We have developed a novel method for generating pure pair plasma which consists of positive- and negative-charged particles with an equal mass. The pair-ion plasma without electrons is generated using fullerene as an ion source through the processes of hollow-electron-beam impact ionization, electron attachment, preferential radial diffusion of ions, and resultant electron separation in an axial magnetic field. Basic characteristics of this plasma are discussed in terms of the differences from ordinary electron-ion plasmas, such as a phenomenon in the absence of sheath and potential structure formation.

Three kinds of electrostatic modes are experimentally observed to propagate along magnetic-field lines for the first time in the pair-ion plasma consisting of only positive and negative fullerene ions with an equal mass. It is found that the phase lag between the density fluctuations of positive and negative ions varies from 0 to pi depending on the frequency for ion acoustic wave and is fixed at pi for an ion plasma wave. In addition, a new mode with the phase lag about pi appears in an intermediate-frequency band between the frequency ranges of the acoustic and plasma waves.

Carbon nanotubes (CNTs) are single- or multi-cylindrical graphene structures that possess diameters of a few nanometers, while the length can be up to a few micrometers. These could have unusual toxicological properties, in that they share intermediate morphological characteristics of both fibers and nanoparticles. To date, no detailed study has been carried out to determine the effect of length on CNT cytotoxicity. In this paper, we investigated the activation of the human acute monocytic leukemia cell line THP-1 in vitro and the response in subcutaneous tissue in vivo to CNTs of different lengths. We used 220 nm and 825 nm-long CNT samples for testing, referred to as "220-CNTs" and "825-CNTs", respectively. 220-CNTs and 825-CNTs induced human monocytes in vitro, although the activity was significantly lower than that of microbial lipopeptide and lipopolysaccharide, and no activity appeared following variation in the length of CNTs. On the other hand, the degree of inflammatory response in subcutaneous tissue in rats around the 220-CNTs was slight in comparison with that around the 825-CNTs. These results indicated that the degree of inflammation around 825-CNTs was stronger than that around 220-CNTs since macrophages could envelop 220-CNTs more readily than 825-CNTs. However, no severe inflammatory response such as necrosis, degeneration or neutrophil infiltration in vivo was observed around both CNTs examined throughout the experimental period.

Graphene nanoribbons combine the unique electronic and spin properties of graphene with a transport gap that arises from quantum confinement and edge effects. This makes them an attractive candidate material for the channels of next-generation transistors. Nanoribbons can be made in a variety of ways, including lithographic, chemical and sonochemical approaches, the unzipping of carbon nanotubes, the thermal decomposition of SiC and organic synthesis. However, the reliable site and alignment control of nanoribbons with high on/off current ratios remains a challenge. Here we control the site and alignment of narrow (∼23 nm) graphene nanoribbons by directly converting a nickel nanobar into a graphene nanoribbon using rapid-heating plasma chemical vapour deposition. The nanoribbons grow directly between the source and drain electrodes of a field-effect transistor without transfer, lithography and other postgrowth treatments, and exhibit a clear transport gap (58.5 meV), a high on/off ratio (>10(4)) and no hysteresis. Complex architectures, including parallel and radial arrays of supported and suspended ribbons, are demonstrated. The process is scalable and completely compatible with existing semiconductor processes, and is expected to allow integration of graphene nanoribbons with silicon technology.

We present the first demonstration of the nonmagnetic catalyzed synthesis of narrow-chirality distributed single-walled carbon nanotubes (SWNTs). Based on the systematic investigation using different combinations of catalyst types (magnetic or nonmagnetic) and chemical vapor deposition (CVD) methods (thermal CVD (TCVD) or plasma CVD (PCVD)), PCVD with the nonmagnetic catalyst under the appropriate H(2) concentration is found to be critical as the methodological element of realizing the narrow-chirality distribution. Electrical measurements of thin film SWNTs produced under the different combinations of catalyst types and CVD methods are also investigated, which reveals the SWNTs grown from the nonmagnetic catalyst with PCVD display the best device performance.

In the high potential plasma, upstream of the double layer, the measured electron energy distribution function ͑EEDF͒ shows a very clear change in slope at energies ͑ break ͒ corresponding to the double layer potential drop. Electrons with lower energy are Maxwellian with a temperature of 8 eV, whereas those with higher energy have a temperature of 5 eV. The EEDF in the downstream plasma has a temperature of 5 eV. Over the range of pressures wherein the double layer and accelerated ion beam are detected by analysis of a retarding field energy analyzer, the strength of the double layer corresponds to the energy where the slope changes in the EEDF ͑ break ͒. We deduce that the downstream electrons come from upstream electrons that have sufficient energy to overcome the potential of the double layer, and that only a single upstream plasma source is required to maintain this phenomenon.

A fullerene pair-ion plasma without electrons is generated and electrostatic modes propagating along magnetic-field lines are externally excited in the range of low frequencies. It is found that four kinds of wave modes, including theoretically unexpected ones, exist in the plasma, and the phase lag between the density fluctuations of positive and negative ions strongly depends on the frequency. In order to illuminate further collective motion of pair-ion plasmas in the range of high frequencies, a concept of a hydrogen pair-ion plasma consisting of only H+ and H− is proposed and an experimental configuration is presented. On the basis of the production of a hydrogen plasma by Penning ionization gauge discharge, the principles of ion cyclotron resonance and E×B drift motion are shown to be effective for ion-species analysis/selection and separated electron detection from negative ions in the generation of pure hydrogen pair-ion plasmas.

Spatially and temporally stable gas‐liquid interfacial plasmas are created using ionic liquids as electrodes of a direct‐current (DC) discharge under a low gas pressure condition. The potential structure formation in the gas‐liquid interfacial region and the resultant behavior of the plasma ions are revealed by changing a polarity of the electrode in the liquid. When the ionic liquid is utilized as a cathode electrode, the positive ions in the plasma are irradiated to the ionic liquid and cause the physical and chemical reactions of the ionic liquid at the interface. The plasma ion irradiation can easily be controlled by changing the plasma parameter and is found to be effective for the metal nanoparticle synthesis in comparison with an electron irradiation.