Ability Of Multi-walled Carbon Nanotubes Research Articles

The Method and Study of Detecting Phenanthrene in Seawater Based on a Carbon Nanotube-Chitosan Oligosaccharide Modified Electrode Immunosensor.

Phenanthrene (PHE), as a structurally simple, tricyclic, polycyclic aromatic hydrocarbon (PAHs), is widely present in marine environments and organisms, with serious ecological and health impacts. It is crucial to study fast and simple high-sensitivity detection methods for phenanthrene in seawater for the environment and the human body. In this paper, a immunosensor was prepared by using a multi-wall carbon nanotube (MWCNTs)-chitosan oligosaccharide (COS) nanocomposite membrane loaded with phenanthrene antibody. The principle was based on the antibody-antigen reaction in the immune reaction, using the strong electron transfer ability of multi-walled carbon nanotubes, coupled with chitosan oligosaccharides with an excellent film formation and biocompatibility, to amplify the detection signal. The content of the phenanthrene in seawater was studied via differential pulse voltammetry (DPV) using a potassium ferricyanide system as a redox probe. The antibody concentration, pH value, and probe concentration were optimized. Under the optimal experimental conditions, the response peak current of the phenanthrene was inversely proportional to the concentration of phenanthrene, in the range from 0.5 ng·mL-1 to 80 ng·mL-1, and the detection limit was 0.30 ng·mL-1. The immune sensor was successfully applied to the detection of phenanthrene in marine water, with a recovery rate of 96.1~101.5%, and provided a stable, sensitive, and accurate method for the real-time monitoring of marine environments.

Investigation on visible light assisted gas sensing ability of multi-walled carbon nanotubes coated with pyrene based organic molecules

Abstract In this work, we have investigated the visible light assisted gas sensing properties of multiwalled carbon nanotubes (MWCNTs) functionalized with two organic molecules namely pyrene tetratopic ligands (PTL), and 1-pyrene acetic acid (PAA). Structural, optical and electrical properties have been examined on pure and functionalized samples using FESEM, Raman spectroscopy, UV–Visible spectroscopy, Photoluminescence (PL) spectroscopy, and current -voltage (I–V) characteristics. Sensor devices have been fabricated and tested in a gas sensor setup by passing saturated vapours of different VOCs like ethanol, n-hexane and triethylamine under dark and visible light conditions. Scanning Kelvin probe (SKP) studies have demonstrated that pyrene-MWCNTs hybrids significantly alter the contact potential difference upon interaction with volatile organic compounds (VOCs) and the response depends on the functional groups. The PTL+MWCNTs (sensitivity = 9.99 × 10−4 ppm−1) hybrid has outperformed when compared to PAA functionalized counterparts (sensitivity = 2.27 × 10−5 ppm−1) with triethylamine exposure. The presence of additional –COOH groups in PTL furnishes strong intermolecular hydrogen bonding through donor-acceptor interactions with the VOCs. Overall, our results suggests that the MWCNTs coated with pyrene molecules bearing suitable functional groups can be efficient sensors for detection of VOCs.

Novel Nanohybrids Based on Supramolecular Assemblies of Meso-tetrakis-(4-sulfonatophenyl) Porphyrin J-aggregates and Amine-Functionalized Carbon Nanotubes.

The ability of multiwalled carbon nanotubes (MWCNTs) covalently functionalized with polyamine chains of different length (ethylenediamine, EDA and tetraethylenepentamine, EPA) to induce the J-aggregation of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) was investigated in different experimental conditions. Under mild acidic conditions, protonated amino groups allow for the assembly by electrostatic interaction with the diacid form of TPPS, leading to hybrid nanomaterials. The presence of only one pendant amino group for a chain in EDA does not lead to any aggregation, whereas EPA (with four amine groups for chain) is effective in inducing J-aggregation using different mixing protocols. These nanohybrids have been characterized through UV/Vis extinction, fluorescence emission, resonance light scattering and circular dichroism spectroscopy. Their morphology and chemical composition have been elucidated through transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). TEM and STEM analysis evidence single or bundles of MWCNTs in contact with TPPS J-aggregates nanotubes. The nanohybrids are quite stable for days, even in aqueous solutions mimicking physiological medium (NaCl 0.15 M). This property, together with their peculiar optical features in the therapeutic window of visible spectrum, make them potentially useful for biomedical applications.

Morphology transition of ZnO and Cu2O nanoparticles to 1D, 2D, and 3D nanostructures: hypothesis for engineering of micro and nanostructures (HEMNS)

A novel approach for fabricating one, two, and three-dimensional hybrid ZnO and Cu2O nanostructures has been developed. We have controlled the thickness of hybrid ZnO nanosheets to reach nanoscale at room temperature. The ability of engineering hybrid ZnO nanowires in few minutes is demonstrated. Moreover, supposed mechanism has been suggested and supported by the in situ SEM analysis for a series of picked samples during the reaction. The morphology transition of Cu2O nanoparticles to hierarchical nanowires and nano-flowers is highlighted as experimental evidences for Abdelmohsen theory for morphology transition engineering (ATMTE). In addition, the ability of multi-walled carbon nanotubes (MWCNTs) to act as a structural directing material for engineering nanowires is introduced. A hypothesis for engineering of micro and nanostructures (HEMNS) that may be applied for nearly all solid materials is demonstrated. Finally, the possibility of engineering Zn-oxidene and thin films are introduced.

Carbon-based nanomaterials as stimulators of production of pharmaceutically active alkaloids in cell culture of Catharanthus roseus

Carbon-based nanomaterials (CBNs) were previously described as regulators of plant cell division. Here, we demonstrated the ability of multi-walled carbon nanotubes (MWCNT) and graphene to enhance biomass production in callus culture of the medicinal plant Catharanthus roseus cultivated in dark conditions. Furthermore, both tested CBNs were able to stimulate biosynthesis of total produced alkaloids in CBN-exposed callus culture of Catharanthus. In one case, total alkaloids in CBN-exposed Catharanthus were double that of unexposed Catharanthus. Analysis of metabolites by HPLC revealed that production of the pharmaceutically active alkaloids vinblastine and vincristine was dramatically enhanced in callus exposed to MWCNT or graphene in both dark and light conditions of callus cultivation. In vitro assays (MTT, flow cytometry) demonstrated that total alkaloid extracts derived from Catharanthus callus treated with CBNs significantly reduced cell proliferation of breast cancer (MCF-7) and lung cancer (A549) cell lines compared to the application of extracts derived from untreated Catharanthus callus.

Atenolol adsorption onto multi-walled carbon nanotubes modified by NaOCl and ultrasonic treatment; kinetic, isotherm, thermodynamic, and artificial neural network modeling.

The removal of pharmaceutical pollutants from the aqueous environment is a great environmental concern, mainly due to their diversity, high consumption, and sustainability. In the current study, we aimed to investigate the ability of multi-walled carbon nanotubes (MWCNTs) modified by sodium hypochlorite (NaOCl) and ultrasonic treatment in refining wastewaters contaminated with Atenolol β-blocker drug (ATN). The physical and structural characteristics of the raw MWCNTs and modified MWCNTs (M-MWCNTs) were analyzed using SEM, TEM, Raman spectroscopy, TGA, and FT-IR techniques. The effects of different parameters, including pH, initial concentration, contact time, and temperature were studied and optimized. Subsequently, the adsorption data were analyzed by several kinetic and equilibrium isotherm equations and modeled by artificial neural network (ANN). Highest ATN removal (87.89%) ((qe,exp= 46.03mgg-1)) occurred on the adsorbent activated within 10s of ultrasonication time and NaOCl 30%. Moreover, adsorbent modification significantly improved the ATN removal, so that the removal rate on the raw MWCNTs was about 58%, but in the same conditions, M-MWCNTs removed more than 92% of the adsorbate. The adsorption process reached equilibrium after 90min under the optimized pH of 6. According to ANN modeling, approximately the whole values dispersed around the 45°line, indicating a good compatibility between the trial results and ANN-predicted data. The modification of MWCNTs in proper ultrasonic power via appropriate concentration of NaOCl solution removed many of the impurities and significantly improved the adsorption performance of MWCNTs.

Adsorption Thermodynamics, Kinetics and Mechanism for the Adsorption of Erythromycin onto Multi-Walled Carbon Nanotubes

The ability of multi-walled carbon nanotubes (MWCNT) to adsorb the Erythromycin antibiotic from aqueous solution was studied through the batch experiments. The adsorption of Erythromycin onto MWCNT was found to be dependent on adsorbent dose, initial concentration and contact time. The experiments were carried out at natural solution pH. Based on the observed results, the highest removal efficiency was achieved to be 99.4% under optimum conditions. The adsorption kinetic results showed that the pseudo-second order model was more suitable to explain the adsorption of Erythromycin onto MWCNT. The adsorption mechanism results showed that the adsorption process was controlled by both the internal and external diffusion of Erythromycin molecules. The values of free energy change (∆G0) and enthalpy change (∆H0) revealed that the adsorption process has the spontaneous, feasible, and endothermic nature.

Surfactant removal with multiwalled carbon nanotubes

The ability of multiwalled carbon nanotubes (MWCNTs) to remove a non-ionic surfactant, Triton X-100 (TX100), an anionic surfactant, sodium dodecylbenzenesulonate (SDBS), and a cationic surfactant, hexadecyltrimethylammonium bromide (CTAB) from the aqueous phase was investigated. Untreated, OH-, and COOH-functionalized MWCNTs with different outer diameters and chemical composition were examined and compared. As both the concentrations of surfactants and MWCNTs initially added may affect removal efficiency of surfactants, a relationship between the initial concentration ratio of surfactants and MWCNTs (Rc) and the removal efficiency (E) was established. The results showed that for a given Rc (e.g., 0.8), removal efficiency of the tested surfactants by a specific MWCNT (e.g., the untreated one with outer diameter <8 nm) decreased in the following order: TX100 (52.3%) > SDBS (26.2%) > CTAB (3.8%). TX100 was more readily removed by MWCNTs than SDBS and CTAB, due to its longer aliphatic chain compared to SDBS and CTAB thus higher hydrophobicity, and stronger π-π interactions with the aromatic structure of the surfaces of graphite sheets relative to CTAB. Based upon the established relationship between Rc and E of surfactants by MWCNTs, the maximum removal efficiency and the most appropriate Rc of TX100 and SDBS by two MWCNTs (UT8 and OH8) were derived. It was interesting to notice that, except for the case to remove TX100 using UT8, even though a large quantity of UT8 or OH8 was added to the TX100 or SDBS removal systems, they cannot be completely removed, with the maximum removal efficiency in the range of 55.88–87.17%. This mostly resulted from strong aggregation of MWCNTs thus reducing their readily accessible surface area and porosity for sorption.

Multi-walled carbon nanotubes (NM401) induce ROS-mediated HPRT mutations in Chinese hamster lung fibroblasts

Although there is an important set of data showing potential genotoxic effects of nanomaterials (NMs) at the DNA (comet assay) and chromosome (micronucleus test) levels, few studies have been conducted to analyze their potential mutagenic effects at gene level. We have determined the ability of multi-walled carbon nanotubes (MWCNT, NM401), to induce mutations in the HPRT gene in Chinese hamster lung (V79) fibroblasts. NM401, characterized in the EU NanoGenotox project, were further studied within the EU Framework Programme Seven (FP7) project NANoREG. From the proliferation assay data we selected a dose-range of 0.12 to 12µg/cm2 At these range we have been able to observe significant cellular uptake of MWCNT by using transmission electron microscopy (TEM), as well as a concentration-dependent induction of intracellular reactive oxygen species. In addition, a clear concentration-dependent increase in the induction of HPRT mutations was also observed. Data support a potential genotoxic/ carcinogenic risk associated with MWCNT exposure.

Mechanical properties of poly(lactic acid)/multiwalled carbon nanotubes nanocomposites

In this study, the mechanical properties of polylactic acid reinforced with carboxylic functionalized multiwalled carbon nanotubes were investigated. The polylactic acid/multiwalled carbon nanotubes nanocomposites were prepared using direct melt-blending method in a counter-rotating twin screw extruder with various loadings of nanotube. The extruded nanocomposites were then pelletized and injection moulded into test specimens for mechanical testing. The effects of the increased content of nanotube on the mechanical properties of polylactic acid nanocomposites were investigated through tensile, flexural and impact tests. The analysis showed that the tensile strength and modulus increase with increasing amount of multiwalled carbon nanotubes, indicating the ability of multiwalled carbon nanotubes to improve the stiffness of polylactic acid. The optimum loading of 5 phr gave the best tensile and flexural strength of 40·949 and 54·132 Mpa, respectively. However, both flexural and the tensile strength experienced rapid decrease after the optimum loading owing to agglomeration of nanotubes. The highest modulus was observed at 7 phr with 3·483 GPa, while the highest flexural modulus was observed at 7 phr with 4·244 GPa. On the other hand, the impact strength decreases with increasing amount of multiwalled carbon nanotubes.

Effect of multiwalled carbon nanotubes on the crystallization and dielectric properties of BP-PEN nanocomposites

In this work, polymer-based nanocomposite films formed from biphenol poly(arylene ether nitrile) (BP-PEN) and multiwalled carbon nanotubes (MWCNTs) were successfully prepared by the solution casting method combined with continuous ultrasonic dispersion technology. The micromorphology, thermal, mechanical and dielectric properties of the nanocomposite films were investigated in detail. Non-isothermal crystallization behavior studies indicate that the presence of MWCNTs enhances the crystallization of BP-PEN in the nanocomposites, which is consistent with the XRD analysis. Most importantly, it could be observed that the film containing 0.8 wt% MWCNTs reached the maximum crystallinity. Although, incorporation of MWCNTs did not obviously increase the mechanical of the films, all the nanocomposite films still exhibited excellent mechanical strength. The SEM micrographs of the nanocomposite films showed that the MWCNTs were uniformly coated by BP-PEN crystals, and indicating significantly improved nucleation ability of MWCNTs for polymer crystallization.

Extracellular HMGB1 regulates multi-walled carbon nanotube-induced inflammation in vivo

Endotoxin is often used to activate NF-κB in vitro when assessing NLRP3 inflammasome activation by various exogenous particles including nanoparticles. However, the endogenous source of this signal 1 is unknown. High-mobility group box 1 (HMGB1) is known to play a critical role in acute lung injury, however the potential contribution of the alarmin HMGB1 to NLRP3 Inflammasome activation has not been determined in response to nanoparticles in vivo. In this study, the ability of multi-walled carbon nanotubes (MWCNT) to cause release of HMGB1 in vitro and in vivo, as well as the potential of HMGB1 to function as signal 1 in vitro and in vivo, was determined. HMGB1 activity in vivo was assessed by administration of HMGB1 neutralization antibodies following MWCNT exposure. Caspase-1−/− mice were utilized to elucidate the dependence of HMGB1 secretion on NLRP3 inflammasome activity. MWCNT exposure increased extracellular HMGB1 levels in primary alveolar macrophages from C57Bl/6 mice and C10 mouse epithelial cell culture supernatants, and in C57Bl/6 mouse lung lavage fluid. MWCNT-induced HMGB1 secretion was dependent upon caspase-1. HMGB1 increased MWCNT-induced IL-1β release from macrophages in vitro, and neutralization of extracellular HMGB1 reduced MWCNT-induced IL-1β secretion in vivo. HMGB1 neutralization was accompanied with overall decreased inflammation. In summary, this study suggests extracellular HMGB1 participates in NLRP3 inflammasome activity and regulates IL-1β associated sterile inflammation induced by MWCNT.

A new nano-composite modified carbon paste electrode as a high performance potentiometric sensor for nanomolar Tl(I) determination

In the present study, a novel nano-composite potentiometric sensor for the determination trace amounts of Tl(I) was prepared containing the room temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, as the conducting binder, and multi-walled carbon nanotubes, TiO2 nanoparticles, graphite powder and also tri-aza dibenzosulfoxide macrocyclic ligand as efficient ionophore. For investigation of the ion-to-electron transducing ability of multi-walled carbon nanotubes, ionic liquid and TiO2 nanoparticles on the electrode surface, the electrochemical impedance spectroscopy measurements were done. Under the optimized experimental conditions, the suggested potentiometric Tl(I) sensor exhibited an excellent Nernstian slope of 59.31mVdecade−1, with rapid response time (5s) and a linear calibration curve that ranged from 8.50×10−9 to 1.00×10−2M was obtained with a detection limit of 5.50×10−9M.

Inflammasome activation in airway epithelial cells after multi-walled carbon nanotube exposure mediates a profibrotic response in lung fibroblasts

BackgroundIn vivo studies have demonstrated the ability of multi-walled carbon nanotubes (MWCNT) to induce airway remodeling, a key feature of chronic respiratory diseases like asthma and chronic obstructive pulmonary disease. However, the mechanism leading to remodeling is poorly understood. Particularly, there is limited insight about the role of airway epithelial injury in these changes.ObjectivesWe investigated the mechanism of MWCNT-induced primary human bronchial epithelial (HBE) cell injury and its contribution in inducing a profibrotic response.MethodsPrimary HBE cells were exposed to thoroughly characterized MWCNTs (1.5-24 μg/mL equivalent to 0.37-6.0 μg/cm2) and MRC-5 human lung fibroblasts were exposed to 1:4 diluted conditioned medium from these cells. Flow cytometry, ELISA, immunostainings/immunoblots and PCR analyses were employed to study cellular mechanisms.ResultsMWCNT induced NLRP3 inflammasome dependent pyroptosis in HBE cells in a time- and dose-dependent manner. Cell death and cytokine production were significantly reduced by antioxidants, siRNA to NLRP3, a caspase-1 inhibitor (z-WEHD-FMK) or a cathepsin B inhibitor (CA-074Me). Conditioned medium from MWCNT-treated HBE cells induced significant increase in mRNA expression of pro-fibrotic markers (TIMP-1, Tenascin-C, Procollagen 1, and Osteopontin) in human lung fibroblasts, without a concomitant change in expression of TGF-beta. Induction of pro-fibrotic markers was significantly reduced when IL-1β, IL-18 and IL-8 neutralizing antibodies were added to the conditioned medium or when conditioned medium from NLRP3 siRNA transfected HBE cells was used.ConclusionsTaken together these results demonstrate induction of a NLRP3 inflammasome dependent but TGF-beta independent pro-fibrotic response after MWCNT exposure.

Absence of mutagenic and recombinagenic activity of multi-walled carbon nanotubes in the Drosophila wing-spot test and Allium cepa test

In order to assess the safety of the carbon nanotubes to human health and the environment, we investigated the potential toxicity and ability of multi-walled carbon nanotubes (NT), to induce DNA damage by employing the Allium cepa genotoxicity/mutagenicity test and the Somatic Mutation and Recombination Test (SMART) in the fruitfly, Drosophila melanogaster. The results demonstrated that NT did not significantly induce genotoxic or mutagenic effects in the Allium cepa test. All concentrations evaluated in the SMART assay showed survival rates higher than 90percent, indicating the absence of chronic toxicity for NT. Furthermore, the various treatments showed no significant increase in the NT mutation and recombination frequencies in mwh/flr3 genotype compared to respective negative controls, demonstrating the absence of DNA damage caused by NT.

Graphene-carbon nanotubes modified graphite electrode for the determination of nicotinamide adenine dinucleotide and fabrication of alcohol biosensor

Through layer-by-layer adsorption (LBL) technique, the positively charged multiwalled carbon nanotubes (MWCNTs) and negatively charged graphene multilayer film were formed on graphite-poly(diallyldimethylammoniumchloride)-polystyrenesulphonate (Gr/PDDA/PSS) modified electrode. Due to large surface area and remarkable electrocatalytic properties of MWCNTs and graphene, the Gr/(PDDA/PSS-[MWCNTs-NH3+-graphene-COO−]5) electrode exhibits potent electrocatalytic activity towards the electro-oxidation of nicotinamide adenine dinucleotide (NADH). A substantial decrease in the overpotential was observed at modified electrode, and the electrode showed high sensitivity to the electrocatalytic oxidation of NADH. The modified electrode was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The diffusion coefficient was calculated by chronocoulometry. Chronoamperometric studies showed the linear relationship between oxidation peak current and the concentration of NADH in the range 25–250 μM (R = 0.999) with the detection limit of 0.1 μM (S/N = 3). Further, dopamine, uric acid, acetaminophen and hydrogen peroxide do not interfere in the detection of NADH. The ability of MWCNTs and graphene to promote the electron transfer between NADH and the electrode exhibits a promising biocompatible platform for development of dehydrogenase-based amperometric biosensors. Alcohol dehydrogenase (ADH) was casted on Gr/(PDDA/PSS-[MWCNTs-NH3+-graphene-COO−]5) electrode; the resulting biosensor showed rapid and high sensitive amperometric response to ethanol with the detection limit of 10 μM (S/N = 3).

Minichannels with carbon nanotube structured surfaces for cooling applications

An experimental study was conducted to determine the heat removal ability of multiwall carbon nanotubes (MWNTs) grown in a silicon minichannel with water as the cooling medium. Two different devices based on different MWNT architectures – one fully covered with MWNTs and the other with 6 × 12 (rows, columns) of MWNT bundles were tested and compared to a device with no MWNTs. The performance was evaluated based on a constant heat flux applied to the silicon base versus the corresponding silicon base temperature. The experiments were performed at two different volumetric flow rates of 40 ml/min and 80 ml/min. The experimental results were also compared to computational modeling results. It was observed that the presence of MWNTs enhanced the heat removal from the silicon base. For the 6 × 12 MWNT bundles device, a silicon base heat flux that was 2.3 times the heat flux to the no MWNTs device can be applied, whereas for the fully covered MWNTs device 1.6 times the heat flux can be applied while still keeping the same silicon base temperature.

Thermo-Responsive Dispersion of Multi-Walled Carbon Nanotubes Modified with Poly(N-Isopropylacrylamide-Co-Acrylic Acid)

Multi-walled carbon nanotubes (MWNTs) were modified with poly(N-isopropylacryl- amide-co-acrylic acid) (P(NIPAAm-co-AA)), and the modified MWNTs can be homogeneously dispersed in aqueous solution. In addition, the MWNTs were endowed with thermo-responsive at 33°C . The MWNTs switched reversibly between aggregated and well-exfoliated states by using temperature as a stimulus. Moreover, the introduction of acrylic acid to copolymerize with N-isopropylacrylamide could greatly enhance the dispersing ability of MWNTs.

In situ characterization of tensile-bending load bearing ability of multi-walled carbon nanotubes in alumina-based nanocomposites

The tensile-bending load bearing ability (LBA) of individual multi-walled carbon nanotubes (MWCNTs) embedded in α-alumina ceramic was examined using a unique, in situ method, in which a nano-manipulator and an electron microscope were simultaneously used. Considerably improved LBA compared to near-perfect, straight, arc discharge-grown MWCNTs in vacuum was observed even for MWCNTs under large deflections, which is attributed to the strong inter-wall shear resistance engineered in MWCNT structure due to the radial compressive stress applied from the surrounding alumina ceramic. Crystallinity and exceptional flexibility of MWCNTs after incorporation into the alumina by using spark plasma sintering were shown to remain unchanged. Our results confirm a mutual strengthening phenomenon in MWCNT/alumina nanocomposites and that even MWCNTs with large deflections are an exceptional reinforcement for alumina-based nanocomposites, though they require uniform dispersion and intimate interfaces.

Nucleating effect of surface modified MWNTs on crystallization of MWNTs/PA6 composites

AbstractThe surface characteristic of multi-walled carbon nanotubes (MWNTs) plays an important role in the crystallization of polyamide 6 (PA6). In this paper, 1,6-hexamethylenediamine(HMD) are grafted on MWNTs. The MWNTs before and after modification are used to fabricate PA6 composites through melt-blending. The nucleating effect of MWNTs with different surface characteristic is investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and Xray diffraction (XRD).The heterogeneous nucleating ability of MWNTs determined by the Dobreva method are higher for pristine than amine-functionalized MWNTs/PA6 composites with 1.0 wt% MWNTs. Addition of MWNTs induce more heterogeneous nucleation and retards the crystal growth of PA6. The presence of MWNTs facilitates the formation of α crystalline form, while amino-functionalization weakens this trend. MWNTs act as effective nucleation agents for PA6, resulting in the increased number and decreased size of spherulites. MWNTs facilitate the formation of α crystalline form of PA6. Amino-functionalization decreases the crystallization and nucleating effect of MWNTs on PA6