Multiwalled carbon nanotubes (MWCNTs) have the potential for widespread applications in engineering and materials science. However, because of their needle-like shape and high durability, concerns have been raised that MWCNTs may induce asbestos-like pathogenicity. Although recent studies have demonstrated that MWCNTs induce various types of reactivities, the physicochemical features of MWCNTs that determine their cytotoxicity and carcinogenicity in mesothelial cells remain unclear. Here, we showed that the deleterious effects of nonfunctionalized MWCNTs on human mesothelial cells were associated with their diameterdependent piercing of the cell membrane. Thin MWCNTs (diameter ∼ 50 nm) with high crystallinity showed mesothelial cell membrane piercing and cytotoxicity in vitro and subsequent inflammogenicity and mesotheliomagenicity in vivo. In contrast, thick (diameter ∼ 150 nm) or tangled (diameter ∼ 2-20 nm) MWCNTs were less toxic, inflammogenic, and carcinogenic. Thin and thick MWCNTs similarly affected macrophages. Mesotheliomas induced by MWCNTs shared homozygous deletion of Cdkn2a/2b tumor suppressor genes, similar to mesotheliomas induced by asbestos. Thus, we propose that different degrees of direct mesothelial injury by thin and thick MWCNTs are responsible for the extent of inflammogenicity and carcinogenicity. This work suggests that control of the diameter of MWCNTs could reduce the potential hazard to human health. environmental health | inflammation | nanotoxicology

We report a rapid and scalable method for the separation of metallic and semiconducting single-wall carbon nanotubes (SWCNTs); the separation is performed by the selective adsorption of semiconducting SWCNTs on agarose gel. The most effective separation was realized by a simple procedure in which a piece of gel containing SWCNTs and sodium dodecyl sulfate was frozen, thawed, and squeezed. This process affords a solution containing 70% pure metallic SWCNTs and leaves a gel containing 95% pure semiconducting SWCNTs. Field-effect transistors constructed from the separated semiconducting SWCNTs have been demonstrated to function without any electrical breakdown.

Property by design is one appealing idea in material synthesis but hard to achieve in practice. A recent successful example is the demonstration of van der Waals (vdW) heterostructures, 1-3 in which atomic layers are stacked on each other and different ingredients can be combined beyond symmetry and lattice matching. This concept, usually described as a nanoscale Lego blocks, allows to build sophisticated structures layer by layer. However, this concept has been so far limited in two dimensional (2D) materials. Here we show a class of new material where different layers are coaxially (instead of planarly) stacked. As the structure is in one dimensional (1D) form, we name it "1D vdW heterostructures". We demonstrate a 5 nm diameter nanotube consisting of three different materials: an inner conductive carbon nanotube (CNT), a middle insulating hexagonal boron nitride nanotube

If the physical properties of C(60) fullerene molecules can be controlled in C(60) products already in use in various applications, the potential for industrial development will be significant. Encapsulation of a metal atom in the C(60) fullerene molecule is a promising way to control its physical properties. However, the isolation of C(60)-based metallofullerenes has been difficult due to their insolubility. Here, we report the complete isolation and determination of the molecular and crystal structure of polar cationic Li@C(60) metallofullerene. The physical and chemical properties of Li@C(60) cation are compared with those of pristine C(60). It is found that the lithium cation is located at off-centre positions in the C(60)-I(h) cage interior and that the [Li(+)@C(60)] salt has a unique two-dimensional structure. The present method of purification and crystallization of C(60)-based metallofullerenes provides a new C(60) fullerene material that contains a metal atom.

We have developed a novel separation method of metallic and semiconducting single-wall carbon nanotubes (SWCNTs) using agarose gel electrophoresis. When the SWCNTs were isolated with sodium dodecyl sulfate (SDS) and embedded in agarose gel, only the metallic SWCNTs separated from the starting gel by an electric field. After 20 min, almost all SWCNTs applied to gel electrophoresis were separated into two fractions, containing $95% semiconducting and $70% metallic nanotubes. The difference in the response to the electric field between metallic and semiconducting SWCNTs can be explained by the higher affinity of semiconducting SWCNTs to agarose than to SDS. # S ingle-wall carbon nanotubes (SWCNTs) have attracted a great deal of attention towards versatile applications, especially in the field of electronics, such as field effect transistors (FETs). 1,2) However, asproduced SWCNTs always contain both metallic and semiconducting SWCNTs, which is one of the most crucial problems preventing useful application of SWCNTs. There are several reports on the separation of metallic and semiconducting SWCNTs (MS separation) by dielectrophoresis, 3) amine extraction, 4) polymer wrapping, 5,6) selective oxidation, 7) and density-gradient ultracentrifugation; 8,9) however, problems in yield, purity, cost, etc. for industrial production of metallic and semiconducting SWCNTs are present in these methods. 10) Here, we report a novel separation method of metallic and semiconducting SWCNTs by agarose gel electrophoresis (AGE) that has high scalability for industrial application.Various SWCNTs synthesized by laser vaporization (LV1, 1:2 AE 0:1 nm in diameter; LV2, 1:4 AE 0:1 nm), high-pressure carbon monoxide processing (HiPco, R500, Carbon Nanotechnology, 1:0 AE 0:3 nm), and arc discharge (electric arc, APJ, Meijou Nano Carbon, 1:4 AE 0:1 nm) were used in this study. LV1 and LV2 SWCNTs were synthesized by conventional laser-oven technique and were highly purified as previously reported. 11) The growth temperatures were 1050 C for LV1-and 1250 C for LV2-SWCNTs. HiPco and arc SWCNTs were used without any purification steps. An SWCNT-dispersed solution was prepared as follows. SWCNTs were dispersed in 2% sodium dodecyl sulfate (SDS; 99%, Sigma-Aldrich) at 0.3 mg/ml and sonicated using a tip-type ultrasonic homogenizer (Taitec VP-30S) for 5.7 h at a duty cycle of 70% (total on-time: 4 h). In the case of arc SWCNTs, the sonication time was prolonged to 22.9 h (total on time: 16 h). The solution was centrifuged to remove bundles and impurities (16;100 Â g for 15 h at 25 C), and the resulting supernatant was collected as an SWCNT dispersion, where SWCNTs were coated with the surfactant.Agarose was chosen for the matrix of gel electrophoresis because agarose gel has been used for the separation of DNA which is almost the same size as SWCNTs. In the case of DNA, they are separated by a difference of length, where a network of the gel functions as a molecular sieve at the separation step and fixes the separated objects after the separation. 12) ...

We present protocols to prepare high-purity metallic single-wall carbon nanotubes (SWCNTs) with three basic colors, cyan, magenta, and yellow, through density gradient centrifugations. Addition of deoxycholate sodium salts as a co-surfactant could improve separation capability for metallic SWCNTs in centrifugations. We applied the improved separation protocols to the SWCNTs with different average diameters (1.34, 1.0, and 0.84 nm), and obtained the metallic SWCNTs with cyan, magenta, and yellow colors. Their optical/conductive characteristics were revealed, and conductive color films were formed from the metallic SWCNTs.

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