Different Types Of Carbon Nanotubes Research Articles

Effect of Monovacancy Defects on Adsorbing of CO, CO<sub>2</sub>, NO and NO<sub>2</sub> on Carbon Nanotubes: First Principle Calculations

We have applied density functional theory to investigate different types of carbon nanotubes (armchair (4,4)CNT and zig-zag (7,0)CNT) as sensors of some pollutant gas molecules, especially CO, CO2, NO and NO2. We show, for the first time, that the adsorption of pollutant gas molecules on carbon nanotubes are improved by introducing the monovacancy defects on the surfaces of (7,0)CNT. The adsorption energies, the optimal adsorption positions and the orientation of these gas molecules on the surfaces of carbon nanotubes are studied. It is found that the most adsorbed pollutant gas is NO molecule on (7,0)CNT.

Application of Functionalized SWCNTs for Increase of Degradation Resistance of Acrylic Paint for Cars

Physical properties of automotive acrylic paint are improved by incorporation of three different types of carbon nanotubes: single-wall carbon nanotubes (SWCNTs), OH-functionalized single-wall carbon nanotubes (OH-SWCNTs), and aniline-functionalized single-wall carbon nanotubes (aniline-SWCNTs). The formed composites are studied by electron miscroscopy methods and Raman spectrometry. It is found that the acrylic paints with addition of OH-SWCNTs and aniline-SWCNTs show better quality for their applications. In particular, the resistance against degradation by electron beam increased in ~500%.

Highly Doped Carbon Nanotubes with Gold Nanoparticles and Their Influence on Electrical Conductivity and Thermopower of Nanocomposites

Carbon nanotubes (CNTs) are often used as conductive fillers in composite materials, but electrical conductivity is limited by the maximum filler concentration that is necessary to maintain composite structures. This paper presents further improvement in electrical conductivity by precipitating gold nanoparticles onto CNTs. In our composites, the concentrations of CNTs and poly (vinyl acetate) were respectively 60 and 10 vol%. Four different gold concentrations, 0, 10, 15, or 20 vol% were used to compare the influence of the gold precipitation on electrical conductivity and thermopower of the composites. The remaining portion was occupied by poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), which de-bundled and stabilized CNTs in water during synthesis processes. The concentrations of gold nanoparticles are below the percolation threshold of similar composites. However, with 15-vol% gold, the electrical conductivity of our composites was as high as ∼6×105 S/m, which is at least ∼500% higher than those of similar composites as well as orders of magnitude higher than those of other polymer composites containing CNTs and gold particles. According to our analysis with a variable range hopping model, the high conductivity can be attributed to gold doping on CNT networks. Additionally, the electrical properties of composites made of different types of CNTs were also compared.

Pharmaceutical Applications of Carbon Nanotube-Mediated Drug Delivery Systems


 Carbon nanotubes, which are elongated fullerenes, resemble graphite sheets wrapped into cylinders with a high length-to-width ratio (few nm in diameter and up to 1 mm in length). Carbon nanotubes are molecular-scale tubes of graphitic carbon with outstanding properties. Carbon nanotubes have drawn great interest and attraction in the field of novel drug delivery system. Nanomedicines can target, diagnose, monitor and treat cancerous cell also. The small nanoscale dimension and astonishing properties make them a distinctive carrier with a wide range of promising applications. These cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology. The various nano-size carrier systems are available for biotechnological applications including the drug delivery. Carbon nanotubes are typically used for bioactive delivery due to their some unique outstanding properties. Carbon nanotubes drug delivery system opens up new potential and possibilities over nanoparticles, dendrimers, liposomes etc. for biomedical applications and new drug delivery. In last few years, Carbon nanotubes (CNTs) have shown unexpected advantages in the field of cancer treatment and drug delivery systems. Present review article discuss in brief about the methods of synthesis, with purification as well as sorting techniques for giving different grades to different types of CNTs and biomedical applications. These show very good adsorption properties which helps in the detection of various chemicals, toxic agents etc. Research done using CNTs for cancer treatment is also discussed in brief.

Synthesis of hybrid polyaniline/carbon nanotubes nanocomposites in toluene by dynamic interfacial inverse emulsion polymerization under sonication

AbstractThis work describes an empirical study of in situ interfacial dynamic inverse emulsion polymerization process under sonication of aniline in the presence of nine different types of carbon nanotubes (CNT) in toluene. The polymerization method described in this work is simple and very fast (5 min) compared to the other literature reports (3–12 h). During polymerization, CNT are coated with polyaniline (PANI) forming a core‐shell structure of nanowires as evidenced by transmission electron microscopy (TEM) and high‐resolution scanning microscopy (HRSEM). HRSEM images and surface resistivity imply that PANI coating of CNT leads to a remarkable improvement in separation and dispersion of CNT in toluene, which otherwise would have rapidly coagulate and settle. Two of the nine different CNT studied have shown the lowest surface resistivities. Films of uniform thickness were successfully produced (HRSEM of cross‐sections). The effect of film thickness on conductivity and optical properties is reported in the work. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Flammability properties of PEEK and carbon nanotube composites

Aryl polyetheretherketones (PEEK) show remarkable thermal stability and low flammability, with an onset of decomposition at around 600 °C, and 60% char formation in the cone calorimeter at 60 kW m−2. However, at lower heat fluxes, and in other small-scale flammability tests, it is difficult to obtain consistent results. PEEK polymer has been modified with different types of carbon nanotubes (CNT), leading to modest improvements in the burning behaviour at addition levels between 0.1 and 1%. The characterisation of the composites indicated satisfactory dispersion, modest enhancements in mechanical properties and thermal stability, and reductions of peak heat release rate for the best performing formulations. Significant differences in thermal stability and burning behaviour were observed as a function of the nature of the CNTs, and the loading level within the polymer.

Toxicity of carbon nanotubes to freshwater aquatic invertebrates

Carbon nanotubes (CNTs) are hydrophobic in nature and thus tend to accumulate in sediments if released into aquatic environments. As part of our overall effort to examine the toxicity of carbon-based nanomaterials to sediment-dwelling invertebrates, we have evaluated the toxicity of different types of CNTs in 14-d water-only exposures to an amphipod (Hyalella azteca), a midge (Chironomus dilutus), an oligochaete (Lumbriculus variegatus), and a mussel (Villosa iris) in advance of conducting whole-sediment toxicity tests with CNTs. The results of these toxicity tests conducted with CNTs added to water showed that 1.00 g/L (dry wt) of commercial sources of CNTs significantly reduced the survival or growth of the invertebrates. Toxicity was influenced by the type and source of the CNTs, by whether the materials were precleaned by acid, by whether sonication was used to disperse the materials, and by species of the test organisms. Light and electron microscope imaging of the surviving test organisms showed the presence of CNTs in the gut as well as on the outer surface of the test organisms, although no evidence was observed to show penetration of CNTs through cell membranes. The present study demonstrated that both the metals solubilized from CNTs such as nickel and the "metal-free" CNTs contributed to the toxicity.

Comparison of the physical properties of epoxy‐based composites filled with different types of carbon nanotubes for aeronautic applications

AbstractThe increased demand for high‐quality multifunctional materials in the aeronautic industry requires the formulation and preparation of advanced nanostructured composites with superior characteristics. In particular, epoxy‐based polymers, exhibiting excellent mechanical properties for structural stability, filled with carbon nanotubes (CNTs: single, double, and multiwalled—SW, DW, and MW), characterized by remarkable mechanical and electrical properties, allow us to manufacture a very versatile class of composites for structural applications in automotive, aeronautics, industry, electronics, etc. Many aspects concerning the optimization of such composite systems are still to be clarified. In this paper, the physical properties of samples based on the epoxy resin with the same weight percentage (0.5%) of different CNTs have been studied. The physical behavior of the nanocomposites resulted to be dependent on the type and on the chemical functionalization of the nanoinclusions. The elastic modulus and the electrical conductivity of composites based on unfunctionalized CNT are higher than those obtained for the functionalized systems. Moreover, the maximum electrical conductivity achieved for the composite based on unfunctionalized MWCNT is not far from the target required for aeronautic applications. The contrasting results obtained for the different physical properties enlighten the difficulty in choosing one of the CNT types for the realization of multifunctional materials. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 31: 205–218, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21284

Tetrathiafulvalene-Based Nanotweezers—Noncovalent Binding of Carbon Nanotubes in Aqueous Media with Charge Transfer Implications

Electron donor-acceptor hybrids based on single wall carbon nanotubes (SWCNT) are one of the most promising functional structures that are currently developed in the emerging areas of energy conversion schemes and molecular electronics. As a suitable electron donor, π-extended tetrathiafulvalene (exTTF) stands out owing to its recognition of SWCNT through π-π stacking and electron donor-acceptor interactions. Herein, we explore the shape and electronic complementarity between different types of carbon nanotubes (CNT) and a tweezers-shaped molecule endowed with two exTTFs in water. The efficient electronic communication between semiconducting SWCNT/multiwall carbon nanotubes (MWCNT), on one hand, and the water-soluble exTTF nanotweezers 8, on the other hand, has been demonstrated in the ground and excited state by using steady-state as well as time-resolved spectroscopies, which were further complemented by microscopy. Importantly, appreciable electronic communication results in the electronic ground state having a shift of electron density, that is, from exTTFs to CNT, and in the electronic excited state having a full separation of electron density, that is oxidized exTTF and reduced CNT. Lifetimes in the range of several hundred picoseconds, which were observed for the corresponding electron transfer products upon light irradiation, tend to be appreciably longer in MWCNT/8 than in SWCNT/8.

A molecular dynamics simulation study for the mechanical properties of different types of carbon nanotubes

Carbon nanotubes have caught tremendous attention of the researchers during the last decade due to their excellent mechanical, electrical, optical and thermal prop- erties. The exploitation of these fibers as reinforcing agents in making strong fiber composites has been a primary research topic in the recent investigations on composite materials. Although the theoretical results are rather opti- mistic, the goal of achieving high strength of the carbon nanotube composites is still not satisfactorily realized. We report here a comparative study of the mechanical properties of single-walled, multi-walled and bundle of single-walled carbon nanotubes. Their mechanical behavior is investigated by molecular dynamics simulation, considering Brenner's second generation reactive empirical bond order interatomic potential between the carbon atoms making a tube. For a long range interaction, we have defined a weak van der Waals force which acts between different layers of a multi-walled tube or between different tubes of a bundle. Samples of three isolated armchair single-wall carbon nanotubes of different diameters, a multi-wall armchair carbon nanotube and finally a bundle of three armchair single-walled nanotubes of same diameter are taken. Their fracture pattern and buckling behavior are modeled and compared. Significant changes are observed in the mechanical properties of the samples of different types of carbon nanotubes which arise due to the interaction between the shells of a multi-walled tube or the tubes in a bundle.

Role of Carbon Source in the Synthesis of Carbon Nanotubes via Catalytic Chemical Vapour Deposition

Development of technology in synthesizing a novel nanoscale material has been the main concern in the current material science. This study investigates the effect of two different carbon sources on the formation of carbon nanotubes (CNTs) via catalytic chemical vapour deposition (CCVD) method. Two types of carbon source i.e. acetylene gas and ethanol liquid were used for the synthesis of CNTs. The catalysts used in the synthesis of CNTs were formulated from nickel (Ni), copper (Cu) and praseodymium (Pr) using the wet impregnation method. The as-synthesized CNTs obtained were characterized using field emission-scanning electron microscope (FE-SEM), Thermal gravimetric analysis (TGA) and transmission electron microscope (TEM). The analysis result confirmed that the prepared catalysts were active for the production of CNTs. TEM analysis revealed that different morphologies of CNTs were formed when different carbon source was used. FE-SEM micrographs confirmed that acetylene proficient in producing multi walled carbon nanotubes (MWCNTs) and ethanol in producing heterojunctions CNTs with diameter range of 60 to 120 nm and 10 to 40 nm, respectively. Meanwhile, TGA analysis revealed thermal stability of each type of CNTs at different temperature of decomposition. Generally, this research has successful produced different types of CNTs when different carbon source is used.

The adsorption kinetics of cadmium by three different types of carbon nanotubes

Oxidized nitrogen-doped multiwall carbon nanotubes (ox-N-MWCNTs), oxidized multiwall carbon nanotubes (ox-MWCNTs), and oxidized single-wall carbon nanotubes (ox-SWCNTs) were evaluated via batch adsorption kinetic experiments to determine the effect of nanotube morphology on the adsorption rate of cadmium. The nanotubes were characterized by HRTEM, XRD and Raman spectroscopy. Cadmium adsorption isotherms were determined at pH 6. Analyses of the kinetic data with an external mass transport model and an intraparticle diffusion model considered two cases: (1) single nanotubes suspended in aqueous solution and (2) agglomerates of nanotubes suspended in aqueous solution. The intraparticle diffusion model produced the best fit to the experimental data. However, only the diffusivity coefficients for single nanotubes suspended in solution were similar to literature values: about 4×10−9, 1×10−9 and 2.4×10−11cm2/s for ox-N-MWCNTs, ox-MWCNTs and ox-SWCNTs, respectively. The morphology of the various carbon nanotubes might determine cadmium diffusivity. The high amount of sidewall pores observed in the single-walled carbon nanotubes could limit cadmium diffusion and account for the slow diffusion rate of 180min. Conversely, the short length, small surface area and bamboo-type morphology observed with nitrogen-doped multiwall carbon nanotubes may account for the relatively fast adsorption rate of 15min as this morphology prevents cadmium diffusion through the internal tubular space of these nanotubes.

Polyamidoamine dendrimer‐functionalized carbon nanotubes‐mediated GFP gene transfection for HeLa cells: Effects of different types of carbon nanotubes

Three types of functionalized carbon nanotubes (f-CNTs), polyamidoamine (PAMAM) dendrimer-functionalized single and multi-walled CNTs (MWCNT-PAMAM-1, MWCNT-PAMAM-2, and SWCNT-PAMAM-3), were prepared by covalent linkage approach. The micro-morphologies of the three f-CNTs and the interaction of MWCNT-PAMAM-2 with HeLa cells were characterized by transmission electron microscopy (TEM). The free amine groups on the surface of the three types of CNTs-PAMAM hybrids were quantitatively analyzed. Their cytotoxicity and transfection efficiency of plasmid DNA of enhanced green fluorescent protein (pEGFP-N1) to HeLa cells were investigated in detail. The results suggest that although all three types of CNTs-PAMAM hybrids can deliver pEGFP-N1 into HeLa cells and the exogenous GFP gene has been successfully expressed, MWCNT-PAMAM-2 with shorter length and larger amount of free amine groups on its surface possesses higher transfection efficiency (6.79%), being about 3.0 and 1.7 times as large as those of MWCNT-PAMAM-1 (2.24%) and SWCNT-PAMAM-3 (4.08%), respectively; their cytotoxicity to HeLa cells decrease following the sequence of SWCNT-PAMAM-3 > MWCNT-PAMAM-2 > MWCNT-PAMAM-1. These results may be useful for understanding the effects of the chemical/physical properties of f-CNTs on their gene transfection efficiency and cytotoxicity, allowing for construction of promising CNT-based intracellular delivery vectors for gene therapy.

Catalytic activity of cobalt and iron phthalocyanines or porphyrins supported on different carbon nanotubes towards oxygen reduction reaction

Non-noble metal catalysts for O 2 reduction were prepared by dispersing iron(II) phthalocyanine, cobalt(II) tetra- tert-butylphthalocyanine, cobalt(II) 2,3,7,8,12,13,17,18-octaethyl-porphine, and cobalt(II) 5,10,15,20-tetrakis(4- tert-butylphenyl)-porphyrine on carbon nanotubes (CNTs) used as high surface area support. Different types of CNTs (SWCNTs, DWCNTs and MWCNTs) were investigated as an effective substitute for commonly used carbon black in carbon-supported phthalocyanines and porphyrins. The oxygen reduction reaction (ORR) activity of those CNT-supported catalysts in alkaline and acidic solutions was studied. The results show that: (i) all catalytic systems including MWCNTs are more efficient for O 2 reduction than those with SWCNTs and DWCNTs, (ii) the oxidative chemical treatment of the CNTs increases the electrocatalytic performance of the corresponding CNT-supported catalysts, (iii) similarly to Vulcan-supported catalysts, iron(II) phthalocyanine gives the best electroactivity among the investigated CNT-supported materials and (iv) finally, the MWCNT-supported iron(II) phthalocyanine catalyst chemically treated in oxidative conditions shows an ORR catalytic activity comparable to a commonly used Pt/C catalyst with similar current densities and a very low overpotential (60 mV).

A Brief Summary of Carbon Nanotubes Science and Technology: A Health and Safety Perspective

Engineered nanomaterials, particularly carbon nanotubes (CNTs), hold great promise for a variety of industrial, consumer, and biomedical applications, due to their outstanding and novel properties. Over the last two decades many different types of CNTs have been produced at the industrial scale. Therefore, the exposure risk to humans associated with such a mass scale production has also increased substantially. This has led to increased concerns about the potential adverse health effects that may be associated with human exposure to CNTs, predominantly because of to their size, their shape, and chemistry. CNTs are also intended for use in many biomedical applications, and therefore their biocompatibility, biodistribution, and fate needs to be carefully assessed. This Minireview intends to highlight the current state of the assessment of potential adverse human health effects possibly associated with CNT exposure, as well as the challenges related to and posed by CNT safety research. The importance of reliability and comparison within and between different studies, as regards the test systems employed, is discussed as well as many other essential aspects relative to CNT safety research, for example efficient and comprehensive characterization, are discussed in the view of an improvement in data collection.

Gel-spun carbon nanotubes/polyacrylonitrile composite fibers. Part I: Effect of carbon nanotubes on stabilization

Addition of carbon nanotubes (CNTs) in polyacrylonitrile (PAN) fibers significantly improves the mechanical properties of the resulting carbon fibers. This study focuses on the effect of different types of CNTs on chemical, mechanical and structural changes during the stabilization of gel-spun CNT/PAN composite fibers. Among the different types of CNTs, it was observed that CNTs containing more walls had lower reinforcement efficiency than CNTs containing fewer walls. Similarly CNTs containing fewer walls exhibited higher orientation of the ladder polymer and greater effect on the formation of β-amino nitrile in the stabilized fibers. Wide angle X-ray diffraction, infrared spectroscopy, and scanning electron microscopy were used to determine the optimum stabilization time. Additionally, it was found that the higher tension applied during stabilization improved the properties of the stabilized fibers, and the addition of CNTs increased the maximum tension that the fiber can bear.

Carbon nanotubes as structural material and their application in composites

In the present paper, we will introduce the synthesis and application of carbon nanotubes as filler for nanocomposite materials. Physical and chemical properties such as mechanical strength, thermal and electrical conductivity, chemical stability, density and affinity with the matrix vary a lot among different types of carbon nanotubes. We first will overview the main component of nanocomposite, carbon nanotube and its synthesis and purification, and introduce some of the nanocomposites and its applications that we have taken part in the development.

High electrical performance of carbon nanotubes/rubber composites with low percolation threshold prepared with a rotation–revolution mixing technique

The present study demonstrates a novel mixing approach for achieving a good dispersion of carbon nanotubes (CNTs) in a styrene–butadiene rubber (SBR), which leads to a significant improvement in electrical properties. Our mixing technique consists of (1) pretreatment by ultrasonication to disentangle the bundles of CNTs in organic solvent and (2) “rotation–revolution” mixing of the CNTs with SBR without mechanical shear, which prevents CNTs from collapsing during the mixing process. The present mixing method does not require the addition of any dispersing agents (amphiphilic molecules) or chemical modification of the CNTs to obtain a good dispersion. Compared with a conventional Banbury mixing technique, our method leads to a significant decrease in the percolation threshold (less than 1 phr), where the electrical conductivity suddenly increases due to the formation of percolation networks of CNTs in SBR. This is because the aspect ratio of the CNTs was maintained even after the mixing process, whereas CNTs were broken during the conventional Banbury mixing. The effect of using different types of CNTs on electrical conductivity was also investigated. The results show that the percolation threshold is largely related to the structural quality (graphitization) of the CNTs as well as their aspect ratio.

Computational study of compressive loading of carbon nanotubes using quasi-continuum method

AbstractA reduced-order general continuum method is used to examine the mechanical behavior of single-walled carbon nanotubes (CNTs) under compressive loading and unloading conditions. Quasi-static solutions are sought where the total energy of the system is minimized with respect to the spatial degrees of freedom. The obtained continuum solution is mapped back to the lattice structure of CNTs. We then provide a detailed analysis of buckled configurations for four different types of CNTs on the lattice level and show that, among the cases studied, the armchair CNT has the strongest resistance to the compressive loading. It is also shown that the buckled CNT will significantly lose its structural strength with the zigzag lattice structure. The post-buckling unloading of CNTs demonstrates that, after the occurrence of buckling, the CNT can return to its original state, making its use desirable in fields such as synthetic biomaterials, electromagnetic devices, or polymer composites.

One‐Pot Triple Functionalization of Carbon Nanotubes

Carbon nanotubes (CNTs) are very promising as carriers for the delivery of bioactive molecules. The multifunctionalization of CNTs is necessary to impart multimodalities for the development of future CNT-based multipotent therapeutic constructs. In this context, we report the first example of covalent trifunctionalization of different types of CNTs. Our strategy is a simple and efficient methodology based on the simultaneous functionalization of the nanotube surface with three different active groups. The reaction is performed in one step by arylation with diazonium salts generated in situ. The CNTs are functionalized with benzylamine moieties blocked with three different protecting groups that can be selectively removed under specific conditions. The trifunctionalized CNTs were characterized by TEM, thermogravimetric analysis, and Raman and UV/Vis/NIR spectroscopy, while the amine loading was determined by using the Kaiser test. The sequential removal of the protecting groups of the amine functions allows the grafting of the molecules of interest on the nanotube surface to be controlled.