With the appropriate surface treatments, graphene sheets can be separated from graphite material and the layer-to-layer distance can be extended. In the present work, graphene nanosheets (GNS) were separated from graphite by an improved, safer and mild method including the steps of oxidation, thermal expansion, ultrasonic treatment and chemical reduction. For the production of advanced polymer nanocomposites, the distinguished properties of GNS were combined with the structural properties of conducting polypyrrole by the proposed simple and low-cost fabrication technique. The changes in surface morphologies and surface functional groups were estimated by controlling the polymer coating on graphite oxide (GO) sheets, expanded GO and GNS.

Catalyzing the combustion of liquid fuels offers interesting prospects for further improvement of the fuel economy and the performance of engines, in particular for jets and advanced propulsion systems. Polyoxometalates are well-known oxidation catalysts which are expected to also catalyze combustion reactions. However, their polarity makes their dispersion in fuels particularly challenging. Herein, functionalized graphene sheets were used as a support due to their high surface area as well as their compatibility with the target reaction. In order to further improve the dispersion of the catalyst in fuels, alkyl chains were grafted to the sheets’ surface. An innovative grafting technique was developed to attach alkyls at a variety of oxygen-containing functionalities already present on reduced graphene oxide, such as hydroxyl and epoxy groups. A phase transfer to the organic phase was observed when dispersing the dry powder in water:toluene mixtures. In addition, the dry alkyl chain-modified graphene sheets readily dispersed in common organic solvents without the assistance of sonication. Polyoxometalates (H3PMo12O40 and H4PMo11VO40) were dispersed on the modified sheets as discrete clusters even at a relatively high loading (20 wt.%). The catalytic activity of these nanostructured materials was demonstrated for the combustion of methylcylcohexane, tested here as a model fuel.

A variety of characterization techniques have been employed to study the growth and structure of nickel carbon thin films fabricated by ionized magnetron sputter deposition. A two target magnetron system is used along with an RF powered coil, to create a secondary plasma, with a DC bias applied at the substrate. By varying the bias it is possible to control the energy of the depositing species as well as a range of other plasma properties and therefore the resulting film microstructure. It has been observed that a change from the metastable hexagonal nickel carbide phase to the stable face centered cubic structure of nickel can be induced. This change in metal crystallinity was accompanied by a change in carbon ordering. The ability to control the film structure and morphology without the need for substrate heating opens up the possibility of depositing a range of structures onto polymers.

A thin film consisting of boron, carbon, and nitrogen (BCN) was grown on a polycrystalline Ni substrate by thermal chemical vapor deposition. The local elemental composition of the BCN film was analyzed by scanning Auger electron spectroscopy. The film is elementally highly inhomogeneous and consists of domains with a typical size of 1-10 μm and irregular shapes. The domain structure is strongly related to the structure of the grains of the polycrystalline Ni film beneath the domain. A thick domain is often formed on a small Ni grain. On a large and flat Ni grain, the film thickness is relatively small, and both the boron and nitrogen contents are often below the detection limit, indicating that it is a graphene domain. Boron and nitrogen contents are highly correlated, which is consistent with formation of hexagonal boron nitride. However, unbalanced boron and nitrogen contents are observed from thick domains.

Medium scale integrated circuits with 108 CNT-TFTs have been fabricated using CNTs grown by plasma enhanced chemical vapor deposition (PECVD) which has the advantage of preferential growth of CNTs with semiconducting behavior in the FET current–voltage characteristics. High-speed operation with a switching time of 0.51 μs/gate, which is highest in the CNT-TFT integrated circuits to our knowledge, was demonstrated by a 53-stage ring oscillator. Characterization of CNT-TFTs using scanning probe microscopy has also been performed. The island-like structure in the electrical properties of the CNT network was observed even in a high-density CNT network in the subthreshold regime. This was explained by the decrease of the effective number of CNTs which contribute the electrical conduction.

Recent advances in terahertz light amplification by stimulated emission of radiation in optically pumped graphene are reviewed. We present, within a picosecond time scale, fast relaxation and relatively slow recombination dynamics of photogenerated electrons and holes in an exfoliated graphene under infrared pulse excitation. We conduct time-domain spectroscopic studies using an optical pump and terahertz probe with an optical probe technique and show that graphene sheet amplifies an incoming terahertz field. The graphene emission spectral dependency on laser pumping intensity shows a threshold-like behavior, testifying to the occurrence of the negative conductivity and the population inversion. The emission spectra clearly narrow at a longer terahertz probe delay time, giving an evidence that the quasi-Fermi energy moves closer to the equilibrium at this longer terahertz probe delay time.

We demonstrate low operating voltage (<|1.5| V) chemical vapour deposited (CVD) graphene transistors using solution processable organic self-assembled monolayers (SAMs) as nanodielectrics. The transistors show weak extrinsic doping, hysteresis-free operation, low gate-leakage current and good operating stability with bias-stress free characteristics. Most importantly we demonstrate that the Dirac potential can be finely tuned by modifying the molecular end-group of the SAMs without compromising the electrical characteristics of the transistors.

The ‘DLC-GFET’, a graphene field effect transistor with a diamondlike carbon (DLC) top-gate dielectric film, is presented. The DLC film was formed ‘directly’ onto the graphene channel without forming passivation interlayers using our original photoemission-assisted plasma-enhanced chemical vapor deposition (PA-CVD), where the plasma was precisely controlled by photoemission from the sample with quite low electric power to minimize plasma damage to the channel. The DLC-GFET exhibits clear ambipolar characteristics with a slightly positive shift of the neutral points (Dirac voltages). Relatively high transconductances were obtained as 14.6 (8.8) mS/mm in the n (p) channel modes, respectively, with a thick gate dielectric of 48 nm and a long gate length of 5 μm, promising vertical scaling-down to improve the high-frequency performance. The positive shift of the Dirac voltage is due to unintentional hole doping from oxygen species in the DLC film into the graphene channel, promising a minute modulation doped structure with oxygen to overcome high resistance in the access region. Hence, a DLC film deposited by PA-CVD is a candidate for the gate dielectric on graphene.

We have used single-walled carbon nanotube field-effect transistor (SWNT-FET) and chemically converted graphene field-effect transistor (CCG-FET) devices to probe the interactions between carbohydrates and their recognition lectins. Porphyrin- and pyrene-based glycoconjugates were used as receptor molecules and the target lectins were two bacterial lectins that present different carbohydrate preference, namely PA-IL, PA-IIL from Pseudomonas aeruginosa and a plant lectin Concanavalin A. The specific binding between lectin and carbohydrate can be transduced to the change in FET device conductance. An initial study with SWNT-FET noncovalently functionalized with porphyrin-based glycoconjugates showed both good selectivity and sensitivity. To compare SWNT and CCG performance, pyrene- and porphyrin-based glycoconjugates were functionalized noncovalently on the surface of CCG-FET and SWNT-FET devices, which were then treated with non-specific and specific lectins. The responses were compared and rationalized using computer-aided models of carbon nanostructure/glycoconjugate interactions. Fluorescence microscopy, atomic force microscopy, UV-vis-NIR spectroscopy and Isothermal titration microcalorimetry (ITC) measurements were used to confirm the electrical results.