In this communication, we describe the finding that sonication of solid single-walled carbon nanotubes (p-SWNT) in an aqueous solution of a pyrene-carrying ammonium ion 1 gave a transparent dispersion/solution of the nanotubes, which was characterized by transmission electron microscopy, UV-vis absorption, fluorescence and 1 H NMR spectroscopies. We showed evidence for the interaction of the nanotube sidewall and the pyrene moiety in the aqueous dispersion/solution.Since the discovery in 1991, 1 carbon nanotubes have been in the forefront of nanoscience and nanotechnology because of their many unique properties.2 Very recently, considerable attention has focused on the preparation of soluble carbon nanotubes 3 that would find many chemical applications in fundamental and practical research fields. Shortened SWNTs have been reported to be soluble in the organic solvents by derivatization with thionyl chloride and octadecylamine.3 Full-length SWNTs were rendered soluble in common organic solvents by ionic complexation with the terminal carboxylic acid in the SWNTs and octadecylamine. 4Carbon nanotubes have been reported to be soluble in the aqueous micellar solution of some detergents 5 and in the aqueous solutions of poly(vinyl pyrrolidone) and poly(styrene sulfonate).6 We describe in this paper the first preparation of sidewall-functionalized water-soluble single-walled carbon nanotubes (SWNTs). Here, a pyrene-carrying ammonium ion, trimethyl-(2-oxo-2-pyren-1-yl-ethyl)-ammonium bromide (1, Chart 1) was designed and synthesized as a solubilizer, since the pyrene moiety has been reported to have affinity with carbon nanotubes. 7SWNTs (HiPco TM ), 8 length obtained from Carbon Nanotechnologies Incorporated were placed in a ceramic boat and heated in a furnace for 18 h at 225 C in humid synthetic air, and then sonicated in concentrated HCl for 15 min. The tubes were collected by a filter (pore size, 100 nm), and then washed with sodium hydrogencarbonate. The nanotubes were collected by a filter (pore size, 100 nm), and then heated at 50C to obtain the purified SWNTs (p-SWNTs). The XPS measurements revealed that for the p-SWNTs, Fe2p 3=2 did not appear in the region of 706-714 eV. This is indicating that Fe from the catalyst for the synthesis of the SWNTs was almost removed by the purification procedure. The reaction of 1-(bromoacetyl)pyrene with trimethylamine in THF gave a precipitate, which was recrystallized from chloroform to give a compound 1 that was identified by 1 H NMR, IR and elemental analysis. 9The maximum solubility of 1 in water was ca. 2 mM (1 M ¼ 1 mol dm À3 ). It was found that 1 does not form a micelle in water since the surface tension of 1 on water was almost constant at 69 AE 1 mN/m for concentrations below 2 mM.About 1 mg of the solid p-SWNTs and compound 1 was sonicated with a bath-type sonicator (Branson 2210) in water (1 ¼ 1 mM) for 1 h. Centrifugation of the suspension for 1 h gave a black-colored transparent supernatant aqueous dispersion/ solution (Figure 1). TEM measurements for the aque...

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There is growing interest in electrical/electrochemical energy-storage devices with both high power and high energy densities for possible application as auxiliary-power sources for electric and/or hybrid-electric vehicles. [1,2] Although lithiumion batteries are attractive power-storage devices with high energy density, their power density is generally low because of a large polarization at high charging-discharging rates. The large polarization is thought to be due to slow lithium diffusion in the solid active material and increases in the resistance of the electrolyte and in the electric resistance of the active materials upon increasing the charging-discharging rate. Therefore, in order to obtain high performance with both high power and high energy densities, it is important to design and fabricate nanostructured electrode materials that provide interconnected nanopaths for electrolyte-ion transport and electronic conduction. Mesoporous materials are quite attractive hosts for Li intercalation because of their large surface area, which decreases the current density per unit surface area; their thin walls, which shorten the Li-diffusion length in the solid phase; and their pores, which enable electrolyte ions to be transported smoothly. Actually, it has recently been reported that control of the porous structure of the active materials is effective in increasing the capacity of Li-intercalating electrode materials, even at high charging-discharging rates. [3][4][5][6] Porous materials are often considered to have the disadvantage of having low volumetric energy density, but this is not always the case for high-rate use: because of the low diffusion coefficient in the solid phase (10 -11 -10 -13 cm 2 s -1 ), only the thin surface layer of the host material is available for Li intercalation at high charging-discharging rates for bulk materials. On the other hand, hosts for Li intercalation generally have a low electronic conductivity, and thus electronic conduction paths are also required in the host material to decrease the polarization. Although conducting additives, such as acetylene black can be mechanically mixed with the host material in conventional Libattery electrodes, it is difficult to mix such large-sized conducting additives with mesoporous host materials, because the wall of the mesoporous structure is easily destroyed by conventional mixing techniques.As a new approach, we have synthesized single-walled carbon nanotube (SWNT)-containing mesoporous TiO 2 by a bicontinuous microemulsion-aided process using a dispersed aqueous solution of cut SWNTs (c-SWNTs) as the water phase of a water/surfactant/oil ternary bicontinuous microemulsion. Although there are some reports on surface modifications of carbon nanotubes with metal oxides, [7][8][9][10] this study is the first attempt to prepare a nanocomposite material with a mesoporous structure consisting of anatase TiO 2 and c-SWNTs. We also demonstrate that the Li-intercalation capacity at high charging-discharging rates increases dramatically for c-SW...

Transmission electron microscopy, atomic force microscopy, and UV-vis-NIR absorption spectroscopy have revealed that deoxyribonucleic acid (DNA) molecules dissolve singlewalled carbon nanotubes in an aqueous solution.

We describe the design of polycyclic aromatic compounds with high performance that dissolve single-walled carbon nanotubes (SWNTs). Synthetic amphiphiles trimethyl-(2-oxo-2-phenylethyl)-ammonium bromide (1) and trimethyl-(2-naphthalen-2-yl-2-oxo-ethyl)-ammonium bromide (2) carrying a phenyl or a naphtyl moiety were not able to dissolve/disperse SWNTs in water. By contrast, trimethyl-(2-oxo-2-phenanthren-9-yl-ethyl)-ammonium bromide (3) solubilized SWNTs, although the solubilization ability was lower than that of trimethyl-(2-oxo-2-pyrene-1-yl-ethyl)-ammonium bromide (4) (solubilization behavior observed by using 4 was described briefly in reference 4a). Transmission electron microscopy (TEM), as well as visible/near-IR, fluorescence, and near-IR photoluminescence spectroscopies were employed to reveal the solubilization properties of 4 in water, and to compare these results with those obtained by using sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (HTAB) as solubilizers. Compound 4 solubilized both the as-produced SWNTs (raw-SWNTs) and purified SWNTs under mild experimental conditions, and the solubilization ability was better than that of SDS and HTAB. Near-IR photoluminescence measurements revealed that the chiral indices of the SWNTs dissolved in an aqueous solution of 4 were quite different from those obtained by using micelles of SDS and HTAB; for a SWNTs/4 solution, the intensity of the (7,6), (9,5), and (12,1) indices were strong and the chirality distribution was narrower than those of the micellar solutions. This indicates that the aqueous solution of 4 has a tendency to dissolve semiconducting SWNTs with diameters in the range of 0.89-1.0 nm, which are larger than those SWNTs (0.76-0.97 nm) dissolved in the aqueous micelles of SDS and HTAB.

The shuttling process of alpha-CyD in three rotaxanes (1-3) containing alpha-cyclodextrin (alpha-CyD) as a ring, azobenzene as a photoactive group, viologen as an energy barrier for slipping of the ring, and 2,4-dinitrobenzene as a stopper was investigated. The trans-cis photoisomerization of 1 by UV light irradiation occurred in both DMSO and water due to the movement of alpha-CyD toward the ethylene group, while the photoisomerization of 2 occurred in DMSO, but not in water. No photoisomerization was observed for 3 in both water and DMSO. The activation parameters of 1 and 1-ref in DMSO are subject to a compensation relation between deltaS(double dagger) and deltaH(double dagger); however, in water, the deltaS(double dagger) terms are not compensated by the deltaH(double dagger) terms. Alternating irradiation of the UV and visible lights resulted in a reversible change in the induced circular dichroism (ICD) bands of trans-1 and cis-1. In contrast, after the UV light irradiation, the ICD band of trans-2 decreased without the appearance of any bands of cis-2. The NMR spectra of 2 in DMSO showed coalescence of the split signals for the methylene and for the viologen protons due to the shuttling of alpha-CyD. Both the NOE differential spectra for cis-1 in water after UV light irradiation and 2 in DMSO after heating to 120 degrees C showed the negative NOE peaks assigned to interior protons of alpha-CyD, suggesting that alpha-CyD in cis-1 exists at the one ethylene moiety, and alpha-CyDs in cis-2 and 2 heated in DMSO exist at the propylene moieties.

The cover picture shows the structure of a water-soluble C 60 -carrying single-chain ammonium amphiphile, 10-(N-Methyl-2-fulleropyrrolidyl)decyltrimethylammonium bromide (1; bottom left), and a typical transmission electron microscopic (TEM) image of 1 in aqueous solution (bottom right). The TEM image revealed that the aqueous solution of 1 forms both fibrous and disk-like aggregates 10 ± 12 nm thick through self-organization of 1 (top). The synthesis, morphology, and electrochemistry of the amphiphile 1 are described in detail by N. Nakashima et al. on p. 1766 ff.