Well-dispersed Single-walled Carbon Nanotubes Research Articles

Achieving Both Ultrahigh Electrical Conductivity and Mechanical Modulus of Carbon Films: Templating-Coalescing Behavior of Single-Walled Carbon Nanotube in Polyacrylonitrile.

Promoting the feasibility of carbon films as electrode applications requires sufficient performances in view of both electrical and mechanical properties. Herein, carbon films with ultrahigh electrical conductivity and mechanical modulus are prepared by high temperature carbonization of polyacrylonitrile (PAN)/single-walled carbon nanotube (SWNT) nanocomposites. Achieving both performances is ascribed to remarkable graphitic crystallinity, resulting from the sequential templating-coalescing behavior of concentrated SWNT bundles (B-CNTs). While well-dispersed SWNTs (WD-CNTs) facilitate radial templating according to their tubular geometry, flattened B-CNTs sandwiched between carbonized PAN matrices induce vertical templating, where the former and latter produce concentric and planar crystallizations of the graphitic structure, respectively. After carbonization at 2500 °C with the remaining WD-CNTs as microstructural defects, the flattened B-CNTs coalesce into graphitic crystals by zipping the surrounding matrix, resulting in high crystallinity with the crystal thicknesses of 27.4 and 39.4nm for the (002) and (10) planes, respectively. For comparison, the graphene oxide (GO) containing carbon films produce a less-ordered graphitic phase owing to irregular templating, despite the geometrical consistency. Consequently, PAN/B-CNT carbon films exhibit exceptional electrical conductivity (40.7× 104 S m-1 ) and mechanical modulus (38.2 ± 6.4GPa). Thus, controlling the templating-coalescing behavior of SWNTs is the key for improving final performances of carbon films.

Wrapping silicon microparticles by using well-dispersed single-walled carbon nanotubes for the preparation of high-performance lithium-ion battery anode.

Silicon microparticles (SiMPs) show considerable promise as an anode material in high-performance lithium-ion batteries (LIBs) because of their low-cost starting material and high capacity. The failure issues associated with the intrinsically low conductivity and significant volume expansion of Si have largely been resolved by designing silicon/carbon composites using carbon nanotubes (CNTs). The CNTs are important in terms of stress dissipation and the conductive network in Si/CNT composites. Here, we synthesized a SiMP/2D CNT sheet wrapping composite (SiMP/CNT wrapping) via a facile freeze-drying method with the use of highly dispersed single-walled CNTs. In this work, the well-dispersed CNTs are easily mixed with Si, resulting in effective CNT wrapping on the SiMP surface. During freeze-drying, the CNTs are self-assembled into a segregated 2D CNT sheet morphology via van der Waals interactions. The resulting CNT wrapping shows a unique wide range of conductive networks and mesh-like CNT sheets with void spaces. The SiMP/CNT wrapping 9 : 1 electrode exhibits good rate and cycle performance. The first charge/discharge capacity of SiMP/CNT wrapping 9 : 1 is 3160.7 mA h g-1/3469.1 mA h g-1 at 0.1 A g-1 with superior initial coulombic efficiency of 91.11%. After cycling, the SiMP/CNT wrapping electrode shows good structural integrity with preserved electrical conductivity. The superior electrochemical performance of the SiMP/CNT wrapping composite can be explained by an extensive conductive CNT network on the SiMPs and facile lithium-ion diffusion via mesh-like CNT wrapping.

Cardanol-derived cationic surfactants enabling the superior antibacterial activity of single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) are potential antibacterial material, and their antibacterial activity in aqueous solutions depends on efficient surfactants to create strong interactions between well-dispersed SWCNTs and bacterial cells. Here, we designed and synthesized a new family of cationic surfactants by introducing different positively charged hydrophilic heads, i.e. –(CH2)6N+(CH3)3Br−, –(CH2)2N+(CH3)3Br− and –(CH2)2N+PyridineBr−, to cardanol obtained from cashew nut shell liquid. These surfactants can efficiently disperse SWCNTs in aqueous solutions because benzene rings and olefin chains in cardanol enable their strong π-stacking on SWCNTs. A much higher fraction of SWCNTs can be dispersed individually compared to the commonly used surfactant, dodecylbenzene-sulfonate sodium (SDBS). SWCNTs dispersed in the cardanol-derived surfactants demonstrate significantly improved antibacterial activity. At the concentration of 0.5 wt%, their minimum inhibitory concentration is 0.33 and 0.02 μg ml−1 against E. coli and S. aureus, respectively, which is only 0.8%–1.5% of that of SDBS-dispersed SWCNTs. The strong antibacterial activity can be attributed to both better dispersion of SWCNTs and positive charges introduced by hydrophilic heads, which are attracted to negatively charged bacterial cell surfaces. These cardanol-derived surfactants are promising as sustainable surfactants for enabling various SWCNT applications.

Well-dispersed carbon nanotube/polymer composite films and application to electromagnetic interference shielding

Flexible and easily-processable materials exhibiting excellent electromagnetic interference (EMI) shielding performance are desirable for EMI shielding applications in electronic devices, which are getting progressively smaller and smarter. This study reports single-walled carbon nanotube (SWCNT)/poly(ethylene-alt-maleic anhydride) (PEMA) composite films with an excellent EMI shielding performance fabricated by a simple bar-coating and doping process. The AuCl3-doped SWCNT/PEMA composite films exhibited an excellent EMI shielding effectiveness (SE) of 96.3dB at a thickness of 0.031mm. The EMI SE values of the AuCl3-doped SWCNT/PEMA composite films are higher than any other reported synthetic materials with a similar thickness. The excellent EMI shielding performance is attributed to the high electrical conductivity. The conductivity of the SWCNT/PEMA composite films can be increased effectively to 8500 S cm-1 through the AuCl3-doping process. It was further confirmed by MD simulations that the introduction of only 30wt.% PEMA polymer is effective for obtaining well-dispersed SWCNTs in the composite films. It is noteworthy that such a small fraction of PEMA polymers is advantageous both for decreasing the volume fraction of the insulating polymers and facilitating the chemisorption of dopants onto the SWCNT surfaces.

High-Performance Fluorinated Ethylene-Propylene/Graphite Composites Interconnected with Single-Walled Carbon Nanotubes

Herein, we report a novel method for the fabrication of highly conductive fluorinated ethylene-propylene (FEP)/graphite nanocomposites for high-temperature bipolar plates (BPs) by incorporating the well-dispersed single-walled carbon nanotube (SWCNT) as a secondary filler in the FEP matrix. The SWCNTs were pre-dispersed with FEP powder by sonication in ethanol and subsequently mixed with graphite powder by ball milling. The composite BPs were prepared from the mixed powder by compression molding. The resulting FEP/graphite/SWCNT nanocomposite containing 80 wt% graphite (500 µm particles) and 0.1 wt% SWCNT exhibited high electrical conductivity (210 S cm−1) superior to that of the composite devoid of SWCNTs (120 S cm−1) by modulating the electrical transportation pathways between graphite particles through the SWCNTs. A small amount of the incorporated SWCNTs (0.1 wt%) also improved chemical inertness to phosphoric acid. Hence, the prepared FEP/graphite nanocomposites with SWCNTs as a secondary filler exhibited a robust performance for application as high-temperature BPs for phosphoric acid fuel cells.

Direct Aqueous Dispersion of Carbon Nanotubes Using Nanoparticle-Formed Fullerenes and Self-Assembled Formation of p/n Heterojunctions with Polythiophene.

Single-walled carbon nanotubes (SWCNTs) have received much attention because of their potential in optoelectronic applications. Pristine SWCNTs exhibit substantial van der Waals interactions and hydrophobic characteristics, so precipitation occurs immediately in most organic solvents and water. Highly toxic and hazardous chemicals are often used to obtain well-dispersed SWCNTs. Developing environmentally friendly processing methods for safe and practical applications is a great challenge. Here, we demonstrate direct exfoliation of SWCNTs in pure water only with n-type semiconducting fullerene nanoparticles. The resultant SWCNTs can be well-dispersed in water, where they remain essentially unchanged for several weeks. Adding an aqueous solution of p-type semiconducting water-soluble polythiophene yields self-assembled p/n heterojunctions between polythiophene and the nanoparticles. The aqueous-dispersed SWCNTs yield photocurrent responses in solution-processed thin films as a potential application of water-dispersed carbon nanomaterials.

(Invited) Organelle-Specific Targeting and Localization of Single Wall Carbon Nanotubes

Subcellular interaction and targeting of nanomaterials is important both to determine toxicity and for potential subcellular therapies of medical nanotechnology. Our collaborative research groups have investigated the intracellular targeting of single wall carbon nanotubes (SWCNTs) to different organelles based on tube varying length and surface coatings. SWCNTs longer than 1 µm do not localize within cells to any appreciable amount except for professional phagosomes such as macrophages. Purified, well-dispersed SWCNTs near 150 nm can be delivered at extremely high levels to numerous cell types, primarily dependent on cell metabolism and SWCNT surface functionalization. We have found that SWCNTs can be readily non-covalently dispersed with different bioactive macromolecules including (but not limited to) PEG triblock PF127 and bovine serum albumin (BSA) protein. SWCNT-PF127 are membrane active, escape endosomes and localize to actin inside the cell wherein many are retained inside of cells. SWCNT-BSA localize with endoplasmic reticulum (ER) and lipid vesicles along the metabolic pathway within cells. SWCNTs-BSA are then lost from cells via exocytosis unless endosomes are disrupted inside cells. Unless specifically targeted, we find that SWCNTs do not localize to the nucleus or mitochondria of cells. Thus, long-term cellular vitality and genetic stability of cells does not appear to be altered with SWCNT exposure. Specifically, mitochondria structure and function are not altered with high levels of SWCNT treatment (either SWCNT-BSA or SWCNT-PF127) including ATP production or any other aspects of long-term cellular toxicity. Generally in these cellular studies, there are unique challenges in merging nanomaterials characterization with cellular science and engineering. Most imaging technologies of cellular structure and function requires optical microscopy including immunocytochemistry, expression of fluorescent-tagged proteins and assays with fluorescent readouts. However, SWCNTs are optically active and quench fluorescence intensity obscuring intensity-based signals, which limits imaging capabilities and alters accuracy and precision of cellular assays. We have utilized the optical activity of the SWCNT as a marker for colocalization by quantifying changes in fluorescence lifetime of the fluorophore within the Förster radius of the SWCNT. This and other complications of nano-cell interactions necessitates the need for numerous complementary techniques when assessing structural and functional association between SWCNTs and cellular organelles and compartments.

A review of toxicity studies of single-walled carbon nanotubes in laboratory animals

We summarized the findings of in vivo toxicity studies of single-walled carbon nanotubes (SWCNTs) in laboratory animals. The large majority addressed the pulmonary toxicity of SWCNTs in rodents. Inhalation, pharyngeal aspiration, and intratracheal instillation studies revealed that SWCNTs caused acute and chronic inflammation, granuloma formation, collagen deposition, fibrosis, and genotoxic effects in the lungs. Pulmonary toxicity of well-dispersed SWCNTs was more potent than less dispersed ones. Airway exposure to SWCNTs also induced cardiovascular diseases in mice. Oxidative stress was caused by the administration of SWCNTs. Injected SWCNTs were distributed throughout most of the organs including the brain, mainly retained in the lungs, liver, and spleen, and eliminated through the kidney and bile duct. Orally administered SWCNTs are suggested to be absorbed from the gastrointestinal tract to the blood circulation in mice and rats. Although no definitive study on the carcinogenicity of SWCNTs is available at present, evidence of carcinogenicity has not been reported in toxicity studies cited in this review. Overall, the available data provides initial information on SWCNT toxicity. To further clarify their toxicity and risk assessment, studies should be conducted using well-characterized SWCNTs, standard protocols, and the relevant route and doses of human exposure.

Carbon nanotubes as non-contact optical strain sensors in smart skins

Progress is reported in the development of a novel non-contact strain measurement technology in which the sensors are single-walled carbon nanotubes. This approach exploits the characteristic short-wave infrared fluorescence signatures of semiconducting single-walled carbon nanotubes and the systematic shifts of their fluorescence wavelengths when the nanotubes are axially strained. A strain-sensing smart skin is prepared by coating the surface to be monitored with a thin film of a composite containing well-dispersed single-walled carbon nanotubes embedded in a urethane varnish host. Strain in the surface transfers through the host polymer to the embedded nanotubes. The nanotube strains are then quantitatively monitored by exciting the region of interest with a visible laser beam and capturing and analyzing the resulting single-walled carbon nanotube fluorescence spectrum. High-quality spectra are shown for strain-sensing smart skin films in which the nanotubes were pre-processed by selective extraction with the organic polymer poly(9,9-dioctylfluorenyl-2,7-diyl) and purification by centrifugation. The design of a compact, field-portable optical system for exciting, collecting, and interpreting strain-sensing smart skin spectral data is also described. This system is used to validate the linear dependence of peak shifts with strain in test specimens subjected to multiple tension cycles inducing strains from 0 to 5000 µε. Adequate linearity is found up to 1500 µε; however, minor hysteresis is observed above this level. The gage length for these measurements can be as small as several micrometers, and the strain resolution is currently between 10 and 100 µε (depending on strain magnitude). Cyclic reversible strain measurements are demonstrated, with minor hysteresis being attributed to imperfect adhesion between nanotube sidewalls and the surrounding polymer host.

Preparation of gold nanoparticles/single-walled carbon nanotubes/polyaniline composite-coated electrode developed for DNA detection

This work details the preparation of gold nanoparticles/single-walled carbon nanotubes/polyaniline composite-modified disposable pencil graphite electrode (AuNPs/SWCNTs/PANI/PGEs), and its application for electrochemical DNA sensing. Disposable pencil graphite electrode was modified with single-walled carbon nanotubes/polyaniline composite via one-step electropolymerization of aniline solution containing well-dispersed single-walled carbon nanotubes. AuNPs were then immobilized onto the SWCNTs/PANI/PGE. Electrochemical results exhibited improved sensitivity for DNA detection with AuNPs/SWCNTs/PANI/PGE compared to the SWCNTs/PANI/PGE, PANI/PGE or unmodified PGE due to the strong interaction between AuNPs, SWCNTs, and PANI based on the effective degree of electron delocalization. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the prepared electrode. Thiol-linked ssDNA was immobilized onto the AuNPs/SWCNTs/PANI/PGE for DNA detection. Experimental parameters such as the concentration of AuNPs and ssDNA were investigated to optimize the experimental conditions.

Processing-structure–property relationships of SWNT–epoxy composites prepared using ionic liquids

Experimentally achieved mechanical properties of nanotube–epoxy composites fail to match theoretical expectations; shortcomings are mainly attributed to poor dispersion. The elastic modulus of a well-dispersed single walled carbon nanotube (SWNT)-ionic liquid-epoxy composite was evaluated in tension and compared to predictions by a micromechanics homogenization model. The model takes into account the mechanical properties of the constituent phases in addition to SWNT aspect ratio, spatial distribution, dispersion, and agglomeration. These parameters were evaluated using information obtained via scanning and transmission electron microscopy. The Young’s modulus of the composite shows excellent agreement with the model at low concentrations, while discrepancies at high SWNT concentrations are possibly due to composite processing limitations. At high concentrations the uncured composite mixture is above the rheological percolation threshold. As the polymer network reaches its maximum capacity for well-dispersed SWNTs, increasing volume fraction does not result in further significant reinforcing effects.

Abnormally enhanced thermoelectric transport properties of SWNT/PANI hybrid films by the strengthened PANI molecular ordering

Single-walled carbon nanotube (SWNT)/polyaniline (PANI) hybrid films were prepared by casting the suspension containing well-dispersed SWNTs and CSA-doped PANI. The electrical conductivity of the SWNT/PANI film at first increased with the increasing SWNT content and then decreased at high SWNT content, whereas the Seebeck coefficient increased monotonically in the present SWNT content range. Moreover, the electrical conductivity values of the SWNT/PANI composites were much higher than the values calculated based on the series-connected two-component mixture model, whereas the dependence of the Seebeck coefficient on the SWNT content fitted well with the mixture model. Thermal conductivities increased with the SWNT content, but the rate of increase was much lower than the values estimated using the mixture model. The maximum values of electrical conductivity and Seebeck coefficient of hybrid films were up to 769 S cm−1 and 65 μV K−1. Consequently, the maximum thermoelectric power factor and ZT value at room temperature reached 176 μW m−1 K−2 and 0.12, respectively. The optimal TE property of the SWNT/PANI hybrid film was remarkably higher than those of either individual component of the composite, and exhibits the highest values for inorganic–organic composite materials reported so far. XRD and Raman analyses revealed that the PANI molecules in the composite film had a more expanded conformation, and were more orderly arranged compared with both pure PANI bulk and pure PANI film. The abnormally enhanced thermoelectric performance is attributed to the highly ordered PANI interface layer on the SWNT surface, which formed by the synergetic effect of chain expansion by the chemical interactions between PANI and the solvent and chain-ordering due to the π–π conjugation between PANI and CNTs.

Bulk Heterojunction Photovoltaic Devices Based on a Poly(2-Methoxy, 5-Octoxy)-1, 4-Phenylenevinylene-Single Walled Carbon Nanotube-ZnSe Quantum Dots Active Layer

A solution-processed bulk heterojunction photovoltaic cell is fabricated based on poly[(2-methoxy, 5-octoxy)-1,4-phenylenevinylene](MOPPV)-single walled carbon nanotube(SWNT)-ZnSe quantum dots. The surface morphology shows the formation of an interpenetrating network between well-dispersed SWNTs and ZnSe in the MOPPV matrix. A blue-shifted absorption band indicates the strong electron interaction between SWNTs, ZnSe and MOPPV. A marked increase in the short-circuit current and power conversion efficiency (PCE) of ITO/PEDOT:PSS/MOPPV-SWNT-ZnSe/LiF/Al devices was achieved and compared with that without SWNTs. Results indicate that the enhanced performance is contributed by a high photocurrent due to efficient exciton dissociation and increased mobility for carrier transport in the SWNT pathway.

Impact of Polymer Matrix on the Electromagnetic Interference Shielding Performance for Single-Walled Carbon Nanotubes-Based Composites

Composites of acrylonitrile butadiene styrene (ABS), epoxy and soluble cross-linked polyurethane (SCPU) with various loadings of single-walled carbon nanotubes (SWCNTs) were prepared. Their electromagnetic interference (EMI) shielding effectiveness (SE) in the frequency range of 8.2-12.4 GHz (X band) was studied. Well-dispersed SWCNT composites were created in these three representative polymer matrixes. The choice of polymer matrix greatly affects the conductivity, percolation threshold, and EMI shielding properties of the SWCNT/polymer composites. Enhanced EMI SE performances were observed for the composites with better dispersed SWCNTs. Moreover, the EMI SE performances strongly correlated with SWCNT loading in the polymer matrix. The best SWCNT dispersion was achieved in the epoxy matrix: 20-30 dB EMI SE was obtained with 15 wt% SWCNTs.

Mode-locked double-clad fiber laser with a carbon nanotubes saturable absorber

In this paper, the mode-locked laser pulse with a maximum power of 366 mW is achieved by using Yb-ions-doped double-clad fiber as the gain medium and single-walled carbon nanotubes (SWCNTs) as the saturable absorber (SA). The saturable absorber with a modulation depth of 27% is fabricated by spreading the well-dispersed SWCNTs on the D-shaped segment of the fiber, which is directly etched on the standard single-mode fiber by water-assisted femtosecond laser ablation. The ring-cavity structure fiber laser is fabricated based on the SWCNT-SA. The mode-locked pulse width of 93.8 fs, central wavelength of 1083.8 nm, and 3 dB bandwith of 8.6 nm at the repetition rate of 5.59 MHz are obtained in the optimized polarization state under a pump power of 4 W.

Pulmonary Toxicity of Well-Dispersed Single-Wall Carbon Nanotubes Following Intratracheal Instillation

Single-Wall Carbon Nanotubes (SWCNTs) Were Well-Dispersed Using Ultrasonication to Conduct an Intratracheal Instillation Study. The Geometric Mean Diameter and Length of the SWCNT in Distilled Water Including 0.1 % Triton X-100 Was 44 Nm and 0.69 μm, Respectively. Rats Intratracheally Received 0.2 Mg or 0.4 Mg of SWCNT, and a Control Group Received Intratracheal Instillation of Distilled Water Containing 0.1 % Triton X-100 . The Rats Were then Sacrificed at 3 Days, 1 Week, 1 Month, 3 Months and 6 Months after Instillation. Bronchoalveolar Lavage Fluid (BALF) and Pathological Features Revealed that the Dose of SWCNT Induced Persistent Neutrophil Infiltration in Rat Lungs. In the Cytokine-Induced Neutrophil Chemoattractants (CINCs) Family, the Concentrations of CINC-1 and CINC-2 in the BALF Increased Persistently in the SWCNT-Exposed Groups. the Concentration of HO-1 in the BALF Was Also up-Regulated Persistently in the Exposed Groups. These Data Suggested that Well-Dispersed SWCNT Had an Inflammatory Potential in the Present Study.

Paper supported immunosensor for detection of antibiotics

Paper supports were used to develop a simple, inexpensive, fast and sensitive electrochemical immunosensor for the analysis of antibiotic residues in milk samples, where single-walled carbon nanotubes (SWNTs) and a simple dip–dry coating method were employed to prepare the highly sensitive biosensor. Well-dispersed SWNTs were impregnated with an antibody against neomycin to obtain a composite coating solution, followed by dipping the filtration paper in the solution to fabricate the sensitive biosensor which had high electrical conductivity. Based on the impedance change in the entire paper supported biosensor with increased concentrations of neomycin, the limit detection of the optimized method was 0.04ngmL−1 and a linear detection range from 0.2 to 125ngmL−1, well below the European Union regulations for neomycin in this matrix. This paper supported biosensor was applied to determine neomycin in milk samples after a simple sample treatment, with spiked recoveries which ranged from 93.25 to 110.47%. A variety of antibiotic residues in milk samples could be determined following similar sensor preparation.

Pulmonary Toxicity of Manufactured Nanomaterials

We introduced the report on the pulmonary toxicity of manufactured nanomaterials as a national project in Japan conducted by the New Energy and Industrial Technology Development Organization (NEDO project). Well-characterized and well-dispersed industrial nanomaterials were used in this project. Using multiwall carbon nanotubes (MWCNTs), we conducted intratracheal instillation and inhalation studies. At a low dose (0.2 mg/rat) and a high dose (1 mg/rat) of almost individual MWCNTs, transient and persistent inflammatory responses were induced in the lungs following intratracheal instillation. Well-dispersed MWCNTs at a low concentration (0.37 mg/m3) did not induce pulmonary inflammation. Using single-wall carbon nanotubes (SWCNTs), we also conducted both studies. At low (0.2 mg/rat) and high doses (0.4 mg/rat) of well-dispersed SWCNTs, persistent inflammatory responses were induced in the lungs following intratracheal instillation. Well-dispersed MWCNTs at low and high concentrations (0.03 mg/m3 and 0.13 mg/m3, respectively) did not induce pulmonary inflammation. On the basis of these data from mainly inhalation studies, the acceptable exposure concentration of carbon nanotubes is proposed to be 0.03 mg/m3 in Japan.

Pulmonary and systemic responses of highly pure and well-dispersed single-wall carbon nanotubes after intratracheal instillation in rats

The present study was conducted to assess the pulmonary and systemic responses in rats after intratracheal instillation of highly pure, well-dispersed, and well-characterized SWCNTs. Exposure to SWCNTs up to 2 mg/kg did not produce mortality, changes in clinical signs, or body weights during the observation period. Dose-dependent changes were observed in the lung weight, BALF inflammatory cells, and biochemical parameters such as LDH value, protein content, IL-1β and IL-6 activity, and histopathology. In the 0.04 mg/kg SWCNT-exposed group, almost no changes were observed during the observation period. In the 0.2 mg/kg SWCNT-exposed group, pulmonary inflammatory responses were observed after instillation. In the 1 mg/kg and 2 mg/kg SWCNT-exposed group, acute lung inflammation and subsequent granuloma accompanied by increased lung weights were observed. Furthermore, the histopathological findings in the lungs of rats exposed to SWCNTs showed inflammatory responses related with the vital reaction to the foreign substance that was instilled intratracheally, and there were no fibrosis, atypical lesion, or tumor-related findings even at the highest dose (2 mg/kg) of SWCNT-exposed groups up to 6 months after instillation. For all groups, histopathological changes due to the instillation exposure of SWCNTs were observed only in the lungs and lung-associated lymph nodes and not in the other tissues examined (i.e. the liver, kidney, spleen, and cerebrum).

Pulmonary toxicity of well-dispersed single-wall carbon nanotubes after inhalation

Single-wall carbon nanotubes (SWCNTs) were well-dispersed by ultrasonication to conduct an inhalation study. SWCNTs were generated using a pressurised nebuliser with liquid suspension of SWCNTs. Wistar rats were exposed to the well-dispersed SWCNT (diameter of bundle: 0.2 μm; length of bundle: 0.7 μm) for 4 weeks. The low and high mass concentrations of SWCNTs were 0.03 ± 0.003 and 0.13 ± 0.03 mg/m3, respectively. The rats were sacrificed at 3 days, 1 month, and 3 months after the end of exposure. There were no increases of total cell or neutrophil counts in the bronchoalveolar lavage fluid (BALF), or the concentration of cytokine-induced neutrophil chemoattractant in the lungs or BALF in both the high and low concentration-exposed groups. Pulmonary infiltration of neutrophils was not observed in either exposed group throughout the observation period. Well-dispersed SWCNT did not induce neutrophil inflammation in the lung under the conditions in the present study.