Efficiency Of Multi-walled Carbon Nanotubes Research Articles

Enhancing in vitro photothermal therapy using plasmonic gold nanorod decorated multiwalled carbon nanotubes.

Photothermal therapy (PTT) is a promising approach for cancer treatment that selectively heats malignant cells while sparing healthy cells. Here, the light-to-heat conversion efficiency of multiwalled carbon nanotubes (MWCNTs) within the near-infrared biological transmission window is enhanced by decorating them with plasmonic gold nanorods (GNRs). The results reveal a significant photothermal enhancement of hybrid MWCNTs-GNRs compared to bare MWCNTs, displaying a 4.9 enhancement factor per unit mass. The enhanced plasmonic PTT properties of MWCNTs-GNRs are also investigated in vitro using PC3 prostate cancer cell lines, demonstrating a potent ablation efficiency. These findings advance innovative hybrid plasmonic nanostructures for clinical applications.

Growth of MWCNTs from Azadirachta indica oil for optimization of chromium(VI) removal efficiency using machine learning approach.

The main objective of the present study is to develop artificial neural networks (ANN) to predict the adsorption efficiency of multi-walled carbon nanotubes (MWCNTs) on Cr(VI) removal. Polydisperse MWCNTs were synthesized at 750°C on alumina supported Fe-Co-Mo catalyst using CVD (chemical vapor deposition)-assisted spray pyrolysis of Azadirachta indica (Neem) oil under inert Argon (Ar) atmosphere. Growth of MCWNTs with inner diameters between 9 and 14nm was corroborated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction analysis (XRD), and Raman spectral evidence assessments. The metal-ion adsorbent capacity (Cr-VI) of the as such prepared MWCNTs was examined for industrial purposes. Different parameters such as adsorption isotherms, kinetics, and thermodynamic parameters were analyzed for the removal of metal ions with MWCNTs. The results of isotherm, kinetic, and thermodynamic study indicated that the process suited well with Langmuir isotherm, pseudo second-order kinetics, and followed endothermic reaction, respectively. The effects of parameters such as adsorbent dosage, concentration of chromium ion (Cr-VI), pH, and contact time were studied to optimize the maximum removal of Cr(VI). In order to optimize the process conditionsusing Artificial Neural Networks, Box-Behnken design (BBD)was used to design the batch adsorption experiments, and the resulting datasets were used as the input for ANN. To predict the adsorption efficiency, various ANN architectures were examined using different training algorithms, number of neurons in the hidden layer, and the transfer function for the hidden and output layers. A neural network structure with Levenberg-Marquardt (LM) training algorithm, 14 hidden neurons, and tangent sigmoid transfer function at the hidden layer and logarithmic sigmoid transfer function at the output layer furnished the best level of prediction results. Comparing with experimental data, the optimal model capitulated mean square error (MSE),and correlation coefficient (R2) of 0.0324 and 0.99512, respectively. The results showed that ANN is well-organized in predicting the adsorption efficiency of MWCNTs for Cr(VI) metal ion removal process.

The effect of thickness on the multiwalled carbon nanotubes performance in glass/epoxy composite laminates under dynamic loading

AbstractThe aim of this research is to investigate the thickness influence on the efficiency of multiwalled carbon nanotubes (MWCNTs) in glass/epoxy composite laminates under the high‐velocity impact. Combining 0.25 wt% of MWCNTs in the 4‐layer and 8‐layer specimens and 0.1 wt% of MWCNTs in the 16‐layer specimen led to the maximum rise in the energy absorption and specific perforation energy compared with the unreinforced laminates. The significant growth in energy absorption in the 4‐layer, 8‐layer, and 16‐layer specimens was 5.8, 8.3, and 14.4 J, respectively. The number of agglomerations (dislocations) in the matrix was consequently increased as a function of thickness, which led to the better performance of MWCNTs with lower weight percentages in the composite laminates containing more layers. The scanning electron microscope was used to observe the dispersion and agglomeration of MWCNTs in the resin epoxy, and there was also an improvement in the fiber–resin bonding.

High-temperature liquid chromatography for evaluation of the efficiency of multiwalled carbon nanotubes as nano extraction beds for removal of acidic drugs from wastewater. Greenness profiling and comprehensive kinetics and thermodynamics studies

The retention behavior of a series of acidic drugs, namely ketoprofen (KET), naproxen (NAP), diclofenac (DIC), and ibuprofen (IBU), on the heat-resisting ZORBAX 300SB-C18 column, was studied thermodynamically using high-temperature liquid chromatography (HTLC). A perfect correlation of the compounds' lipophilicity and the calculated thermodynamic indicators evidenced its contribution to the retention behavior. Besides, the steric fitting has a subsidiary effect on IBU retention. Isocratic HTLC separation of the four compounds was achieved using an aqueous mobile phase containing 30% acetonitrile-0.2% acetic acid-0.2% triethylamine at 60 °C. This method has been utilized to monitor the adsorption efficiency of multiwalled carbon nanotubes (MWCNTs) for the removal of the four NSAIDs from water. Different variables affecting the remediation process have been optimized such as the time of contact, pH, ionic strength, temperature, and the mass of MWCNTs. The kinetics and thermodynamics of the adsorption were investigated. The adsorption was evidenced to take place via pseudo-second-order kinetics and the intraparticle diffusion is the rate-controlling step. The thermodynamic investigation showed that the adsorption process is exothermic and enthalpy-driven, and the adsorption is more extensive at a lower temperature. The MWCNTs showed excellent adsorption efficiency of about 76.4 to 97.6% at the optimum conditions. The obtained results are promising and encouraging for the full-scale application of MWCNTs for remediation of NSAIDs-related water pollution. The green analytical chemistry metric “AGREE” and the analytical eco-scale score tool confirmed that the developed protocol is greener and more favorable to the environment and user than most of the reported literature.

Влияние облучения ионами аргона на фильтрационные свойства многостенных углеродных нанотрубок

The wettability and filtration efficiency of multi-walled carbon nanotubes (MWCNT) under irradiation with Ar+ ions with an energy of 100 keV have been investigated. Energy dispersive X-ray spectroscopy, Raman spectroscopy, and scanning electron microscopy were used to study the residual manganese content in the filter, as well as to study the structure of irradiated MWCNTs. High fluence irradiated MWCNT (HR-MWCNT) filters showed an improvement in Mn removal of up to 99.6% at a Mn concentration of 10 ppm. HR-MWCNT based filters are extremely hydrophilic, with a 66° wetting angle and high absorption capacity. The efficiency of manganese removal from an aqueous medium has been studied as a function of pH, initial concentration, and mass of MWCNT.

Comparing the strengthening efficiency of multiwalled carbon nanotubes and graphene nanoplatelets in aluminum matrix

The research work comprehensively evaluates and compares the strengthening efficiency of multiwalled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs), two of the most promising nano-size reinforcements, which could be employed for fabricating high strength-low weight nanocomposites. High energy ball milled Al powder and different loadings of CNT and GNP (0.5 and 1.0 wt%) were mixed and subsequently consolidated via spark plasma sintering to synthesize Al-CNT and Al-GNP nanocomposites. A clean Al-CNT/GNP interface devoid of traces of any micro-pores and reaction products was achieved. Al-1.0 wt% CNT/GNP showed lower crystallite size and relative density as compared to Al-0.5 wt% CNT/GNP counterpart. Al-1.0 wt% GNP exhibited the lowest relative density (96%) owing to very high volume and surface area of GNP which resulted in rapid agglomeration. Al-CNT nanocomposites exhibited better compression properties as compared to Al-GNP nanocomposites. During compression, for 0.5 wt% reinforcement, the reinforcing efficiency of CNT was 12.4, whereas, that of GNP was 5.3. Tensile test revealed that as compared to milled Al powder compact, Al-0.5 wt% CNT and Al-0.5 wt% GNP exhibited 70% and 85% higher yield strength, respectively. The contributions from different strengthening mechanisms were calculated to predict the yield strength of the sintered nanocomposites. It was found that, for 0.5 wt% reinforced CNT and GNP, the experimentally obtained yield strength of respective nanocomposites were about 91% and 97% closer to the predicted values confirming the effective translation of different strengthening mechanisms towards the strength of the nanocomposites. Further increase in the CNT/GNP content to 1.0 wt% led to deterioration in the compression and tensile properties due to extensive aggregation of respective reinforcements in the Al matrix and the extent of deterioration was substantial for Al-1.0GNP.

Efficiency of Multi Walled Carbon Nanotubes for Removing Direct Blue 71 from Aqueous Solutions

Dye wastewater produced from industrial activity is usually toxic, resistant to biodegradation and persistent in the environment. The aim of this study was to evaluate the efficiency of multiwalled carbon nanotubes (MWCNTs) for decolorization of Direct Blue 71 (DB71). In this experimental study, the effect of various variables including contact time, solution pH, adsorbent dose, and initial dye concentration was evaluated in a batch reactor. The adsorption and kinetic models were evaluated to explain the adsorbed dye and dynamic reaction. The results of this study showed that the efficiency of dye removal increased, as the contact time and adsorbent dose increased, but as pH and initial dye concentration increased, removal efficiency decreased. The maximum efficiency of Direct Blue 71 removal was observed at acidic solution (pH=3), contact time of 90 minutes, adsorbent dose of 0.6 g/l and initial dye concentration of 25 mg/l. The adsorption of direct blue 71 best fitted the Langmuir isotherm (R2=0.87) and pseudo first order kinetic equation (R2=0.99). According to the results obtained, multiwalled nanotubes was offered as an effective adsorbent for removing direct blue 71. © Authors.

Efficiency enhancement of multi-walled carbon nanotubes by ozone for benzene removal from aqueous solution

Aims: Modification of multi-walled carbon nanotubes (MWCNTs) via ozone was carried out to enhance removal benzene from aqueous solutions. Materials and Methods: Multi-walled carbon nanotubes purchased from the Iranian Research Institute of the Petroleum Industry was oxidized by ozone generator at %80 intensity for 5 min and in 30% NaOCl. Results: The Fourier transform infrared analysis showed that the peaks corresponded to the hydroxyl and carboxylic acid groups in modified MWCNTs (MMWCNTs) are more intense than that in non-MMWCNTs. The images of scanning electron microscopy indicated that the MMWCNTs have a lower degree of entanglement with increased porosity compared to the nonmodified one. X-ray diffraction test showed that structural crystallization was increased following the modification. After modification, the efficiency of MWCNTs was increased by 20%. The optimum condition for initial benzene concentration, MWCNT dose, contact time, and pH was: 100 mg/L, 2000 mg/L, 20 min, and 5 respectively. Conclusion: Our research suggested that ozone modification can be a simple method in improvement of the MWCNTs efficiency for removal of benzene from aqueous solution.

Efficiency of Multi-Walled Carbon Nanotubes in Adsorbing Humic Acid from Aqueous Solutions

Efficiency of Multi-Walled Carbon Nanotubes in Adsorbing Humic Acid from Aqueous Solutions

Evaluation of effective mechanical properties of nanocomposites reinforced with multiwalled carbon nanotube

Effective mechanical properties of nanocomposites reinforced with multiwalled carbon nanotubes (MWCNTs) have been determined using Finite Element Analysis (FEA). The effects of several parameters on nanocomposite effective mechanical properties are investigated. First, FEA models are created consisting of MWCNTs with different spring constants to investigate the effects of the interlayer van der Waals forces. Next, the reinforcing efficiency of MWCNTs in different matrices is investigated using models consisting of matrices with different moduli of elasticity. In addition, the effects of MWCNT volume fraction are investigated. Finally, models were created to determine effective mechanical properties of nanocomposites reinforced with Single-Walled Carbon Nanotubes (SWCNTs). Comparison of the results suggests that SWCNTs are more efficient in strengthening the matrix than MWCNTs. Also, Young’s modulus prediction for multiwalled carbon nanotube in a propylene matrix is compared to experimental data investigated by Andrews et al. (2002), and good agreement is observed.

Mechanical properties of Fe-based composites reinforced with multi-walled carbon nanotubes

Reinforcing efficiency of multi-walled carbon nanotubes (MWCNTs) has been investigated for Fe-based composites by powder metallurgy routes. For the mechanically milled Fe powder containing dispersed MWCNTs, first, the composite are produced by hot-pressing at 570°C for 2h under 140MPa, in which MWCNTs provide a high reinforcement factor of 0.6 and a yield stress of 2.2GPa at the 4vol% MWCNTs. On the other hand, for the composites produced by compaction and then sintering at 850°C, the dispersed MWCNTs decompose to be a Fe–C interstitial alloyed phase, in which the composite shows a relatively low yield stress of 450MPa at the 8.3vol% Fe–C phase. For the composite sintered at high temperature of 1150°C, the reinforcement factor is found to be 0.2 and a yield stress of 280MPa at the 9.2vol% Fe3C. These results demonstrate that MWCNTs with a high aspect ratio and a strong bonding character with the matrix have a great role in reinforcing the Fe-based composites.

Adsorption kinetics and thermodynamics of hydrophobic natural organic matter (NOM) removal from aqueous solution by multi-wall carbon nanotubes

The objective of this research was to study the efficiency of Multi-Walled Carbon Nanotubes (MWCNTs) for the adsorption of hydrophobic natural organic matter (NOM) from aqueous solution under different operational conditions of contact time, pH, initial concentration of NOM and temperature. MWCNTs were synthesized via chemical vapor deposition (CVD) with average diameter of 10–50 nm. The results illustrated that both as-prepared and functionalized MWCNTs showed high adsorption capacity for the NOM studied. Functionalization of MWCNT affected the surface area and introduced oxygen-containing functional groups to the surface of MWCNT which depressed the adsorption of NOM onto MWCNTs-COOH. The obtained data were studied using Freundlich, Langmuir and BET isotherms; NOM adsorption data had the best conformity to the Freundlich isotherm. Kinetic studies were performed and the adsorption kinetics successfully followed the pseudo-second-order kinetic model. Thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were determined and evaluation of them showed that the adsorption process for NOM is general spontaneous, endothermic and thermodynamically favorable.

Heating efficiency of multi-walled carbon nanotubes in the first and second biological windows

Quantum dot based-thermometry, in combination with double beam confocal microscopy and infrared thermal imaging, has been used to investigate the heating efficiency of multi-walled carbon nanotubes (MWCNTs) under optical excitation within the first (808 nm) and second (1090 nm) biological windows as well as in the spectral region separating them (980 nm). It has been found that for the three excitation wavelengths the heating efficiency of MWCNTs (10 nm in diameter and 1.5 μm in length) is close to 50%. Despite this "flat" heating efficiency, we have found that the excitation wavelength is, indeed, critical during in vivo experiments due to the spectral dependence of both tissue absorption and scattering coefficients. It has been concluded that efficiency and selectivity of in vivo photothermal treatments based on MWCNTs are simultaneously optimized when laser irradiation lies within the first or second biological window.

The effect of milling conditions on microstructures and mechanical properties of Al/MWCNT composites

Strengthening efficiency of multi-walled carbon nanotubes (MWCNTs), depending on their morphology and interface structure, is investigated for aluminum-based composites. The composites were fabricated by hot-rolling the powders which were ball-milled under various conditions. Milling variables affect the dispersion, dimension and interface structure of MWCNTs. With an insufficient milling intensity, MWCNTs are mostly located on the surface of powder, exposed to severe impact, and readily damaged. As the milling intensity increases, MWCNTs are embedded inside the powder and then dispersed through plastic deformation of the powder. Furthermore, aluminum infiltrates the core of MWCNTs during milling, increasing the diameter of MWCNTs. The outer surface of the Al-infiltrated MWCNTs sticks to the matrix, providing a strong interface by mechanical interlocking. The Al-infiltrated MWCNTs exhibit superior strengthening efficiency. On the other hand, the composite with unfilled MWCNTs, fabricated with a higher milling intensity, exhibits better ductility and pull-outs of the tubes in tensile fracture.

Kinetics and Equilibrium Studies on Adsorption of Acid Red 18 (Azo‐Dye) Using Multiwall Carbon Nanotubes (MWCNTs) from Aqueous Solution

Azo dyes are one of the synthetic dyes that are used in many textile industries. Adsorption is one of the most effective techniques for removal of dye‐contaminated wastewater. In this work, efficiency of multiwalled carbon nanotubes (MWCNTs) as an adsorbent for removal of Acid Red 18 (azo‐dye) from aqueous solution was determined. The parameters affecting the adsorption process such as contact time, pH, adsorbent dosage, and initial dye concentration were studied. Experimental results have shown by increasing the adsorbent dosage, the rate of dye removal was increased, but the amount of adsorbed dyes per mass unit of MWCNTs was declined. pH as one of the most important influencing factors on the adsorption process was evaluated. The best pH for adsorption process was acidic pH of about 3. To describe the equilibrium of adsorption, the Langmuir, Freundlich and Temkin isotherms were used. The Langmuir isotherm (R2=0.985) was the best fitted for experimental data with maximum adsorption capacity of 166.67 mg/g. A higher correlation value of the kinetic′s model was observed close to pseudo second order (R2=0.999) compared to other kinetic models.

Grain size effect on the strengthening behavior of aluminum-based composites containing multi-walled carbon nanotubes

Strengthening efficiency of multi-walled carbon nanotubes (MWCNTs) is investigated for aluminum-based composites with grain sizes ranging from ∼250 to ∼65 nm. The strength of composites is significantly enhanced proportional to an increase of the MWCNT volume. However, the increment differs depending on deformation mode of the matrix. The strengthening efficiency of MWCNTs in ultrafine-grained composites is comparable with that predicted by the discontinuous fiber model, whereas the efficiency becomes half of the theoretical prediction as grain size is reduced below ∼70 nm. For nano-grained aluminum, activities of forest dislocations diminish and dislocations emitted from grain boundaries are dynamically annihilated during the recovery process, providing a weak plastic strain field around MWCNTs. The observation may provide a basic understanding of the strengthening behavior of nano-grained metal matrix composites.

Effective Modulus of Single- and Multi-Walled Carbon Nanotubes in Melt-Compounded Polycarbonate Nanocomposites

This study compares the reinforcing efficiency of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) in polycarbonate (PC) films processed using melt-compounding followed by hot-pressing. The effect of carbon nanotube (CNT) type on composite properties is studied by means of dynamic mechanical analysis (DMA). Composite theory is used to analyse the results. It is found that, despite the good dispersion and interfacial interactions reported in the literature for PC/CNT nanocomposites, SWNTs and MWNTs efficiently reinforce PC only at nanofiller contents below 0.3 wt.% and 0.5 wt.%, respectively. Nevertheless, effective moduli of CNTs (in particular SWNT) close to the theoretical values were achieved for low nanofiller content.

Protein Profiles of Human Serum by SELDI-TOF-MS with Multiwalled Carbon Nanotubes as Absorbent

The present paper describes a biomarker capturing strategy based on the enrichment efficiency of multiwalled carbon nanotubes (MWCNTs) for peptides and proteins from human serum. The method is shown to enrich proteins/peptides, and the captured molecules were profiled using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). Mass spectra of the MWCNTs-treated human serum samples showed a significant enrichment of proteins by MWCNTs. Preliminary results indicated a good level of reproducibility in serum profiles with coefficients of variation (CVs) on signal intensity ranging from 8.9% to 25.2%. The developed method holds promise for improving the discovery of low-abundance serum biomarkers.

Critical evaluation and comparison of enrichment efficiency of multi-walled carbon nanotubes, C18 silica and activated carbon towards some pesticides from environmental waters

In this work, optimization of multi-residue solid phase extraction (SPE) procedures coupled with high-performance liquid chromatography for the determination of Propoxur, Atrazine and Methidathion from environmental waters is reported. Three different sorbents were used in this work: multi-walled carbon nanotubes (MWCNTs), C18 silica and activated carbon (AC). The three optimized SPE procedures were compared in terms of analytical performance, application to environmental waters, cartridge re-use, adsorption capacity and cost of adsorbent. Although the adsorption capacity of MWCNT was larger than AC and C18, however, the analytical performance of AC could be made close to the other sorbents by appropriate optimization of the SPE procedures. A sample of AC was then oxidized with various oxidizing agents to show that ACs of various surface properties has different enrichment efficiencies. Thus researchers are advised to try AC of various surface properties in SPE of pollutants prior to using expensive sorbents (such as MWCNT and C18 silica).

Effect of oxidation and dimensions of multi-walled carbon nanotubes on solid phase extraction and enrichment of some pesticides from environmental waters prior to their simultaneous determination by high performance liquid chromatography

In this novel study, some factors that affect the enrichment efficiency of multi-walled carbon nanotubes (MWCNTs) towards some pesticides in environmental water samples were studied. The effect of oxidation of MWCNTs with various oxidizing agents and the effect of length and external diameter of MWCNTs were investigated. Model pesticides were selected from various common categories of pesticides, viz. Atrazine, Propoxur, Methidathion. Variables optimized included external diameter and length of the MWCNT, oxidation of the MWCNT, mass of the MWCNT, volume and pH of water sample, composition and volume of eluting solvent and washing solvent. It was found that short-nitric acid oxidized-MWCNT exhibited higher enrichment efficiency, especially for Methidathion, than non-oxidized long MWCNT. The optimized SPE procedure is capable of determining Propoxur (detection limit: 220 ng L −1, linear range: 10–50 ng mL −1, <3.0% RSD), Atrazine (detection limit: 57.5 ng L −1, linear range: 10–100 ng mL −1, <2.8% RSD) and Methidathion (detection limit: 37.5 ng L −1, linear range: 10–50 ng mL −1, <2.5% RSD). Application of the optimized SPE procedure to determine the three target pesticides in real environmental waters (tap water, reservoir water and stream water) gave spike recoveries in the range of 81.0–108%.