Characterization Of Single-walled Carbon Nanotubes Research Articles

Effects of carbon nanomaterials on the migration and fate of organic pollutants in the ecological environment

The purpose of this study was to investigate the mechanism of adsorption reaction between heterocyclic organic compounds with different number of ring atoms and different atoms replacing carbon atoms and carbon nanotubes with different surface functional groups. Based on the current situation of research on adsorption of carbon nanomaterials adsorbing organic pollutants, the existing problems and limitations were analyzed by studying the properties and characterization of single-walled carbon nanotubes, oxidized single-walled carbon nanotubes and non-porous graphite powder, such as elemental analysis, transmission electron micrograph, zero charge point, etc. The three adsorption materials were investigated by batch experiment. Six compounds of thiophene, pyrimidine, benzene, aniline, 2-aminopyrimidine and 4,6-diaminopyrimidine were selected as the adsorbate for detecting adsorption capacity. The results showed that the affinity of different adsorbents on different adsorbents varied greatly. The adsorption capacity of heterocyclic compounds containing N and S was greatly enhanced by non-hydrophobic action. And the degree of oxidation of the adsorbent and the ph of the solution determined the adsorption capacity of the adsorbent for nitrogen-containing heterocyclic compounds. Therefore, in the ecological environment, the migration of hydrophilic organic pollutants in the environment can be reduced by the preparation of appropriate carbon nanotubes.

Determination of fundamental coupled torsional—radial frequency of single-walled carbon nanotubes

Research indicates that single-walled carbon nanotubes have a unique coupled torsional–radial vibration as one of their fundamental modes. Determination of their vibration frequency is required for efficient use of single-walled carbon nanotube in nano-electromechanical systems. However, there is no mathematical expression for these frequencies and their dependence on single-walled carbon nanotube geometry is unknown. This article examines the effect of diameter, length, and chirality on the fundamental coupled torsional–radial vibration frequency of single-walled carbon nanotube using molecular–structural–mechanics–approach, finite element analysis, and regression analyses. Consequently, a first-ever mathematical form of this frequency is derived. The form quickly and accurately predicts these frequencies at 1.5% in-sample, and 7.2% out-sample mean absolute percentage error. single-walled carbon nanotubes’ fundamental coupled torsional–radial vibration frequency is found independent of diameter and inversely proportional to length where the proportionality constant depends on chirality. The coupling of modes and the similarity of the frequency form with cylindrical shell suggest that single-walled carbon nanotube behave like thin shells in these vibrations. A form for effective circumferential shear modulus of single-walled carbon nanotube is also derived. This modulus is found to depend only on the chirality where achiral single-walled carbon nanotubes have higher values than chiral single-walled carbon nanotubes. Proposed mathematical forms can be used for characterization of single-walled carbon nanotubes, determination of single-walled carbon nanotubes’ effective shear modulus, and tuning operational frequency of single-walled carbon nanotube-based nano-electromechanical systems.

Electrochemical measurement of serotonin by Au-CNT electrodes fabricated on microporous cell culture membranes

Gut–brain axis (GBA) communication relies on serotonin (5-HT) signaling between the gut epithelium and the peripheral nervous system, where 5-HT release patterns from the basolateral (i.e., bottom) side of the epithelium activate nerve afferents. There have been few quantitative studies of this gut-neuron signaling due to a lack of real-time measurement tools that can access the basolateral gut epithelium. In vitro platforms allow quantitative studies of cultured gut tissue, but they mainly employ offline and endpoint assays that cannot resolve dynamic molecular-release patterns. Here, we present the modification of a microporous cell culture membrane with carbon nanotube-coated gold (Au-CNT) electrodes capable of continuous, label-free, and direct detection of 5-HT at physiological concentrations. Electrochemical characterization of single-walled carbon nanotube (SWCNT)-coated Au electrodes shows increased electroactive surface area, 5-HT specificity, sensitivity, and saturation time, which are correlated with the CNT film drop-cast volume. Two microliters of CNT films, with a 10-min saturation time, 0.6 μA/μM 5-HT sensitivity, and reliable detection within a linear range of 500 nM–10 μM 5-HT, can be targeted for high-concentration, high-time-resolution 5-HT monitoring. CNT films (12.5 μL) with a 2-h saturation time, 4.5 μA/μM 5-HT sensitivity, and quantitative detection in the linear range of 100 nM–1 μM can target low concentrations with low time resolution. These electrodes achieved continuous detection of dynamic diffusion across the porous membrane, mimicking basolateral 5-HT release from cells, and detection of cell-released 5-HT from separately cultured RIN14B cell supernatant. Electrode-integrated cell culture systems such as this can improve in vitro molecular detection mechanisms and aid in quantitative GBA signaling studies.

Synthesis and structural characterization of single-walled carbon nanotubes functionalized with fluorinated phosphonate analogues of phenylglycine, as promising materials for synthetic and biomedical applications

Through chemical functionalization the prerequisites for possible applications of such nanostructures as single-walled carbon nanotubes (SWCNTs) are established. In this study, modifications of SWCNTs by fluorinated phosphonate analogue of phenylglycine, compound belonging to important group of natural amino acid mimetics, using two approaches are presented. The first one was based on noncovalent functionalization of SWCNTs with the phosphono-perfluorophenylglycine analogue. In the second approach, SWCNTs were covalently bonded to the fluorinated α-aminophosphonates in one-step or multi-step reactions. The investigation of the functionalization effect on the dispersibility, thermal properties and the structure of SWCNTs was performed by using of X-Ray spectroscopy, TGA and Raman spectroscopy. Both approaches indicated promising methods for fast and efficient modification of carbon nanotubes (CNTs) also with other representatives of previously synthesized fluorinated aminophosphonates. Functionalized with such compounds CNTs can constitute materials for synthetic and biomedical applications. Due to their biological activity and structural analogy to corresponding α-amino acids, fluorinated α-aminophosphonates provide an important source for drug discovery. Therefore functionalization of SWCNTs with such molecules can provide an important platforms for drug delivery applications. Due to the presence of perfluorinated phenyl rings various nucleophiles can be introduced by nucleophilic aromatic substitution reactions to the functionalized SWCNTs leading to obtaining completely new materials.

Covalent functionalization and characterization of Single-walled carbon nanotubes with Cu (II) complexes of meso-tetra(4-aminophenyl)porphyrin

5,10,15,20-tetra(4-aminophenyl)porphyrinatocopper(II) [CuTAP] was covalently linked via amide bond with SWCNTs. Notable changes in the FT-IR spectra reveal the covalent linking of the porphyrin chromophore with SWCNTs. Further, covalent functionalization was confirmed by the hypsochromic shift of this nano-hybrid in the UV-visible spectra as compared to that of pristine CuTAP. 38 % weight loss observed in the TGA due to the extent of Cu-TAP functionalization. Morphology study of this nano-hybrid reveals the tubular structure, which is retained even after covalent functionalization. SWCNT-CuTAP nano-hybrid shows the hypsochromic shift and hypochromic shift compared to reported TAP or Zn-TAP due to Cu metal ion substitution.

Experimental assignment of phonon symmetry of G+ and G− peaks from single-walled carbon nanotubes

Raman scattering spectroscopy is widely used for the characterization of single-walled carbon nanotubes (SWCNTs). Although the G-band is one of the most important peaks of SWCNTs, the phonon symmetry of the most and second strong peaks in the G-band (G+ and G− peaks) is still veiled. Here, we show the experimental evidence of their phonon symmetry by using single-suspended SWCNT samples and polarized Raman scattering spectroscopy. The G+ and G− peaks come from A symmetry phonons, and the resonance effect to the excitonic excitation and the depolarization effect are dominant in the polarization characteristics of G+ and G− peaks.

Nonlinear optical response of liquid crystalline matrix doped with single walled carbon nanotube and graphene sheets

In this work, the nonlinear optical characterization of single-walled carbon nanotubes (SWCN) and graphene in guest-host liquid crystal system have been investigated using z-scan technique and far-field diffraction patterns. The guest materials have been dispersed in 8CB smectic liquid crystal at different concentration and specific thermal conditions. Z-scan measurements with continuous wave (CW) He:Ne laser beam at 632.8nm have been used for determining the nonlinear refractive index (n2) of guest-host system. It was found that n2 depends substantially on the concentration of the SWCN and graphene layers doped in SLCs, and it led to a significant growth in the nonlinear refractive index. Furthermore, the results of far-field optical diffraction patterns under CW HeNe laser illumination have been verified the result of nonlinear properties of Z-scan measurements.

Tensile Characterization of Single-Walled Carbon Nanotubes with Helical Structural Defects.

Recently, evidence was presented that certain single-walled carbon nanotubes (SWNTs) possess helical defective traces, exhibiting distinct cleaved lines, yet their mechanical characterization remains a challenge. On the basis of the spiral growth model of SWNTs, here we present atomic details of helical defects and investigate how the tensile behaviors of SWNTs change with their presence using molecular dynamics simulations. SWNTs have exhibited substantially lower tensile strength and strain than theoretical results obtained from a seamless tubular structure, whose physical origin cannot be explained either by any known SWNT defects so far. We find that this long-lasting puzzle could be explained by assuming helical defects in SWNTs, exhibiting excellent agreement with experimental observation. The mechanism of this tensile process is elucidated by analyzing atomic stress distribution and evolution, and the effects of the chirality and diameter of SWNTs on this phenomenon are examined based on linear elastic fracture mechanics. This work contributes significantly to our understanding of the growth mechanism, defect hierarchies, and mechanical properties of SWNTs.

Covalent functionalization of single-walled carbon nanotubes with polytyrosine: Characterization and analytical applications for the sensitive quantification of polyphenols

This work reports the synthesis and characterization of single-walled carbon nanotubes (SWCNT) covalently functionalized with polytyrosine (Polytyr); the critical analysis of the experimental conditions to obtain the efficient dispersion of the modified carbon nanotubes; and the analytical performance of glassy carbon electrodes (GCE) modified with the dispersion (GCE/SWCNT-Polytyr) for the highly sensitive quantification of polyphenols. Under the optimal conditions, the calibration plot for the amperometric response of gallic acid (GA) shows a linear range between 5.0 × 10−7 and 1.7 × 10−4 M, with a sensitivity of (518 ± 5) m AM−1 cm−2, and a detection limit of 8.8 nM. The proposed sensor was successfully used for the determination of total polyphenolic content in tea extracts.

Fabrication and adsorption characterization of single-walled carbon nanotube (SWNT) buckypaper (BP) for use in air samplers

Single-walled carbon nanotubes (SWNTs) have been investigated as a promising sorbent for volatile organic compound (VOC) sampling.

In situRaman monitoring of single-walled carbon nanotube filling with copper chloride

<italic<In situ</italic< characterization of single-walled carbon nanotubes during their gas-phase filling with copper chloride (CuCl) was performed with Raman spectroscopy. The time dependence of positions and intensities of G, 2D, and radial breathing modes was investigated. It was demonstrated that the adsorption of copper chloride from gas phase on the external and internal surfaces of nanotubes leads to the Raman mode shifting. However, this effect is weaker than in case of formation of one-dimensional CuCl crystals inside nanotubes.

Thermo-Mechanical Characterization of Single-Walled Carbon Nanotube (SWCNT)-Based Through-Silicon via (TSV) in (100) Silicon

Thermo-Mechanical Characterization of Single-Walled Carbon Nanotube (SWCNT)-Based Through-Silicon via (TSV) in (100) Silicon

Elemental characterization of single-wall carbon nanotube certified reference material by neutron and prompt γ activation analysis.

Instrumental neutron activation analysis with both relative and k0 standardization was used in four experienced laboratories to determine element mass fractions in single-wall carbon nanotube certified reference material (CRM) SWCNT-1. Results obtained were evaluated using the National Institute of Standards and Technology (NIST) "Type B On Bias" approach and yielded consensus values in agreement with National Research Council Canada (NRCC) certified values for Fe, Co, Ni, and Mo and provided mass fraction values for 13 additional elements, namely, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Br, La, W, and Au. In addition, prompt γ neutron activation analysis was employed to determine mass fractions of H, B, Co, Ni, and Mo. Results of this work provide a basis for the establishment of reference values of element mass fractions in CRM SWCNT-1, thus expanding its usability for more accurate characterization and benchmarking of similar nanotechnology materials.

Characterization of Single-Walled Carbon Nanotubes and Adsorption of Perchlorate in Water

The current study focuses on the removal of perchlorate in water using single-walled carbon nanotubes (SWCNTs) and granular ferric hydroxide as sorbents. The randomly distributed tubes were observed by scanning electron microscopy. The influence of temperature and content of natural humic acid on the perchlorate adsorption capacity was examined at pH 3. The adsorption data were fitted with three models: modified Freundlich, pseudo-first order, and pseudo-second order. The modified Freundlich model produced the best fit to describe the kinetic adsorption processes. The adsorption capacities of perchlorate measured at 25 °C and pH 3 using single-walled carbon nanotubes and granular ferric hydroxide were about 6 and 3 mg/g, respectively. The influence of natural humic acid on perchlorate adsorption by SWCNTs was examined. Natural humic acid was derived from raw water in Gao-Ping River in south Taiwan. Lower adsorption reaction rates of perchlorate were obtained at higher humic acid concentrations. High humic acid concentrations induce the compression of the electric double layer that consequently reduces the surface potential energy and electrostatic repulsion.

Mechanical characterization of single-walled carbon nanotubes: Numerical simulation study

The mechanical behaviour of non-chiral and chiral single-walled carbon nanotubes under tensile and bending loading conditions is investigated. For this purpose, three-dimensional finite element modelling is used in order to evaluate the tensile and bending rigidities and, subsequently, the Young's moduli. It is shown that the evolution of rigidity, tensile and bending, as a function of diameter can be described by a unique function for non-chiral and chiral single-walled nanotubes, i.e. regardless of the index or angles of chirality. A comprehensive study of the influence of the nanotube wall thickness and diameter on the Young's modulus values is also carried out. It is established that the evolution of the Young's modulus as a function of the inverse of the wall thickness follows a quasi-linear trend for nanotubes with diameters larger than 1.085 nm. The current numerical simulation results are compared with data reported in the literature. This work provides a benchmark in relation to ascertaining the mechanical properties of chiral and non-chiral single-walled carbon nanotubes by nanoscale continuum models.

Micromechanical characterization of single-walled carbon nanotube reinforced ethylidene norbornene nanocomposites for self-healing applications

We report on the fabrication of self-healing nanocomposite materials, consisting of single-walled carbon nanotube (SWCNT) reinforced 5-ethylidene-2-norbornene (5E2N) healing agent—reacted with ruthenium Grubbs catalyst—by means of ultrasonication, followed by a three-roll mixing mill process. The kinetics of the 5E2N ring opening metathesis polymerization (ROMP) was studied as a function of the reaction temperature and the SWCNT loads. Our results demonstrated that the ROMP reaction was still effective in a large temperature domain ( − 15–45 °C), occurring at very short time scales (less than 1 min at 40 °C). On the other hand, the micro-indentation analysis performed on the SWCNT/5E2N nanocomposite material after its ROMP polymerization showed a clear increase in both the hardness and the Young modulus—up to nine times higher than that of the virgin polymer—when SWCNT loads range only from 0.1 to 2 wt%. The approach demonstrated here opens new prospects for using carbon nanotube and healing agent nanocomposite materials for self-repair functionality, especially in a space environment.

In Situ Atomic Force Microscopy Tip-Induced Deformations and Raman Spectroscopy Characterization of Single-Wall Carbon Nanotubes

In this work, an atomic force microscope (AFM) is combined with a confocal Raman spectroscopy setup to follow in situ the evolution of the G-band feature of isolated single-wall carbon nanotubes (SWNTs) under transverse deformation. The SWNTs are pressed by a gold AFM tip against the substrate where they are sitting. From eight deformed SWNTs, five exhibit an overall decrease in the Raman signal intensity, while three exhibit vibrational changes related to the circumferential symmetry breaking. Our results reveal chirality dependent effects, which are averaged out in SWNT bundle measurements, including a previously elusive mode symmetry breaking that is here explored using molecular dynamics calculations.

Application of Resonance Raman Spectroscopy in the Characterization of Single-Walled Carbon Nanotubes

Application of Resonance Raman Spectroscopy in the Characterization of Single-Walled Carbon Nanotubes

Terahertz Characterization of Single-Walled Carbon Nanotube and Graphene On-Substrate Thin Films

In this paper, single-walled carbon nanotube (SWNT) thin films with thicknesses on the order of hundreds nanometers on glass substrates and a graphene thin film (2-3 layers) on a glass substrate are characterized via terahertz time-domain spectroscopy. The substrate permittivity is first characterized. The thin film is then treated as a surface boundary condition between the substrate and air. Using the uniform field approximation, the surface conductivities of these films are extracted. To improve accuracy, precise thickness of the sample substrate is calculated through an iteration process in both dielectric constant extraction and surface conductivity extraction. Uncertainty analysis of the measured thin-film properties is performed. The SWNT results show consistent surface conductivities for samples on different substrates and with different film thicknesses. The measured graphene terahertz conductivity is comparable to the values reported in the literature at dc and optical frequency. This characterization method has been successfully applied as a means to evaluate metallic content of SWNT samples to verify a metallic SWNT removing process using high-power microwave irradiation.

Single-walled carbon nanotube microsensors for nerve agent simulant detection

In this work we report on the fabrication and characterization of single-walled carbon nanotubes (SWCNTs) as sensitive layers for the detection of simulants of Chemical Warfare Agents (CWAs). The microsensor fabrication has been achieved after the wafer scale integration of the selective synthesis of SWCNTs as sensitive layer. Their electrical characterization has been carried out by measuring the resistance changes of the SWCNT networks when interacting with very low concentrations of CWA simulants such as dimethyl methyl phosphonate (DMMP), dipropylene glycol methyl ether (DPGME) and dimethylacetamide (DMA) at low temperatures, which are simulants of Sarin, Nitrogen Mustard and Distilled Mustard, respectively.