Pure Carbon Nanotubes Research Articles

A molecular dynamics study on the buckling behavior of cross-linked functionalized carbon nanotubes under physical adsorption of polymer chains

The buckling behavior of cross-linked functionalized carbon nanotubes (CNTs) with polyethylene (PE) chains under physical adsorption of polymers (cfCNTs/polymer) is studied by classical molecular dynamics (MD) simulations, and the results are compared with those for the pure CNTs under the physical adsorption of polymers. Considering non-covalent functionalization, the effect of type of functional group, i.e. aramid and PE chains, on the interactions between polymers and cfCNTs is investigated. Based on the results, the gyration radius of cfCNTs/polymer increases by raising the weight percentage of non-covalent polymer chains. Also, the simulation results for most cases demonstrate that the gyration radius of cfCNTs/polymer is larger than that of pure CNTs/polymer for the similar weight percentage of non-covalent polymer chains. Moreover, the critical buckling force and the critical buckling strain of the cfCNTs/polymer are lower than those of pure CNT/polymer for the similar weight percentage of non-covalent polymer chains, although some exceptions can be observed. Besides, by raising the weight percentage of non-covalent polymer chains, the critical buckling force cfCNTs/polymer increases for a specific weight percentage of cross-linked PE chains.

Improving Single-Carbon-Nanotube-Electrode Contacts Using Molecular Electronics.

We report the use of an electroactive species, acetaminophen, to modify the electrical connection between a carbon nanotube (CNT) and an electrode. By applying a potential across two electrodes, some of the CNTs in solution occasionally contact the electrified interface and bridge between two electrodes. By observing a single CNT contact between two microbands of an interdigitated Au electrode in the presence and absence of acetaminophen, the role of the molecular species at the electronic junction is revealed. As compared with the pure CNT, the current magnitude of the acetaminophen-modified CNTs significantly increases with the applied potentials, indicating that the molecule species improves the junction properties probably via redox shuttling.

Modification of Carbon Nanotube for Synthesis of Titania Nanotube (Tint)-Carbon Nanotube (Cnt) Composite

Carbon nanotube (CNT) is a material widely chosen for object of research in nano technology. Apart from its good absorbent property, CNT also has a unique structure, superior mechanic and electric properties and its high strength. The property of CNT above is to be expected to improve performance of Titania nanotube (TiNT) composite. Properties of pure CNT are hydrophobic at the surface and low dispersion stability. To improve dispersability of CNT then modification need to be modified. Adding Cetyl trimethyl ammonium bromide (CTAB) surfactant on CNT is a way to increase dispersion stability of TiNT-CNT. The objective of the research was to study influence of adding of Cetyl trimethyl ammonium bromide (CTAB) surfactant to synthesis of TiNT-CNT composite in degrading phenol compound. Pure CNT was added with CTAB surfactant in liquid, then was sonificated and dried. Surfactant Cetyl trimethyl ammonium bromide (CTAB) added CNT then composited with TiNT. Phenol degradation then tested by using TiNT-CNT (CTAB) in reactor for 4.5 hours. Then sample was characterized by employing Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) and UV-vis Spectroscopy. The result of experiments from FESEM characterization showed forming of TiNT-CNT composites morphology. From X–ray Diffraction (XRD) characterization showed crystal formed on TiNT-CNT only of anatase crystal. Degradation of TiNT-NT composite (CTAB) to phenol was also studied.

Self-Expansion Construction of Ultralight Carbon Nanotube Aerogels with a 3D and Hierarchical Cellular Structure.

A novel and simple strategy is developed to construct ultralight and 3D pure carbon nanotube (CNT) aerogels by the spontaneous expansion of superaligned CNT films soaked in a piranha (mixed H2 SO4 and H2 O2 ) solution, followed by cryodesiccation. The macroscopic CNT aerogels have an extremely low apparent density (0.12 mg cm-3 ), ultrahigh porosity (99.95%), high specific surface area (298 m2 g-1 ), and a hierarchical cellular structure with giant and ultrathin CNT sheets as cell walls. The pure CNT aerogels show high adsorption abilities for various kinds of solvents, and have great potential in widespread applications such as energy storage, catalysis, and bioengineering.

Recent developments in electrochemical sensors based on nanomaterials for determining glucose and its byproduct H2O2

The development in glucose and H2O2 electrochemical sensors has significantly progressed using some original nanomaterials, such as nanoparticles and nanowires in metal, metal oxide, or carbon nanomaterials. In this review, we discussed and analyzed the mechanism, performance, and characteristics of the enzyme/nonenzyme glucose and H2O2 electrochemical sensors based on some pure metal (Au, Pd, Ni, Pt, and Cu), metal oxide (ZnO, NiO, CuO x , TiO2, and Co3O4), and carbon (nanotubes and graphene) nanomaterials. Although the introduction of nanomaterials can effectively improve the sensitivity of enzyme glucose/H2O2 sensors by enhancing the activity of protein enzyme, the enzymes are sensitive to the biochemical environment. Meanwhile, the sensing performance of nonenzyme glucose/H2O2 sensors significantly depends on the morphology, uniformity, and distribution of nanomaterials.

Antibacterial Carbon Nanotubes by Impregnation with Copper Nanostructures

The addition of metal-based nanoparticles on carbon nanotubes (CNT) is a relevant method producing multifunctional materials. In this context, CNT were dispersed in an ethanol/water solution containing copper acetate for their impregnation with different copper nanostructures by either a non-thermal or a thermal post-synthesis treatment. Our simple method is based on pure CNT in an air atmosphere without any other reagents. Particles without thermal treatment were present as a well-dispersed layered copper hydroxide acetate nanostructures on CNT, as confirmed by scanning and transmission (TEM) electron microscopies, and showing a characteristic x-ray diffraction peak at 6.6°. On the other hand, by thermal post-synthesis treatment at 300°C, these layered nanostructures became Cu2O nanoparticles of around 20 nm supported on CNT, as confirmed by TEM images and x-ray diffraction peaks. These copper nanostructures present on the CNT surface rendered antibacterial behavior to the resulting hybrid materials against both Staphylococcus aureus and Escherichia coli. These findings present for the first time a simple method for producing antibacterial CNT by direct impregnation of copper nanostructures.

A research of the influence of the content and purification of CNTs on the property of composites

ABSTRACTFirstly, purify Carbon nanotubes (CNTs) with mixed acid(the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 1:3), secondly, manufacture CNTs/Al2024 composites with different CNTs content by adopting high-energy ball milling method, thirdly, shape the mix powder by using cold-pressing and sintering methods. When the content of CNTs and milling time were 1.5 wt% and 2.5 h, CNTs would disperse homogeneously with a good interfacial bonding between CNTs and Al-2024. Under this conditions, the tensile strength of the composites was 254.4 MPa compared to the matrix, up to 77.2% in tensile strength.

(Invited) Polypeptides As Complexing Units

One of our research field concerns porphyrin-functionalized a-polypeptides to control the spatial organization of the chromophores and enable exciton migration through the pool of porphyrins to mimic the light harvesting antennae of the photosynthetic system.1 In the photosynthetic system, the solar energy is collected by pigment molecules attached to the light harvesting complexes, in which the chlorophylls are held in a parallel orientation by fairly short α-helical polypeptides. When a photon hits one of the chlorophylls, the absorbed energy spreads extremely rapidly to the others until the reaction center is reached.1 Succeeding in organizing the porphyrins in a similar way as nature does should provide information about the relation existing between the orientation of the chlorophylls and the efficiency of nature in transferring an excited state over a very long distance and with minimal loss of energy. The right-handed 310 helical conformation adopted by our poly-L-lysine functionalized with eight porphyrins induces an overlap of the chromophores (studies realized in collaboration with Prof. T. Keiderling, University of Chicago, US), which thus present sufficient electronic coupling to promote a good exciton migration within the molecular wire. The properties of our peptides with pendant porphyrins were studied extensively in collaboration with with Professor S. Fukuzumi (Univeristy of Osaka, Japan) and applications were found as organic photovoltaic cells,2 multiple photosynthetic reaction centers3 and for the successful purification of Single-Walled Carbon Nanotubes.4 Acknowledgements This work was supported by the CNRS and the French Ministry of Research. References W. Kühlbrandt, Nature 1995, 374, 497-498.T. Hasobe, K. Saito, P. V. Kamat, V. Troiani, H. Qiu, N. Solladié, K. S. Kim, J. K. Park, D. Kim, F. D'Souza, S. Fukuzumi, J. Mater. Chem. 2007, 39, 4160-4170.S. Fukuzumi, K. Saito, K. Ohkubo, V. Troiani, H. Qiu, S. Gadde, F. D’Souza and N. Solladié, Phys. Chem. Chem. Phys. 2011, 13, 17019-17022. Kenji Saito, Vincent Troiani, Hongjin Qiu, Nathalie Solladié, Takao Sakata, Hirotaro Mori, Mitsuo Ohama, Shunichi Fukuzumi, J. Phys. Chem. C 2007, 111, 1194-1199. Figure 1

Surface functionalized carbon nanotube with polyvinylidene fluoride: Preparation, characterization, current-voltage and ferroelectric hysteresis behaviour of polymer nanocomposite films

A comparative study of current-voltage characteristics and ferroelectric properties of polyvinylidene fluoride (PVDF) based nanocomposite films with pure multiwall carbon nanotubes (MWCNTs) and surface functionalized MWCNTs by different type of functionalize groups (-COOH, -OH, -NH2) as filler, was reported. The flexible nanocomposite films based on PVDF and surface modified MWCNTs were fabricated via solution casting method. The current voltage characteristics suggests that –COOH and –OH functionalize MWCNT loading PVDF films are semiconducting in nature whereas raw MWCNT and –NH2 functionalize MWNCT loading PVDF films are comparatively conducting in nature. Experimental data of current density-electric field were fitted with different existing theoretical models. It is observed that just by changing the functionalization group the electrical conductivity of the composite films significantly changes which is discernible from the current-voltage characteristic. From ferroelectric study the energy density of –COOH, -OH loaded PVDF films are doubled and tripled compare to the pure PVDF film. This work may provide a rout for using different functionalize MWCNTs into polymer matrix to enhance either the energy density or conducting nature of polymer nanocomposite.

Synergetic enhancement of thermal conductivity for highly explosive‐filled polymer composites through hybrid carbon nanomaterials

The one‐dimensional (1D) carbon nanotubes (CNTs) and two‐dimensional (2D) graphene nanoplatelets (GNPs) were adopted to enhance the thermal conductivity (K) of polymer‐bonded explosives (PBX). Seven 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB)‐based PBX formulations without or with 1.31 vf % carbon materials were designed and fabricated. The results indicated that, the K was only slightly improved by pure GNPs or CNTs. However, a remarkable synergetic effect between GNPs and CNTs in improving the K of PBX was demonstrated. The K of PBX with hybrid GNPs and CNTs was obviously higher than that of PBX with pure GNPs or CNTs. The bridging interactions between GNPs and CNTs could lead to the formation of a more efficient 3D percolating network. Moreover, the presence of CNTs triggered the percolation effect in the GNPs as the enhanced K was more pronounced with increasing GNPs. Additionally, the nonlinear dependence of the K of PBX on GNPs content was fitted by an analytical model which incorporated the percolation effect. The theoretical results were found to be in reasonably good agreement with the experimental data. Finally, the thermal shock resistance of PBX with hybrid CNT/GNP was significantly enhanced. POLYM. COMPOS., 39:E1452–E1462, 2018. © 2017 Society of Plastics Engineers

Methods for the chemical synthesis of carbon nanotubes: an approach based on hemispherical polyarene templates

Abstract Hemispherical polyarenes represent attractive templates from which carbon nanotubes of the same diameter and rim structure (chirality) might be grown by repetitive annulation reactions. The resulting single-index (n,m) nanotubes would have one end open and the other end capped by the original template. Efforts in the author’s laboratory to synthesize (5,5) and (6,6) nanotube end-caps are described. Nitroethylene is shown to serve well as a “masked acetylene” for the conversion of polyarene bay regions into new unsubstituted benzene rings by a Diels-Alder cycloaddition/aromatization process. Benzyne reacts similarly, both in solution and in the gas phase. These annulation reactions are proposed as methods for elongating large-diameter templates that have bay regions on their rims into structurally uniform, single-walled carbon nanotubes. Unfortunately, the bay regions on the strongly curved rim of the small-diameter (5,5) nanotube end-cap 3 resist Diels-Alder cycloadditions with both nitroethylene and benzyne. Pentabenzocorannulene (14) is proposed as a promising candidate for surface-catalyzed cyclodehydrogenation to a surface-bound hemispherical polyarene that could serve as a template for synthesis of pure (5,5) carbon nanotubes.

Activation and Decomposition of Methane over Cobalt‐, Copper‐, and Iron‐Based Heterogeneous Catalysts for COx‐Free Hydrogen and Multiwalled Carbon Nanotube Production

AbstractMonometallic 50 wt % Cu/Al2O3 catalyst and bimetallic catalysts containing 25 wt % Co/25 wt % Cu, 25 wt % Co/25 wt % Fe, and 25 wt % Cu/25 wt % Fe, supported on Al2O3, were prepared by impregnation and coimpregnation methods. For bimetallic catalysts, metal oxides were in the form of spinel oxides, which exhibited a strong metal–support interaction. The decomposition of methane over these catalysts led to the formation of pure hydrogen and carbon nanotubes on their surfaces. The activation energy, total carbon yield, and amount of hydrogen formed, by using the prepared catalysts, were in agreement with the metal dispersion and acid–base site ratio on the surface of the catalysts. Cu−Fe/Al2O3 catalyst exhibited a stable hydrogen formation rate of 58 mmol min−1 g−1 at a temperature of 650 °C. All catalysts exhibited deactivation after 500 min, which occurred due to the formation of carbon on the surface of the catalysts. The carbon material deposited predominantly assumed the form of multiwalled carbon nanotubes, as evidenced by high‐resolution TEM and Raman spectroscopy. Thermogravimetric analysis finally confirmed that Cu−Fe/Al2O3 exhibited a higher yield of multiwalled carbon nanotubes.

Dispersion of Single-Walled Carbon Nanotubes with Oligo(p-phenylene ethynylene)s: A DFT Study

Pure carbon nanotubes (CNT) and CNT–polymer composites have many useful properties, ranging from electrical conductivity to superior mechanical strength. However, the full potential of using CNTs as reinforcements (in a polymer matrix, for example) has been severely limited because of complications associated with the dispersion of CNTs. CNTs tend to entangle with each other, forming materials with properties that fall short of expectations. One of the effective ways of dispersing CNTs is the use of short π-conjugated oligomers like oligo(p-phenylene ethynylene)s (OPEs) as dispersants. In this study, we provide a comprehensive investigation of the interactions between single-walled CNTs (SWCNTs) and OPEs with two different end groups; aldehyde (ALD) and dithiafulvene (DTF). The hybrid B3LYP and the dispersion (D)- and/or the long-range (LR)-corrected density functional theory (DFT) methods such as B97D, wB97XD, and CAM-B3LYP with the 6-31G(d) basis set are employed in obtaining electronic structure inform...

Adsorption of Toluene and Paraxylene from Aqueous Solution Using Pure and Iron Oxide Impregnated Carbon Nanotubes: Kinetics and Isotherms Study.

Multiwall carbon nanotubes (CNTs) and iron oxide impregnated carbon nanotubes (CNTs-iron oxide) were investigated for the adsorption of hazardous toluene and paraxylene (p-xylene) from aqueous solution. Pure CNTs were impregnated with iron oxides nanoparticles using wet impregnation technique. Various characterization techniques including thermogravimetric analysis, scanning electron microscopy, elemental dispersion spectroscopy, X-ray diffraction, and nitrogen adsorption analysis were used to study the thermal degradation, surface morphology, purity, and surface area of the materials. Batch adsorption experiments show that iron oxide impregnated CNTs have higher degree of removal of p-xylene (i.e., 90%) compared with toluene (i.e., 70%), for soaking time 2 h, with pollutant initial concentration 100 ppm, at pH 6 and shaking speed of 200 rpm at 25°C. Pseudo-second-order model provides better fitting for the toluene and p-xylene adsorption. Langmuir and Freundlich isotherm models demonstrate good fitting for the adsorption data of toluene and p-xylene.

Pressure-sensitive properties of carbon nanotubes/bismuth sulfide composite materials

In this work, the pressure-sensitive properties of pure multi-walled carbon nanotubes and multi-walled carbon nanotubes/bismuth sulfide composite are investigated and compared. Composite was prepared by 50 wt% of each ingredient. Sandwich-type pressure-sensitive pellets (Ag/CNT/Ag and Ag/CNT-Bi2S3/Ag) of 2 mm in thickness and 15 mm in diameter were fabricated at a pressure of 6894.8 kNm−2by Mortar and Pestle/Hydraulic Press technique. Both sides of the prepared samples were painted with silver paste to provide low resistance electrical contacts. Both the samples exhibited decrease in direct current resistance with the increase in the applied pressure (0–16.9 kNm−2). However, decrease in the resistance of multi-walled carbon nanotubes/bismuth sulfide composite was 1.2 times and sensitivity was 1.07 times higher than the pure carbon nanotubes. Experimental results were compared with simulated results that showed excellent agreement with each other.

A general polymer-assisted strategy enables unexpected efficient metal-free oxygen-evolution catalysis on pure carbon nanotubes

A conceptually new and general polymer-assisted strategy was proposed to enable unexpected efficient metal-free oxygen-evolution catalysis on pure carbon nanotubes.

Wettability tailoring of nanotube carpets: morphology-chemistry synergy for hydrophobic–hydrophilic cycling

Carpet-like arrays of carbon nanotubes (CNTs) on graphitic carbon materials have been investigated in order to understand all-carbon hierarchical structures for multifunctional surface-active devices. Pure CNT carpets are seen to be super-hydrophobic as long as they are well aligned. For future applications involving aqueous environments, the ability to tailor the surface wettability and switch it on demand can be very useful, and enable unprecedented devices related to microfluidics, catalysis and sensing/detection systems. In this study, microwave plasma treatments were used to functionalize CNT carpets for a progressive increase in wettability so that they could eventually become super-hydrophilic. This change could be reversed by heating. Alternating between microwave plasma treatment and heating enabled repeated cycling of the CNT carpets between super-hydrophobic and super-hydrophilic states. This paper focuses on the influence of these two treatments on surface chemical states and multiscale morphology of CNT carpets, and their relation to wettability. It was shown by X-ray Photoelectron Spectroscopy (XPS) that oxygen-containing groups attached to surface carbon atoms are created during plasma treatment. These species desorb at temperatures of about 110 °C. The strength of C 1s and O 1s XPS signals from these radicals were seen to have direct correlation with water contact angles. In addition to surface chemistry, carpet morphology plays an important role in contact angle variations. Extreme surface roughness caused by high aspect-ratio of nanotubes would strongly accentuate both hydrophobic and hydrophilic behavior compared to flat surfaces. Classical geometric models of liquid droplets on uneven solids have been considered. Topological image analysis combined with intrinsic contact angle on flat graphene is used to predict the contact angle of these carpets, which matches well with experimental results. This analysis further explains why observed contact angles change if the vertical alignment of CNT is disturbed.

Exploring the upper limit of single-walled carbon nanotube purity by multiple-cycle aqueous two-phase separation

Ultrahigh purity semiconducting single-walled carbon nanotubes (S-SWCNTs) are required for high-performance transistors. Aqueous two-phase (ATP) separation is an attractive method to obtain such SWCNTs due to its simplicity and scalability. This work targeted two questions; namely what is the upper limit of S-SWCNT purity that can be achieved by multiple cycles of ATP separation from the most commonly used polyethylene glycol and dextran system and how accurately can commonly used methods characterize the improvement in purity? SWCNT purity in nanotube dispersions obtained by multi-cycle ATP separation (2, 4, 6 and 8 cycles) was evaluated by three methods, including UV-vis-NIR absorption spectroscopy analysis, performance of thin-film field effect transistors (FETs) prepared by drop casting and short-channel FET devices prepared by dielectrophoresis deposition. Absorption spectroscopic analysis and the performance of the thin-film FET devices can hardly differentiate metallic SWCNT residues in the dispersions obtained after 4 cycles with the purity above 99.5%, and the short channel FET devices prepared by dielectrophoresis deposition are more sensitive towards tiny metallic SWCNT residues. A new method was also demonstrated to visualize the minor metallic content in the nanotube suspension using voltage contrast imaging in a scanning electron microscope, which enables rapid screening of many devices and the accurate obtainment of metallic content without performing a large number of individual transconductance measurements.

Acrylonitrile, an advantageous precursor to synthesize nitrogen doped carbon nanotubes

The nitrogen doped carbon nanotubes present specific characteristics that offer better performance than pure carbon nanotubes for application like biomedicine, hydrogen adsorption and electrocataytic devices. This work present a simple method to obtain well-aligned nitrogen doped multi wall carbon nanotubes, which present open channels with diameter around 50nm. These carbon nanotubes are obtained using acrylonitrile as carbon and nitrogen source, which offers some advantages on the use of other precursors like ammonia, pyridine, benzylamine, acetonitrile or melamine.

High-Energy Dissipation Performance in Epoxy Coatings by the Synergistic Effect of Carbon Nanotube/Block Copolymer Conjugates.

Hierarchical assembly of hard/soft nanoparticles holds great potential as reinforcements for polymer nanocomposites with tailored properties. Here, we present a facile strategy to integrate polystyrene-grafted carbon nanotubes (PSgCNT) (0.05-0.3 wt %) and poly(styrene-b-[isoprene-ran-epoxyisoprene]-b-styrene) block copolymer (10 wt %) into epoxy coatings using an ultrasound-assisted noncovalent functionalization process. The method leads to cured nanocomposites with core-shell block copolymer (BCP) nanodomains which are associated with carbon nanotubes (CNT) giving rise to CNT-BCP hybrid structures. Nanocomposite energy dissipation and reduced Young's Modulus (E*) is determined from force-distance curves by atomic force microscopy operating in the PeakForce QNM imaging mode and compared to thermosets modified with BCP and purified carbon nanotubes (pCNT). Remarkably, nanocomposites bearing PSgCNT-BCP conjugates display an increase in energy dissipation of up to 7.1-fold with respect to neat epoxy and 53% more than materials prepared with pCNT and BCP at the same CNT load (0.3 wt %), while reduced Young's Modulus shows no significant change with CNT type and increases up to 25% compared to neat epoxy E* at a CNT load of 0.3 wt %. The energy dissipation performance of nanocomposites is also reflected by the lower wear coefficients of materials with PSgCNT and BCP compared to those with pCNT and BCP, as determined by abrasion tests. Furthermore, scanning electron microscopy (SEM) images taken on wear surfaces show that materials incorporating PSgCNT and BCP exhibit much more surface deformation under shear forces in agreement with their higher ability to dissipate more energy before particle release. We propose that the synergistic effect observed in energy dissipation arises from hierarchical assembly of PSgCNT and BCP within the epoxy matrix and provides clues that the CNT-BCP interface has a significant role in the mechanisms of energy dissipation of epoxy coating modified by CNT-BCP conjugates. These findings provide a means to design epoxy-based coatings with high-energy dissipation performance.