Search

A new dispersive micro solid-phase extraction method which uses single-walled carbon nanohorns (SWNHs) as sorbent is proposed. The procedure combines the excellent sorbent properties of the nanoparticles with the efficiency of the dispersion of the material in the sample matrix. Under these conditions, the interaction with the analytes is maximized. The determination of polycyclic aromatic hydrocarbons was selected as model analytical problem. Two dispersion strategies were evaluated, being the functionalization via microwave irradiation better than the use of a surfactant. The extraction was accomplished by adding 1 mL of oxidized SWHNs (o-SWNHs) dispersion to 10 mL of water sample. After extraction, the mixture was passed through a disposable Nylon filter were the nanoparticles enriched with the PAHs were retained. The elution was carried out with 100 μL of hexane. The limits of detection achieved were between 30 and 60ngL(-1) with a precision (as repeatability) better than 12.5%. The recoveries obtained for the analytes in three different water samples were acceptable in all instances. The performance of o-SWNHs was favourably compared with that provided by carboxylated single-walled carbon nanotubes and thermally treated carbon nanocones.

Carbon nanotubes grown from discrete Fe-containing nanoparticles dispersed on a silicon nitride transmission electron microscope grid were systematically studied. The (n,m) indices of produced single-walled carbon nanotubes (SWNTs) were deduced from their electron diffraction patterns. Relatively small diameter SWNTs with a narrow diameter distribution (0.7-1.6 nm) were produced using CO as the carbon source at 800 °C, while large diameter SWNTs ranging from 1.0 nm to 4.7 nm were synthesized when using CH(4) as the carbon source. The chiral angle distributions of the SWNTs produced from different carbon sources are also different, which are attributed to the preferred cap nucleation associated with the carbon feed rate on the catalyst instead of carbon nanotube growth kinetics. Furthermore, growth of carbon laminar nanoclusters inside carbon nanotubes was achieved at a higher growth temperature, suggesting that dissociated carbon diffuses across the nanoparticle during the nanotube growth process.

Single-walled carbon nanohorns (SWCNHs) hybridized with palladium (Pd) nanoparticles were synthesized by a single-step gas-injected arc-in-water method (GI-AIW) with a Pd wire inserted inside the anode hole. In the arc zone, carbon and Pd were vaporized simultaneously, leading to the formation of hybrid material of SWCNHs and Pd nanoparticles due to effective quenching. Based on TEM and CO chemisorption analyses, Pd nanoparticles were found to be embedded inside SWCNH aggregates. The size of Pd nanoparticles, determined by X-ray diffraction, was in the range of 3–6 nm when Pd wires with diameters of 0.1 and 0.3 mm were used. Using a Pd wire with a diameter larger than 0.5 mm results in larger Pd nanoparticles which tend to be exposed to the outer surface of the hybrid material. According to thermogravimetric analyses, the weight fraction of Pd nanoparticles is increased by increasing the Pd wire diameter although the yield of Pd nanoparticles decreased. SWCNHs hybridized with dispersed Pd nanoparticles, synthesized with 0.1 mm Pd wire, exhibited strong anti-oxidation resistance with a highly graphitic structure.

The effects of gamma-irradiation on the modification of the surface and structure of multi-walled carbon nanotubes were studied. Gamma-irradiation affected the graphitization properties of functional groups, and decreased the diameter of multi-walled carbon nanotubes. The irradiated multi-walled carbon nanotubes with the absorbed dose of 100 kGy exhibited a larger specific surface area and microporous volume as compared with the other samples. The Raman spectroscopy and X-ray photoelectron spectroscopy showed that the interaction between the gamma-irradiation and the multi-walled carbon nanotubes with the absorbed dose of 150 kGy destroyed the nanostructure of carbons, leading to the formation of diamond-like structures and carbon oxides. In addition, gamma-irradiation with the absorbed dose of 100 kGy improved multi-walled carbon nanotubes graphitization and surface properties while at higher absorbed dose (150 kGy), it induced damaged structures (sp 3 bonds and oxygen compositions).

This paper reviews progress that has been made in the use of Raman spectroscopy to study graphene and carbon nanotubes. These are two nanostructured forms of sp2 carbon materials that are of major current interest. These nanostructured materials have attracted particular attention because of their simplicity, small physical size and the exciting new science they have introduced. This review focuses on each of these materials systems individually and comparatively as prototype examples of nanostructured materials. In particular, this paper discusses the power of Raman spectroscopy as a probe and a characterization tool for sp2 carbon materials, with particular emphasis given to the field of photophysics. Some coverage is also given to the close relatives of these sp2 carbon materials, namely graphite, a three-dimensional (3D) material based on the AB stacking of individual graphene layers, and carbon nanoribbons, which are one-dimensional (1D) planar structures, where the width of the ribbon is on the nano...

Synthesis of carbon nanotubes from V-type pyrolysis flame is a kind of new method. It has potential for carbon nanotubes preparation in mass production. Carbon monoxide was as carbon source and the acetylene/air premixed gas provides heat by combustion. Hydrogen/helium premixed gas acted as diluted and protection gas. Pentacarbonyl iron was served as catalyst. Carbon nanotubes with less impurity and high yield were captured successfully in the V-type pyrolysis flame. The diameter of carbon nanotubes was approximate between 10nm and 20nm, and its length was dozens of microns. The size of catalyst nanoparticles approximately was from 5 nm to 8nm in diameter. This study aims to examine the formation process of typical carbon nanotubes from pyrolysis flame and to characterize their morphology and structure. The morphology and structural of carbon nanotubes were characterized by scanning electron microscope and transmission electron microscopy respectively. Temperature was the key parameter in the process of synthesis carbon nanotubes. The concentration of catalyst had important influence on the synthesis of carbon nanotubes. Sampling time directly determined whether carbon nanotubes formation was completely. The carbon “dissolved-proliferation-separate out” theory can be used to explain that pentacarbonyl iron catalyses carbon monoxide in the process of carbon nanotube formation.

A novel composite is presented as a supercapacitor electrode with a high maximum power rating (990 kW/kg; 396 kW/l) exceeding power performances of other electrodes. The high-power capability of the electrode stemmed from its unique meso-macro pore structure engineered through the utilization of single-walled carbon nanotubes (20 wt %) as scaffolding for single-walled carbon nanohorns (80 wt %). The novel composite electrode also exhibited durable operation (6.5% decline in capacitance over 100 000 cycles) as a result of its monolithic chemical composition and mechanical stability. The novel composite electrode was benchmarked against another high-power electrode made from single-walled carbon nanotubes (Bucky paper electrode). While the composite electrode had a lower surface area compared to the Bucky paper electrode (280 vs 470 m(2)/g from nitrogen adsorption), it had a higher meso-macro pore volume (2.6 vs 1.6 mL/g from mercury porosimetry) which enabled the composite electrode to retain more electrolyte, ensuring facile ion transport, hence achieving a higher maximum power rating (970 vs 400 kW/kg).

In this study, carbon nanotubes were formed from camphor oil decomposition on Fe/Ni/Mg catalysts at 650°C by fluidized floating catalyst method. X-ray diffraction (XRD) was used to examine the characteristics of carbon nanotubes. The carbon nanotubes were also examined both by FESEM and Raman spectroscopy to define their appearance and structure which revealed that dense bundle of mixed multi-walled and single-walled carbon nanotubes. The diameters of the single-walled carbon nanotubes were estimated to be around 0.86–2.31 nm. Little amount of carbon nanotubes were found on the Fe/Ni/Mg catalyst surface at 550°C; while a significant amount of carbon nanotubes were observed at 650°C. According to the XRD spectrum, there was carbon and graphite present in the deposited samples. Raman spectroscopy revealed two peaks at 1347–1357 cm−1 (D band, disorder mode, amorphous carbon) and 1572 cm−1 (G band, graphite sp2 structure). FESEM results indicated the Fe/Ni/Mg could catalyze the camphor oil decomposition to form carbon nanotubes even at a lower temperature.

Nanoparticles have significant potential as selective photo-absorbing agents for laser based cancer treatment. This study investigates the use of single walled carbon nanohorns (SWNHs) as thermal enhancers when excited by near infrared (NIR) light for tumor cell destruction. Absorption spectra of SWNHs in deionized water at concentrations of 0, 0.01, 0.025, 0.05, 0.085, and 0.1 mg/ml were measured using a spectrophotometer for the wavelength range of 200-1,400 nm. Mass attenuation coefficients were calculated using spectrophotometer transmittance data. Cell culture media containing 0, 0.01, 0.085, and 0.333 mg/ml SWNHs was laser irradiated at 1,064 nm wavelength with an irradiance of 40 W/cm{sup 2} for 0-5 minutes. Temperature elevations of these solutions during laser irradiation were measured with a thermocouple 8 mm away from the incident laser beam. Cell viability of murine kidney cancer cells (RENCA) was measured 24 hours following laser treatment with the previously mentioned laser parameters alone or with SWNHs. Cell viability as a function of radial position was determined qualitatively using trypan blue staining and bright field microscopy for samples exposed to heating durations of 2 and 6 minutes alone or with 0.085 mg/ml SWNHs. A Beckman Coulter Vi-Cell instrument quantified cell viability of samples treated with varyingmore » SWNH concentration (0, 0.01, 0.085, and 0.333 mg/ml) and heating durations of 0-6 minutes. Spectrophotometer measurements indicated inclusion of SWNHs increased light absorption and attenuation across all wavelengths. Utilizing SWNHs with laser irradiation increased temperature elevation compared to laser heating alone. Greater absorption and higher temperature elevations were observed with increasing SWNH concentration. No inherent toxicity was observed with SWNH inclusion. A more rapid and substantial viability decline was observed over time in samples exposed to SWNHs with laser treatment compared with samples experiencing laser heating or SWNH treatment alone. Samples heated for 6 minutes with 0.085 mg/ml SWNHs demonstrated increasing viability as the radial distance from the incident laser beam increased. The significant increases in absorption, temperature elevation, and cell death with inclusion of SWNHs in laser therapy demonstrate the potential of their use as agents for enhancing photothermal tumor destruction.« less

Electrically conductive carbon nanotubes (CNTs) with high aspect ratios emit electrons at low electric fields, thus applications to large-area field emission (FE) devices with CNT cathodes are attractive to save energy consumption. However, the poor dispersion and easy bundling properties of CNTs in solvents have hindered this progress. We have solved these problems by growing single-walled CNTs (SWNTs) on single-walled carbon nanohorn (SWNH) aggregates that have spherical forms with ca. 100-nm diameters. In the obtained SWNT-SWNH hybrids (NTNHs), the SWNTs diameters were 1-1.7 nm and the bundle diameters became almost uniform, that is, less than 10 nm, since the SWNTs were separated by SWNH aggregates. We also confirmed that a large-area FE device with NTNH cathodes made by screen printing was highly and homogeneously bright, suggesting the success of the hybrid strategy.

Spherical aggregates of single-walled carbon nanohorns (SWNHs) produced by CO2 laser ablation of graphite contain thin graphene sheets (TGSs), and their quantities depend on formation conditions. To adjust laser ablation condition to increase TGS quantities, TGS quantification in products is necessary; however, its method has not been established. We have found that high resolution thermogravimetric analysis (HRTGA) showed SWNHs and TGSs combusting at 554 and 581 °C, respectively. Transmission electron microscopy observations of HRTGA-residues obtained by stopping HRTGA on the way supported these assignments. Thus TGS was able to be quantified by analyzing derivative curves of weight vs. temperature curves.

Consideration has been given to the current status of research on the use of radiation techniques for synthesizing new carbon nanomaterials based on fullerenes, carbon nanotubes, and graphene sheets and their derivatives, which are promising for practical application due to their unique properties. An analysis has been made of the existing experimental and theoretical works on studying different processes induced by the action of radiation on carbon nanostructures (melting of cross-linking carbon nanotubes and formation of molecular junctions between them, polymerization of fullerene layers, formation of new structures, radiation chemistry of fullerenes, and others).

Indocyanine green (ICG) is an effective light absorber for laser-mediated photodynamic therapy. However, applications of ICG are limited due to its rapid degradation and poor photostability in water. Herein, we report the development of a multifunctional nanoplatform by coating ICG on the surface of single-walled carbon nanohorns (SWNHs) through π-π stacking, obtaining SWNH-ICGs with high solubility and stability under physiological conditions. The SWNH-ICGs could be used as a single nanoplatform to simultaneously produce satisfactory hyperthermia and reactive oxygen species under near-infrared (NIR) laser irradiation. In addition, the SWNH-ICGs not only improved the photostability of ICG in different media, but also protected it from light degradation. The SWNH-ICGs exhibited highly efficient thermal/photoacoustic (PA) imaging-guided photothermal therapy (PTT) and photodynamic therapy (PDT) effects, even under low-power laser irradiation (0.3 W cm-2 ) in vitro. Combined PTT and PDT effectively killed triple-negative breast cancer 4T1 cells, demonstrating a markedly improved and synergistic therapeutic effect compared to PTT or PDT alone. Furthermore, significant tumor growth inhibition as well as tumor cell death were observed following PTT/PDT at 808 nm laser irradiation, confirming the synergistic effects of SWNH-ICGs over free ICG in vivo. This facile and simple methodology for thermal/PA imaging-guided PTT/PDT suggests that SWNH-ICGs may serve as an effective nanoplatform for cancer therapy.

Single-walled carbon nanohorns (SWNHs), distinguished by their high purity and distinct structure, were noncovalently functionalized with poly(sodium 4-styrenesulfonate). The functionalized SWNHs were characterized by scanning electron microscopy, atomic force microscopy, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetry. Heme protein myoglobin was adsorbed onto surface of functionalized SWNHs to prepare electrochemical biosensor. Surface assembly process and direct electrochemistry of immobilized myoglobin were investigated by electrochemical impedance spectroscopy and cyclic voltammetry, respectively. The proposed biosensor exhibited good electrocatalysis to the reduction of hydrogen peroxide. The response was linear over the range 3-350 microM with a detection limit of 0.5 microM. Good reproducibility and stability of the biosensor were obtained toward hydrogen peroxide detection.

Carbon Nanotubes (CNTs) have been a subject of interest for most of the researches after their discovery, due to their superior mechanical properties and ability to be used as the reinforcement phase in nanocomposites. The other carbon structure which was discovered a few years after the discovery of CNTs was Carbon Nanohorns (CNHs). The structure of CNH is cone-shaped compared to the cylindrical shape of CNT’s structure. This cone-shaped structure causes difficulties in finding the stress distribution in CNHs when embedded in the matrix phase of nanocomposites. In this paper the governing differential equation of the stress distribution on the CNHs placed in a nanocomposite matrix is derived using some simplifying assumptions. It has been shown here that while the stress distribution is symmetric for the special case of CNT, it is non-symmetric for the general CNHs and the maximum stress shifts toward the tip of CNH.

This paper describes for the first time the use of single-walled carbon nanohorns (SWNHs) as pseudostationary and stationary phases for EKC and CEC, respectively, taking advantage of their characteristic features, such as conical-end termination, formation of spherical assemblies dahlia-flower like superstructure and easy functionalization. The use of SWNHs as pseudostationary phase for EKC required the study of their dispersion in different surfactants as well as their compatibility with the electrophoretic system. The carboxylation and subsequent immobilization of carboxylated SWNHs in fused-silica capillary to obtain useful, reproducible and stable stationary phases for CEC has also been investigated, with promising results. The electrophoretic separations obtained for water-soluble vitamins in both modalities (EKC and CEC) have been systematically compared with those obtained with single-walled carbon nanotubes.

Double-walled carbon nanotubes were synthesized by a carbon arc discharge using Fe catalyst. Electron microscopy revealed that the dominant fraction of nanotubes appears in bundles and has outer diameters between 2.5 and 4.0 nm. The by-products (catalyst particles and amorphous carbon) were readily removed using diluted nitric acid. The success of the purification was tracked by electron microscopy and X-ray photoelectron spectroscopy. The surface of purified nanotubes was found to be covalently functionalized with carbonyl-containing groups, which were subsequently removed by thermal annealing. The developed synthesis route has high selectivity for double-walled carbon nanotubes and uses simple starting materials.

A high-speed vibration milling (HSVM) method was applied to synthesize water dispersible single-walled carbon nanohorns (SWNHs). Highly reactive free radicals (HOOCCH2CH2•) produced from an acyl peroxide under HSVM conditions react with hydrophobic SWNHs to produce a highly water dispersible derivative (f-SWNHs), which has been characterized in detail by spectroscopic and microscopic techniques together with thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The carboxylic acid functionalized, water-dispersible SWNHs material are versatile precursors that have potential applications in the biomedical area.

Finite carbon chains encapsulated into carbon nanotubes are investigated by using first-principles calculations based on spin density functional theory. Dimerization is observed in carbon chains formed by an even number of carbon atoms, but not in carbon chains containing an odd number of carbon atoms. All carbon chains inside the carbon nanotubes are spin-polarized due to spin-split energy levels around the Fermi level. By comparing the results of carbon chains inside the carbon nanotubes and isolated charged carbon chains, we found that the charge transfer from the carbon nanotubes to the carbon chains leads to the structure transformation and the spin-polarization of the carbon chains when encapsulated inside the carbon nanotubes, whereas the orbital hybridization removes the degeneracy of energy levels around the Fermi levels. Our results provide a deep understanding on the interaction between the carbon chains and the carbon nanotubes.

Notable electronic communication within ZnPc-SWNHox nanoensembles, where ZnPc is zinc phthalocyanine and SWNHox is an oxidized single-walled nanohorn, in both the ground and excited states is revealed by steady-state absorption and fluorescence spectroscopy measurements. The details of electron transfer reported here with time-resolved absorption and fluorescence measurements may broaden the use of SWNHox nanoensembles in photochemistry and photobiology.

Nickel nanoparticles have been deposited on carbon nanotubes by spray pyrolysis of toluene as carbon source and nickelocene as catalyst at different temperatures. The optimum temperature to produce well‐grown Ni/carbon nanotubes was found to be 850°C. The carbon nanotubes were characterized by SEM, TEM, XRD, Raman spectroscopy and TGA‐DTA. The microscopy studies show that the produced carbon nanotubes have disorder morphologies with diameters between 60 and 100 nm and lengths of a few hundred microns. Ni particles of 40 nm are well dispersed along the carbon nanotubes. XRD patterns show the crystalline planes corresponding to graphite and metallic Ni. The TGA‐DTA results indicate a Ni loading of 20wt%. Raman spectroscopy reveals that the grown carbon nanotubes are graphitized, showing both the D and G bands at 1330 cm−1 and 1590 cm−1, respectively. The corresponding intensity ratio of these bands (ID/IG) varies with respect to synthesis temperature and catalyst concentration.

In this contribution we present a facile alcohol chemical vapor deposition route for the synthesis of non-magnetic bamboo-like carbon nanotubes and branched bamboo-like carbon nanotubes. The use of copper as the catalyst yields a non-magnetic sample, which is important for some fundamental scientific studies and also certain applications. Our findings show copper requires a pre-synthesis heat treatment in air to be catalytically active. Further, our studies show the mean diameter of the carbon nanostructures can be tailored via the reaction temperature. Improved crystallinity of the non-magnetic bamboo-like carbon nanotubes and branched bamboo-like carbon nanotubes is obtained at the lower synthesis temperatures explored. These studies serve to broaden our understanding of catalyst choice and growth mechanisms in carbon nanotube formation.

Single-walled carbon nanohorns (SWNHs) are single-graphene tubules that have shown high potential for drug delivery systems. In drug delivery, it is essential to quantitatively determine biodistribution and ultrastructural localization. However, to date, these determinations have not been successfully achieved. In this report, we describe for the first time a method that can achieve these determinations. We embedded Gd(2)O(3) nanoparticles within SWNH aggregates (Gd(2)O(3)@SWNHag) to facilitate detection and quantification. Gd(2)O(3)@SWNHag was intravenously injected into mice, and the quantities of Gd in the internal organs were measured by inductively coupled plasma atomic emission spectroscopy: 70-80% of the total injected material accumulated in liver. The high electron scattering ability of Gd allows detection with energy dispersive X-ray spectroscopy and facilitates the ultrastructural localization of individual Gd(2)O(3)@SWNHag with transmission electron microscopy. In the liver, we found that the Gd(2)O(3)@SWNHag was localized in Kupffer cells but were not observed in hepatocytes. In the Kupffer cells, most of the Gd(2)O(3)@SWNHag was detected inside phagosomes, but some were in another cytoplasmic compartment that was most likely the phagolysosome.

Detailed volumetric neon adsorption isotherms were measured between 22.670 and 31.444 K on a sample of closed, mostly bud-like, aggregates of single-walled, carbon nanohorns, produced by NanoCraft, Inc. The results are compared to those recently reported on closed dahlia-like nanohorn aggregates. While for the closed dahlia-like aggregates the data shows that there are two groups of sites with different binding energies present at relatively low loadings, only one group of adsorption energies is present for the closed bud-like aggregates at comparable loadings. We measured the isosteric heat of adsorption and its dependence on substrate loading. From the low-loading limit of this quantity, we determined that the binding energy of the sites present on the bud-like aggregates have a value intermediate between that obtained for adsorption on planar graphite and that measured on the grooves of close-ended bundles on nanotubes for the same adsorbate.

We investigated the inner structure of an aggregate made of single-wall carbon nanohorns (SWNHs). This structure has not been clarified because the thousands of SWNHs are densely packed and difficu...

Synthesis of single‐walled carbon nanotubes by arc‐discharge technique has been realized in nitrogen atmosphere with Ni:Y2O3 catalyst. Presence of carbon nanotubes in the synthesized material has b...

Carbon nanotubes with uniform density were synthesized on carbon fiber substrate by the floating catalyst method. The morphology and microstructure were characterized by scanning electron microscopy and Raman spectroscopy. The results of field emission showed that the emission current density of carbon nanotubes/carbon fibers was 10 μA/cm2 and 1 mA/cm2 at the field of 1.25 and 2.25 V/μm, respectively, and the emission current density could be 10 and 81.2 mA/cm2 with the field of 4.5 and 7 V/μm, respectively. Using uniform and sparse density distribution of carbon nanotubes on carbon fiber substrate, the tip predominance of carbon nanotubes can be exerted, and simultaneously the effect of screening between adjacent carbon nanotubes on field emission performance can also be effectively decreased. Therefore, the carbon nanotubes/carbon fibers composite should be a good candidate for a cold cathode material.

The biosensing application of single-walled carbon nanohorns (SWCNHs) was demonstrated through fabrication of an amperometric glucose biosensor. The biosensor was constructed by encapsulating glucose oxidase in the Nafion–SWCNHs composite film. The cyclic voltammograms for glucose oxidase immobilized on the composite film displayed a pair of well-defined and nearly symmetric redox peaks with a formal potential of −0.453 V. The biosensor had good electrocatalytic activity toward oxidation of glucose. To decrease detection potential, ferrocene monocarboxylic acid was used as a redox mediator. The mediated glucose biosensor shows a linear range from 0 to 6.0 mM. The biosensor shows high sensitivity (1.06 μA/mM) and stability, and can avoid the commonly coexisted interference. Because of impressive properties of SWCNHs, such as high purity and high surface area, SWCNHs and their composites are expected to be promising material for biomolecular immobilization and biosensing applications.

The growth of multiwalled carbon nanotubes (MWCNTs) on carbon black has been studied using a combustion oxygen/acetylene flame method. Different types of carbon black and reaction temperatures were evaluated for the growth of carbon nanotubes. The reaction was stopped after different short duration times of deposition in an attempt to observe the growth of carbon nanotubes. The samples were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and by Raman Spectroscopy. We have observed the transformation of the carbon black surface into graphitic sheets and the start formation of tubes from these graphitic sheets. The length of the tubes is increased but the diameter is decreased with increased deposition times. Carbon nanotubes with 10–20 nm of diameter and a length of about 50 µm are obtained after 1 min deposition. The growth of multiwalled carbon nanotubes on carbon black is a phenomenon that can not be fully explained by carbon nanotubes growth models currently known. Our results lead us to propose a mechanism for the solid-state transformation of the carbon black particles surface into nanotubes in the oxygen/acetylene flame.

Single-walled carbon nanohorn (SWCNH) paste electrode was used for amperometric determination of concentrated hydrogen peroxide, and was compared with other carbon electrodes. The calibration plots are linear from 0.5 to 100 mM at activated SWCNH paste electrode and edge plane graphite (EPG) electrode. In contrast, the calibration plots are linear only at concentrations lower than 45 mM at graphite paste electrode, multi-walled carbon nanotube paste electrode, and glassy carbon electrode. Our results show that SWCNH paste electrode and EPG electrode are interesting alternatives to high surface area platinum electrode for determination of concentrated hydrogen peroxide. Because of its high-purity, metal-free SWCNH is a user-friendly and attractive material for electrochemical study. Keywords: Single-walled carbon nanohorn, Carbon nanotube, Edge plane graphite electrode, Electrochemical determination, Hydrogen peroxide

Single-walled carbon nanotubes were produced by the conventional arc discharge method, and purified with a two-step treatment. First, the raw soot containing single-walled carbon nanotubes was burned up at ca. 350 °C in air to remove amorphous carbon, and then it was treated by strong acidic solvents to remove metal catalysts. Near-edge X-ray absorption fine structure spectroscopy was applied to analyze the defects on single-walled carbon nanotubes in whole purification process, so the experimental conditions can be optimized, and finally high-purity single-walled carbon nanotubes were obtained as revealed by various spectroscopic characterizations such as scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and Raman spectroscopy.

We fabricated a gas sensor using single-walled carbon nanohorns (SWNHs) produced by the gas-injected arc-in-water method. This gas sensor consisted of agglomerated SWNHs as a coating film between Al electrodes on a glass substrate and the shift of the electric resistance of this coating film caused by gas adsorption was monitored. Its sensing property was examined for the detection of NH3 and O3 at room temperature. It was confirmed that the electrical resistance of the SWNHs film increases with adsorption of NH3, whereas the adsorption of O3 induced the decrease of the resistance. A model to correlate the gas concentration and the sensing property was proposed focusing on the detection of NH3 based on mono-layer adsorption and a second-order interaction of adsorbed gas molecules for charge transfer.

Previous studies have suggested that single-walled carbon nanotubes (SWCNTs) may pose a pulmonary hazard. We investigated the pulmonary toxicity of single-walled carbon nanohorns (SWCNHs), a relatively new carbon-based nanomaterial that is structurally similar to SWCNTs. Mice were exposed to 30 µg of surfactant-suspended SWCNHs or an equal volume of vehicle control by pharyngeal aspiration and sacrificed 24 hours or 7 days post-exposure. Total and differential cell counts and cytokine analysis of bronchoalveolar lavage fluid demonstrated a mild inflammatory response which was mitigated by day 7 post-exposure. Whole lung microarray analysis demonstrated that SWCNH-exposure did not lead to robust changes in gene expression. Finally, histological analysis showed no evidence of granuloma formation or fibrosis following SWCNH aspiration. These combined results suggest that SWCNH is a relatively innocuous nanomaterial when delivered to mice in vivo using aspiration as a delivery mechanism.

Raman spectroscopy has, for long, been utilized to investigate material systems on the micro and mesoscales. Recently, the technique has proven its ability in exploring systems on the nanoscale. In this paper, we review our recent work on the Raman investigation of molecular adsorption from liquid mixtures on surfaces of single-walled carbon nanotubes and fullerene nanospheres, emphasizing the following major research findings: the development of a Raman-based technique capable of sensing local chemical interactions on the surface of carbon nanotubes and spheres; the molecular simulation results supporting the Raman investigation; the possibility of creating mesostructures based upon mixtures of carbon nanotubes and nanospheres that are crucial for selective adsorption. The current findings represent a major new thrust for the development of new nanostructured materials with superior adsorption capabilities and unique applications. Copyright © 2007 John Wiley & Sons, Ltd.

Growing interest in the environmental and health effects of engineered nanostructured materials requires accurate control of cluster morphology and size in order to make valid interpretations of nanomaterial toxicity. Pressure-driven atomization/nebulization, ultrasonic generation, and electrospraying are common aerosol generation techniques that are currently used. Electrospray produced monodispersed isolated particles, when the original material was reasonably monodisperse, which may be most suited for use in experiments requiring single-size aerosol population. The technique however requires the use of a conductive solution that may not be suitable in biological experiments. Also, in the generation of single walled carbon nanohorns (SWNHs), we found that electrospray produced an anonymous peak that was not consistent with currently known SWNH nanostructures. This adds to an uncertainty about its utility in nanotoxicological experiments. Though producing controllable larger cluster sizes, ultrasonic gen...

Carboxylic-group-functionalized single-walled carbon nanohorns (SWCNHs-COOH) have been found to possess peroxidase-like activity for the first time. Similar to natural peroxidase, SWCNHs-COOH can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine by H2O2 to produce a blue color solution. Compared with horseradish peroxidase, SWCNHs-COOH exhibit higher activity and stability under harsh reaction conditions. The catalytic activity of SWCNHs-COOH depends on the concentration of H2O2. A colorimetric method for glucose detection was developed by combining the SWCNH-COOH catalytic reaction and the generation of H2O2 by the enzymatic oxidation of glucose with glucose oxidase. Taking into account the advantages of good stability, high biocompatibility in aqueous solutions, being metal-catalyst free, and high purity, SWCNHs-COOH are expected to have potential applications in biotechnology and clinical diagnostics as enzymatic mimics.

The application of macrocyclic hosts for construction of different electrochemical devices and separation matrices has attracted much attentions due to their benign biocompatibility and simplicity of synthesis. Myricetin and rutin are considered two of the most bioactive flavonoids, which have been proved to exhibit various physiological functions. This work reports a simple and facile approach for the synthesis of β-cyclodextrin-gold@3, 4, 9, 10-perylene tetracarboxylic acid functionalized single-walled carbon nanohorns (β-CD–Au@PTCA–SWCNHs) nanohybrids. The simultaneous electrochemical determination of myricetin and rutin using a β-CD–Au@PTCA–SWCNHs-modified glassy carbon electrode was established. The results show that the β-CD–Au@PTCA–SWCNHs-modified electrode displayed electrochemical signal superior to those of Au@PTCA–;SWCNHs and SWCNHs towards myricetin and rutin. The proposed modified electrode has a linear response range of 0.01–10.00 μM both for myricetin and rutin with relatively low detection limits of 0.0038 μM for myricetin and 0.0044 μM (S/N = 3) for rutin, respectively. The excellent performance of the sensing platform is considered to be the synergic effects of the SWCNHs (e.g. their good electrochemical properties and large surface area) and β-CD (e.g. a hydrophilic external surface, a high supramolecular recognition, and a good enrichment capability).

The quenching of electrochemiluminescence by single-walled carbon nanohorn has been demonstrated for the first time. Moreover, a sensitive, label-free, and signal-on electrochemiluminescence ATP aptasensor was developed using single-walled carbon nanohorn as both quencher and scaffold.

Carbon nanotubes and carbon nanofibers were grown at different temperatures on porous ceramic Al 2 O 3 substrates with single channel geometry by means of a chemical vapor deposition technique using methane as carbon source and palladium as catalyst. Time-resolved in-situ Fourier transformed infrared spectroscopy was used for the investigation of methane decomposition for characterizing the catalyst’s performance. With increasing synthesis temperature, a structural transition from carbon nanofibers to carbon nanotubes was observed. At a synthesis temperature of 700 °C, solely carbon nanofibers were found, whereas at 800 °C a mixture of two types of bamboo-shaped carbon nanofibers were obtained, suggesting a structural transition. A synthesis temperature to 850 °C results in bamboo-shaped multi-walled carbon nanofibers and multi-walled carbon nanotubes. The carbon products and the observed structural transition were characterized by means of field emission scanning electron microscopy, high-resolution transmission electron microscopy, thermal gravimetric analysis, and Raman spectroscopy.

Due to the simplicity of the process, holes in the graphene walls of single-wall carbon nanotubes (SWNTs) and single-wall carbon nanohorns (SWNHs) have often been opened using O2 gas at high temperatures, even though this contaminates the nanotubes with carbonaceous dust (C-dust). To open holes with less C-dust contamination, we found that a slow temperature increase of 1 degrees C/min or less, in air, was effective. We also found that SWNHs having little C-dust could store a large quantity of materials inside the tubes. We infer that the local temperature increase due to the exothermic reaction of combustion may have been suppressed in the slow combustion process, which was effective in reducing the C-dust.

We demonstrate that oxidized single-wall carbon nanohorns (SWNHs), a type of single-wall nanotube, entrap cisplatin, an anticancer agent. We found that the cisplatin structure was maintained inside the SWNHs and that the cisplatin was slowly released from the SWNHs in aqueous environments. The released cisplatin was effective in terminating the growth of human lung-cancer cells, while the SWNHs themselves had no such effect. Cisplatin-incorporated oxidized SWNHs are thus a potential drug delivery system. Keywords: Carbon nanotube; carbon nanohorn; anticancer drug; drug carrier; cisplatin

Multi-wall carbon nanotubes (MWCNT) were fabricated directly on the carbon cloth utilizing bias-assisted microwave plasma enhanced chemical vapor deposition system. The deposition of catalysts for carbon nanotubes growth was carried out by e-beam evaporation technologies. Scanning electron microscopy and transmission electron microscopy were used for characterizing the morphologies and structures of carbon nanotubes. The depositions of platinum particles on carbon nanotubes were achieved by electroless plating and sputtering. High resolution transmission electron microscopy showed that the diameters of nanotubes and platinum particles are about 20 nm and 2–5 nm, respectively. BET measurement indicated higher surface area of carbon nanotubes than carbon cloth. The electrochemical properties of carbon nanotubes electrode have been investigated by cyclic votammetry. These carbons nanotubes are very suitable for the electrodes and catalyst support of proton exchange membrane fuel cells (PEMFC). D 2005 Elsevier B.V. All rights reserved.

We demonstrate that the field emission efficiency was greatly improved by reducing the density of carbon nanotubes (CNTs). In this study, catalyst composed of gold and nickel was deposited by e-gun evaporation before pre-treatment of furnace annealing. Carbon nanotubes were then grown on silicon substrate using bias-assisted microwave plasma chemical vapor deposition. Vertical aligned carbon nanotubes were grown with gas mixture of methane and hydrogen under external DC bias. The surface morphology and the tubular structure of carbon nanotubes were confirmed by electron microscopy and the density of carbon nanotubes could be controlled by the composition of the catalyst. The field emission properties were investigated through I – V measurement and the effects are discussed.