The dispersion behavior of n-hexadecylamine-intercalated silylated graphite oxide in a chloroform/cyclohexane mixture was investigated. When 1.2 molecules of n-hexadecylamine per graphite oxide unit were added, the interlayer gallery of the silylated graphite oxide was saturated by n-hexadecylamine molecules, and the interlayer spacing reached 3.1 nm. The resulting intercalation compounds dispersed well in a chloroform/cyclohexane solution. After centrifugation, the intercalation compounds with lower n-hexadecylamine contents mostly precipitated, however, the dispersion of those with higher n-hexadecylamine contents were stable until the concentration reached 0.6 g of graphite oxide/L. This was ascribed to the weaker interaction between the alkyl chains bonded to the adjacent graphite oxide layers forming a bilayer of alkyl chains within a gallery.

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We prepared special aggregates of single-wall carbon nanohorns (SWNHs) having plenty of few-graphene sheets with petal-like forms (P-FGS). The P-FGS/SWNH aggregates were oxidized by light-assisted oxidation with hydrogen peroxide to remove SWNHs from P-FGS/SWNH (P-FGSox). FT-IR absorption spectra indicated that P-FGSox had oxygenated groups such as carboxyl groups. To identify their locations, they were modified with Pt-ammine complexes. Transmission electron microscopy observations indicated that Pt-ammine complexes had sub-nanometer sizes and were located mainly at the graphene edges. This means that the oxygenated functional groups existed at the graphene edges and reacted selectively with Pt-ammine complexes. We also confirmed that, on reduction in hydrogen, the Pt-ammine complexes moved freely on FGSox to stabilize at the steps of the few graphene sheets.

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Electronic properties of a graphene monolayer and multilayers are reviewed from a theoretical point of view. Graphenes are characterized by gap-less band structures, which differ from those of conventional metals and also vary depending on the number of layers. We argue that those exotic band structures lead to unusual properties of graphenes in optical absorption, conductivity and orbital magnetism.

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We present a review of our experiments on graphene transistors. For the preparation of graphene films on a substrate, a quick formation method is introduced in which the number of layers can be precisely confirmed. Fabrication of gate electrodes specialized for the graphene system is also explained for the application of a high electric field in the graphene transistor. In this short review paper, our original method of fabrication and structure of gate electrodes for the graphene transistor will be introduced.

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Recent progress in fine processing technology enables us to fabricate graphene devices. In this article, we show how the graphene edges and their shape crucially affect the physical properties of nano-graphene and related systems. The crossover of magnetism from low-temperature paramagnetic to high-temperature diamagnetic behavior, the electronic current control due to graphene edge engineering and the presence of a perfectly conducting channel in disordered graphene nanoribbons are discussed.

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The dc resistance primary standard is currently realized by quantized Hall resistance (QHR) on GaAs/AlGaAs heterostructure substrates. In spite of the fact that the resistance is determined by only fundamental physical constants, it is not very straightforward to operate this standard because a very low temperature and an intense magnetic field are required. Since the quantum Hall effect in graphene at room temperature was reported in recent years, the quantum resistance standard with graphene which is relatively easy to operate, is expected to become possible. In the present paper, a dc resistance measurement traceability system is described, and challenges and current status to apply graphene to a new dc resistance standard are discussed.

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One commercially available polyimide film, Kapton, and three kinds of polyimide films prepared from different precursors in our laboratory were carbonized at 750°C in Ar atmosphere. The electrical resistance of the resulting carbon films showed semi-conductive temperature dependence. The estimated values of the activation energy for exciting an electron from the π band to an acceptor level decreased with increasing carbonization temperature, from 0.110 eV (640°C) to 0.025 eV (750°C). The thermoelectric power of a carbon film derived from Kapton was estimated to be +13 μVK⁻¹ at room temperature, indicative of hole conduction. The resistance of this film increased with the adsorption of molecules such as acetone, ethanol, etc. and then turned to decrease during desorption of these molecules. On the contrary, no resistance change was observed for the adsorption of benzene.

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High improvement in the battery performances such as low temperature characteristics, thermal stability and high rate charge/discharge is urgently requested. Because EC-based solvents should be used for graphite anode, lithium-ion batteries currently used have difficulty for the use at low temperatures. In the present study, surface fluorination using F₂, ClF₃, NF₃ and plasma-treatment was applied to natural graphite samples. Surface fluorination highly increased surface disorder in all fluorinated natural graphite samples, reducing the electrochemical decomposition of PC. Due to decrease in the decomposition of PC, first coulombic efficiencies increased by 10–20%.
High safety is one of the most important issues for the application of lithium-ion batteries to hybrid cars and electric vehicles because lithium-ion batteries use flammable organic solvents. Organo-fluorine compounds are new candidates since fluorine substitution of organic compounds reduce HOMO level, i.e. increases oxidation stability. In the present study, thermal and electrochemical oxidation stability of organo-fluorine compound-mixed electrolyte solutions was evaluated, and charge/discharge characteristics of natural graphite were investigated using fluorine compound-mixed electrolyte solutions. It was found that organo-fluorine compounds improved thermal and electrochemical oxidation stability of electrolyte solutions, and highly increased first coulombic efficiencies for graphite in PC-containing electrolyte solution.

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