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Electrically conductive nano-fillers, such as carbon nanotubes (CNT), carbon black (CB) and carbon fibers (CF), have been of great interest to polymer scientists because their reinforcement into polymer matrices gives rise to conductive thermoplastics. However, it is found that their orientation distributions after the injection molding process reduce the interparticle contacts between particles and thus decreases the electrical conductivity. In this study, it is shown that electrically conductive networks can be re-tailored through post-processing annealing at a temperature higher than the glass-rubber transition temperature of the polymer. We demonstrate these results for polycarbonate (PC) composites produced by injection molding using different fillers including single-walled CNT (SWCNT), multi-walled CNT (MWCNT), CB and CF. The annealing-induced increase in the electrical network path is proved by electrical conductivity improvement. It can be explained by a transition from aligned, unconnected particles before annealing to an interconnected network after annealing through the viscoelastic relaxation of the polymer. Compared with CB- and CF-based PC composites, CNT-based PC composites at low contents exhibited outstanding conductivity improvement after isothermal annealing for several minutes. Moreover, the CNT network helps to keep the composite shape and strength after annealing. Especially, SWCNT nanocomposites have potential to rapid the tailoring process of the electrical network without significant size extension and strength reduction. The post-processing annealing may exploit the future applications of injection-molded CNT polymer composites.

Fibres composed of carbon nanotubes (CNT) can be used to make lightweight materials with high mechanical strength and electrical conductivity. However, the reported properties have been much poorer than those of the individual CNT. To address this discrepancy, it is necessary to elucidate the relationship between the fibres' structure and their properties. Here, we systematically investigated the CNT length and fibre density dependences of the electrical and the mechanical properties of CNT fibres produced by the wet-spinning method. The obtained specific conductivities of the fibres were almost proportional to the effective CNT lengths, whereas such correlations were less apparent for the fracture strengths and Young's moduli.

To realize the potential applications of carbon nanotube (CNT) polymer composites produced using injection molding, the CNT networks in composite parts need to be tailored and controlled by processing conditions. In this study, microinjection-molded polycarbonate matrix composite filled with multi-walled carbon nanotubes were prepared from twin-crew extruded pellets using plate-shaped double-cavity. The CNT electrical network in these microinjection-molded parts was observed directly in both cross-section and longitudinal-section using the lock-in thermography technique (LIT). The results showed the skin/shell-core structure with the high degree of inter-connected CNT in the core region, the inhomogeneous conductivity along the injection direction and the lower conductivity near the gate. This is confirmed by inspecting the scanning electron microscopy and polarized Raman mapping images. The effect of total injection molding time, mold temperature and melt temperature on the electrical network and conductivity were also investigated. The observed conductivity variations were explained in term of the processing conditions that induced the CNT network structures in the skin and core regions.

Cellulose nanofibers (CNFs) with different degrees of fibrillation are prepared by the mechanical fibrillation of kraft pulp using wet disk milling, and dispersions of the prepared CNFs were subjected to differential centrifugal sedimentation (DCS) in order to estimate the diameter distributions of the CNFs. The low-fibrillated CNFs (fiber diameter (d):10 μm) had a weak reinforcing effect on natural rubber (NR), while the medium-fibrillated CNFs (d: 0.1-10 μm) dramatically improve the initial modulus and decrease the elongation at break. The high-fibrillated CNFs (d:0.1 μm) enhanced the tensile strength even further while maintaining the elongation at break. The reinforcing mechanism of the NR composites reinforced by the CNFs (NR-CNFs) was confirmed by field-emission scanning electron microscopy imaging, dynamic mechanical analysis, and toluene uptake measurements. It was concluded that these characteristic mechanical properties of the NR-CNFs were determined by the morphologies of the CNFs. The branching structure of the medium-fibrillated CNFs affected high improvement of the initial modulus, and the network formed by the high-fibrillated CNFs were involved in enhancement of the tensile strength without compromising viscoelastic properties. Understanding the effect of their diameter distribution can potentially reduce the production cost of CNFs and thus expand their applicability.

Quantification of the cellular uptake of nanomaterials is crucial for studies of their toxicity and medical applications. However, our knowledge of the behaviors of carbon nanotubes (CNTs) in cells or tissues remains incomplete due to the lack of appropriate methods for quantitative analysis. Here, we present a unique methodology for quantitatively assessing the cellular uptake of CNTs, taking advantage of their absorption of light in the near-infrared region. Measurement of CNT concentration in cell lysates by monitoring absorbance at 750 nm enabled highly accurate quantification of CNTs accumulated within cells. In a comparative study of eight commercially available CNTs with dynamic size ranging from 30 to 400 nm, we obtained the first quantitative evidence that cellular uptake of CNTs by RAW264.7 macrophages depends on their sizes, specifically on the widths of their bundles in dispersion, regardless of type or manufacturer. Specifically, uptake of CNTs increased linearly with dynamic size, and cytotoxicity increased along with uptake.

We have measured the absorption and Raman spectral change induced by the irradiation of e-beam. By the irradiation of e-beam on SWNTs thin films, the intensity of defect related Raman band increase, and the peak energy of IR absorption bands shift to the higher energy side. These results indicate that the origin of infrared band is due to the plasmon resonance of finite-length SWNT. We have estimated the effective tube length and defect density from IR absorption peak energy.

A nondestructive method of evaluating the curing degree (crosslinking density) of cured rubbers and their nanocomposites based on attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was proposed and applied to fluorine-based rubber (FKM), in which triallyl-isocyanurate (TAIC) was employed as a curing agent. ATR-FTIR spectroscopy demonstrated that the C O band in TAIC at 1699 cm−1 decreased in intensity and broadened as the curing reaction progressed. A calibration model relating the crosslinking density in the FKM with the full width at half maximum (FWHM) of the band of the C O bond was developed. The model showed good applicability to both FKM and FKM nanocomposites with various nanofillers, including single- and multi-walled carbon nanotubes (CNTs), carbon black and silica particles. Interestingly, when the fillers, especially CNTs, were added to the rubber, the FWHM was more sensitive to the change in the crosslinking density than the change in the Young's modulus.

In this work, a new poly(9,9-dioctylfluorene) (PFO) derivative (named PFIID) with the large conjugated planar surfaces was designed and synthesized, and the ability to sort sc-SWCNTs was investigated in detailed. The absorption spectra of sorted SWCNT solutions demonstrated that PFIID exhibited the ability to selectively and efficiently sort sc-SWCNTs from commercial arc discharge carbon nanotubes. The underlying separation mechanism was studied with the aid of photoluminescence excitation (PLE) spectra and the molecular dynamic simulation. It was found that the simulation results agreed well with the experimental data. PFIID-sorted sc-SWCNTs were acted as the channel materials to construct printed thin-film transistors (TFTs) and nitrogen dioxide gas sensors. Printed SWCNT TFTs exhibited superior performance with good uniformity, high on/off ratios (∼106), high effective hole mobility (∼29.8 cm2 V−1 s−1) and small subthreshold swing (SS) (142–163 mV/dec) at low operating voltage (±2 V). NO2 gas sensors also showed good performance with high sensitivity (ΔR/Ro∼96%), fast response (30 s), good stability and the recovery time of 30 s when exposed to 60 ppm NO2 at room temperature. Both of the sensitivity and recovery time are one of the best performances reported for NO2 gas sensors at room temperature.

We study single-walled carbon nanotube (SWCNT) growth from Pt catalysts by a cold-wall chemical vapor deposition (CVD) method in a high vacuum using a nozzle injector for the ethanol gas supply. By optimizing the ethanol pressure, we could grow SWCNTs between 330 and 700 °C, and the optimal ethanol pressure to obtain the highest SWCNT yield was reduced as the growth temperature decreased. Using transmission electron microscopy, Raman spectroscopy and photoluminescence measurements, we determined the diameters and chirality distribution of the SWCNTs and showed that the grown SWCNTs have a narrow chirality distribution and that the diameters of most SWCNTs were below 1.0 nm. In addition, based on the size distribution and the chemical states of Pt catalyst particles, we proposed a growth model of the SWCNTs.

Improvement of the properties of polymer materials can extend the applicable fields of their usage. In this study, we present that the dispersibility of carbon nanotubes (CNTs) plays a critical role in the thermal stability of CNT/silicone rubber nanocomposites. Appropriate dispersion, which can be confirmed by a Raman mapping technique, can increase the temperatures at 5% weight loss (Td,5%) of the CNT/silicone rubber nanocomposites. Moreover, thermal aging tests have revealed that CNT/silicone rubber nanocomposites fabricated by appropriate dispersion process can retain rubbery elasticity after 7 days at 280 °C, at which condition pristine silicone rubber become embrittled only after one day. Furthermore, we found that these improvements in thermal stability of CNT/silicone rubber nanocomposites can be achieved by loading only of 0.05 wt% CNT in optimized conditions. Our findings indicate that appropriate dispersion can extract the potential of CNTs, and can impart objective properties effectively to their nanocomposites.

We showed that vertically aligned single-walled carbon nanotubes (VA-SWCNTs) can be grown by alcohol chemical vapor deposition (CVD) with an Ir catalyst in a cold-wall CVD system. VA-SWCNTs were grown on SiO2/Si substrates without any buffer layers under an ethanol pressure of 1 × 10−1 Pa at 800 °C. The SWCNT length increased with increasing growth time. The VA-SWCNT thickness reached almost 5 μm for a growth time of 180 min. Raman and photoluminescence spectroscopies showed that the diameters of the grown SWCNTs were mainly between 0.8 and 1.1 nm; this is much smaller than those of VA-SWCNTs grown with Fe and Co catalysts in previous studies. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectroscopy showed that the Ir catalyst retained the metallic state during SWCNT growth. We suggest that highly efficient suppression of aggregation, an appropriate carbon–Ir bond strength and dissociation of ethanol molecules led to the growth of vertically aligned small-diameter SWCNTs with an Ir catalyst.

Boron neutron capture therapy requires boron carriers that can deliver abundant boron to tumors. To obtain such a carrier, we have prepared boron nitride (BN) containing carbon nanohorn aggregate (CNH) by heating CNHs with ammonia borane at 800 °C. The obtained BN-CNH had a C:B:N mole ratio of 5:2:2, as estimated from X-ray photoemission spectroscopy. The nanohorn tubule walls had graphene–BN double layers or BN–graphene–BN triple layers. The graphite-like sheets constituting the CNHs together with the nanohorn tubules also had BN layers on their surfaces. BN release from BN-CNH was small in cell culture medium, and about 70–80% of the BNs remained on the CNHs. For selective accumulation in tumor cells, the BN-CNH was coated with phospholipid polyethylene glycol having folate (BN-CNH/PLPEG-FA). In primary cell culture experiments, human tumor KB cells overexpressing FA receptors ingested more BN-CNH/PLPEG-FA than those without FA, while normal human FHs 173We cells did not show preferential uptake due to FA. The quantity of boron per cell exceeded the criteria required for boron neutron capture therapy by more than 100 times in the cell experiments. These results suggest that BN-CNH is potentially a good carrier for boron neutron capture therapy.

In this work, we investigated the ability of several poly(9,9-dioctylfluorene) (PFO) derivatives to selectively separate semiconducting single-walled carbon nanotube (sc-SWCNT) from commercial arc discharge SWCNTs. The results illustrated that the separation efficiency of PFO derivatives and the stability of sc-SWCNT inks increased with the sizes of conjugated systems in subunits. The relative height of sc-SWCNTs peaks and the shelf life of sc-SWCNT inks can be up to 0.71 and 5 months when being sorted by poly{(9,9-dioctylfluorene)-2,7-diyl-alt-[3,6-dithiene-2-yl-2,5-di(2-ethylhexyl) pyrrolo[3,4-c] pyrrole-1,4-dione-5,5"-diyl} (PF8-DPP). Electrical properties of thin film transistors (TFTs) and sensors based on PF8-DPP-sorted sc-SWCNTs were also investigated. Printed TFTs showed excellent performance with on/off ratios of 106, effective mobility of 22.6 cm(2) V(-1)s(-1), subthreshold swing of 178 mV/dec and small hysteresis at low operating voltage. PF8-DPP-sorted sc-SWCNTs were used as sensing material for selectively detecting ammonia gas at room temperature. Upon exposure to 0.6% NH3 at room temperature, the ammonia sensors based on sorted sc-SWCNTs exhibited high sensitivity (Delta R/Ro similar to 54.4%), fast response (30 s) and good stability. The desorption rate of NH3 from carbon nanotube surface can be controlled by tuning the voltage of heating resistor integrated into the platforms, and excellent reversibility can be achieved within 1 min at applied voltage of 1.5 V. (C) 2015 Elsevier Ltd. All rights reserved.

We performed the ultraviolet photoemission spectroscopy study of single-walled carbon nanotubes (SWCNTs) encapsulating C 59 N. The work function of the C 59 N@SWCNT is estimated to be larger than that of the SWCNT. The π states of the SWCNT shift toward the Fermi level upon encapsulation of C 59 N. The C 59 N pea spectrum is roughly similar to that of the (C 59 N) 2 , but some peaks shift. The results suggest a small charge transfer from the SWCNT to the C 59 N pea, which is in contrast to the previously reported n-type FET characteristics. This discrepancy is probably due to the difference in the molecular form of C 59 N.

We report ballistic charge transport phenomena observed in carbon nano-peapod quantum dots. We find atom-like behaviors (shell filling) sensitive to applied back-gate voltages (V"b"g) by single electron spectroscopy. Doubly degenerate electronic levels are found only around ground states at very low V"b"g. Those correlations with the presence of nearly free electron states unique to the peapods are discussed. Moreover, we find power laws in conductance versus energy relationships with anomalously high values of power, which are strongly associated with shell filling to the doubly degenerate levels. It is investigated that the powers originate from Tomonaga-Luttinger liquid via the occupied doubly degenerate levels. These results imply that a ballistic charge transport is still preserved at low-V"b"g regions in carbon nano-peapod quantum dots in spite of the presence of the encapsulated C"6"0 molecules.

The total quenching rate constants (sum of physical quenching and chemical reaction) of singlet oxygen 1 O 2 by various fullerenes (C 60 , C 70 , C 76 , C 82 , La@C 82 , Ce@C 82 , Ce 2 @C 80 ) were determined. The 1 O 2 quenching capabilities of C 82 and endohedral metallofullerenes are found to be comparable to that of β-carotene, a well-known strong 1 O 2 quencher. This remarkable 1 O 2 quenching by metallofullerenes is explicable in terms of a combination of energy and charge transfer processes.

The deactivation rate constant of singlet oxygen 1O2 by single-wall carbon nanohorns (SWNHs) was determined. The estimated rate constant by SWNHs, 8 × 104 L g−1 s−1, was significantly larger than the physical quenching rate constant by α-Tocopherol, 0.9 × 104 L g−1 s−1. The origin of this remarkable efficiency of SWNHs for 1O2 deactivation is ascribed to the unique curvature of the graphitic tube in their horn shaped structure.

Proteins were screened by preparing dispersions of SWNTs to investigate the driving force of the interaction between single-walled carbon nanotubes (SWNTs) of mean diameter 1 nm and water-soluble proteins. Egg white lysozyme (LYS) and bovine serum albumin (BSA) dispersed SWNTs, whereas papain and pepsin could not. Far-UV circular dichroism spectra indicated that the LYS and BSA molecules that coat SWNT surfaces were partially denatured. From the amino acid composition, we ascribed the main driving force to the hydrophobic interactions between the side-wall of the SWNT and the inner hydrophobic domain exposed to the solvent during the three-dimensional change of the protein induced by sonication.

Band gap photoluminescence (PL) behaviors of single-walled carbon nanotubes (SWNTs) grown by the methods of chemical vapor deposition and pulsed-laser vaporization are investigated over the wide diameter range (≈0.8–1.4 nm). The peak intensity of the PL signals strongly depends on chirality and the ‘(2n + m) family type’ of SWNTs. Based on the PL results, a population analysis of these SWNTs is conducted by combining the calculated PL yields for each (n, m) tube. The results are directly compared with the histograms of diameter distributions estimated by the transmission electron microscope (TEM) observations to check the validity of the analysis.

Double-wall carbon nanotubes (DWNTs) have been selectively synthesized by catalytic chemical vapor deposition of alcohol over Fe/Co loaded mesoporous silica. The as-grown carbon nanotubes are purified using a multi-step process involving heat treatment in air followed by alkali and acid treatments. The nanotubes are characterized as-grown and after each step of the purification stage by thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. It is observed that most of the mesoporous silica and metal particles have been removed from the as-grown nanotubes by these treatments. The carbon content of the nanotube material obtained after the purification is found to be more than 90 wt%.

Ultraviolet photoelectron spectra (UPS) of metallofullerenes with multiple atoms inside the cage, Ti 2 @C 80 , Ti 2 @C 84 and Y 2 C 2 @C 82 , have been measured with a synchrotron orbital radiation light source. The spectra were compared with those of other metallofullerenes. Spectral onsets of these metallofullerenes are 0.7–0.8 eV, which is close to those of group II metal atom encapsulated metallofullerenes but much larger than those of other group III mono-metal atom encapsulated ones. The spectra are compared with molecular orbital calculation to estimate the amounts of transferred electrons and the cage structure.

Photoelectron spectra of the metallofullerene Tb@C82 (I) were measured using a synchrotron radiation source. The band intensity of the Tb@C82 (I) spectra was found to depend on the incident photon energy, as has been observed for other fullerenes. The spectral onset energy is 0.25 eV below the Fermi level. This value is nearly equal to that for La@C82 (I) and is smaller than that for the empty C82. The spectral shapes of Tb@C82 (I) resemble those of La@C82 (I).

Ultraviolet photoelectron spectra of metallofullerene Ti 2 @C 80 were measured using a synchrotron orbital radiation light source. The band intensity of the Ti 2 @C 80 spectra was found to be dependent on the incident photon energy, similar to observations for other fullerenes. The spectral onset energy was 0.8 eV below the Fermi level, and was comparable to that of Ca@C 82 , but smaller than that of the empty C 80 . Using comparisons between UPS and molecular orbital calculations, the number of electrons transferred from the titanium atom to C 80 was estimated.

We present transport properties of various fullerene nanopeapods used as channels of field effect transistors (FET). C 6 0 and C 7 8 fullerenes and Gd@C 8 2 and Dy@C 8 2 metallofullerenes peapods FET show both p- and n-type ambipolar behavior. In case of C 9 0 -peapods, all devices have shown so far metallic properties. These novel electronic properties of the peapods can be explained by the so-called band-gap modulation originated from the encaging fullerenes and metallofullerenes in nanotubes.

Double-wall carbon nanotubes (DWNTs) have been synthesized in high-yield (>80%) by catalytic chemical vapor deposition (CCVD) of acetylene over well- dispersed metal particles (typically Co/Fe binary system) embedded in heat-resistant zeolites at temperatures above 900 °C. The synthetic yield of DWNTs has been sensitively affected by reaction conditions of the CCVD such as zeolite support materials, the sintering of the metal particles, hydrocarbon sources and reaction temperatures. High-resolution transmission electron microscopy together with Raman spectroscopy shows that the outer tube diameter varies from 3 to 6 nm with inner–outer tube separations of 0.36–0.37 nm, which is much larger than the interlayer distance of graphite (0.335 nm).

A metallofullerene, Gd@C82, encapsulated in the inside space of single walled carbon nanotube (SWNT) has been identified as an STM image of a carbon cage and a Gd atom by a measurement of the tunnel currents onto the SWNT surface. This fact indicates that there is a substantial local interaction between the wall of SWNT and the Gd ions close to the wall. The origin of this interaction is not yet clear, but its existence has also been supported by the results of axially- and peripherally-resolved STS measurements around the Gd ion sites in the peapod.

We report a simplified production method for single-wall carbon nanotubes (SWNTs) by hot-filament assisted chemical vapor deposition (HFCVD) using pure alcohol vapor (ethanol, methanol and 2-propanol) as a carbon source. Under the optimized conditions, high-purity SWNTs are synthesized for the first time in large quantities. Raman spectra of the synthesized SWNTs show similar G/D ratios and the peak distribution of radial breathing mode to those obtained by the conventional CVD method with an electric furnace. The efficiency of the SWNTs synthesis has been increased by the hot-filament-induced pyrolysis of carbon sources, which promises an easy scale-up of the production of SWNTs at a low cost.

Lineshapes of radial breathing mode (RBM) Raman scattering from single-wall carbon nanotubes (SWNTs) encasing the fullerenes vary depending on the sizes of fullerenes. The lineshape fit using Lorentzian lines to the spectrum indicates downshift of ωr (RBM frequency) for most lines as compared with those observed in empty-SWNTs, except for one upshifted line associating with the stress to the tube-wall from the inside fullerenes. The smallest limit of tube diameters (d) is determined from this upshifted line, and they are resulting to be ∼1.37 nm for C60, ∼1.45 nm for both C76 and C78, and ∼1.54 nm for C84 when using ω r ( cm −1 )=246/d ( nm ) .

Ultrafast temperature rise after the deactivation of the electronically excited state of 2-hydroxybenzophenone in various solvents is investigated by two photothermal techniques; temperature lens and acoustic peak delay methods, and by the population grating technique. The results from these methods show that the thermalization process takes place by two phases; fast (

We report the first isolation of a series of Sm-containing metallofullerenes, Sm@C 74 , Sm@C 76 (I, II), Sm@C 78 , Sm@C 80 , Sm@C 82 (I, II, III) and Sm@C 84 (I, II, III), and their characterization by UV–VIS–NIR absorption spectroscopy and electron energy-loss spectroscopy (EELS). The UV–VIS–NIR absorption spectra of Sm@C 74 , Sm@C 80 , Sm@C 82 (I, II, III) and Sm@C 84 (I, II) are quite similar to those of the corresponding Ca-, Sr-, Ba-, Eu-, Tm-, Yb-based metallofullerenes. In contrast, the absorption spectra of Sm@C 76 (I, II), Sm@C 78 and Sm@C 84 (III) show a novel feature: the onset for Sm@C 78 is observed ∼2600 nm, which corresponds to a small band gap (∼0.5 eV). Furthermore, the oxidation state of Sm atom in Sm@C 82 (II) is investigated by EELS, which reveals that the Sm atom takes +2 oxidation state in this fullerene cage.

The molecular dynnamics after the photoexcitation of 1′, 3′, 3′-trimethylspiro-8-nitro(2H-1-benzopyran-2′, 2′-indoline) (8-nitroBIPS) were investigated by the transient grating (TG) method. When the excitation laser power is low, the TG signal consists of three components which reflect the thermal diffusivity in the solution and the translational diffusion of the colourless and coloured forms of 8-nitroBIPS. The diffusion constants of the colourless form is found to be approximately 1.5 times larger than that of the coloured form, and this result is explained in terms of the photoinduced electric dipole moment of the coloured form. With stronger excitation light, another new TG signal is observed in the longer time region in non-polar solvents. This signal is attributed to the intensity grating produced by probe light scattering due to the microcrystal of 8-nitroBIPS. From the temporal profile of this new TG signal (aggregate grating signal), the dynamics of the aggregate formation process can be investigated.

The translational diffusion coefficients (D) of N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) and its cation radical were measured by the transient grating method. The D value of the free cation radical is about twofold smaller than that of the neutral molecule. The D values of both species were calculated on the basis of the Stokes-Einstein (SE) relation, the Spernol-Wirtz modification of the SE relation and the Hubbart-Onsager theory. The calculations and comparisons with previously determined D values of neutral radicals suggest that, contrary to the intuitive picture of the diffusion of charged species, it may be the unpaired electron and not the charge that mainly governs diffusion.

The electronic and geometric structures of the Sm-metallofullerene peapods (Sm@C82)n@SWNTs, are investigated by in situ high-resolution transmission electron microscopy (HRTEM) and electron energy-loss spectroscopy (EELS). The obtained EELS spectra reveal that the encapsulated Sm ion takes +2 state in (Sm@C82)n@SWNTs irrespective of the physical and the electronic properties of single-wall nanotubes.