Dynamics of nonlinear coupling between electron-temperature-gradient mode and drift-wave mode in linear magnetized plasmas.

A high-frequency (∼0.4  MHz) fluctuation is excited by an electron temperature gradient (ETG) perpendicular to magnetic field lines, which is consistent with an ETG mode. When the fluctuation amplitude of the ETG mode exceeds a certain threshold, the mode gradually becomes saturated and a low-frequency (∼7  kHz) fluctuation which is originally caused by a drift wave is enhanced, corresponding to the saturation of the ETG mode.

C59N peapods sensing the temperature.

We report the novel photoresponse of nanodevices made from azafullerene (C(59)N)-encapsulated single-walled carbon nanotubes (C(59)N@SWNTs), so called peapods. The photoconducting properties of a C(59)N@SWNT are measured over a temperature range of 10 to 300 K under a field-effect transistor configuration. It is found that the photosensitivity of C(59)N@SWNTs depends very sensitively on the temperature, making them an attractive candidate as a component of nanothermometers covering a wide temperature range.

Direct growth of doping-density-controlled hexagonal graphene on SiO2 substrate by rapid-heating plasma CVD.

A transfer-free method for growing carrier-density-controlled graphene directly on a SiO(2) substrate has been realized for the first time by rapid-heating plasma chemical vapor deposition (RH-PCVD). Using this method, high-quality single-layer graphene sheets with a hexagonal domain can be selectively grown between a Ni film and a SiO(2) substrate. Systematic investigations reveal that the relatively thin Ni layer, rapid heating, and plasma CVD are critical to the success of this unique method of graphene growth.

Site- and alignment-controlled growth of graphene nanoribbons from nickel nanobars.

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.

Electrically moving single-stranded DNA into and out of double-walled carbon nanotubes.

Our study indicates that it is possible to move single-stranded DNA (ssDNA) molecules into and out of double-walled carbon nanotubes by utilizing DC electric fields with different polarities.

Direct growth of short single-walled carbon nanotubes with narrow-chirality distribution by time-programmed plasma chemical vapor deposition.

We have realized the direct growth of the short-length (<100 nm) single-walled carbon nanotubes (SWNTs) with a narrow-chirality distribution by time-programmed plasma chemical vapor deposition (TP-PCVD). Transmission electron microscope and atomic force microscope analyses reveal that the very short (<100 nm) SWNTs are selectively grown by precisely controlling their growth time on the order of a few seconds. Direct photoluminescence excitation measurements also show that the chirality distribution of the short SWNTs is fairly narrow, and (7, 6) and (8, 4) dominant short SWNTs are successfully synthesized by TP-PCVD.

Narrow-chirality distributed single-walled carbon nanotube growth from nonmagnetic catalyst.

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.

Control of electron temperature and space potential gradients by superposition of thermionic electrons on electron cyclotron resonance plasmas.

An electron temperature gradient (ETG) is formed perpendicular to the magnetic field lines by superimposing low-temperature thermionic electrons emitted from a tungsten hot plate upon high-temperature electrons of an electron cyclotron resonance plasma, which pass through two different-shaped mesh grids. The radial profile of the plasma space potential can be controlled independent of the ETG by changing the bias voltages of the hot plate.

Synthesis and property characterization of c(69)n azafullerene encapsulated single-walled carbon nanotubes.

Our study demonstrates that the C(69)N azafullerene can be encapsulated inside single-walled carbon nanotubes (SWNTs), which is confirmed by TEM, UV-vis-IR spectroscopy, Raman spectroscopy, and UPS. The electrical transport properties of SWNTs are found to change drastically due to the encapsulated C(69)N azafullerene. Our experimental results indicate that C(69)N encapsulated SWNTs show the high-performance n-type behavior compared with p-type characteristics of pristine SWNTs and C(70) encapsulated SWNTs.

Synthesis of monodispersed nanoparticles functionalized carbon nanotubes in plasma-ionic liquid interfacial fields.

Metal nanoparticles intercalated into and encapsulated inside single-walled (SWNTs) and double-walled (DWNTs) carbon nanotubes are synthesized using a plasma technique combined with the introduction of ionic liquids under low gas pressures. Owing to the synthesis in nano-spaces of the SWNTs and DWNTs as a template, high-density and monodispersed metal nanoparticles are realized, which could be applied to specific composite-nanodevices based on carbon nanotubes.

Photoswitching in azafullerene encapsulated single-walled carbon nanotube FET devices.

The photoinduced electrical transport properties of C(59)N@SWNTs are investigated by assembling them into FET devices. Our findings demonstrate that azafullerene molecules inside SWNTs make nanotube FET devices very sensitive to UV light exposure by the decrease of source-drain current upon light exposure. The photoswitching effect is found to be dependent on wavelengths of light and becomes negligible when the wavelength is increased to 480 nm.

Exciton energy transfer-assisted photoluminescence brightening from freestanding single-walled carbon nanotube bundles.

Photoluminescence (PL) brightening is clearly observed through the direct morphology transition from isolated to thin bundled vertically- and individually freestanding single-walled carbon nanotubes (SWNTs). On the basis of the precise spectra analysis and equation-based estimation of the PL time trace, the origin of the PL brightening is consistently explained in terms of the exciton energy transfer through the tube bundles. The PL brightening is also revealed to obviously depend on SWNT diameters.

Azafullerene encapsulated single-walled carbon nanotubes with n-type electrical transport property.

Electrical transport properties of C60 and C59N encapsulated single-walled carbon nanotubes (SWNTs) are investigated by fabricating them as the channels of field effect transistor (FET) devices at room temperature. Their measurements indicate that C60@SWNTs exhibit the enhanced p-type characteristics compared with the case of pristine SWNTs, whereas C59N@SWNTs show the n-type behavior. The novel transport properties of peapods can be explained by the charge-transfer effect, which can modify the electronic structure of SWNTs.

Magnetic characterization of Fe-nanoparticles encapsulated single-walled carbonnanotubes.

Magnetic Fe nanoparticles less than 1 nm have been successfully filled in single-walled carbon nanotubes (SWNTs), and their magnetic properties are characterized by means of SQUID measurements in the temperature range of 5-300 K.

Influence of length on cytotoxicity of multi-walled carbon nanotubes against human acute monocytic leukemia cell line THP-1 in vitro and subcutaneous tissue of rats in vivo.

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.

Strict preparation and evaluation of water-soluble hat-stacked carbon nanofibers for biomedical application and their high biocompatibility: influence of nanofiber-surface functional groups on cytotoxicity.

Water-soluble H-CNFs modified with a carboxyl group possessed the ability to induce TNF-alpha, whereas CHAPS-treated H-CNFs possessed significantly greater activity and were also found to activate NF-kappaB reporter activity, to a significantly greater level than H-CNFs; furthermore the functional group modified or coated on the surface of H-CNFs was a significant cytotoxic factor that affected cell activation.

Plasma state transition originating from local production of massive negative ions.

A dynamic evolution of plasma structures and its associated state transition due to local production of massive negative ions are investigated by the particle-in-cell simulation which is based on an experimental configuration of an open plasma system (Q machine). Two different states, a stationary state and a dynamic state, are achieved depending on the production rate of massive negative ions. The plasma is stationary for a low production rate, while solitary pulses and fluctuations are spontaneously excited and the plasma state is unstable for a high production rate.

Pair-ion plasma generation using fullerenes.

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.

Formation and structural observation of cesium encapsulated single-walled carbon nanotubes.

Cesium encapsulation inside single-walled carbon nanotubes (SWNTs) is for the first time realized by ion irradiation of SWNTs immersed in a magnetized alkali-metal plasma, the configuration of which is confirmed to comprise three varieties by field emission type transmission electron microscopy (FE-TEM) and scanning TEM (STEM) observation.