Application Of Multiwalled Carbon Nanotubes Research Articles

Application of multiwalled carbon nanotubes modified by diphenylcarbazide for selective solid phase extraction of ultra traces Cd(II) in water samples and food products

A novel sorbent for separation of cadmium ions was prepared by functionalizing multiwall carbon nanotubes with diphenylcarbazide and underutilised to develop a solid-phase extraction method to separate and concentrate trace amounts of cadmium ions from some real samples by flame atomic absorption spectrophotometry measurements. The optimum experimental conditions such as pH, flow rates, type and the smallest amount of eluent for elution of cadmium ions, break through volume and effect of coexisting ions on the separation and determination of cadmium ions were evaluated.In the proposed method, the extraction efficiency for cadmium ions were greater than 97% and limit of detection (LOD) was 0.05ngmL−1. The preconcentration factor was 360 for cadmium and the relative standard deviation (RSD) of the method was 2.4%. The adsorption capacity of the modified MWCNT was 86mgg−1 for cadmium ions. Validation of the outlined method was performed by analysing certified reference material soil (NCS DC 73323). The practical applicability of the developed sorbent was examined in some real samples.

Adsorption and desorption of thallium(I) on multiwalled carbon nanotubes

Increasing applications of multiwalled carbon nanotubes (MWCNTs) and thallium (Tl) would raise their exposure risks to aquatic environment. MWCNTs might affect the environmental behavior of Tl(I) by adsorption, and it is critical to understand the interactions between them. The adsorption kinetics, isotherms, thermodynamics, and desorption of Tl(I) by three MWCNTs were studied. In addition, the influences of solution pH, ionic strength on adsorption were also evaluated. The adsorption of Tl(I) on MWCNTs started at very low pH values and increased abruptly, then maintained high level with increasing pH values at pH>6.5. MWCNTs with more hydrophilic groups and negative surface charges had the greatest Tl(I) absorption capacity. The existence of K+ significantly inhibited Tl(I) adsorption on purified-MWCNTs. Tl(I) adsorption on MWCNTs was spontaneous occurred by ion exchange with H+/Na+/K+ at the exchange sites and forming outer-sphere surface complex. Moreover, Tl(I) could be easily desorbed from MWCNTs and the lower pH benefited the desorption.

Multi-walled carbon nanotubes and metal–organic framework nanocomposites as novel hybrid electrode materials for the determination of nano-molar levels of lead in a lab-on-valve format

Metal-organic frameworks have been the subject of intense research because of their unique physicochemical properties. The presented study investigates the application of multi-wall carbon nanotubes and metal-organic frameworks (MWCNTs@Cu3(BTC)2) nanoparticles-modified electrode for the determination of trace levels of lead. The nanocomposites were prepared by solvothermal synthesis and characterized in detail. The experimental procedure was carried out by accumulating lead on the electrode surface and subsequently measuring with differential pulse anodic stripping voltammetry in a lab-on-valve format. The main parameters affecting the analytical performance, including the amount of MWCNTs@Cu3(BTC)2 suspension, supporting electrolyte and its pH, stripping mode, and flow rate, have been investigated in detail. Under the optimum conditions, the oxidation peak current displayed a calibration response for lead over a concentration range from 1.0 × 10(-9) to 5.0 × 10(-8) molL(-1) with a excellent detection limit of 7.9 × 10(-10) molL(-1). The relative standard deviation of 7 successive scans was 3.10% for 1.0 × 10(-8) molL(-1) lead. The established method showed a great improvement in sensitivity and sample throughput for lead analysis.

Voltammetric determination of 6-mercaptopurine using a multiwall carbon nanotubes paste electrode in the presence of isoprenaline as a mediator

In this study, we describe the application of multiwall carbon nanotubes paste electrode (MWCNTPE) in the presence of isoprenaline (ISPT) as the suitable mediator for voltammetric determination of 6-mercaptopurine (6-MP) in aqueous buffer solution (pH 4.0). The results indicate that the electrode is efficient in terms of its electrocatalytic activity for the oxidation of 6-MP in the presence of ISPT as a mediator. Using chronoamperometry, the catalytic reaction rate constant was calculated at 1.68×10−3μM−1s−1. The catalytic peak current was linearly dependent on 6-mercaptopurine concentration in the range of 0.5–900μM 6-MP. The detection limit (3σ) obtained by linear sweep voltammetry (LSV) was 0.1μM. Finally, the proposed method was also examined as a selective, simple and precise electrochemical sensor for the determination of 6-MP in real samples such as urine and tablet.

Electrochemical production, characterization, and application of MWCNTs

The subject of this study is production of carbon nanotubes (CNTs) using an original procedure of reduction of lithium molten salts onto graphite cathode; their structural characterization and application as support material for electrocatalysts aimed for hydrogen evolution. As-produced CNTs were characterized by means of scanning and transmission electron microscopy (SEM and TEM), Raman spectroscopy, and thermogravimetric and differential thermal analysis (DTA). SEM and TEM images have shown that nanotubes are mostly of curved shape with length of 1–20 μm and diameter of 20–40 nm. Raman peaks indicate that the crystallinity of produced nanotubes is rather low. The obtained results suggest that formed product contains up to 80 % multiwalled carbon nanotubes (MWCNTs), while the rest being non-reacted graphite and fullerenes. DTA curves show that combustion process of the nanotubes takes place in two stages, i.e., at 450 and 720 °C. At the lower temperature, combustion of MWCNTs occurs, while at higher one, fullerenes and non-reacted graphite particles burn. As-produced MWCNTs were used as electrocatalyst’s support materials and their performance was compared with that of traditional carbon support material Vulcan XC-72. MWNTs have shown almost twice higher real surface area, and electrocatalyst deposited on them showed better catalytic activity than corresponding one deposited on Vulcan XC-72.

Photovoltaic performance of dye-sensitized solar cells with various MWCNT counter electrode structures produced by different coating methods

We report the successful application of multi-walled carbon nanotubes (MWCNTs) as electrocatalysts for triiodide reduction in dye-sensitized solar cells (DSSCs). To improve the photovoltaic performance of DSSCs, upgrade the quality of MWCNT structure and obtain an optimum deposition approach regarding a counter electrode, the present study was investigated. Three different MWCNT structures, raw, purified and purified and ground, were investigated as platinum (Pt) alternatives for counter electrodes in DSSCs. The counter electrodes were prepared on fluorine-doped tin oxide (FTO) glass substrates by two different techniques: spin coating from fluid-type MWCNTs and screen printing from paste-type MWCNTs. By utilizing a spin-coating technique, a DSSC that was fabricated with a purified and ground MWCNT counter electrode achieved an overall photovoltaic efficiency of 4.94%. This photovoltaic performance is comparable to that of a DSSC using a conventional “Pt” counter electrode fabricated under the same conditions. We found that the grinding method is powerful for increasing specific surface area and porosity. With this technique, macropores can be transformed into mesopores, thereby reducing the agglomeration of the MWCNTs, and with an additional modification, an increased DSSC photovoltaic efficiency results.

Surface modification of multiwalled carbon nanotubes via gliding arc plasma for the reinforcement of polypropylene

AbstractTo increase the applicability of multiwalled carbon nanotubes (MWCNTs), functional groups were generated on the generally inert surface of MWCNTs using gliding arc (GA) plasma. MWCNTs were modified using plasma polymerization with styrene (St) as monomer. The surface compositional and structural changes that occur on MWCNTs were investigated using FT‐IR, Raman spectroscopy, BET surface area, and elemental analysis. Dispersion of the treated MWCNTs in different solvents was evaluated. Transmission electron microscopy images showed that the plasma‐treated MWCNTs had a better dispersion than the untreated ones in nonpolar solvents. Subsequently, MWCNTs‐reinforced polypropylene (PP) composites were prepared by internal batch mixing with the addition of 1.0 wt % MWCNTs. The morphology of MWCNTs/PP nanocomposites was studied through scanning electron microscopy. Observations of SEM images showed that the plasma‐treated MWCNTs had a better dispersion than the untreated MWCNTs either on the composite fracture surfaces or inside the PP matrix. Moreover, the mechanical tests showed that the tensile strength and elongation at break were improved with the addition of polystyrene‐grafted MWCNTs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

MULTIWALLED CARBON NANOTUBES BASED NANOCOMPOSITES FOR SUPERCAPACITORS: A REVIEW OF ELECTRODE MATERIALS

Electrode materials are the most important factors to verify the properties of the electrochemical supercapacitor. In this paper, the storage principles and characteristics of electrode materials, including carbon-based materials, transition metal oxides and conducting polymers for supercapacitors are depicted in detail. Other factors such as electrode separator and electrolyte are briefly investigated. Recently, several works are conducted on application of multiwalled carbon nanotubes (MWCNTs) and MWCNTs-based electrode materials for supercapacitors. MWCNTs serve in experimental supercapacitor electrode materials result in specific capacitance (SC) value as high as 135 Fg-1. Addition of pseudocapacitive materials such as transition metal oxides and conducting polymers in the MWCNTs results in electrochemical performance improvement (higher capacitance and conductivity). The nanocomposites of MWCNTs and pseudocapacitive materials are the most promising electrode materials for supercapacitors because of their good electrical conductivity, low cost and high mass density.

Evaluation of Exposure Risk in the Weaving Process of MWCNT-Coated Yarn with Real-time Particle Concentration Measurements and Characterization of Dust Particles

Various applications of multiwalled carbon nanotubes (MWCNT) have been developed. One of these applications is an efficient sheet heating element that is woven from MWCNT-coated yarn. In this research, we assessed the exposure to MWCNT and/or the probability of particle release from broken MWCNT-coated yarn during the weaving process. This was accomplished using particle concentrations, microscopic observation, and carbon analysis. In the weaving process, neither an increase in the number of particles nor a difference in particle-size distribution was observed. In the scanning electron micrographic observation, nanosize MWCNT particles were not detected, but there were micron-size particles containing MWCNT as fragments of the yarn. Carbon analysis showed the concentration of micron-size particles containing MWCNT did not exceed 0.0053 mg-C/m(3) around the loom. This value was much lower than the respirable dust mass concentration. Most of micron-size particles seemed to originate from polyester yarn without MWCNT coating. It is recommended that workers use conventional (even not specialized for nanoparticles) personal protective equipment such as respirators and gloves to prevent exposure to respirable-size MWCNT-containing particles. The probability of MWCNT fall-off from the MWCNT-coated yarn was not detected by transmission electron microscopic observation of MWCNT-coated yarn before or after the weaving process.

Application of multiwall carbon nanotubes impregnated with 5-dodecylsalicylaldoxime for on-line copper preconcentration and determination in water samples by flame atomic absorption spectrometry

The paper presents application of multiwall carbon nanotubes (MWCNTs) modified with 5-dodecylsalicylaldoxime to copper(II) flow-injection on-line preconcentration and flame atomic absorption spectrometric (FAAS) determination. Two new sorbents were obtained by impregnation of MWCNTs with Cu(II)-LIX 622® complex, however in the first case modification was preceded by carbon wall activation via oxidization (Cu-LIX-CNT-A sorbent), and in the second one no surface activation was performed (Cu-LIX-CNT sorbent). It was found that effective leaching of initially introduced copper and Cu(II) retained in preconcentration process could be realized with the use 7% and 5% (v/v) nitric acid, for particular sorbents. Testing the influence of loading solution pH and rate of loading on sorption it was found out that optimal range of loading solution pH was about 4.5–6.3 for activated and 6.15–6.25 for non-activated CNT. Investigation of sorption kinetics showed that the process can be described by pseudo-second order reaction model. Sorption equilibrium conditions (90% sorption) for LIX-CNT-A and LIX-CNT were obtained after 8–15min, respectively and maximum sorption capacity for the new sorbents amounted to 18.1mgg−1 and 31.6mgg−1, respectively. For the examined sorbents enrichment factors increased with extension of loading time up to 180s: linearly for activated and non-linearly for non-activated MWCNTs. Influence of potential interferents such as Cd(II), Zn(II), Fe(III), Mg(II) and Ca(II) ions on copper(II) sorption on the new CNT materials was examined individually and with the use of 25–2 factorial design. The study revealed significant interference from iron, magnesium and calcium ions at relatively high concentrations. Applicability of the proposed sorbents was tested for Cu(II) determination in various kinds of water samples and the results were compared with those obtained with the use of ICP MS as a reference technique. Copper(II) determination in two certified reference materials: waste water (EU-H-3) and ground (ES-H-2) water was performed in order to assess trueness of the evaluated preconcentration procedures. Satisfactory values of relative errors were obtained for both procedures.

Selective Separation/Preconcentration of Silver Ion in Water by Multiwalled Carbon Nanotubes Microcolumn as a Sorbent

AbstractThe present paper proposes the application of multiwalled carbon nanotubes (MWCNTs) as a solid adsorbent for selective separation/preconcentration of silver(I) in water samples prior to flame atomic absorption spectrometry. The procedure is based on the solid phase extraction of Ag(I)–2‐mercaptobenzothiazole chelate on MWCNTs. The elution step is carried out with 5 mL of 2 mol L−1 HNO3 in acetone solution at a flow rate of 1.0 mL min−1. The influences of the various analytical parameters including pH of the solution, eluent type, sample volume, flow rates of eluent, matrix ions were investigated for optimization of the presented procedure. Tests of addition/recovery for analyte ion in real samples were performed with satisfactory results. Preconcentration factor and limit of detection for Ag(I) were 160 and 0.21 µg L−1, respectively. The synthesized MWCNT exhibited excellent stability in eluent solution and its adsorption capacity was 5.4 mg of silver per gram of sorbent. The proposed method was successfully applied to trace silver determination in a variety of environmental water samples.

Investigation of Vibration Properties of Multi-Walled Carbon Nanotubes

Based on an explicit van der Waals (vdW) model, which can reproduce the interaction between any two layers of multi-walled carbon nanotube (MWCNT) and is dependent on the change of interlayer spacing and on the tube radii, the vibration analysis of multi-walled carbon nanotubes is carried out by using of the multi-layered Flugge shells model. The natural frequencies are analyzed in detail for with various radii and number of tubes. Furthermore, the natural frequencies of double-walled carbon nanotube with the innermost radii of 0.6 nm predicted based on the Flugge shell model are well compared with those from the Donnell shell one. The present investigation will be meaningful for the design and application of multi-walled carbon nanotubes as nano- resonators.

Application of multi-walled carbon nanotubes modified carbon ionic liquid electrode for electrocatalytic oxidation of dopamine

A simple, sensitive, and reliable method based on a multi-walled carbon nanotubes (MWNTs) modified carbon ionic liquid electrode (CILE) has been successfully developed for determination of dopamine (DA) in the presence of ascorbic acid (AA). The acid-treated MWNTs with carboxylic acid functional groups could promote the electron-transfer reaction of DA and inhibit the voltammetric response of AA. Due to the good performance of the ionic liquid, the electrochemical response of DA on the MWNTs/CILE was better than that of other MWNTs modified electrodes. Under the optimum conditions a linear calibration plot was obtained in the range 5.0×10(-8) to 2.0×10(-4) mol L(-1) and the detection limit was 1.0×10(-8) mol L(-1).

Defect-related hysteresis in nanotube-based nano-electromechanical systems

The electronic properties of multi-walled carbon nanotubes (MWCNTs) depend on the positions of their walls with respect to neighboring shells. This fact can enable several applications of MWCNTs as nano-electromechanical systems (NEMS). In this article, we report the findings of a first-principles study on the stability and dynamics of point defects in double-walled carbon nanotubes (DWCNTs) and their role in the response of the host systems under inter-tube displacement. Key defect-related effects, namely, sudden energy changes and hysteresis, are identified, and their relevance to a host of MWCNT-based NEMS is highlighted. The results also demonstrate the dependence of these effects on defect clustering and chirality of DWCNT shells.

Radiofrequency field absorption by carbon nanotubes embedded in a conductive host

Understanding the electromagnetic response of carbon nanotubes (CNTs) in the radio frequency range is very important for experimental development of therapeutic and diagnostic CNT applications, including selective thermolysis of cancer cells and thermoacoustic imaging. In this study, we present the theory of electromagnetic wave scattering by several finite length CNT configurations, including singlewall CNT’s having a surfactant coating, CNT bundles, and multiwall CNTs. Absorption cross-sections of these structures in a conductive host region are theoretically studied in the radio frequency range. Strong local field enhancement due to edge effects is predicted to be inherent to metallic singlewall CNTs in the near-field zone, providing an additional mechanism of energy dissipation in a conductive host. Due to the screening effect the application of singlewall CNTs for the enhancement of energy dissipation is more effective than the application of multiwall CNTs or CNT bundles at the same mass fraction of CNT inclusions. The presence of a lossy dielectric (surfactant) coating can significantly increase the absorption cross section of singlewall CNTs.

Removal of 4,4′-dichlorinated biphenyl from aqueous solution using methyl methacrylate grafted multiwalled carbon nanotubes

Methyl methacrylate (MMA) is grafted on multiwalled carbon nanotubes (MWCNTs) by using N 2 plasma technique. The MMA grafted MWCNTs (MWCNT- g-pMMA) are characterized by using Raman spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, thermo gravimetric analysis–differential thermal analysis (TGA–DTA), and potentiometric acid-base titration method. The application of MWCNT- g-pMMA in the removal of 4,4′-dichlorinated biphenyl (4,4′-DCB) from large volumes of aqueous solutions is investigated under ambient conditions. The results indicate that the adsorption of 4,4′-DCB on MWCNT- g-pMMA is much higher than that of 4,4′-DCB on MWCNTs, and the adsorbed 4,4′-DCB is difficult to be thermally decomposed from MWCNT- g-pMMA according to the TGA–DTA analysis. MWCNT- g-pMMA are suitable materials in the preconcentration and immobilization of polychlorinated biphenyls (PCBs) from large volumes of aqueous solutions in environmental pollution cleanup.

Preconcentration of Pb 2+ from aqueous solution using poly(acrylamide) and poly(N,N-dimethylacrylamide) grafted multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) were grafted with poly(acrylamide) (PAAM) and with poly(N,N-dimethylacrylamide) (PDMA) at same grafting percentage by using N 2 plasma technique. The PAAM grafted MWCNTs (MWCNT- g-PAAM) and PDMA grafted MWCNTs (MWCNT- g-PDMA) were characterized by using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermo gravimetric analysis-differential thermal analysis (TGA–DTA), scanning electron microscopy (SEM), and potentiometric titration. The results indicated that the grafting processes occurred on the surfaces of MWCNTs without destroying the framework of MWCNTs. The application of MWCNTs, MWCNT- g-PAAM, and MWCNT- g-PDMA in the removal of Pb 2+ from aqueous solution was investigated under ambient conditions. The grafted PAAM and PDMA improved MWCNT adsorption capacity in the removal of Pb 2+ from large volumes of aqueous solutions. MWCNT- g-PAAM had much higher adsorption capacity than MWCNT- g-PDMA, which was attributed to higher amide group content in acrylamide than that in N,N-dimethylacrylamide.

Surface modification and application of multi-walled carbon nanotubes in fire-retardant coatings

Multi-walled carbon nanotubes (MWCNTs) were modified by grafting an amphiphilic polymer,which were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. The modified MWCNTs were added to an intumescent fire-retardant coating and their effects on the performance of the coating were studied. Results show that the amphiphilic polymer can be attached to the surface of MWCNTs by appropriate processing,and the modified MWCNTs exhibit a remarkable solubility in butyl acetate and distilled water. The modified MWCNTs added to the coating can strengthen the carbonized layers,increase intumescent times and decrease the increasing rate of the rear temperature when the coating was exposed to a fire. The modified MWCNTs can also enhance the crack resistance of the coating.

Application of multi-walled carbon nanotubes to enhance anodic performance of an Enterobacter cloacae -based fuel cell

The effect of multi-walled carbon nanotube (MWCNT) modification of anodes and the optimisation of relevant parameters thereof for application in an Enterobacter cloacae microbial fuel cell were examined. The H – type microbial fuel cells were used for the fundamental studies, with a carbon sheet as a control anode and platinum coated carbon sheets as the cathode. Anodes were correspondingly modified with MWCNTs dispersed in either 0.1% chitosan or 1% Nafion®. Maximum power output was observed four hours after inoculation of the anode chamber with the microorganism. A 252.6% increase in power output of the fuel cell was observed at an anode modified with 10 mg MWCNTs/ml dispersed in 0.1% chitosan compared to unmodified anodes (13.8 iW). MWCNTs dispersed in chitosan yielded nearly 50% greater power outputs than when dispersed in Nafion®; attributed to increased aggregation in the latter as evidenced by scanning electron microscopy imaging. When NafionTM 117 membrane was used as a proton exchanger it generally resulted in higher power outputs than the CMI 7000S membrane. These studies also showed that the time-consuming carboxylic acid functionalisation of MWCNT for such applications is not a necessary requirement for enhancing power outputs. The studies thus illustrate the utility of a MWCNT modified anode as a support matrix for E. cloacae in a microbial fuel cell and provide clarity on parameters which can be applied to other such studies in the emerging area of nanostructured material utilisation in alternative energy generation.

Efficient Dye-Sensitized Solar Cells with Catalytic Multiwall Carbon Nanotube Counter Electrodes

We report the successful application of multiwall carbon nanotubes (CNTs) as electrocatalysts for triiodide reduction in a dye-sensitized solar cell (DSSC). Defect-rich edge planes of bamboolike-structure multiwall CNTs facilitate the electron-transfer kinetics at the counter electrode-electrolyte interface, resulting in low charge-transfer resistance and an improved fill factor. In combination with a dye-sensitized TiO2 photoanode and an organic liquid electrolyte, a multiwall CNT counter-electrode DSSC shows 7.7% energy conversion efficiency under 1 sun illumination (100 mW/cm(2), air mass 1.5 G). The short-term stability test at moderate conditions confirms the robustness of CNT counter-electrode DSSCs.