Toxicity of Multi-Walled Carbon Nanotubes,Graphene Oxide,and Reduced Graphene Oxide to Zebrafish Embryos

Objective This study was aimed to investigate the toxic effects of 3 nanomaterials, i.e. multi-walled carbon nanotubes （MWCNTs）, graphene oxide （GO）, and reduced graphene oxide （RGO）, on zebrafish embryos. Methods The 2-h post-fertilization （hpf） zebrafish embryos were exposed to MWCNTs, GO, and RGO at different concentrations （1, 5, 10, 50, 100 mg/L） for 96 h. Afterwards, the effects of the 3 nanomateria on spontaneous movement, heart rate, hatching rate, length of larvae, mortality, and malformations Is were evaluated. Results Statistical analysis indicated that RGO significantly inhibited the hatching of zebrafish embryos. Furthermore, RGO and MWCNTs decreased the length of the hatched larvae at 96 hpf. No obvious morphological malformation or mortality was observed in the zebrafish embryos after exposure to the three nanomaterials. Conclusion MWCNTs, GO, and RGO were all toxic to zebrafish embryos to influence embryos hatching and larvae length. Although no obvious morphological malformation and mortality were observed in exposed zebrafish embryos, further studies on the toxicity of the three nanomaterials are still needed.

In situ synthesis of palladium nanoparticles on multi-walled carbon nanotubes and their electroactivity for ethanol oxidation

Pd nanoparticles(Pd-NPs)were prepared and directly anchored on the surface of multi-walled carbon nanotubes(MWCNTs)in the absence of chemical reduction agent,where MWCNTs were used as both the chemical reduction agent and the support substrate of Pd-NPs.Effect of various surfactants on the in situ deposition of PdNPs on MWCNTs was investigated.When MWCNTs were modified with a cationic surfactant(hexadecyl trimethyl ammonium bromide,CTAB),the amount of the Pd-NPs(Pd-NP/CTAB-MWCNT)generated by such an in situ deposition method gets a notable increase,and the size of the as-synthesized Pd-NPs becomes smaller,compared with those in the absence of any surfactant(Pd-NP/MWCNT)or in the presence of an anionic surfactant SDS(Pd-NP/SDS-MWCNT)and a neutral surfactant OP(PdNP/OP-MWCNT).Results show that the MWCNTs modified with CTAB are propitious to the in situ reduction of Pd2?.Among the prepared catalysts,Pd-NP/CTABMWCNT displays the highest electroactivity for ethanol oxidation in alkaline media.

Adsorption and desorption phenomena on thermally annealed multi-walled carbon nanotubes by XANES study

The multi-walled carbon nanotubes(MWCNTs) studied in this work were synthesized by the catalytic chemical vapor deposition(CCVD) process, and were thermally annealed by the hot filament plasma enhanced(HF PE) method at 550℃ for two hours.The x-ray absorption near edge structure(XANES) technique was used to investigate the adsorption and desorption phenomena of the MWCNTs at normal and grazing incidence angles.The adsorbates were found to have different sensitivities to the thermal annealing.The geometry of the incident beam consistently gave information about the adsorption and desorption phenomena.In addition, the adsorption of non-intrinsic potassium quantitatively affected the intrinsic adsorbates and contributed to increase the conductivity of the MWCNTs.The desorption of potassium was almost 70% greater after the thermal annealing.The potassium non-intrinsic adsorbates are from a physisorption mechanism whereas the intrinsic adsorbates result from chemisorption.

Ultrasensitive electrochemical determination of metronidazole based on polydopamine/carboxylic multi-walled carbon nanotubes nanocomposites modified GCE

An ultrasensitive electrochemical sensor based on polydopamine/carboxylic multi-walled carbon nanotubes(MWCNTs à COOH) nanocomposites modified glassy carbon electrode(GCE) was presented in this work, which has been developed for highly selective and highly sensitive determination of an antimicrobial drug, metronidazole. The preparation of polydopamine/MWCNTs–COOH nanocomposites/GCE sensor is simple and possesses high reproducible, where polydopamine can be coated on the surface of MWCNTs–COOH via a simple electropolymerization process. Under optimized conditions, the proposed sensor showed ultrasensitive determination for metronidazole with a wide linear detection range from5 to 5000 mmol/dm^3 and a low detection limit of 0.25 mmol/dm^3(S/N=3). Moreover, the proposed sensor has been successfully applied for the quantitative determination of metronidazole in real drug samples. This work may provide a novel and effective analytical platform for determination of metronidazole in application of real pharmaceutical and biological samples analysis.

Production of High Purity Multi-Walled Carbon Nanotubes from Catalytic Decomposition of Methane

Acid-based purification process of multi-walled carbon nanotubes （MWNTs） produced via catalytic decomposition of methane with NiO/TiO2 as a catalyst is described. By combining the oxidation in air and the acid refluxes, the impurities, such as amorphous carbon, carbon nanoparticles, and the NiO/TiO2 catalyst, are eliminated. Scanning electron microscopy （SEM） and transmission electron microscopy （TEM） images confirm the removal of the impurities. The percentage of the carbon nanotubes purity was analyzed using thermal gravimetric analysis （TGA）. Using this process, 99.9 wt% purity of MWNTs was obtained.

Preparation of multi-walled carbon nanotube–Fe composites and their application as light weight and broadband electromagnetic wave absorbers

Multi-walled carbon nanotube （MWCNT）-Fe composites were prepared via the metal organic chemical vapor deposi- tion by depositing iron pentacarbonyl on the surface of MWCNTs. The structural and morphological analyses demonstrated that Fe nanoparticles were deposited on the surface of the MWCNTs. The electromagnetic properties of the MWCNTs were significantly changed, and the absorbing capacity evidently improved after the Fe deposition on the MWCNT surface. A minimum reflection loss of -29.4 dB was observed at 8.39 GHz, and the less than -10 dB bandwidth was about 10.6 GHz, which covered the whole X band （8.2-12.4 GHz） and the whole Ku band （12.4-18 GHz）, indicating that the MWCNT-Fe composites could be used as an effective microwave absorption material.

FLEXURAL WAVE DISPERSION IN MULTI-WALLED CARBON NANOTUBES CONVEYING FLUIDS

Motivated by the great potential of carbon nanotubes for developing nanofluidic devices, this paper presents a nonlocal elastic, Timoshenko multi-beam model with the second order of strain gradient taken into consideration and derives the corresponding dispersion relation of flexural wave in multi-walled carbon nanotubes conveying fuids. The study shows that the moving flow reduces the phase velocity of flexural wave of the lowest branch in carbon nanotubes. The phase velocity of flexural wave of the lowest branch decreases with an increase of flow velocity. However, the effects of flow velocity on the other branches of the wave dispersion are not obvious. The effect of microstructure characterized by nonlocal elasticity on the dispersion of flexural wave becomes more and more remarkable with an increase in wave number.

Crystallization Behavior and Mechanical Properties of Poly(vinylidene fluoride)/multi-walled Carbon Nanotube Nanocomposites

Poly（vinylidene fluoride）（PVDF）/multi-walled carbon nanotube（MWCNT） nanocomposites were prepared by means of ultrasonic dispersion method. X-ray diffraction（XRD） results indicate that incorporating MWCNTs into PVDF caused the formation of β phase. A thermal annealing at 130 ℃ confirmed that the β phase was stable in the nanocomposites. Differential scanning calorimetry（DSC） results indicate that the melting temperature slightly increased while the heat of fusion markedly decreased with increasing MWCNT content. The tensile strength and modulus of PVDF were improved by loading the MWCNTs. The scanning electron microscopy（SEM） observations showed that MWCNTs were uniformly dispersed in the PVDF matrix and an interfacial adhesion between MWCNT and PVDF was achieved, which was responsible for the enhancement in the tensile strength and modulus of PVDE.

Adsorption of Cr(Ⅵ) in wastewater using magnetic multi-wall carbon nanotubes

Magnetic multi-wall carbon nanotubes were prepared with wet chemical treatments and characterized by a transmission electron microscope （TEM） and X-ray diffraction （XRD）. They were used as adsorbents for the removal of Cr（VI） in aqueous solutions. The effects of adsorbent dosage, the concentration of Cr（VI） in aqueous solution, temperature, and pH value on the removal efficiency were studied. Results showed that the adsorption capacity of the magnetic multi-wall carbon nanotubes increased with the initial Cr（VI） concentration, but decreased with the increase of adsorbent dosage. The adsorption amount increased with contact time. The adsorption kinetics were best represented by the pseudo second-order kinetic model, and the adsorption isotherms indicated that the Langmuir model better reflected the adsorption process. The ob- tained calculation results for the Gibbs free energy revealed that the adsorption was a spontaneous and endothermic process. The enthalpy deviation was 3.835 kJ.mol 1. The magnetic multi-wall carbon nanotubes showed significant potential for application in adsorption of heavy metal ions.

Polyaniline and multi-walled carbon nanotube composite electrode for rechargeable battery

The multi-walled carbon nanotube was introduced into the polymer matrix (PANI) to improve the electric conductivity as well as mechanical properties of the original polymer matrix.PANI/multi-walled carbon nanotube (MWCNT) composites were synthesized via ex-situ and in-situ polymerization to improve their electrical property.And the DC conductivities of PANI/MWCNT according to content and diameter of MWCNT were measured by four-point probe.The highest electric conductivity of PANI/MWCNT composite is 20 S/cm when 0.3% (mass fraction) MWCNTs with 10 nm in diameter and 15 μm in length are added in composite.

Preconcentration of copper with multi-walled carbon nanotubes pretreated by potassium permanganate cartridge for solid phase extraction prior to flame atomic absorption spectrometry

A procedure for the preconcentration of copper was described in this paper using multi-walled carbon nanotubes (MWCNTs) oxidized by potassium permanganate as the adsorbent for the enrichment of trace copper in water samples. Important parameters, such as the sample pH, the concentration and volume of eluent, sample flow rate and volume, and interference of coexisting ions, were investigated. The obtained results indicated that proposed method possessed an excellent analytical performance. The linear range, the detection limit, and precison (RSD) were 1–100 ng/mL (R(2) = 0.9993), 0.32 ng/mL and 2.88%, respectively. The results showed that copper could be adsorbed quantitatively on the pretreated MWCNTs with potassium permanganate, and proposed method was very useful in the monitoring of copper in the environment.

Electrochemical Reduction of Oxygen on Multi-walled Carbon Nanotubes Electrode in Alkaline Solution

The multi-walled carbon nanotubes (MWNTs) electrode was constructed using poly-tetrafluoroethylene as binder, and the electrochemical reductive behavior of oxygen in alkaline solution was first examined on this electrode. Compared with other carbon materials, MWNTs show higher electrocatalytic activity, and the reversibility of O2 reduction reaction is greatly improved. The experiments reveal that the electrochemical reduction of O2 to HO2- is controlled by adsorption. The preliminary results illustrate the potential application of MWNTs in fuel cells.

Acetylcholinesterase Biosensor Based on Poly(diallyldimethylammonium chloride)-multi-walled Carbon Nanotubes-graphene Hybrid Film

In this paper, an amperometric acetylcholinesterase(ACh E) biosensor for quantitative determination of carbaryl was developed. Firstly, the poly(diallyldimethy-lammonium chloride)-multi-walled carbon nanotubes-graphene hybrid film was modified onto the glassy carbon electrode(GCE) surface, then ACh E was immobilized onto the modified GCE to fabricate the ACh E biosensor. The morphologies and electrochemistry properties of the prepared ACh E biosensor were investigated by using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. All variables involved in the preparation process and analytical performance of the biosensor were optimized. Based on the inhibition of pesticides on the ACh E activity, using carbaryl as model compounds, the biosensor exhibited low detection limit, good reproducibility and high stability in a wide range. Moreover, the biosensor can also be used for direct analysis of practical samples, which would provide a new promising tool for pesticide residues analysis.

Determination of 6-Mercaptopurine in Rat Blood by Microdialysis Coupled with High Performance Liquid Chromatography on a Functionalized Multi-wall Carbon Nanotubes Modified Electrode

A new chemically modified electrode(CME) immobilized on the surface of multi-wall carbon nanotubes functionalized with carboxylic groups was fabricated. The results indicate that the CME exhibits efficiently electrocatalytic oxidation of 6-mercaptopurine(6-MP). The CME can be used as the working electrode in the liquid chromatography for the determination of 6-MP. The peak current of 6-MP is linearly changed with its concentration ranging from 4.0×10 -7 to 1.0×10 -4 mol/L with the calculated detection limit (S/N=3) of 2.0×10 -7 mol/L. Coupled with microdialysis sampling, the method has been successfully applied to assessing the content of 6-MP in rat blood.

Synthesis and Characterization of W-doped TiO_2 Supported by Hybrid Carbon Nanomaterials of Multi-walled Carbon Nanotubes and C_(60) Fullerene by a Hydrothermal Method

W-doped TiO2 supported by hybrid carbon nanomaterials of multi-walled carbon nanotubes and C60 fullerene was synthesized by a simple hydrothermal method. The material displayed high visible light photocatalytic activity. X-ray diffraction, field emission transmission electron microscopy, ultra violet/visible light absorption and photoluminescence spectroscopy were used to characterize the material as photoeatalyst. Photocatalytic activity on the degradation of Rhodamine B dye in an aqueous solution under ultraviolet light and visible light irradiation was also studied. The experimental results indicated that the photocatalytic activity of the material was much higher than that of pure TiO2 or Degussa P25 TiO2.

Electrical measurement on individual multi-walled carbon nanotubes

The characterization of electrical property of multi-walled carbon nanotubes (MWCNTs) on a nanometer scale is essential for their potential application in nano-electronic devices. The MWCNTs were synthesized on Fe2O3/SiO2/Si substrate and Pt plate substrate by simple thermal chemical vapor deposition (STCVD) technique and the electrical measurements of individual MWCNT grown on silicon substrate and Pt plate substrate were performed by home-made 'nano-manipulator', respectively. According to current-voltage curves obtained in the experiments the current density that the MWCNTs can carry is calculated to be about 107 A/cm2, which is much larger than that of normal metals.

Purified oxygenand nitrogen-modified multi-walled carbon nanotubes as metal-free catalysts for selective olefin hydrogenation

Oxygen and nitrogen-functionalized carbon nanotubes （OCNTs and NCNTs） were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.

Glassy carbon electrode modified with multi-walled carbon nanotubes sensor for the quantihication of antihistamine drug pheniramine in solubilized systems

A sensitive electroanalytical method for quantification of pheniramine in pharmaceutical formulation has been investigated on the basis of the enhanced electrochemical response at glassy carbon electrode modified with multi-walled carbon nanotubes in the presence of sodium lauryl sulfate.The experimental results suggest that the phcniramine in anionic surfactant solution exhibits electrocatalytic effect resulting in a marked enhancement of the peak current response.Peak current response is linearly dependent on the concentration of pheniramine in the range 200-1500 μg/mL with correlation coefficient 0.9987.The limit of detection is 58.31 μg/m L.The modified electrode shows good sensitivity and repeatability.

Preparation and Surface Modification of High-Density Chitosan/Functionalized Multi-walled Carbon Nanotubes Hollow Fibers

Functionalized multi-walled carbon nanotubes( fMWNTs) were prepared with chitosan via controlled surface deposition and crosslinking process and scanning electron microscopy( SEM),Fourier translation infrared spectroscopy( FT-IR) and Xray diffraction( XRD) are used to character properties. A novel high-density chitosan( HCS) was dissolved in f-MWNTs dispersed dilute acetic acid with a maximal concentration of 5. 8%. The hollow fibers can be made by extruding the solution into a dilute alkali solution through a wet-spinning process and the tensile properties of the materials were evaluated by universal tester. The surface property of fibers,pretreated by Helium( He) and the following grafted with gelatin was evaluated with X-ray photoelectron spectroscopy( XPS).As the hollow fibers were intended for neural tissue engineering,its suitability was evaluated in vitro using rat Schwann cells( RSC96) as model cells. The cells attachment,proliferation and morphology,were studied by various microscopic techniques. Based on the results,the gelatin grafted HCS / f-MWNTs hollow fibers could be used as a potential cell carrier in neural tissue engineering.

Ruthenium Catalyst Supported on Multi-Walled Carbon Nanotubes for CO Oxidation

This work proposes the synthesis of the 5%wt Ru on MWCNT catalyst and the influence of feed rate and testing variables for low-temperature oxidation affecting the CO2 yield. Morphology and incorporation of the nanoparticles in carbon nanotubes were investigated by specific surface area (BET method);thermogravimetric analyses (TGA);X-ray diffraction;Raman spectroscopy, transmission electron microscopy (TEM) and XPS. The conversions of CO and O2 were mostly 100% in groups C1 and C2 (temperature between 200 and 500°C with low WHSV). In order to assess the effect of mass on catalytic activity, condition C3 was tested at even lower temperatures. In the tested catalyst, high activity (100% CO and O2 conversion) was observed, keeping it active under reaction conditions, suggesting oxi-reduction of the RuO2 at surface without affecting the MWCNT but Lewis acid influencing the CO2 yield.