Carbon nanotubes (CNTs) are materials of interest in many fields of science and technology because of their remarkable electronic, mechanical, and thermal properties.[1] Soluble CNTs [2] and CNT-polymer nanocomposites, including CNT-DNA (RNA), possess unique superstructures. [3] It is known that patterned carbon nanotubes are formed on prepatterned substrates or prepatterned catalysts during the synthesis of carbon nanotubes. [4] Jiang and co-workers [5] reported the selfassembly formation of large-scale micropatterns on aligned multiwalled carbon nanotubes by the aid of the capillary action of water. Very recently, Li et al. [6] and Zheng and coworkers [7] described polymer-crystallization-driven periodic patterning on CNTs and controlled two-dimensional patterns of spontaneously aligned CNTs from DNA-wrapped CNTs on a SiO 2 surface. We now report the discovery that self-assembly of single-walled CNTs (SWNTs) with a honeycomb structure is spontaneous on solid substrates by simple solution casting of a SWNT-lipid conjugate (complex 1). Since the first report by François and co-workers [8] that selforganized honeycomb structures are formed from star-shaped poly(styrene) or poly(styrene)-poly(paraphenylene) block copolymers in carbon disulfide under flowing moist gas, considerable attention has focused on this area; that is, such superstructures are formed from the solution casting of: i) symmetric diblock copolymers, [9] ii) rod-coil diblock copolymers, [10] iii) a coil-like polymer, [11] iv) ion-complexed polymers, [12] lipid-packaged Pt complexes, [13] v) poly(D,L-lactic-co-glycolic acid), [14] and vi) polysulfone.[15]As shown in Figure 1, complex 1 was easily obtained by the so-called polyion-complexed method; [16] that is, the mixing of an aqueous solution of shortened-SWNTs (s-SWNTs-COO -Na + ) and molecular bilayers of tridodecylmethylammonium chloride (3 C 12 N + Cl -) [17] in water produced a precipitate, which was collected to obtain complex 1. Mioskowski and coworkers [18] used lipids to dissolve CNTs in water; they described the formation of a supramolecular assembly of the lipids-multiwalled CNTs. The Raman spectra of the s-SWNTs and complex 1 were virtually identical (see Fig. S1 in the Supporting Information). The thermogravimetric analysis (TGA) curve (data not shown) of complex 1 revealed that the composition ratio, s-SWNTs/3 C 12 N + , was roughly 1:1 (w/w). Complex 1 was insoluble in water and in organic solvents, such as alcohols, acetone, and ethyl acetate, but soluble in several organic solvents including dichloromethane, chloroform, benzene, and toluene. In Figure 1, photographs of complex 1 and s-SWNTs-COOH only in chloroform are shown (for photographs in other solvent systems, see Fig. S2 in the Supporting Information). It is clear that complex 1 produces a transparent black solution/dispersion in the solvent. The asymmetric and symmetric methylene stretching vibrations in the Fourier transform infrared (FTIR) spectrum of a cast film of complex 1 appeared at 2924 and 2854 cm -1 , respect...

No abstract

We designed and synthesized 4-dodecyloxybenzenediazonium tetrafluoroborate (1), which preferentially reacts with metallic single-walled carbon nanotubes (SWNTs) by kinetic control. We first determined the suitable experimental conditions for the preferential reaction of 1 with individually dissolved SWNTs by monitoring the decrease in absorbance for the metallic SWNT in the range of 400-650 nm in the absorption spectrum of the SWNTs. The reacted SWNTs were thoroughly rinsed with THF to obtain THF-insoluble SWNTs. The Raman spectrum of the THF-insoluble SWNTs showed a strong peak near 180 cm(-1), which corresponds to a semiconducting breathing band. The metallic breathing bands (approximately 220 cm(-1)) and Breit-Wingner-Fano (BWF) modes (1520 cm(-1)) corresponding to the metallic SWNTs were much weaker than those of the pristine SWNTs. We also confirmed that metallic peaks in the range of 400-650 nm in the absorption spectrum of THF-insoluble SWNTs that were individually dissolved in an aqueous micelle of sodium cholate were almost nondetectable. All the results indicate that the THF-insoluble SWNTs are semiconducting.

No abstract

Acrylic acid (AAc) and diallyldimethylammonium chloride (DADMAc) were photograft-polymerized onto the surfaces of perfluorosulfonic acid (Nafion) membranes using 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamide (ACMP) or Mohr's salt as a polymerization initiator. The degree of photografting changed from 1 wt% to 13.7 wt% depending on the experimental conditions (monomer, initiator and UV-light irradiation time). Shortened single-walled carbon nanotubes (s-SWNTs) prepared by a mixed acid treatment were immobilized in the grafted Nafion films by two different methods (methods A and B). Method A is a covalent-modification of the s-SWNTs with an acrylic acid (AAc)-photografted Nafion membrane in the presence of a diamine and a condensation reagent. Method B uses ion-complexation between the s-SWNTs with an anionic charge and a DADMAc-photografted Nafion film with a cationic charge. Based on the characterization of the hybrid materials by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), it was found the s-SWNTs were immobilized into the photografted-Nafion films by both methods.