Ethylene gas was used to modify the surface of carbon nanofibers (CNFs) by plasma polymerization. The modified CNFs were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, dispersion test in chloroform and high resolution transmission electron microscopy (HRTEM).

The results of dispersion test in chloroform showed that the plasma treatment promoted a stable dispersion of the treated nanofibers in the solvent. The FTIR results indicated that an organic polymer was deposited on the surface of the CNFs, and the Raman spectra showed evidence of the chemical interaction between the nanofibers and the polyethylene (PE) deposited by plasma. The presence of the thin polymer coating on the surface of CNFs was confirmed by HRTEM.

The unique one-dimensional electronic and optical properties attributed to single-walled carbon nanotubes (SWCNTs) are mainly related to the peculiar local arrangement of sp2 hybridised carbon atoms. This structural configuration gives raise to interesting features, which can be identified with various spectroscopic techniques. In the case of SWCNTs, high energy spectroscopy methods represent effective key tools to analyse the modifications of the underlying basic correlation effects in the bonding environment, the charge transfer between functionalized nanotubes, and on-wall doping. More specifically, in this article we review the shape of the C1s photoemission (PES) response related to the density of states (DOS) of the valence band (VB) in SWCNTs and its changes upon on-wall functionalization and metallicity-sorting. In the last, the progress in the identification of changes in the site selective valence-band electronic structure is clarified in detail.

In this paper, the impurity influences of BNNTs on photoluminescence (PL) analysis have been investigated systematically. Similar PL spectra were obtained from bulk disk of the cold-pressed BNNTs and dispersed individual BNNTs deposited on CaF2 substrate. Metal impurities such as Fe and Au do not affect PL emissions of the BNNTs strongly possibly because Au doping creates sever structural damages but do not change the electronic structure.

Several purification and processing techniques for laser-produced single wall carbon nanotube (SWCNT) soot were investigated and the resulting changes in the mechanical properties were characterized. SWCNT ribbons had non-nanotube carbonaceous content modified via thermal oxidation and the relationship between oxidation parameters and mechanical strength studied. SWCNT/Polyamide composites were developed and exhibited improved toughness, tensile strength and elongation before break. The composite material is observed to have a greater tensile strength than either the baseline paper or the added nylon.

The properties of a carbon nanotube (CNT), in particular a single-wall carbon nanotube (SWNT), are highly sensitive to the atomic structure of the nanotube described by its chirality (chiral indices). We have grown isolated SWNTs on a silicon substrate using chemical vapor deposition (CVD) and patterned sub-micron probes using electron beam lithography. The SWNT was exposed by etching the underlying substrate for transmission electron microscope (TEM) imaging and diffraction studies. For each individual SWNT, its electrical resistance was measured by the four-probe method at room temperature and the chiral indices of the same SWNT were determined by nano-beam electron diffraction. The contact resistances were reduced by annealing to typically 3-5 kΩ. We have measured the I-V curve and determined the chiral indices of each nanotube individually from four SWNTs selected randomly – two are metallic and two are semiconducting. We will present the electrical resistances in correlation with the carbon nanotube diameter as well as the band gap calculated from the determined chiral indices for the semiconducting carbon nanotubes. These experimental results are also discussed in connection with theoretical estimations.

Boron carbon nitride (B-C-N) thin films are attractive due to their potential as hard coatings and as semiconductors with varying band gap. Both B-C-N (BC0.24N0.24) thin films and boron carbide (B4C) thin films were deposited by radio-frequency magnetron sputtering at room temperature. Also, the transition of boron carbide to B-C-N was studied by bombarding the boron carbide thin film by ∼1 uA/cm2 4 keV N+ ions. The results show that the UV-Vis transmittance of B-C-N thin films is better than that of amorphous boron carbide and both B-C and B-N bonds exist in our B-C-N thin films. The nitrogen in our B-C-N thin films bonded with boron causes the XPS B 1s core level to shift 2 eV from that in the B4C boron carbide thin film. Ion bombardment shows that the N+ ion primarily reacts with boron to form B-N and this reaction causes the environmental change of carbon in the thin film and then the XPS C 1s core level to shift to 283.5 eV from 282.8 eV.

Carbon nanotubes (CNT) have seen a wide variety of applications, spread well beyond the semiconductor industries - especially in field emission related devices. For its widest possible application, it has become very much important to grow CNTs on a variety of metallic substrates and understand their field emission response. In the present study, multiwall CNTs (MWCNT), grown on pure metallic substrates like Cu, Al and W, were subjected to field emission tests under DC and AC bias. Choice of diffusion barrier layer and catalyst was also varied, to verify their effects on the emission response. Field emission behaviors from all such structures were compared with MWCNTs grown on Si. It was found that the MWCNTs grown on pure Cu substrate showed excellent field electron emission response, in terms of low turn-on field, high emission current, long time stability and very high field enhancement factor.

A concept of nanoscale bearing structures utilizing nanocarbon materials is presented based on the prediction via molecular dynamics simulations. The proposed mechanism consists of a graphene layer, intercalated single walled carbon nanotubes (SWNTs), and substrate graphenes. It is found that the friction against the movement of the uppermost graphene is smallest for the 1 SWNT model.

We studied the effects of annealing in H2O2 on the morphologies and structures of “as grown” high-density, well-aligned multi-walled carbon nanotube (MWNT) films formed by surface decomposition of SiC. After annealing in H2O2 solution at 100°C for 3 h, the G/D ratio increased from 1.44 to 2.33, the FWHM of the G band peak became narrower, and a D′ shoulder peak appeared. Transmission electron microscopy (TEM) revealed that the dispersion of MWNTs in dimethylformamide (DMF) solution was improved, suggesting that film impurities were reduced and that damage to the MWNTs was negligible. After annealing for 9 h, the G/D ratio decreased to 1.57, and exfoliation of some MWNTs was observed. In addition, several functional groups such as carboxylic (-COOH) and hydroxyl (-OH) were formed on the surface of the MWNTs. From these results, we conclude that annealing in H2O2 under proper conditions can effectively purify “as grown” MWNT films formed by surface decomposition of SiC.

For the first time, patterned growth of boron nitride nanotubes (BNNTs) on Si substrates has been achieved by catalytic chemical vapor deposition (CCVD). Following the boron oxide chemical pathway and our growth vapor trapping approach, high quality and quantity BNNTs can be produced. Effective catalysts have been found to facilitate the growth of BNNTs, while some critical parameters of the synthesis have also been identified to control the quality and density. The success of patterned growth of high quality BNNTs not only explains the roles of the effective catalysts during the synthesis process, but could also be of technologically important for future device fabrication.

We have designed a field emission microscope (FEM) coupled to a chemical vapor deposition (CVD) reactor in order to observe directly the growths of individual carbon nanotubes (CNTs) from the nucleation stage. Catalyst metals are first deposited in situ on a sharp metallic tip during direct FEM imaging and formed into nanoparticles by dewetting. CNTs are then grown directly on these nanoparticles by CVD in acetylene or other hydrocarbon gases at appropriate temperatures (600-900°C). The FEM patterns are formed by electrons emitted from individual CNT caps. The videos are analyzed to extract the growth rates and models. In situ field emission I/V measurements are also performed. The most interesting new discovery is that the CNTs often rotate axially during growth, thus strongly supporting a recently proposed model of ‘screw-dislocation-like’ (SDL) mechanism. The event is not rare as four rotating CNT growths versus six non-rotating growths were observed. In one case the CNT rotated quite uniformly ∼180 times during its 11 min growth. This observation should aid researchers to better understand and control the growth of SWNTs.

Using a novel in-situ scanning tunneling microcopy integrated into a 200Kv transmission electron microscopy, we have shown that boron nitride nanotubes (BNNTs) posses remarkable flexibility and convert from insulator to semi-conductor upon bending. To measure the electrical properties, the BNNT was bent between two gold contacts constructing a metal-semiconductor-metal circuit. The resistivity of the BNNT under bending condition was measured to be ∼460 MΩ from the experimentally recorded current-voltage data. Our finding suggests that mechanical straining can improve the electrical transport in BN nanotubes via reducing the band gap.

Composites of single walled carbon nanotube dispersed within polymeric matrices have been investigated by spectroscopic techniques (Raman and Wide Angle X-Ray Spectroscopy). Raman investigations included an in depth analysis of the radial breathing mode (for single wall carbon nanotubes) and a brief analysis of the lines originating from the polymeric matrix. Raman spectra were successfully simulated by computer assuming that the as recorded spectrum is a convolution of lines whose line shape is well described by a modified Breit-Wigner-Fano equation. The dependence of the position of the lines belonging to the radial breathing mode on the concentration of single walled carbon nanotube has been investigated, with emphasis on information pertinent to the stress transfer from the macromolecular matrix to the filler and to the coating of single walled carbon nanotube by polymeric chains. Complementary Wide Angle X-Ray Spectroscopy measurements provided information about the effect of the loading with single walled carbon nanotube on the crystal structure of the polymeric matrix. The research aims to a better understanding of the interactions between polymeric matrices and nanofillers.

This work reports a low-cost method for large scale production of high quality graphene via radio-frequency chemical vapor deposition. High quantities of graphene were successfully synthesized on the Fe-Co/MgO (2.5:2.5:95 wt.%) catalytic system utilizing acetylene as a hydrocarbon source at 1000 °C. The as-produced graphene sheets were purified in a single step by washing with a diluted hydrochloric acid solution under sonication. Next, they were thoroughly characterized by microscopy, spectroscopy, and X-Ray diffraction. Advanced transmission electron microscopy and atomic force microscopy analyses have indicated the formation of 3-5 layered graphene nanosheets. Thorough analyses by Raman spectroscopy were also performed demonstrating the presence of high quality and few-layer graphene samples. This low cost and highly reproducible method may be applied in a straightforward way to produce large quantities of graphene for various advanced applications.

In this work, we employed three different methods to fabricate solar cell structures on indium tin oxide (ITO) substrates. For the first method, multi-layered structures were prepared by using single walled carbon nanotubes (SWCNTs) and tin oxide (SnO2). First, a SWCNT layer was deposited on the ITO substrate; and photoactive material was then coated on the top of the SWCNT layer. For the second method, photoactive particles were added to a solution of SWCNTs. The SWCNT/SnO2 solution was mechanically stirred and then deposited on the ITO substrate. For the third method, we synthesized photoactive particles on SWCNTs through a chemical-solution routine using SnCl4 as a precursor. We characterized the morphology and structure of the SWCNTs coated with SnO2 nanoparticles prepared with the three different methods by using a field emission scanning electron microscope equipped with an X-ray energy dispersive spectrometer. We characterized the photoelectrochemical properties of all electrodes by using an electrochemical station; mainly, we examined the photocurrent generated under periodic illumination. Our results indicate that there are significant differences in the photocurrent in the presence of SWCNTs. We propose the following hypothetical mechanism: without carbon nanotubes, generated electrons (when light is absorbed by SnO2 particles) must cross the particle network to reach an electrode. Many electrons never escape this network to generate an electrical current. The carbon nanotubes “collect” the electrons and provide, therefore, a more direct route to the electrode, thus improving the efficiency of the solar cells.

The first paper showing the great potentiality of Carbon Nanotubes Field Effect transistors (CNTFETs) for gas sensing applications was published in 2000 [1]. It has been demonstrated that the performances of this kind of sensors are extremely interesting: a sensitivity of around 100ppt (e.g. for NO2 [2]) has been achieved in 2003 and several techniques to improve selectivity have been tested with very promising results [2]. The main issues that have not allowed, up to now, these devices to strike more largely the market of sensors, have been the lack of an industrial method to obtain low-cost devices, a demonstration of their selectivity in relevant environments and finally a deeper study on the effect of humidity and the possible solutions to reduce it. This contribution deals with CNTFETs based sensors fabricated using air-brush technique deposition on large surfaces. Compared to our last contribution [3], we have optimized the air-brush technique in order to obtain high performances transistors (Log(Ion)/Log(Ioff) ∼ 5/6) with highly reproducible characteristics : this is a key point for the industrial exploitation. We have developed a machine which allows us the dynamic deposition on heated substrates of the SWCNT solutions, improving dramatically the uniformity of the SWCNT mats. We have performed tests using different solvents that could be adapted as a function of the substrates (e.g. flexible substrates). Moreover these transistors have been achieved using different metal electrodes (patented approach [4]) in order to improve selectivity. Results of tests using NO2, NH3 with concentrations between ∼ 1ppm and 10ppm will be shown during the meeting.

The AC powered electric arc has been used to synthesize single wall carbon nanohorns aggregates with Ca dispersed inside. To this purpose the electric arc has been ignited between two electrodes, one of which was constituted by a mixture of graphite and CaCO3. The experimental evidence on the microstructure and on the chemical composition has been obtained by observation with a transmission electron microscope equipped with X-ray microanalysis. X-ray diffraction revealed the presence of residual CaCO3 indicating that the process has still to be optimized. The experiment represents a first attempt to decorate carbon nanostructures with alkaline earth metals, in particular Ca, by this relatively simple method. These composites are theorized to adsorb relevant amounts of hydrogen. Further work will be focused to optimize the dispersion of Ca atoms in the carbon nanostructure.

We investigated the interactions of water soluble single-walled carbon nanotubes (SWNT) with unicellular organisms, in particular a ciliated protozoan (Tetrahymena thermophila) and a bacteria (Escherichia coli), which are common constituents of natural fresh water. The ciliates could effectively incorporate SWNT into natural organic matter (NOM), and therefore into normal ecological processes. Further, SWNT induced the ciliates to egest viable bacteria in membrane-enclosed vesicles. The egested bacteria aggregates had escaped digestion by the protozoan and were able to proliferate and resist antibiotic/disinfectant treatments, which may have important implications to public health. This work highlights the importance of studies on nanoparticle ecotoxicology.

Due to their excellent properties, single-walled carbon nanotubes (SWNTs) have been regarded as one of the most potential materials for future applications in nanoelectronic devices. However, there is a huge gulf between production and applications. To meet the needs for applications, SWNTs' chirality, metallic/semiconducting property and morphology should be controlled in the growth process. Together with our recent works, we present herein a brief review on the growth of SWNTs on surface with controlled structures, including 1) Cap engineering for SWNTs growth with controlled chirality; 2) Reaction activity diversity induced growth of semiconducting SWNTs; and 3) Combination of two growth modes for fabricating SWNTs on surface with controlled morphology.

Field emission from carbon nanotubes (CNTs) has been known for more than a decade but there is no commercialized product available in the market. Apparently, we need to improve our basics understanding on stable field emission from CNTs. Here we compared the field emission properties of as grown vertically-aligned multi-walled carbon nanotubes (MWCNTs) to two types of modified MWCNTs: 1) Conical bundles of opened-tip MWCNTs, and 2) Opened-tip MWCNTs embedded in poly-methyl methacrylate (PMMA). We found that both types of modified MWCNTs have lower emission thresholds and better emission stability than the as grown samples. Among these modified samples, MCNTs embedded in PMMA has lower emission thresholds and better emission stability. We attributed these improvements to the filling of spacing between MWCNTs with PMMA that has higher dielectric constant than vacuum.