiconductor character has thus been demonstrated. [2][3][4][5] It would be very desirable to make these materials solution (or more accurately, dispersion) processable by coating or printing, which will open applications for large and/or flexible substrates. Graphite oxide (GO) is a possible candidate for this because it is a precursor to graphene through deoxidation either thermally or by chemical reduction. [6][7][8] Although GO itself has been studied for over a century, [9] its structure and properties remain elusive, and progress has been made only recently to give materials with limited dispersability and electronic quality. [10][11][12][13][14] Here we show that substoichiometric GO nanosheets can be surface-functionalised and purified to show excellent dispersability at the single-sheet level, >15 mg mL À1 in organic solvents, sufficient for spincoating and printing onto a variety of substrates. The films could then be deoxidised to graphene (ca. 80% completion at 300 8C) to give a network of low-dimensional ''graphenite'' tracks and dots on the nanosheets. Though imperfect and disordered, these show well-behaved and trap-free field-effect transistor charge-carrier mobilities for both electrons and holes of the order of 10 cm 2 V À1 s À1 , limited presently by the density of this graphenite network. Devices can be operated continuously in air for both p-and n-channels. The transport activation energies are in the meV region at low temperatures which together with the delocalisation of carriers indicate bandlike transport. The density-of-states at the Fermi level deduced by electrical measurements is higher than in graphite. MNDO-PM3 semiempirical electronic structure calculations relate this to defects in the 1D graphenite network. The fact that charge carriers can still be sufficiently delocalised in such disordered graphenites opens new opportunities for graphenes. It is well-known that chemical oxidation of graphite crystals gives GO which can be exfoliated by rapid-thermal-anneal >1000 8C, [15] or in solvents to give few-layer stacks that aggregate over time. [16,17] Recent work has shown that chemical functionalisation of GO can improve dispersability, particularly in the presence of stabilising polyelectrolytes. [10][11][12][13] However it is crucial to achieve more stable and concentrated dispersions without the added polyelectrolytes or ions, for electronic applications. We show here that substoichiometric (i.e. under-oxidised) GO can be obtained by a modified Staudenmaier oxidation of graphite with potassium chlorate [15] in a concentrated sulphuric-nitric acid mixture to give a material with an empirical formula containing less oxygen than the fully oxidised GO (C 2.0 O 1.0 H x ), [8,9,18] for example, C 2.0 O 0.77 H 0.75 . This material...

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A detailed study of poly(alkylthiophene) self-assembly and organization on single-walled carbon nanotubes (SWNTs) is presented. Monolayers of regioregular poly(3-hexyl thiophene) (rrP3HT) adsorbed on SWNTs have been imaged by using scanning tunneling microscopy. Our results show that the rrP3HT interchain distance is greater for rrP3HT monolayers adsorbed onto the curved surfaces of SWNTs than on the flat surfaces of highly ordered pyrolytic graphite samples. Comparisons between the native polymer deposited on graphite and the composite structure confirmed that the presence of carbon nanotubes in rrP3HT produces a new material with a high degree of order at the molecular level.

Initial stages of two-dimensional crystal growth of the double-decker sandwich complex Lu(Pc*)2 [Pc* = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] have been studied by scanning tunneling microscopy at the liquid/solid interface between 1-phenyloctane and highly oriented pyrolytic graphite. High-resolution images strongly suggest alignment of the double-decker molecules into monolayers with the phthalocyanine rings parallel to the surface. Domains were observed with either hexagonal or quadrate packing motifs, and the growing interface of the layer was imaged. Molecular resolution was achieved, and the face of the phthalocyanine rings appeared as somewhat diffuse circular features. The alkyl chains are proposed to be interdigitating to maintain planar side-by-side packing.

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Although all graphites share the same idealized chemical structure, marked differences in fact exist between their reactivities, such as the propensity for oxidation, that need to be taken into consideration for the development of applications. Here we show that five different commercially sourced natural and synthetic graphites differ significantly in their response to a modified Staudenmaier oxidation that produces substoichiometric graphene oxides (sub-GOx). The dominant oxidation product is hydroxyl groups, which can be dehydrate to epoxy groups under mild heating even below 120 °C. The extent of oxidation correlates broadly with the defect band intensity in the starting graphites as measured by Raman spectroscopy. FTIR shows there is a significant concentration of H defects at the % atom level. The results suggest that defects in the graphite plane are more prevalent than previously thought. Finally, the properties of the thermally reduced sub-GOx are also different. The product from the least defective starting graphite ultimately exhibits the lowest activation energies for both electron and hole transport, of the order of 10 μeV below 25 K, that is characteristic of band-like transport. These results are important because they show that the quality of the starting graphite significantly affects the properties of the derived products.