Single-walled Carbon Nanotubes Concentration Research Articles

Development of SWCNTs-reinforced EPDM/SBR matrices for shock absorbing applications

The present research investigates the effects of various concentrations of single-walled carbon nanotubes (SWCNTs) on the viscoelastic and thermomechanical characteristics of styrene-butadiene/ethylene propylene diene polymer (SBR/EPDM) blended polymeric matrices (60:40). Standard elastomeric methods are used to synthesise SWCNTs-reinforced EPDM/SBR nanocomposite blends. The results reveal that high SWCNTs concentrations offer remarkable thermal stability enhancement. SWCNTs reinforced with 0.6 mass% EPDM/SBR become 20% harder, with Tangent Delta values boosted by 70% with maximum cross-linking, elongation enhanced by 38% and tensile strength improved by 35%. With the 38% elongation enhancement, storage modulus is increased by 80%, whereas compressive strain is reduced by 20%. The planned hybrid nanocomposites exhibit viscoelastic characteristics against applied shock, in which the viscous component is associated with spongy structure, whereas the elastic component is associated with spring-like response.

Single-walled carbon nanotubes loaded hydroxyapatite-alginate beads with enhanced mechanical properties and sustained drug release ability.

Single-walled carbon nanotubes (SWCNTs) containing biomaterial with enhanced mechanical properties for the potential orthopedic application were synthesized and investigated. X-ray diffraction and X-ray fluorescence analysis were indications of the formation of calcium-deficient (Ca/P = 1.65) hydroxyapatite (HA) with a small carbonate content under influence of microwave irradiation. The investigated mechanical properties (maximal relative deformation, compressive strength and Young's modulus) of SWCNT loaded HA-alginate composites confirm their dependence on SWCNTs content. The compressive strength of HA-alginate-SWCNT and the HA-alginate control (202 and 159MPa, respectively) lies within the values characteristic for the cortical bone. The addition of 0.5% SWCNT, in relation to the content of HA, increases the Young's modulus of the HA-alginate-SWCNT (645MPa) compared to the SWCNT-free HA-alginate sample (563MPa), and enhances the material shape stability in simulated physiological conditions. Structural modeling of HA-alginate-SWCNT system showed, that physical adsorption of SWCNT into HA-alginate occurs by forming triple complexes stabilized by solvophobic/van der Waals interactions and H-bonds. The high-performance liquid chromatography demonstrated the influence of SWCNTs on the sustained anaesthesinum drug (used as a model drug) release (456h against 408h for SWCNT-free sample). Cell culture assay confirmed biocompatibility and stimulation of osteoblast proliferation of 0.05% and 0.5% SWCNT-containing composites during a 3-day cultivation. All these facts may suggest the potential possibility of using the SWCNT-containing materials, based on HA and alginate, for bone tissue engineering.

Estimation of the concentration of single-walled carbon nanotubes in polyethylene by spectral correlation method

Estimation of the concentration of single-walled carbon nanotubes in polyethylene by spectral correlation method

Open Circuit Voltage and Single Walled Carbon Nanotube (wt%) Dependency in Solid-State Complementary Metal Oxide Semiconductor-Compatible Glucose Fuel Cells

Solid-state complementary metal oxide semiconductor (CMOS)-compatible glucose fuel cells, with single-walled carbon nanotube (SWCNT) films and different amounts of carbon nanotube (wt%) were investigated. Those with a SWCNT content of 3 wt% were found to develop the highest open circuit voltage (OCV) of 400 mV, together with a high electrical conductivity, a power density of 0.53 μW/cm2 and current density of 1.31 μA/cm2. Measurements were performed by dipping the anode into a 30 mM glucose solution. The OCV and power density increased together with the fuel cell concentration. The developed fuel cell uses materials that are biocompatible with the human body (single-walled carbon nanotube-glucose). As a result, it was possible to attain an OCV of 400 mV with a single-walled carbon nanotube content of 3 wt% while improvements in the performance of the CMOS-compatible glucose fuel cell were obtained, and the parameters affecting the performance of the fuel cell were identified. This bio-fuel cell was fabricated using CMOS semiconductor processes on a silicon wafer. These findings are significant to realizing mobile or implantable devices that can be used for biomedical applications.

Enhanced thermoelectric properties of copper phthalocyanine/single-walled carbon nanotubes hybrids

Copper phthalocyanine (CuPc)/single-walled carbon nanotube (SWCNT) hybrids were prepared by high energy ball milling combined with cold pressing method. The electrical conductivity of the hybrids increased with the increasing SWCNT content, whereas the Seebeck coefficient decreased. Moreover, the electrical conductivity of CuPc/SWCNT hybrids were much higher than the values calculated based on the general parallel and series connected two-component mixture model. SEM, TEM, XPS, Raman and XRD analyses indicated that there existed a large number of CuPc-SWCNT nano-interfaces in the hybrids. The strong donor-acceptor and π-π conjugation interactions between CuPc molecules and SWCNTs can induce CuPc to highly ordered face-on packing on the surface of SWCNTs, which contributed to the efficient interface charge transport between CuPc and the surface of SWCNTs, and therefore both the carrier concentration and carrier mobility of CuPc/SWCNT hybrids were significantly increased. Finally, the maximum thermoelectric (TE) power factor at room temperature reached 70.1 μW m−1 K−2. The optimal TE property of the CuPc/SWCNT hybrids is remarkably higher than those of either individual component of the hybrid, and is among the highest values of metal-organic small molecules based TE materials. This study may provide a new route to enhance the TE properties of metal-organic small molecules materials.

Electromagnetic interference shielding of carbon nanotube-fluoropolymer elastomer composites with layered structure

This paper presents carbon nanotubes-containing polymer composites with layered gradient structure having electromagnetic interference (EMI) shielding properties. Polymer composite films were obtained on metal surface by aerosol deposition of a dispersion of carbon nanotubes in the solution of a copolymer of vinylidene fluoride with hexafluoropropylene (SCF-26) in acetone. Single-wall TUBALL (OCSiAl) carbon nanotubes were used. Three-layer coatings were formed with a concentration of nanotubes decreasing in each subsequent deposited layer. The reflection coefficient of electromagnetic radiation in the range of 20–35 GHz was measured. Gradient samples had significantly better characteristics compared to samples with uniform concentration of carbon nanotubes: the reflection coefficient reached −6dB at 35 GHz. The outer layer of gradient structure with 0.1 wt % CNT provides a better matching of the wave resistance with free space and a smooth entrance of an electromagnetic wave into the sample. The subsequent layers with an increasing concentration of single-walled carbon nanotubes (0.3 and 0.5%) absorb electromagnetic radiation. Polymer elastomer composite EMI shielding coatings with concentration gradient can be applied by aerosol deposition to the surfaces of any composition and shape. Our results could serve as a design tool in carbon nanotubes - based EMI shielding flexible polymer coatings.

Temperature dependence of the Seebeck coefficient for mixed semiconducting and metallic single-wall carbon nanotube bundles

The temperature (T) dependence of the Seebeck coefficient (S) for single-wall carbon nanotube (SWCNT) bundles was systematically investigated as a function of the chemical potential (μ) through theoretical simulations employing non-equilibrium Green’s function theory. The bundles were modeled as laterally aligned parallel circuits of semiconducting and metallic SWCNTs. The T dependence of S varied substantially with μ and with metallic SWCNT content. The calculated results semi-quantitatively reproduced the typical behavior observed experimentally for SWCNT films with chemical doping reported previously.

Strain and crack growth sensing capability of SWCNT reinforced epoxy in tensile and mode I fracture tests

Since the invention of Carbon Nanotubes (CNTs), the self-sensing capability of Multi-walled Carbon Nanotubes (MWCNT) based nanocomposites has been widely analyzed, whilst Single-Walled Carbon Nanotubes (SWCNTs) have been studied less extensively. Moreover, brittleness of epoxy based materials made them vulnerable to crack propagation, necessitating the monitoring of crack initiation and propagation. While research activities on strain monitoring of CNT based epoxy subject to tensile and flexural tests are present in the literature, works on the crack growth sensing capability under fracture toughness tests have not been reported. The present paper was therefore aimed to investigate the piezoresistive characteristics of epoxy-based nanocomposite loaded at different SWCNTs contents i.e. 0.25, 0.5 and 0.75 wt%, under tensile and mode I fracture toughness tests in order to compare and correlate the developed microstructures, including well-dispersed CNTs and aggregates, with the electromechanical properties of the epoxy based nanocomposites. SEM and FESEM analysis were conducted to investigate the fracture surface morphology and the state of the CNTs dispersions. A uniformly dispersed CNTs as well as proper cohesive bonding were obtained at CNTs content of 0.25 and 0.5 wt% whereas CNTs loading of 0.75 wt% resulted in excessive amount of aggregates accompanied with weak CNTs/epoxy bonding. Tunneling effect between neighboring CNTs was the dominant conductive mechanism, responsible for achieving proper sensitivity. For tensile tests, at a relatively low strain (less than 1%), the highest sensitivity was obtained at a SWCNTs content of 0.25 wt%, however showing a nonlinear trend in normalized resistance versus strain, i.e. the sensitivity increased by increasing strain. In fracture test, the SWCNT-doped materials were found to be capable of detecting damage initiation and extension by showing an abrupt increase in normalized electrical resistance upon the onset of crack growth while the piezo-resistivity before failure was either linear or nonlinear depending on the CNTs loading.

Investigation of thermal conductivity coefficient of aqueous suspension with carbon nanotubes

The dependence of thermal conductivity of suspension on the concentration of single-walled carbon nanotubes was investigated. Mass concentration of nanotubes ranged from 0.05 to 0.5%. Sodium dodecyl sulfate was used as a surfactant. The enhancement of 34.8% were achieved for thermal conductivity coefficient of suspensions at 0.5wt.% of CNT.

The study of the interaction mechanism between bovine serum albumin and single-walled carbon nanotubes depending on their diameter and concentration in solid nanocomposites by vibrational spectroscopy.

The results of the study of composites based on bovine serum albumin (BSA) and single-walled carbon nanotubes (SWCNT) are presented. Nanocomposites were created by evaporation of the water-albumin dispersion with nanotubes using diode laser with temperature control. Two types of nanotubes were used. SWCNT I were synthesized using the electric arc method, SWCNT II were synthesized using the gas phase method. SWCNT I had a diameter and length less than SWCNT II. The mechanism of interaction between BSA and SWCNT in solid nanocomposites is considered. An experimental and theoretical studies of the interaction between aspartic (Asp) and glutamic (Glu) amino acids located on the outer surface of BSA and nanotubes using of vibrational spectroscopy (Fourier-transform infrared (FTIR) and Raman spectroscopy) was carried out. The possibility of nanotubes functionalization by oxygen atoms of negative amino acid residues Asp and Glu, which are on the outer surface of BSA, is shown by molecular modeling. The formation of covalent bonds between BSA and SWCNT in nanocomposites with different concentrations of nanotubes (0.01, 0.1 and 1 g/l) was confirmed by vibrational spectra. The covalent interaction between BSA with SWCNT under the laser irradiation leads to the conformational changes in the secondary and tertiary structures of albumin. This is confirmed by a significant decrease in the intensity of the absorption bands in the high-frequency region. The calculation of the vibrational spectra of the three Glycine:Glycine, Glutamic acid:Threonine and Aspartic acid:Lysine complexes, which take into account hydrogen, ion-dipole and ion-ion bonds, showed that a disturbance in the intermolecular interaction between amino acid residues led to significant decrease in the intensity of absorption bands in the region of stretching vibrations bonds OH and NH. From the Raman spectra, it was found that a significant number of defects in SWCNT is caused by the covalent attachment of oxygen atoms to the graphene surface of nanotubes. An increase in the diameter of nanotubes (4 nm) has practically no effect on the absorption spectrum of nanocomposite, while measuring the concentration of SWCNT affects the FTIR spectra. This confirmed the hydrophobic interaction between BSA and SWCNT. Thus, it was shown that BSA solid nanocomposites with CNTs can interact either with the help of hydrophobic forces or with the formation of covalent bonds, which depends on the diameter of the used nanotubes. The viability of connective fibroblast tissue cells on nanocomposites with both types of SWCNT was demonstrated. It was found that nanocomposites based on SWCNT I provide slightly better compatibility of their structure with fibroblasts. It allows to achieve better cell adhesion to the nanocomposite surface. These criteria make extensive use of scaffold nanocomposites in biomedicine, depending on the requirements for their quality and application.

Swelling and electrical properties of LLDPE reinforced by SWCNTs nanocomposites for radiation and sensors applications

Linear low-density polyethylene (LLDPE) incorporated with single-walled carbon nanotubes (SWCNTs) by mistreatment casting technique. The result of various weight percentage loadings of SWCNTs on the swelling and electrical properties of LLDPE/SWCNTs nanocomposite also γ-irradiation effects had been investigated. It was found that, at low concentration, it uniformly disperses into an LLDPE matrix and provides LLDPE/SWCNTs nanocomposites with abundant improved electrical properties by nine orders of magnitude. Positive temperature coefficient of conductivity (PTCC)/negative temperature coefficient of conductivity (NTCC) was affected by the SWCNT contents. Transmission electron microscopy and scanning electron microscope techniques were used to investigate the dispersion of SWCNTs in the LLDPE matrix. Linear exceptional modification within direct current electrical conduction of percolative threshold-loaded LLDPE as a perform of γ-irradiation dose will be used as a nontoxic, easy, inexpensive, and sensitive method to evaluate the irradiation dose in range 10 Gy–1 kGy also can be used in fabrication of firing sensors with various ranges of temperatures.

Influence of single-walled carbon nanotubes induced exciton dissociation improvement on hybrid organic photovoltaic devices

Torch-plasma-grown single-walled carbon nanotubes (SWCNTs) are integrated with regioregular poly(3-hexylthiophene) (P3HT) and a fullerene derivative 1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61 (PCBM) as a hybrid photoactive layer for bulk heterojunction solar cell devices. We demonstrate that molecular information could be accurately obtained by time-of-flight secondary ion mass spectrometry throughout the hybrid organic photoactive solar cell layers when sputtering is performed using a Cs+ 2000 eV ion source. Furthermore, the photovoltaic (PV) performance of the fabricated devices show an increase in the short-circuit current density (Jsc) and the fill factor (FF) as compared to the pristine devices fabricated without SWCNTs. The best results are obtained with 0.5 wt. % SWCNT loads, where an open-circuit voltage (VOC) of 660 mV is achieved, with a Jsc of 9.95 mA cm−2 and a FF of 54%, leading to a power conversion efficiency of 3.54% (measured at standard test conditions, AM1.5 g). At this optimum SWCNT concentration of 0.5 wt. %, and to further understand the charge-transfer mechanisms taking place at the interfaces of P3HT:PCBM:SWCNT, Jsc is measured with respect to the light intensity and shows a linear dependency (in the double logarithmic scale), which implies that losses in the charge carrier are rather governed by monomolecular recombination. Finally, our results show that our hybrid devices benefit from the fullerene electron accepting nature and from the SWCNT fast electron transportation feature that improve substantially the exciton dissociation efficiency. The influence of the SWCNTs on the Fermi level and the work function of the photoactive composite and its impact on the PV performance is also investigated.

Influence of Submicron Anthracite Particles on the Conditions of Aerosol Synthesis and the Properties of Carbon Nanotubes

Properties of single-walled carbon nanotubes (SWCNTs) obtained by the floating catalyst CVD method using ethyl alcohol and coal (anthracite and semi-anthracite) particles are investigated. Structural and vibrationalcharacteristics of synthesis products are determined. It is revealed that enrichment of the reaction mixture by anthracite particles increases the concentrations of CO and CH4 in the reaction zone, which contributes to the growth of the SWCNTs. A comparison of the Raman spectra of the samples shows an increase in the content of small-diameter semiconductor SWCNTs, whereas a set of chirality indices of the resulting nanotubes remains unchanged.

Toward high thermoelectric performance for polypyrrole composites by dynamic 3-phase interfacial electropolymerization and chemical doping of carbon nanotubes

Polymer thermoelectric composites have received significant attention in recent years. To achieve high thermoelectric performance is one main aim, especially when being compared with their inorganic counterparts. Here, we report high-performance thermoelectric composites based on single-walled carbon nanotube (SWCNT) and polypyrrole (PPy), which are prepared by dynamic 3-phase interfacial electropolymerization and subsequent physical mixing. We found that both SWCNT content and chemical doping of SWCNT dramatically affected the composite thermoelectric performance. The maximum power factor at room temperature of the PPy composite reaches as high as 240.3 ± 5.0 μW m−1 K−2, which may be the highest value for PPy and its composites reported so far. The present study demonstrates that the dynamic 3-phase interfacial electropolymerization combining SWCNT chemical doping is effective to fabricate high-performance polymer thermoelectric composites.

On the effect of electric field application during the curing process on the electrical conductivity of single-walled carbon nanotubes–epoxy composites

Single-walled carbon nanotube (SWCNT)/epoxy composites were cured under external electric fields and the influence of the processing parameters (electric field magnitude and frequency, SWCNT concentration and curing temperature) on the electrical response of the system was evaluated. A mold for the electric field application was designed and manufactured, allowing in situ measurements of the electrical resistivity of the composite, during and after the curing process. The resulting electrical properties revealed a strong dependence on the processing parameters. By rising the curing temperature, the solid bulk resistivity was decreased by one order of magnitude. Further reduction was observed with electric fields, up to an additional order of magnitude. Such improvements can be related with the decrease in viscosity and improvement of interconnected-nanotube paths within the polymer matrix. The effect of the electric field on the rotation and interconnection of the SWCNTs was investigated using a classical mechanics model based on the dielectrophoretic theory for the liquid state. The influence of inter-nanotube distances on the bulk electrical properties was calculated at different particle concentrations, using finite element models of the microstructure. This processing technique presents promising results for enhancing the electrical conductivity of polymer composites with carbon-based nanoparticles.

Bath sonication for the scalable separation of semiconducting single walled carbon nanotubes

Commercially available single-walled carbon nanotubes (SWNTs) consist of a mixture of metallic (m-SWNTs) and semiconducting SWNTs (sc-SWNTs), and therefore cannot be used as they are for applications where pure semiconductors or metallic materials are needed. Hence, the separation of sc-SWNTs from pristine SWNT mixtures is an essential process that precedes the evaluation of SWNTs. The polymer wrapping method, which is one of the well-known methods for separating sc-SWNTs, can separate sc-SWNTs by forming a sc-SWNT/polymer complex in which sc-SWNTs are selectively wrapped with a conductive polymer over metallic SWNTs. This process is generally realized using a tip sonicator, which enables the polymer wrapping and dispersion for SWNTs. However, this conventional tip sonication has several drawbacks, such as difficulties with respect to mass production, contamination, and high cost of equipment. In this work, the selective dispersion and separation of sc-SWNTs were achieved using bath sonication, which can overcome the drawbacks related to conventional tip sonication process. It was confirmed that bath sonication can achieve a similar level of sc-SWNT dispersion efficiency to that of tip sonication. The variation in the dispersion efficiencies with respect to the dispersion time, SWNT concentration, SWNT types, polymer concentration, and solvent types and concentrations was investigated. Furthermore, the dispersion stability was compared by measuring the particle sizes of the sc-SWNT/conductive polymer composites obtained using the bath sonication and tip sonication methods via electrophoretic light scattering as a function of time.

CERAMIC COMPOSITE BASED ON ZIRCONIA REINFORCED BY SINGLE-WALLED CARBON NANOTUBES

The effect of the relative content of single-walled carbon nanotubes (SWCNTs) on the compaction, phase composition, microstructure, and mechanical properties of composites based on yttria-stabilized zirconia obtained via spark plasma sintering is studied. We found that a substantial increase in the relative density from 98.26 to 99.98% is observed in the composites containing 0.1 and 0.5 wt % SWCNT. It is established that SWCNTs partially limit the monoclinic–tetragonal transition occurring during high-temperature treatment of zirconia. The fracture toughness of the composite containing 1 wt % SWCNT increases by 38% compared to ceramics without additives.

Phage shock protein and gene responses of Escherichia coli exposed to carbon nanotubes

Two-dimensional electrophoretic, western blotting, and quantitative polymerase chain reaction analyses of Escherichia coli cells exposed to pristine single walled carbon nanotubes (SWCNTs), and hydroxyl and carboxylic functionalized SWCNTs (SWCNT-OHs and SWCNT-COOHs) were conducted. SWCNT concentration and length were experimental variables. Exposing E. coli cells to SWCNTs led to changes in protein and gene expressions. Several proteins altered their regulations at a low SWCNT concentration (10 μg/ml) and were shut down at a high SWCNT concentration (100 μg/ml). The expressions of the phage shock protein (psp) operon including pspA, pspB, and pspC genes responded to the membrane stressors, SWCNTs, were also examined. While pspA and pspC expressions were influenced by the length, concentration, and functional groups of SWCNTs, pspB expression was not induced by SWCNTs. The alterations in phage shock protein and gene expressions indicated that SWCNTs caused cell membrane perturbation.

Quantification of the Number of Adsorbed DNA Molecules on Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs) have unique photophysical properties and promise many novel applications. Their functionalization is crucial, but the organic phase around SWCNTs is poorly understood. Noncovalent functionalization with single-stranded DNA (ssDNA) is one of the most used approaches to solubilize SWCNTs in water, and variation of ssDNA sequences leads to major advances in separation of SWCNT chiralities and SWCNT-based sensors. However, the exact number of adsorbed ssDNA molecules on ssDNA/SWCNT complexes and consequently the surface coverage are not precisely known. Here, we determine the number of adsorbed/bound ssDNA molecules per SWCNT for different ssDNA sequences. For this purpose, we directly quantify free and bound/adsorbed ssDNA and the concentration of SWCNTs using an approach based on filtration, absorption spectroscopy, and atomic force microscopy. We found that the number of adsorbed ssDNA molecules on 600 nm long (6,5)-SWCNTs varies between ∼860 for (GT)5 and ∼130 for (...

Non-aligned ZnO nanowires composited with reduced graphene oxide and single-walled carbon nanotubes for highly responsive UV–visible photodetectors

A comprehensive comparison study of the UV–visible photoresponse properties of non-aligned carbothermal ZnO nanowires (ZNWs) composited with reduced graphene oxide (RGO) and single-walled carbon nanotubes (SWCNTs) is presented. The RGO/ZNWs composites (GZWs) and SWCNTs/ZNWs composites (CZWs) have been successfully synthetized through UV-assisted photochemical reduction of GO in ZNWs suspension and ultrasonic stirring technology, respectively. The optimal contents of RGO and SWCNTs incorporated into ZNWs were determined for achieving maximum photoresponse, respectively. Experimentally, the optimal GZWs and CZWs exhibit significant enhancement in photoelectric properties than pure ZNWs. It is demonstrated that the GZWs-based photodetector has higher photoresponsivity (∼16 AW-1) than CZWs-based photodetector under low UV irradiation (<10 μWcm−2) and at 1.0 V bias, while the CZWs-based photodetector has higher on/off current ratio (8.41 × 104) and faster response time (1.99 s of rise-time and 0.39 s of decay-time) than GZWs-based one. The detail physics mechanism on the effects of RGO and SWCNTs on photoelectric characteristics of ZNWs is presented with the interface charge transfer due to the chemisorption and photo-desorption of oxygen.