Separation of single-walled carbon nanotubes (SWNTs) according to their handedness has been attracting growing interest. Our methodology to separate the enantiomers of SWNTs is based on molecular recognition with chiral diporphyrin nanotweezers. Herein, we report novel nanotweezers 1 consisting of two chiral porphyrins and phenanthrene in between. These nanotweezers 1 are rationally designed to discriminate diameter and handedness simultaneously by taking into account the relationship between the (n, m) selectivity and the structures of previously reported chiral nanotweezers. Owing to the relatively narrow cleft made by two porphyrins, the nanotweezers 1 showed high selectivity toward (6,5)-SWNTs possessing the smallest diameter among the major components of CoMoCAT-SWNTs. In addition, the chiral diporphyrin 1 discriminated the left- and right-handed structures of (6,5)-SWNTs, providing high enantiomeric excess (67% ee on the basis of the (6,5)-SWNTs with high optical purity recently reported by Weisman). In conclusion, only the single stereoisomer of (6,5)-SWNTs was highly enriched through the extraction of CoMoCAT-SWNTs with phenanthrene-bridged chiral diporphyrin nanotweezers 1.

A novel series of soluble conjugated random and alternating copolymers (PFO-TST) derived from 9,9-dioctylfluorene (FO) and 1,1-dimethyl-3,4-diphenyl-2,5-bis(2‘-thienyl)silole (TST) were synthesized by palladium(0)-catalyzed Suzuki coupling reactions. The feed ratios of FO to TST were 99:1, 95:5, 90:10, 80:20, and 50:50. Chemical structures and optoelectronic properties of the copolymers were characterized by elemental analysis, NMR, UV absorption, cyclic voltammetry, photoluminescence (PL), electroluminescence (EL), a photovoltaic cell, and a field effect transistor. The elemental analyses of the copolymers indicated that FO and TST contents in the copolymers were very close to the feed compositions. The random copolymers exhibited a PFO-segment-dominated UV absorption peak at ∼385 nm and a narrow band gap TST absorption at ∼490 nm. For the alternating copolymer, only a broad absorption band was found, demonstrating a mixed and TST-dominated electronic configuration. Compared with the solution PL, complete PL excitation energy transfer from the PFO segment to the TST unit could be achieved by film PL at lower TST content. It was found that the EL spectra of the copolymers with a device configuration of indium−tin oxide/poly(3,4-ethylenedioxythiophene)/poly(vinylcarbazole) (PVK)/copolymer/Ba/Al were red shifted and had better red light CIE coordinates with improved external quantum efficiency, compared with corresponding device performances without the PVK layer. With the alternating copolymer as the electron donor and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester as the electron acceptor, an energy conversion efficiency of 2.01% was achieved under an AM1.5 simulated solar light at 100 mW/cm2, which is among the highest values so far reported for bulk-heterojunction photovoltaic cells. The field effect hole mobility of the alternating copolymer is 4.5 × 10-5 cm2/(V s) using polyacrylonitrile as an organic insulator on a gate electrode.

Structural control of single-walled carbon nanotubes (SWNTs) is attracting enormous interest in view of their applications to nanoelectronics and nanooptics. Actually, more than 200 papers regarding separation of SWNTs have been published since 1998. In this review, they are classified into the following five sections according to the separation methods; electrophoresis, centrifugation, chromatography, selective solubilization and selective reaction. In each method, all literature is summarized in tables showing the separated objects (metallic/semiconducting (M/S), length, diameter, (n, m) structure and/or handedness), the production process of the used SWNTs (CoMoCAT, HiPco, arc discharge and/or laser vaporization) and the employed chemicals, such as detergents and polymers. Changes in annual number of publications related to this subject are also discussed.

We have been developing the methodology to discriminate the handedness and diameter of single-walled carbon nanotubes (SWNTs) through molecular recognition using chiral diporphyrin nanotweezers. Although relatively small diameters of SWNTs (<1.0 nm) were recognized well, nanotweezers were not able to form stable complexes with the SWNTs having the diameters >1.0 nm. In this context, we designed chiral diporphyrin with a much larger cavity, namely, "nanocalipers". The feature of the newly designed host molecule is: (1) long spacer with more than 1.4 nm consisting of three aromatic moieties; (2) nearly parallel orientation of the two porphyrins; (3) restricted conformation by biaryl linkages of the porphyrin-carbazole and carbazole-anthracene; (4) strong interaction of two porphyrins and anthracene with the surface of a SWNT through π-π stacking; and (5) stereogenic centers at the periphery of porphyrins discriminating helicity of SWNTs. As expected, we obtained optically active SWNTs with >1.0 nm in diameter and, unexpectedly, enriched metallic SWNTs over semiconducting ones. The optically active metallic SWNTs are identified for the first time, in addition to the optically active semiconducting SWNTs with such large diameters. The nanocalipers are found to recognize the diameter, handedness, and metallicity of SWNTs simultaneously.