Kinds Of Multi-walled Carbon Nanotubes Research Articles

Facile detection of pesticides using atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry with multi-walled carbon nanotubes-based matrix

A novel atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry (AP-MALDI-MS) method was established for the facile detection of pesticides in ambient environment. Four kinds of multi-walled carbon nanotubes (MWCNTs)-based matrix were synthesized and utilized to enhance the ionization efficiency of pesticides. Organophosphorus, anilinopyrimidine, carbamate, triazine, triazole and benzimidazole pesticides were directly desorbed and ionized from MWCNTs-based matrix in ambient environment, showing clear background and good sensitivity. In a comparison, Fe 3 O 4 -doped MWCNTs improved the intensity of pesticide ions more than the other three matrices. Moreover, MWCNTs-based matrix exhibited better performance than organic matrix. Quantitative analysis of pesticides using AP-MALDI-MS was validated to be adequate linearity, repeatability and sensitivity. Overall, AP-MALDI-MS combined with MWCNTs-based matrix enables the directly qualitative and quantitative analysis of pesticides in ambient environment. In this work, a novel atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry (AP-MALDI-MS) method for the facile detection of pesticides was established.

One-Step Construction of Multi-Walled CNTs Loaded with Alpha-Fe2O3 Nanoparticles for Efficient Photocatalytic Properties.

The aggregation and the rapid restructuring of the photoinduced electron−hole pairs restructuring in the process of photoelectric response remains a great challenge. In this study, a kind of Multi-walled carbon nanotubes loaded Alpha-Fe2O3 (CNTs/α-Fe2O3) heterostructure composite is successfully prepared via the one-step method. Due to the synergistic effect in the as-prepared CNTs/α-Fe2O3, the defect sites and oxygen-containing functional groups of CNTs can dramatically improve the interface charge separation efficiency and prevent the aggregation of α-Fe2O3. The improved photocurrent and enhanced hole–electron separation rate in the CNTs/α-Fe2O3 is obtained, and the narrower band gap is measured to be 2.8 ev with intensive visible-light absorption performance. Thus, the CNTs/α-Fe2O3 composite serves as an excellent visible light photocatalyst and exhibits an outstanding photocatalytic activity for the cationic dye degradation of rhodamine B (RhB). This research supplies a fresh application area forα-Fe2O3 photocatalyst and initiates a new approach for design of high efficiency photocatalytic materials.

Thermal and thermo-mechanical characterization of MWCNTs integrated E-glass/carbon fabric reinforced composites

The prime objective of this work is to interpret the effects of different kinds of multi-walled carbon nanotubes (MWCNTs) on thermal and thermo-mechanical properties of E-glass/carbon fabric reinforced hybrid composites. MWCNTs enhanced composites are fabricated by vacuum-assisted resin transfer molding method. The thermal and thermo-mechanical characterizations are carried out using a differential scanning calorimeter, thermogravimetric analyzer and dynamic mechanical analyzer, while the morphological structure is examined by scanning electron microscope. The results show that the addition of MWCNTs and changing the fabric stacking sequences do not have effects on the phase changes of the materials but have reducing effects on the void ratio. Besides, it is observed that the added MWCNTs increase the degradation temperature of the composite material and the modulus values. The pristine MWCNT is found more effective on thermal and thermo-mechanical properties of composite structures than functionalized ones.

Effect of pretreatment on the microstructure of multiwalled carbon nanotubes

Four kinds of multi-walled carbon nanotubes pretreated by different methods were studied. Chemically functionalized (hydroxylation and carboxylation) CNTs were prepared by oxidizing original CNTs in H2SO4 solutions of different temperatures and concentrations by KMnO4. Graphitized CNTs were prepared by heat-treating original CNTs in an inert gas at 2800°C for 20 hours. CNTs Nickel plating on the surface was obtained by electroless plating. The effect of pretreatment on the surface state and microstructure of carbon nanotubes was also studied. The results showed that Chemical functionalization could form some functional groups on the surface of CNTs, which could not only improve the compatibility of CNTs with some solvents, but also purified CNTs, which had a positive effect on the preparation of composite materials. High-temperature graphitization treatment could significantly increase the degree of crystallization of carbon nanotubes and reduce structural defects. After electroless nickel plating, evenly distributed nano-sized metal particles were formed on the surface of the CNTs, and the interface between the two was well bonded.

Effect of diameter of multi-walled carbon nanotubes on mechanical properties and microstructure of the cement-based materials

This paper is intended to investigate the effects of multi-walled carbon nanotubes (MWCNTs) with different inner diameters on the mechanical properties (flexural strength and compressive strength) and microstructures of cement-based materials. Three kinds of multi-walled carbon nanotubes (MWCNTs) with diameter of 10–20 nm, 20–40 nm and 40–60 nm were ready to reinforce cement-based materials. And each batch incorporated 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt% MWCNTs by cement weight. To obtain a uniform distribution of MWCNTs in the cement-based materials, the effects of ultrasonic dispersion time and intensity on the properties of MWCNTs cement-based materials were studied. In addition, the relationships between mechanical properties, porosity and diameter of MWCNTs were investigated. Experimental results showed that the improvements of flexural strength and compressive strength of cement-based materials were altered by increasing the diameter of MWCNTs. Microstructure analysis by SEM and MIP tests indicated that MWCNTs with diameter of 10–20 nm have the best effect on optimizing pore structure. The results of this study were useful to determine the diameter and content of MWCNTs required for optimum pore structure and maximum strength enhancement of cement-based materials.

Carbon material-immobilized ionic liquids were applied on absorption of Hg2+ from water phase.

In this study, several immobilized ionic liquid adsorbents on carbon materials were synthesized with impregnation method. The carrier materials were activated carbon and three kinds of multi-walled carbon nanotubes. And the synthetic adsorbents immobilized different kinds of ionic liquids were characterized by Boehm titration, FT-IR, XPS, TG, and BET analysis, respectively. Finally, carbon materials after [C4mim]HSO4 immobilization were selected as adsorbent to remove Hg2+ from water phase. The optimum conditions of adsorption test of ionic liquid immobilized by multi-walled carbon nanotubes were as follows: the initial concentration of Hg2+ was 400 mg/L, the adsorbent addition amount was 40 mg, the temperature was 20 °C, the reaction time was 200 min, the removal rate of Hg2+ peaked at 62.95%, the adsorption capacity was reached 79.00 mg/g. The optimum conditions of adsorption test of ionic liquid immobilized by activated carbon were as follows: the initial concentration of Hg2+ was 300 mg/L, the adsorbent addition amount was 0.2 g, the temperature was 20 °C, pH was 2.0, the reaction time was 100 min, the removal rate of Hg2+ was more than 99%, the adsorption capacity was 118.65 mg/g. The adsorption isotherm fitting study found that the adsorption of adsorbent on Hg2+ was more in line with the Langmuir model, and the adsorption kinetics study shows that the adsorption process is consistent with the pseudo-second-order kinetic equation. The results of kinetic analysis are further verified by thermodynamic analysis.

Endoplasmic reticulum stress mediated apoptosis via JNK in MWCNT-exposed in vitro systems: size, surface functionalization and cell type specificity.

The aim of the present study was to evaluate the underlying mechanism of multi-walled carbon nanotubes (MWCNT) induced cellular response and their potential cross-talk, specifically, between endoplasmic reticulum (ER) stress, MAPK activation and apoptosis and how these nano-bio interactions depend on the physico-chemical properties of MWCNT. For this purpose, human bronchial epithelial (Beas2B) and human hepatoma (HepG2) cell lines, were exposed to five kinds of MWCNTs which differ in functionalization and aspect ratios. Tissue-specific sensitivity was evident for calcium homeostasis, ER-stress response, MAPK activation and apoptosis, which further depended on surface functionalization as well as aspect ratios of MWCNT. By applying specific pharmaceutical inhibitors, relevant biomarkers gene and proteins expressions, we found that possibly MWCNT induce activation of IRE1α-XPB1 pathway-mediated ER-stress response, which in turn trigger apoptosis through JNK activation in both type of cells but with variable intensity. The information presented here would have relevance in better understanding of MWCNT toxicity and their safer applications.

An image-driven finite element modeling method for evaluating the stress and strain distribution in carbon nanotubes/epoxy composites

Due to the complex morphology of carbon nanotubes (CNTs) in an epoxy resin, it is difficult to establish finite element (FE) models using common methods. Therefore, this study introduces an approach using real TEM images of CNTs/epoxy composites to establish FE models and obtain real stress and strain distributions. Two kinds of multi-walled carbon nanotubes (MWCNTs), unmodified and plasma-treated MWCNTs, were also used to investigate the effects of the dispersion state of MWCNTs on the mechanical properties of MWCNTs/epoxy composites. Due to the real-shape models, the simulation results clearly showed that well-dispersed MWCNTs more effectively transferred stresses, and thus reduced localized stress concentration and improved the deformation resistance in composites. The composite with poorly-dispersed MWCNT exhibited a higher stress concentration at MWCNTs and more severely strained areas in the epoxy resin. In this case, debonding was very likely to occur at the interface of the two substances, and caused the formation of preliminary cracks in the components.

Comparison of the effects of multiwall carbon nanotubes on the epithelial cells and macrophages

Effects of two kinds of multiwall carbon nanotubes (MWCNTs) on cells were examined. The effects of MWNT-7, which has been reported to be carcinogenic, and MWCNT-B, whose toxicity is unclear, were examined in both epithelial cells and macrophages. Human lung carcinoma A549 cells were used as representative epithelial cells and differentiated human monocyte THP-1 cells, as well as rat pulmonary macrophages NR8383, were employed to examine possible harmful effects of the MWCNTs. The MWCNTs induced the production of chemokines such as interleukin-8 (IL-8). MWCNTs were found to more strongly affect macrophages than epithelial cells. In addition, the toxicity was more pronounced in the MWNT-7 exposed cells than in those exposed to MWCNT-B. Cytochalasin D and amiloride treatment of differentiated THP-1 cells reduced cell-associated MWCNTs and IL-8 induction. To confirm these cellular influences in vivo, intratracheal administration of each type of MWCNT was performed by pharyngeal aspiration in the mouse lung. Analysis of bronchoalveolar lavage fluid (BALF) showed increase of inflammatory monocyte in MWNT-7 exposed animals at 1week after. In addition, neutrophils in the BALF were also significantly increased MWNT-7 exposed animals at 1 week and 1 month after. Aspiration of MWNT-7 caused formation of granulomas in the lung. Formation of the granulomas was not observed in the case of MWCNT-B. These results suggest that cellular uptake of the MWCNTs by phagocytosis and chemokine induction is important aspects of their toxicity.

Investigation of the effect of CNTs on the mechanical properties of LPET/glass fiber thermoplastic composites

Within this research, four kinds of multiwalled carbon nanotubes (MWCNTs; 0.0, 0.7, 0.9, and 1.1 wt%) integrated thermoplastic composites with commingled yarns (low melting point polyethylene terephthalate fiber/glass fiber) were fabricated using hot-press machine. The fabricated composites were tested against tensile and three-point flexural loadings. Specimens with 0.9-wt% MWCNTs in 90° direction showed the highest values of tensile and flexural properties with an improvement of about 7% and 33% in tensile and flexural modulus and about 3% and 65% in tensile and flexural strength compared to specimens without MWCNTs in 90° direction. This improvement can most likely be attributed to an increase in interfacial adhesion due to the presence of the carbon nanotubes.

New Approach to Increase CNT Contents in Electrodeposited Ni-CNT Composite Thin Films by Modified Current Conditions

In this paper, an electrodeposition method for nickel (Ni)-multiwalled carbon nanotubes (MWCNTs) composite thin films is presented. The composite film is deposited using an electrolyte in which MWCNTs are randomly dispersed. Two kinds of MWCNTs annealed at 1200 °C and 2600 °C were used for the electrodeposition using pulse or sine waveforms. An electrodeposition condition using CNT annealed at 1200 °C and sine waveform with maximum current 0.2 A and frequency 5.0 Hz results in a maximum CNT weight fraction of 5.4% in the composite film. The electrodeposited film with the maximum CNT content shows a microindentation hardness of 17.0 GPa, which is approximately 1.45 times greater than that of a pure Ni film. Moreover, mechanical strengthening is found in the composite films due to the addition of CNTs. This result shows that the electrodeposition for the Ni-MWCNT composite thin film with modified current condition would be applicable to microsystem, which requires micromechanical components with high mechanical strength.

Preparation, characterization and toxicity evaluation of [formula omitted] and NiO-filled multi-walled carbon nanotubes loaded to chitosan

Multi-walled Carbon nanotubes (MWCNTs) have been extensively explored for a variety of biomedical and tissue engineering applications. Their high surface area provides tunable multiple attachment sites for acquiring appropriate biological and biomechanical properties. Despite, the cytotoxicity of MWCNTs is dubious with or without surface functionalization. In the present study, two different kinds of multi-walled carbon nanotubes (MWCNTs) in the presence of cobalt oxide (Co3O4) and nickel oxide (NiO) nanoparticles have been prepared through a simplistic and effective method, and thus, the Co3O4/MWNT and NiO/MWNT structures are loaded to chitosan in methanol solution at 65°C. Results upon the synthesis and structural characterization were obtained by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM), respectively. It has been shown that the tuned functionalized MWCNTs are able to reduce cytotoxic effects and improve biocompatibility and be more appropriate for potential future clinical applications.

Carbon nanotube-impeded transport of non-steroidal anti-inflammatory drugs in Xiangjiang sediments.

Carbon nanotubes (CNTs), usually with a superior affinity with organic chemicals, are expected to ultimately released to the environment through their manufacturing, usage, and eventual disposal, which will influence the mobility and environmental risk of nonsteroidal anti-inflammatory drugs (NSAIDs). In this study, batch and column experiments were performed to examine the effects of two kinds of multi-walled carbon nanotubes (MWCNTs: MWCNT2040, MWCNT0815) and one kind of single-walled carbon nanotubes (SWCNTs) on the environmental fate of two NSAIDs, paracetamol (PA) and diclofenac sodium (DS), in sediments. Impact ways of CNTs including addition in inflow and mixing with sediments were investigated. The adsorption capacity of NSAIDs on sediments increased with increasing CNTs/sediments ratios and in an order of MWCNT2040<MTWCNT0815<SWCNT. In column tests, PA showed a higher mobility than DS. With CNTs in inflow, the amounts of NSAIDs leached from sediment columns reduced because of the association with CNTs. For the sediment columns mixed with CNTs, breakthrough of the two NSAIDs was dramatically retarded, and the NSAIDs were hard to separate from CNT-polluted sediments. Our work provides useful insights into fate, transport and risk assessment of NSAIDs in the presence of CNTs.

Contact resistance of multi-walled carbon nanotube/natural rubber nanocomposites with metallic ball

This paper reports on the contact resistance (Rc) between carbon filler/natural rubber (NR) nanocomposite and gold ball: three varieties of nanocomposites were prepared from carbon black (CB) and two kinds of multi-walled carbon nanotubes (MWCNTs) with different diameter. Rc of MWCNT/NR nanocomposite was remarkably less than that of CB/NR nanocomposites. The relationship between Rc of MWCNT/NR nanocomposites and applied load was expressed in the formula, Rc=C·P−n (P: load, C and n: constant): for the MWCNTs (diameters of 13nm)/NR and MWCNTs (diameters of 67nm)/ NR nanocomposites, they were expressed as Rc=1724·P−0.6 and Rc=344·P−0.37, respectively. The former (MWCNT, ϕ13nm) showed higher Rc than the latter (MWCNT, ϕ67nm) over whole region of applied load. The mechanical hardness of the former was higher (90 HsA) than that of the latter (82 HsA). Therefore, the smaller contact area between the nanocomposite and gold ball of the former resulted in higher Rc. The apparent specific contact resistivity was calculated from the observed values of Rc and contact area: 130Ωmm2 and 127Ωmm2 for the former (MWCNT, ϕ13nm) and the latter (MWCNT, ϕ67nm), respectively.

Fragmentation characteristics of undoped and nitrogen-doped multiwalled carbon nanotubes in aqueous dispersion in dependence on the ultrasonication parameters

Sonication techniques are commonly used to disagglomerate carbon nanotube bundles into more or less uniformly distributed individual tubes. The present study discusses the statistical length distribution of multiwalled carbon nanotubes (MWCNTs) as affected by varied sonication time, sonication amplitude and overall energy input applied. Undoped and nitrogen-doped multiwall carbon nanotubes (N-MWCNTs) were investigated, and the influence of nitrogen in the carbon structure on the length-reduction behavior during sonication was assessed. Both kinds of MWCNTs were synthesized using the same process, an Aerosol Assisted Chemical Vapor Deposition (AACVD), utilizing cyclohexane and acetonitrile as precursors. X-ray photoelectron spectroscopy (XPS) clarified the chemical bonding in the CNTs and proved the incorporation of nitrogen in the carbon lattice. A drastically shortening of the initial length, i.e. the carpet length, after short times was shown. It was also found that such incorporation of nitrogen results in distinctly modified length reduction behavior during ultrasonication. The N-MWCNTs showed a much more pronounced length-reduction with higher ultrasonication amplitude than the undoped MWCNTs. This can be explained by the weaker chemical bond between C and N in a CNT-lattice, as compared to that among the carbon atoms only. On the other hand, sonication time has no particular effect on the fracture of N-MWCNTs when compared to the undoped MWCNTs.

Comparative investigation into surface charged multi-walled carbon nanotubes reinforced Cu nanocomposites for interconnect applications

Abstract We present the electrodeposition of copper (Cu) nanocomposites with a high content of carbon nanotubes (CNTs), and evaluate the mechanical and thermal properties of the nanocomposites. Two kinds of multi-walled CNTs (MWCNTs), thermally-annealed at 1200 °C and 2600 °C, are pretreated in a polyelectrolyte solution to show positive charges on their surfaces and added into a sulfuric Cu electroplating solution. The weight fractions of the MWCNTs in the electroplated composites are 5.3 wt% and 2.8 wt%, respectively. The Young's moduli of the composites are approximately 1.2 times and 1.1 times greater than that of a pure Cu thin film, and the coefficients of thermal expansion (CTEs) of the composites are reduced to be 77% and 85% of the CTE of the pure Cu film, respectively. The mechanical strengthening and thermal expansion reduction are found in the composite. These results show that the nanocomposites would be used instead of Cu thin film for interconnect applications.

Effect of blending carbon nanoparticles and nanotubes on the formation of porous structure and the performance of proton exchange membrane fuel cell catalyst layers

Different kinds of sub-micron structured carbon, namely carbon black and multi-walled carbon nanotubes (MWCNTs), were blended in catalyst ink in order to fabricate catalyst layers having differing porous structures. Carbon black is used as catalyst support in the conventional catalyst layers; the pore structure depends strongly on its aggregate structure. MWCNTs have a structure completely different from the carbon black at sub-micron scale. Two kinds of MWCNT, of differing diameters, were used as blending materials in the catalyst ink with the platinum-supported carbon, and their effects on the porous structure and cell performance were investigated. The catalyst layer containing thick MWCNT had lower porosity, fewer micro-cracks and larger pores than the conventional catalyst layer blended with carbon black. The MWCNT diameter influenced the distribution of pore sizes in the catalyst layers. The catalyst layer containing the smaller diameter MWCNTs displayed a shift in the peak of the pore size distribution, toward smaller size. These characteristic porous structures affected the performance of the resulting cell and caused a large voltage drop at high current densities in the polarization curve. This is because of the porosity and also the pore size.

Bioactivity of MWCNT in Conidia of Entomopathogenic Fungus Isaria fumosorosea

The bioactivity of three kinds of multi-walled carbon nanotubes (MWCNT) towards the conidia of entomopathogenic fungus Isaria fumosorosea was examined in an in vitro study. Commercial—raw and functionalized—carboxylated MWCNT were applied. A fungal conidia suspension was placed in contact with dispersed MWCNT over different time-periods. After contact with the nanomaterial, the conidia were cultured on dishes and both the linear vegetative mycelium growth and the sporulation and germination of the spores derived from the culture were investigated. Also, the pathogenicity of the conidia after contact with MWCNT was examined in relation to test larvae. No fungistatic activity of MWCNT relative to I. fumosorosea conidia was demonstrated. Conidia contact with MWCNT resulted in the following changes in vital processes in the subsequent culture compared to the control standard culture: (1) raw MWCNT limited mycelium inoculation, but the growth rate observed later in the log-phase was more intense; (2) after 24-h conidia contact with all MWCNT types, the mycelium sporulated the most intensively; longer contact resulted in sporulation process limitation. Germination of conidia after contact with the MWCNT was not significantly modified. Raw MWCNT potentiated conidia pathogenicity towards test insects. It was observed that carboxylation of MWCNT reduces the bioactivity of this nanomaterial towards the investigated conidia.

Subchronic toxicity and cardiovascular responses in spontaneously hypertensive rats after exposure to multiwalled carbon nanotubes by intratracheal instillation.

The tremendous demand of the market for carbon nanotubes has led to their massive production that presents an increasing risk through occupational exposure. Lung deposition of carbon nanotubes is known to cause acute localized pulmonary adverse effects. However, systemic cardiovascular damages associated with acute pulmonary lesion have not been thoroughly addressed. Four kinds of multiwalled carbon nanotubes (MWCNTs) with different lengths and/or iron contents were used to explore the potential subchronic toxicological effects in spontaneously hypertensive (SH) rats and normotensive control Wistar-Kyoto (WKY) rats after intratracheal instillation. MWCNTs penetrated the lung blood-gas barrier and accumulated in the liver, kidneys, and spleen but not in the heart and aorta of SH rats. The pulmonary toxicity and cardiovascular effects were assessed at 7 and 30 days postexposure. Compared to the WKY rats, transient influences on blood pressure and up to 30 days persistent decrease in the heart rate of SH rats were found by electrocardiogram monitoring. The subchronic toxicity, especially the sustained inflammation of the pulmonary and cardiovascular system, was revealed at days 7 and 30 in both SH and WKY rat models. Histopathological results showed obvious morphological lesions in abdominal arteries of SH rats 30 days after exposure. Our results suggest that more attention should be paid to the long-term toxic effects of MWCNTs, and particularly, occupationally exposed workers with preexisting cardiovascular diseases should be monitored more thoroughly.

Structure Formation and Characterization of PEMFC Catalyst Layers Blended with Multi-Walled Carbon Nanotubes

Different kinds of sub-micron structured carbon, which are carbon black and multi-walled carbon nanotubes (MWCNTs), were blended in catalyst ink to fabricate catalyst layers which differ in pore structure. Carbon black is used as catalyst support in the conventional catalyst layers and the porous structure strongly depends on its aggregate structure. MWCNTs have completely different structure with the carbon black in sub-micron scale. Therefore, two kinds of MWCNTs were blended with the platinum-supported carbon in the catalyst ink and the effects on the structure were investigated. The catalyst layer which contains MWCNT showed lower porosity, fewer micro-cracks and large pores than the conventional catalyst layer which was blended with carbon black. These characteristic porous structure affected cell performance and showed large voltage drop at high current density in its polarization curve.