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Boron nitride nanotubes (BNNTs) are simultaneously isolated and dispersed in organic solvents using a non‐aromatic and highly flexible polymer ethyl cellulose (EC). The colloidal dispersion containing individualized EC‐wrapped BNNTs is stabilized via non‐covalent functionalization through CH‐π and OH‐π interactions between EC and BNNTs. FESEM, TEM, UV‐VIS, FT‐IR, and TG analyses confirm the efficiency of using a simplified and less destructive method without prior heat treatment to enhance the purity and dispersibility of BNNTs in our designed system. This provides a practical approach to the purification and dispersion of BNNTs from a bulk‐produced source, for the fabrication of materials that require large amount of high‐quality BNNTs.

Heavy doping is inevitable for utilizing single-walled carbon nanotubes for wiring. However, the electrical conductivity of their films is currently as low as one tenth of the films made from typical metal pastes. Herein we report on metal-comparable electrical conductivity from single-walled carbon nanotube network films. We use ionic liquids and crown ether complexes for p-type and n-type doping, respectively. The encapsulation of counterions into carbon nanotubes promotes the conductivities in the range of 7000 S cm-1 , approximately ten times larger than those of undoped films.

We propose a transfer technique of single-wall carbon nanotube (SWCNT) films to be applied to a wide variety of flexible electronic devices. SWCNT films were first heat-treated in advance to remove solvents and dispersants in the films on high heat-resistant Cu substrates and were then poly (methyl methacrylate)-supported transferred onto low heat-resistant polyethylene terephthalate and paper substrates. We characterized the flexibility and electrical properties of the films transferred by this technique. The transferred films showed high flexibility and high electrical conductivity (8.4 × 104 ∼ 1.1 × 105 S/m). X-ray photoelectron spectroscopy measurements revealed that the transferred films were free from Fe residues. Although a slight amount of the Cu residues existed, it was found that the residues did not contributed to the electrical conduction. By using this technique, we enabled to fabricate highly flexible and highly electrical conductive SWCNT films on flexible substrates with low heat resistance, which provide further potential for the application of these films to flexible electronic devices.

Chemically-synthesized semiconductor nanostructures have the potentials for the exploration of unprecedented electronic and thermoelectric properties. Such materials possess the surface area much larger than their bulk forms, resulting that surface chemical functionalization may alter electronic properties. Here we report on the modulation of majority carriers in semiconductor nanowires by the addition of organic salts. The p-type nanowires were successfully converted to n-type forms to which large cations such as onium ions and metal-crown ether complexes are coordinated.

We here focus on the chiroptical response of a glutathione (GS)-protected bimetallic (AuAg)18 nanocluster containing comparable amounts of Au and Ag atoms. X-ray photoelectron spectroscopy (XPS) as well as the electrophoretic pattern allow us to determine the chemical composition of the nanocluster as Au8.5Ag9.5(SG)14. Chiroptical activity of the Au8.5Ag9.5 nanocluster is enhanced as compared to that of the corresponding monometallic Au counterpart, whereas that of bimetallic (AuAg)18 nanocluster with the atomic ratio of Au/Ag = 4.0 (Au14.4Ag3.6) decreases. Since thiolate-protected Au18 nanocluster has recently been revealed to consist of a face-fused Au9 bioctahedral kernel protected by one Au4(SR)5 tetramer, one Au2(SR)3 dimer, and three Au(SR)2 monomers, we use density functional theory (DFT) calculations to predict the lowest-energy structure of a model cluster compound Au9Ag9(SH)14 on the basis of this geometry, yielding a Agcore–Austaple intact core–shell configuration. This structure is in good agr...

The structure of carbon nanotubes and their electronic interaction with a matrix are important for extracting the unprecedented electronic properties, which have yet to be explored. Here we investigate the dispersibility of single-walled carbon nanotubes (SWNTs) in ionic liquid-derived polymers (PILs), revealed by cross-sectional transmission electron microscopy, infrared optical spectroscopy, and Raman spectroscopy. Surprisingly, SWNTs studied here are highly dispersed, at least down to 7.5 nm-fibres, in a trimethylammonium-suspended PILs. Based on this discovery, we found that the well-dispersed and almost fully dispersed SWNTs in PILs are responsible for the enhanced thermoelectric properties, a future energy harvesting technique.

Noncovalent interactions play a critical, but not yet understood, role in enhancing the thermoelectric properties of carbon nanotube composites. We herein report the dispersion of synthetic MoS2 flakes and their self-assembly with single-walled carbon nanotubes via in-plane and multipoint S-π interactions. The hybridization of MoS2 and carbon nanotubes leads to improved electrical and thermoelectric transport, and resulted in a tenfold enhancement of the thermoelectric figure-of-merit of nanotube-based films. The present technique could contribute to advancing the flexible energy materials that harvest abundant waste heat.

One-dimensional coordination polymers (1D-CPs) tend either to dissociate into constitutive ligands and metals readily in solution, or to aggregate randomly and amorphously, which prevents them from widespread application. In the present research, 1D-CPs comprising bridging dipyrrin ligands and divalent metal ions (Zn2+, Ni2+, and Cu2+) are synthesized. A liquid/liquid interfacial reaction gives rise to single crystals suitable for X-ray diffraction analysis: A dichloromethane solution of the ligand is layered with aqueous metal(ii) acetate, such that the coordination reaction proceeds at the liquid/liquid interface. Isolated single fibers of the zinc coordination polymer may be exfoliated from the single crystal or bulk solid upon ultrasonication. Atomic force microscopy (AFM) detects the isolated fibers with lengths of more than several μm. The exfoliated 1D-CP wires feature good processability, realizing a conjugate with single-wall carbon nanotubes (SWCNTs), and a thin film on a transparent SnO2 electrode. The processed materials show electric conversion ability: For example, the modified SnO2 electrode serves as a photoanode for a photoelectric conversion system. The designability and tunability of the present 1D-CPs is demonstrated by a ligand modification, affording a luminescent property and an extension of the photoelectric conversion response to longer wavelengths.

We examine the effect of UV/O3 oxidation on the thermoelectric properties of semiconducting carbon nanotube films. The oxidative UV/O3 treatment leads to the introduction of epoxy and carbonyl groups and a significant increase in the thermoelectric power factor up to 140 μW m−1 K−2. This power factor is three times larger than that of chemically-doped films because of the enhanced Seebeck coefficient. Characterization with Raman and mid-IR absorption/extinction spectroscopy reveals that the UV/ozone treatment results in simultaneous charge carrier doping and defect formation. This simple way of enhancing thermoelectric properties is suitable for the production of large-area, flexible thermoelectric devices based on semiconducting carbon nanotubes.

The thermally-triggered n-type doping of single-walled carbon nanotubes is demonstrated using 1,1'-bis(diphenylphosphino)ferrocene, a novel n-type dopant. Through a simple thermal vacuum process, the phosphine compounds are moderately encapsulated inside single-walled carbon nanotubes. The encapsulation into SWNTs is carefully characterized using Raman/X-ray spectroscopy and transmission electron microscopy. This easy-to-handle doping with air-stable precursors for n-type SWNTs enables the large-scale fabrication of thermoelectric materials showing an excellent power factor exceeding approximately 240 μW mK(-2) .

The self-assembly of Prussian blue nanoparticles and single-walled carbon nanotubes is demonstrated by using analytical TEM. The nanotube composites containing compositionally tunable Prussian blue...

Luminescent composite materials based on semiconductor nanocrystals (NCs) with ionic liquid and subsequently with an ionic liquid-based polymer have been prepared. Cationic CdTe NCs passivated with thiocholine bromide (TCB) were prepared in an aqueous phase and easily transferred to hydrophobic ionic liquids by means of a simple biphasic extraction process without using any surfactant. TCB-capped CdTe NCs were stably dispersed in hydrophobic ionic liquids and their absorption spectra and optical density (extinction coefficient) were maintained even after the extraction. While the emission peak position was also identical with the original one, its intensity increased almost twice. The efficient extraction and photoluminescence enhancement of CdTe NCs were generally observed for the hydrophobic ionic liquids based on both bis(trifluoromethanesulfonyl)imide (TFSI) and hexafluorophosphate (PF6) anions. However, the generation of a trace of hydrofluoric acid gradually collapsed the CdTe NCs in a PF6-based ionic liquid. A polymerizable ionic liquid which possesses an acrylate group could also extract the CdTe NCs from water and gave a CdTe NC-polymer composite with strong luminescence by the polymerization of ionic liquid. Copyright © 2008 John Wiley & Sons, Ltd.

We demonstrate a photopolymerization sensitized by CdTe nanocrystals in room temperature ionic liquid. The kinetics of photoinduced electron transfer from cationic CdTe nanocrystals to polymerization initiators in several kinds of ionic liquids is also studied. From the analyses of photoluminescence quenching measurement, the electron transfer rates from CdTe nanocrystals to organic electron acceptors are anomalously large in the ionic liquid medium.

Semiconductor nanocrystal has been demonstrated as a photosensitizer for the photopolymerization of acrylic monomer in combination with an onium salt coinitiator. An acrylic monomer designed based on ionic liquid was able to dissolve both coinitiator and cationic CdTe nanocrystals and polymerized by visible irradiation. Since the onium salt has no sensitivity in the visible region, the polymerization occurred by the indirect activation of coinitiator. Emission quenching study of CdTe nanocrystals with the coinitiator and electrochemical studies on them revealed that the polymerization was initiated by the photoinduced electron transfer from the CdTe nanocrystal to the onium salt. The polymerization kinetics was compared with the organic dye sensitized photopolymerization system by monitoring the conversion of monomer with FT-IR. The large extinction coefficient and long excitation lifetime of CdTe nanocrystals were considered to be responsible for the efficient electron transfer with onium salt and the ef...

Size- and temperature-dependence of photoluminescence from CdTe nanocrystals has been studied in a room-temperature ionic liquid. With temperature decreasing from room temperature to 14 K, the photoluminescence intensity increases considerably and the emission quantum yield reaches almost 0.95 below 100 K. The emission profile below 150 K can be deconvoluted into two Gaussian peaks; one is an excitonic band and the other is a trap-related one. The temperature dependence of each band is characterized with regard to its intensity and energy. The energy splitting in the exciton fine structure of the zinc-blende CdTe nanocrystal is clearly demonstrated, and its degree can be estimated to be 5 and 13 meV for the larger (3.0 nm) and the smaller (1.9 nm) CdTe nanocrystals. The existence of the fine structure in the trap emission state and its size-dependent nature are also proposed.

Single-walled carbon nanotubes are promising candidates for light-weight and flexible energy materials. Recently, the thermoelectric properties of single-walled carbon nanotubes have been dramatically improved by ionic liquid addition; however, controlling factors remain unsolved. Here the thermoelectric properties of single-walled carbon nanotubes enhanced by electrolytes are investigated. Complementary characterization with absorption, Raman, and X-ray photoelectron spectroscopy reveals that shallow hole doping plays a partial role in the enhanced electrical conductivity. The molecular factors controlling the thermoelectric properties of carbon nanotubes are systematically investigated in terms of the ionic functionalities of ionic liquids. It is revealed that appropriate ionic liquids show a synergistic enhancement in conductivity and the Seebeck coefficient. The discovery of significantly precise doping enables the generation of thermoelectric power factor exceeding 460 µW m–1 K–2.

We examined mesoporous TiO(2) as a photosensitizer and template for creating hybrid TiO(2)-polypyrrole materials. Optical excitation of mesoporous TiO(2) was used to generate the electronic potential necessary for the oxidation and polymerization of the pyrrole monomer. The photopolymerization process was monitored by the quartz crystal microbalance, nitrogen sorption, and thermogravimetric techniques. In situ generation of polypyrrole was observed to be self-limiting after approximately 20-30% filling of the mesoporous TiO(2) network. In situ generation of a complementary phase by means of charge transfer from an active host phase represents an alternative means of assembling hybrid inorganic-organic materials with potential applications ranging from electrocatalysis to photovoltaics.

Thiol-capped CdTe nanocrystals are synthesized directly in an ionic liquid by means of microwave irradiation in a similar manner to an aqueous synthetic route. The combination of ionothermal synthesis with microwave heating offers a quick route to highly luminescent CdTe nanocrystals with zincblende crystal structure. The growth of nanocrystals is considered based on a universal growth model under the assumption that the growth rate exponentially converges as the reaction proceeds. The analysis indicates that the ionothermal conditions with high temperature promote the steady growth of nanocrystals after the nucleation, while the microwave irradiation plays a pivotal role in the limiting step of the growth of nanocrystals including the activation of nanocrystal precursor and the subsequent formation of nuclei.