Voltage-dependent artificial ion channels 3 and 4 were synthesized. Two cholic acid derivatives were connected through a m-xylylene dicarbamate unit at 3-hydroxyl groups. Asymmetries were introduced by terminal hydrophilic groups, carboxylic acid and phosphoric acid for 3 and hydroxyl and carboxylic acid for 4. Under basic conditions, these headgroups in 3 and 4 are expected to be dissociate into -1/-2 (pH 8.2) and 0/-1 (pH 7.2), respectively. Single ion channel properties were examined by a planar bilayer lipid membrane method under symmetrical 500 mM KCl at pH 8.2 or 7.2. When 3 and 4 were introduced into the bilayer membrane under application of positive voltage (a positive-shift method), the current values at positive applied voltage were larger than the corresponding ones at the negative applied voltage. The current-voltage plots were fitted by curves through a zero point to show clear rectification properties. The direction of rectification could be controlled by positive- or negative-shift methods. Vectorial alignment of terminal headgroup charges by the voltage-shift incorporation is essential for giving voltage-dependent rectified ion channels.

Water-dispersed organic base nanoparticles are utilized for the highly stable n-type doping of single-walled carbon nanotubes in aqueous dispersion. Long-term stability is often a critical challenge in the application of n-type organic conductors. The present n-type organic materials exhibit almost no degradation in the thermoelectric properties over months, in air.

Atomic doping is the most fundamental approach to modulating the transport properties of carbon nanotubes. In this paper, we demonstrate the enhanced thermoelectric properties of boron-substituted single-walled carbon nanotube (B-SWCNT) films. The developed two-step synthesis of large quantities of B-SWCNTs readily enables the measurements of thermoelectricity of bulk B-SWCNT films. Complementary structural characterization implies the unique configuration of boron atoms at the doping sites of SWCNTs, successfully enabling carrier doping to SWCNTs. The developed boron substitution, in combination with chemical doping, is found to substantially improve the thermoelectric properties.

The effects of polymer structures on the thermoelectric properties of polymer-wrapped semiconducting carbon nanotubes have yet to be clarified for elucidating intrinsic transport properties. We systematically investigate thickness dependence of thermoelectric transport in thin films containing networks of conjugated polymer-wrapped semiconducting carbon nanotubes. Well-controlled doping experiments suggest that the doping homogeneity and then in-plane electrical conductivity significantly depend on film thickness and polymer species. This understanding leads to achieving thermoelectric power factors as high as 412 μW m−1 K−2 in thin carbon nanotube films. This work presents a standard platform for investigating the thermoelectric properties of nanotubes.

The precise control of carbon nanotube structures plays a crucial role in understanding their intrinsic transport as well as in utilizing them for energy harvesting applications. In this paper, we elucidate that slight differences in the purity and diameter distribution of semiconducting single-walled carbon nanotubes (sc-SWCNTs) lead to the significant modulation of thermoelectric transport in their networks. Conducting polymers examined here enable the sorting of the sc-SWCNTs with desired purity and diameter distribution, as well as fixed solid state morphology. Particularly, the approximately tenfold enhancement of thermoelectric power factors is achieved by improving sc-SWCNT purity from 94% to 99% and increasing mean diameters from 1.0 to 1.2 nm. This work provides a rational design for boosting the thermoelectric properties of sc-SWCNT networks.

Enhancement of the thermoelectric properties of n-type single-walled carbon nanotubes, SWCNTs, is strongly desired for future thermopower source. We here report remarkable simultaneous enhancement of the thermoelectric properties by secondary...

The insolubility of single‐walled carbon nanotubes (SWCNTs) in most common organic solvents has been the cause of a bottleneck in their practical utilization. Aqueous SWCNT inks containing amphiphilic surfactants are widely used for processing including coatings and composite fabrication. Most practical processes are, however, designed to be compatible with organic solvents, generating a technological mismatch between production and utilization. This work reports on the surfactant‐assisted dispersion of SWCNTs in useful organic solvents, at up to quantitative yields. A feature extraction based on machine learning offers seemingly important, highly intuitive physicochemical factors that lead to efficient dispersion. These elucidated factors are associated not only with solvents–surfactant, but also solvent–SWCNT interactions. The organic SWCNT dispersion as well as its research methodology developed here may find widespread applications ranging from nanofluidics to functional materials design.

No abstract