Study Of Multi-walled Carbon Nanotubes Research Articles

High-energy X-Ray diffraction study of multiwalled carbon nanotubes fabricated by arc discharge plasma process

Structural features of multiwalled carbon nanotubes (MWCNTs) have been analyzed quantitatively by high-energy X-ray diffraction (HE-XRD) with atomic pair distribution function (PDF) technique. It has been found that the nanotubes are mainly of scroll type and own an atomic arrangement defined on the nanometer length scale in terms of a unit cell and symmetry. They exhibit multipart local (sub-nanometer) and intermediate range (on nano-length-scale) structures. The structural information at different length-scales was used to probe the interlayer spacing distribution within the nanotubes. The radial dependence of interlayer spacing observed in pristine nanotubes presents tendency for alteration to uniform spacing of layer in the course of heating-cooling cycle in the range of 298–450 K. These spatial changes illustrate modification of Fermat type stroll with uneven interlayer distances in pristine nanotubes to more stable equidistant interlayer Archimedean spiral type in the heating-cooling treated ones.

Acute toxicity and 28-day repeated dose studies of multi-walled carbon nanotubes

In the light of the increased production and use of multi-walled carbon nanotube (MWCNT) in consumer products, there is a need for screening the potential toxicity of this nanomaterial. In the present study, the researchers have investigated the acute dermal and acute eye irritation in rabbits and acute oral irritation and 28-day repeated administration of MWCNT in rats. A single dose of 5000 mg/kg was used to test Albino Rabbits for acute dermal and eye irritation test. Similar dose was given to Sprague Dawley Rats for the acute oral and 28-day repeated dose test. Clinical signs/manifestations were closely observed for the first four (4) hours post sample administration and was continued for 1,2,3,7 and 14-day observation period. In acute toxicity study, no treatment-related death or toxic signs were observed with MWCNT. In the 28-day repeated dose study, no significant differences in hematology and clinical biochemistry were detected between control and MWCNT. However, histopathology results revealed mild periarteriolar lymphoid cell depletion in the spleen and mild tubular cell degeneration on the cortex and medulla of both kidneys of the rats while no remarkable lesions were seen on the other organs of both female and male rats.

Calorimetric, NEXAFS and XPS studies of MWCNTs with low defectiveness

DSC and calorimetric studies of multi-walled carbon nanotubes (MWCNTs) with average diameters in the range 7, 9 and 18 nm were carried out. MWCNTs were obtained by the CVD method. The kinetic processes in MWCNTs were studied from room temperature to 550 °C in a nitrogen flow using differential scanning calorimetry (DSC) on a Perkin – Elmer — 8000. It was found that exo- and endothermic peaks are not observed on the DSC curves after water evaporation. This indicates that all studied MWCNTs have a small number of defects, functional groups, and other impurities. The heat capacity of MWCNTs was measured by the relaxation method in the temperature range from 2 to 275 K by using PPMS. In the temperature dependences of the specific heat were observed that for MWCNTs with the decrease of the temperature below 20 K the curves shift to lower values with an increase the average diameter. The main result was that at temperatures below 45 K with the decreasing of the nanotubes diameter the ratio of heat capacity of nanotubes to the heat capacity of graphite increases. The perfection of structure and low amount of the defects, functional groups and impurity contamination for MWCNTs were demonstrated in the comparison of the XPS and NEXAFS spectra for these nanotubes with CVD prepared nanotubes (18 nm) after mechanical and chemical functionalization.

Nanotubes with horns: a clue to the growth mechanism?

A high-resolution transmission electron microscopy (HRTEM) study of multi-walled carbon nanotubes (MWCNTs) produced by a variant of the arc-discharge process is described. It is found that the nanotubes are frequently coated with a disordered carbon, and that the tubes are often incompletely formed, with nanohorn-like structures attached to the caps. This suggests that carbon nanohorns may be the precursors for the formation of nanotubes by arc-discharge. A possible mechanism for this process is suggested.

Structural and optical studies of multi-walled carbon nanotubes

This paper aims to synthesize MWCNTs by using the spray pyrolysis technique. The X-ray diffraction technique is done to accomplish structural characterizations and optical characterizations are done by using UV–visible spectro-photometry, Fourier-transform spectroscopy. A scanning electron micrograph has studied the morphology of these nanotubes. The SEM images show the tube-shape structure of MWCNTs, and XRD peaks at 26.04°, 44.12°, and 53.81° confirm that the MWCNTs were successfully synthesized by spray pyrolysis and have average particle size 8.9 nm. Optical bandgap found as ∼4.28 eV using Tauc’s plot.

Synthesis and photocatalysis study of multiwalled carbon nanotubes grown in a lead-based microspherical support

ABSTRACTPlumbonacrite films were used as support material for growth of carbon nanotubes and the resulting nanocomposite was tested as photocatalysts for the degradation of methylene blue dye. The plumbonacrite films were deposited on silicon substrates by a simple alkaline chemical bath deposition process. After the CNT growth process, the resulting nanocomposite samples were analyzed by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The high temperature during the CNT growth process decomposed the plumbonacrite material into lead microspheres, which were covered by the CNT constituting the nanocomposite films. Afterwards, the nanocomposite films were applied for the photodegradation of methylene blue molecules using natural sunlight. The nanocomposite films were reused for up to three cycles obtaining efficiencies in the degradation of the dye superior to 92% and a first order kinetics with rate constants of 8.9 × 10−3 min−1 in a maximum irradiation time of 240 minutes.

Cytotoxic, genetic and statistical analytical evaluation of functionalized CNTs with C2C12 cells

The present work was designed to apprehend the cytotoxic and genetic evaluation study of multiwalled carbon nanotubes (MWCNTs). The CNTs were surface functionalized via HNO3 and H2SO4 digestion process, confirmed via FTIR spectroscopy whereas the structure of CNTs was visualized with TEM. The obtained CNTs structures were utilized to control the proliferation rate of C2C12 cells. The cells were cultivated and % viabile and non viable cells % were checked by MTT assay with the influence of dose-dependent (500 ng/mL, 1000 ng/mL, 100 μg/mL) CNTs. Further the density of live and dead cells in liquid was also clearifies via confocal laser scanning microscopy (CLSM). Containing these, the genetic study to know the apoptosis caused due to CNTs were checked in presence of caspases 3 and 7 genes. The up-regulation data clearly favours the CNTs are responsible in cells death in C2C12 with the treatment at low (500, ng/mL) and (1000 ng/mL) high dosese. The statistical studies were also performed to authenticate the data for CNTs with different optimized parameters such as detection limit at low concentrations level, recoveries and relative standard deviation at measures 95% confidence level. The analyses palyses a significant role on C2C12 cells with the large effect of CNTs.

RENO-PROTECTIVE EFFICACY OF AQUEOUS CINNAMON BURMANNI EXTRACT ON MULTI-WALLED CARBON NANOTUBES-INDUCED TOXICITY

Multi-walled carbon nanotubes (MWCNTs) are widely used in industrial and biomedical applications. Exposure to these tubes causes inflammation, oxidative stress and/or function disorders in the body tissues and systems. The use of certain natural products that have antioxidant and/or anti-inflammatory activities might decrease this toxicity. Thus, the present study aims to assess the four weeks toxicity effect of inhaled MWCNTS on the kidneys of male rats, and the possible protective effect of aqueous extract of Cinnamon Burmanni (C. Burmanni). MWCNTs were synthesized in nano-photonic lab (Faculty of Science, Beni-Suef University). Thirty-two male rats (Rattus norvegicus) were divided equally into 4 groups: control group, cinnamon-treated group (daily, orally administrated 75 mg/kg body weight of aqueous C. Burmanni extract for 4 consecutive weeks), MWCNTs-treated group (animals were subjected to wood shaving cage litter containing 1.0 g MWCNTs/kg body weight, twice a week), and cinnamon and MWCNTs-treated group (treated simultaneously with both MWCNTs and aqueous C. Burmanni extract). Estimation of nitrite content, total thiols and reduced glutathione (GSH) concentrations, as well as glutathione S-transferase (GST) and glutathione peroxidase (GPx) activities in serum, in addition to the histopathological examination of kidney sections, were carried out. MWCNTs exposure resulted in significant elevation of nitrite content with significant decrease in GSH and total thiols levels and GST activity, and non-significant change in GPx activity in the serum samples. Histopathological studies of MWCNTs inhaled rats showed proteinaceous material accumulation in the lumen of renal tubules, vacuolation and congestion of glomerular tufts and perivascular oedema. Aqueous C. Burmanni extract greatly ameliorated these lesions via a significant decrease in serum nitrite content and significant elevation of serum GSH and total thiols contents as well as GST and GPx activity compared to their respective controls. In conclusion, aqueous C. Burmanni extract showed reno-protective effect against MWCNTs-induced cytoxicity via lowering reactive nitrogen species level and alleviating antioxidant enzymatic and non-enzymatic markers.

A 90-days inhalation toxicity study of multi-walled carbon nanotubes (MWCNTs) in Fisher 344 rats

A 90-days inhalation toxicity study of multi-walled carbon nanotubes (MWCNTs) in Fisher 344 rats

Transmission electron microscopy study of multi-walled carbon nanotubes of different morphology oxidized with nitric acid

Oxidation of conical and cylindrical carbon nanotubes (CNTs) was studied by physicochemical methods including high-resolution transmission electron microscopy. Differences in mechanisms of oxidation of these CNTs were revealed. The oxidation of conical CNTs with nitric acid first results in the formation of oxygen-containing groups uniformly distributed over the CNT surface, and then the carbon material undergoes fragmentation and destruction. The treatment of cylindrical CNTs with nitric acid results in oxidation at defect sites followed by a decrease in the tube thickness and a change in the pore structure of the carbon material.

Investigation on the thermal conductivity and rheological properties of multiwalled carbon nanotube (MWCNT)—dowtherm a nanofluids

ABSTRACTIn the present work, the thermal conductivity and viscosity studies of multiwalled carbon nanotubes (MWCNTs)—Dowtherm A (eutectic mixture of biphenyl (C12H10) and diphenyl oxide (C12H10O)) nanofluids—are presented considering the influence of particle weight percentage (0.001–0.005 wt%) and temperature ranging from 303 K to 323 K. As-received MWCNTs are characterized using x-ray diffraction (XRD), FT-Raman spectroscopy, thermogravimetric analysis, and transmission electron microscopy (TEM). The suspensions consist of MWCNTs dispersed in Dowtherm A and they are stabilized by sonication. The result shows that the thermal conductivity of MWCNT–Dowtherm A nanofluids depends strongly on particle concentration and temperature which increases linearly with both the weight percentage of nanoparticles and also with that of temperature. It is also observed that the viscosity of nanofluids increases with the increase in concentration of nanoparticle and decreases with the rise in temperature. Stabilization mechanisms of dispersions are analyzed by UV-visible (Vis) spectrophotometry measurement to quantitatively characterize the colloidal stability of the MWCNT dispersions.

Highly enhanced and temporally stable field emission from MWCNTs grown on aluminum coated silicon substrate

In this work, a detailed field emission study of multi-walled carbon nanotubes (MWCNTs) grown on Si and Al coated Si substrates is reported. Morphological and microstructural studies of the films show higher entanglement of CNTs in the case of CNT/Si film as compared to CNT/Al/Si film. Raman studies show that the defect mediated peak (D) is substantially suppressed as compared to graphitic peak (G) resulting in significant reduction in ID/IG value in CNT/Al/Si film. Field emission (FE) current density of CNT/Al/Si film (∼25 mA/cm2) is significantly higher as compared to that of CNT/Si film (∼1.6 mA/cm2). A substantial improvement in temporal stability is also observed in CNT/Al/Si film. This enhancement in field emission current is attributed to strong adhesion between substrate and CNTs, low work function, high local field enhancement factor at the CNT tips and less entanglement of CNTs grown on Al/Si. The temporally stable CNT/Al/Si cold cathode can be a potential candidate to replace conventional electron sources in prototype devices.

Measuring Nanomaterial Release from Carbon Nanotube Composites: Review of the State of the Science

Hazard studies of “as-produced” nanomaterials are increasingly available, yet a critical gap exists in exposure science that may impede safe development of nanomaterials. The gap is that we do not understand what is actually released because nanomaterials can change when released in ways that are not understood. We also generally do not have methods capable of quantitatively measuring what is released to support dose assessment. This review presents a case study of multi-walled carbon nanotubes (MWCNTs) for the measurement challenge to bridge this gap. As the use and value of MWCNTs increases, methods to measure what is released in ways relevant to risk evaluation are critically needed if products containing these materials are to be economically, environmentally, and socially sustainable. This review draws on the input of over 50 experts engaged in a program of workshops and technical report writing to address the release of MWCNTs from nanocomposite materials across their life cycle. The expert analyses reveals that new and sophisticated methods are required to measure and assess MWCNT exposures for realistic exposure scenarios. Furthermore, method requirements vary with the materials and conditions of release across life cycle stages of products. While review shows that the likelihood of significant release of MWCNTs appears to be low for many stages of composite life cycle, measurement methods are needed so that exposures from MWCNT-composites are understood and managed. In addition, there is an immediate need to refocus attention from study of “as-produced” nanomaterials to coordinated research on actual release scenarios.

Health surveillance study of workers who manufacture multi-walled carbon nanotubes

While many in vivo and in vitro toxicology studies of multi-walled carbon nanotubes (MWCNTs) have already indicated that exposure to MWCNTs can potentially induce health effects in humans, the actual health effects of MWCNTs among exposed workers are not yet known. Moreover, the levels of exposure and internal doses of MWCNTs are becoming more and more important for estimating the health effects resulting from exposure to MWCNTs. However, information on biomonitoring and exposure to MWCNTs remains limited. Therefore, the authors conducted a health surveillance study in a workplace that manufactures MWCNTs, including assessment of the personal and area exposure levels to MWCNTs, a walk-through evaluation of the manufacturing process, and collection of blood and exhaled breath condensates (EBCs) from the MWCNT manufacturing and office workers. In addition, a pulmonary function test was also conducted on the MWCNT manufacturing workers (9) and office workers (4). The worker exposure to elemental carbon was found to be 6.2–9.3 μg/m3 in the personal samplings and 5.5–7.3 μg/m3 in the area samplings. Notwithstanding, the workers exhibited a normal range of hematology and blood biochemistry values and normal lung function parameters. When analyzing the EBCs, the malondialdehyde (MDA), 4-hydroxy-2-hexenal (4-HHE) and n-hexanal levels in the MWCNT manufacturing workers were significantly higher than those in the office workers. The MDA and n-hexanal levels were also significantly correlated with the blood molybdenum concentration, suggesting MDA, n-hexanal and molybdenum as useful biomarkers of MWCNT exposure.

Functionalization of Multi-walled Carbon Nanotubes with 6-Aminobenzothiazole and their Temperature-dependent Magnetic Studies

Magnetically responsive functionalized multi-walled carbon nanotubes (Bet-f-MWCNTs) were prepared using 6-Aminobenzothiazole (ABT) through acid functionalization. Bet-f-MWCNTs were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, Ultra violet-visible-near infrared spectroscopy (UV-VIS-NIR) and powder X-Ray Diffraction (XRD). The transmission electron microscopy (TEM) images were visualized as further evidence for the successful modifications on the sidewalls of the MWCNTs. The temperature dependent magnetization and hysteresis studies of multiwalled carbon nanotubes (MWCNTs), carboxylic acid functionalized MWCNTs (Acid-f-MWCNTs) and Bet-f-MWCNTs were investigated for the first time. The change in the magnetic behavior of Bet-f- MWCNTs at lower temperature was attributed to the functionalization of MWCNTs by the organic moiety benzothiazole (BT). Interestingly, Bet-f-MWCNTs showed higher saturation magnetization value of 0.94 emu/g compared to MWCNTs and Acid-f-MWCNTs at low temperature. Moreover, Bet-f-MWCNTs exhibited higher coercive value of 109 Oe compared with the value of 90 Oe for MWCNTs indicating the functionalized MWCNTs as a promising candidate in electrical motors and magnetic recording media.

Morphology and Structural Studies of Multi-walled Carbon Nanotubes by Spray Pyrolysis using Madhuca Longifolia Oil

Morphology and Structural Studies of Multi-walled Carbon Nanotubes by Spray Pyrolysis using Madhuca Longifolia Oil

Comparative studies of multi-walled carbon nanotubes (MWNTs) and octadecyl (C18) as sorbents in passive sampling devices for biomimetic uptake of polycyclic aromatic hydrocarbons (PAHs) from soils

To avoid overestimating the risk of polycyclic aromatic hydrocarbons (PAHs), research is needed to evaluate the bioavailable portion of PAHs in the environment. However, limited PSDs were developed for a terrestrial soil system. In this study, two sorbents, octadecyl (C18) and multi-walled carbon nanotubes (MWNTs), were individually evaluated as sorbents in passive sampling devices (PSDs) as biomimetic samplers to assess the uptake of PAHs from soil. C18-PSDs were an excellent biomimetic tool for PAHs with a low molecular weight in complex exposure conditions with different soil types, types of PAHs, aging periods, and initial PAH concentrations in soil. The utility of MWNT-PSDs was limited by extraction efficiencies of PAHs from MWNTs. However, when compared to C18-PSDs, they had higher adsorption capacities and were less expensive. This study provides data regarding useful techniques that can be used in risk assessment to assess the bioavailability of PAHs in soil.

Depolarized dynamic light scattering study of multi-walled carbon nanotubes in solution

Depolarized dynamic light scattering study of multi-walled carbon nanotubes in solution

The study of multi-walled carbon nanotubes with different diameter as anodes for lithium-ion batteries

Multi-walled carbon nanotubes (MWCNTs) with different diameter range are employed as the anode materials in lithium-ion batteries (LIBs). The influence of diameter and pore structure on the electrochemical behavior of MWCNTs has been investigated by characterization of morphology and structure, nitrogen adsorption and desorption measurement, charge/discharge tests, and electrochemical impedance spectroscopy (EIS). The results show that MWCNTs with a diameter of 40–60nm display the highest specific capacity (187.4mAhg−1 at the charge/discharge rate of 50mAg−1) and good cyclability (101.9% Coulomb efficiency after 50 cycles). The excellent electrochemical performance verifies the feasibility of MWCNTs as a promising candidate for the anode of LIBs.

XANES study of multi-walled carbon nanotubes modified by HNO3 vapor

A simple, efficient, and practical method for the surface modification of multi-walled carbon nanotubes (MWCNTs) by nitric acid vapor is presented. X-ray absorption near edge structure (XANES) spectroscopy has been applied to study the temperature dependent evolution of the electronic structure of HNO3 vapor treated MWCNTs. After treatment the formation of oxygen containing functional groups was observed in C K-edge and O K-edge XANES spectra of MWCNTs. Moreover, the degree of oxidation made to MWCNTs can be easily controlled by changing treatment temperature. Compared to the conventional liquid HNO3 treatment, the advantages of this method should allow effective large-scale production of oxygenated MWCNTs for the applications.