Graphitic Multi-walled Carbon Nanotubes Research Articles

Redox behaviour of boron subphthalocyanine carbon nanotube composites

Organic redox-active carbon composites can be used as sustainable electrode materials in electrochemical energy storage systems. Among numerous redox active species, peripherally dodecafluorinated boron subphthalocyanines (F12BsubPcs) have shown electrochemical redox activities in the solution phase. Nonetheless, the electrochemical properties of solid F12BsubPcs when compositing with nano carbon warrants further investigation for potential applications in energy storage. In this work, nanometer scale axially brominated F12BsubPcs (Br-F12BsubPcs) were coated onto bare graphitized multiwalled carbon nanotubes (GCNT) and COOH-functionalized GCNT (COOH-GCNT) by a facile dip coating method to produce two composites and to compare the effects of the surface functional group interactions with Br-F12BsubPcs. While the surface chemical and morphological characterizations confirmed the presence of Br-F12BsubPc coating on both bare and COOH-GCNTs, the coverage on the latter was higher. Cyclic voltammetric studies in acidic electrolyte revealed a highly reversible redox couple on both composites with Br-F12BsubPc coated COOH-GCNT demonstrating up to c.a. 70% higher redox peak currents than with Br-F12BsubPc coated GCNT. Further analyses of the coated COOH-GCNT suggested a 2-electron transfer process. The charge transfer has fast-kinetics and a strong dependence on the proton concentration. The composites produced in this work demonstrate potential for future application in energy storage and can provide a strategy for developing BsubPc-based carbon composites.

Correlation between the as-grown carbon nano tubes and prolonged activity toward hydrogen production over Co–Mo/MgO

Novel proposal for the developed highly graphitized multi-walled carbon nanotubes (MWCNTs) over Co–Mo/MgO which served as a secondary support toward hydrogen production from low-density polyethylene waste (PE) was presented using two-stage system. Doping of Co3O4 with MoO3 into MgO exposed extra dispersion function through MoO3 and Co, Mo and MgO mixed oxides as well as further distribution of the active cobalt nano particles over the well graphitized thinner MWCNTs. Both of fresh and used Co/MgO and CoMo/MgO catalysts were characterized by XRD, TPR, Raman, TEM and TGA. Furthermore, the concentrations of released hydrogen through the reaction period were detected via online gas chromatography within 150 min. It was found that Mo improved the overall catalyst reducibility to be easier and distributed the active species in different forms of mixed species. Moreover, the catalytic performance toward hydrogen production from low density polyethylene waste was jumped from 51% to 81% after Mo addition within the reaction end. Also, full catalytically action was noticed for CoMo/MgO toward whole the charged hydrocarbon gases from the first decomposition stage without any deactivation. Additionally, the developed multi-walled carbon nanotubes were highly graphitized and more homogenous rather than over Co/MgO which deposited less graphitized carbon nano fibers.

Pulmonary inflammatory and fibrogenic response induced by graphitized multi-walled carbon nanotube involved in cGAS-STING signaling pathway

Graphitized multi-walled carbon nanotubes (GMWCNTs) are a new type of nanomaterial. Recently, their production and application in biological medicine have grown rapidly. However, GMWCNTs may cause adverse health effects, including the common occupational disease of pulmonary fibrosis. Pulmonary fibrosis is a serious progressive disease that often leads to lung failure, high mortality, and disability, and there is no effective therapy currently available. Therefore, identifying new biomarkers of the disease is important to better understand the disease mechanisms and explore new therapeutic strategies. In this study, 40 μg of GMWCNTs was used to treat mice in vivo by pharyngeal aspiration, and different genes were screened by transcriptome sequencing. Activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon gene (STING) signal pathway had an important effect on the development of pulmonary inflammation and fibrosis. GMWCNTs were then administered to the mice with a STING inhibitor (C-176). Inhibition of STING effectively decreased pulmonary inflammation and fibrosis in mice induced by GMWCNTs. Collectively, activation of the cGAS-STING signaling pathway is involved in GMWCNT-induced pulmonary inflammation and fibrosis in mice.

A key role of inner-cation-π interaction in adsorption of Pb(II) on carbon nanotubes: Experimental and DFT studies

Herein the adsorption and desorption of Pb2+ on oxidized (O-CNTs) and graphitized multi-walled carbon nanotubes (G-CNTs) were studied, and detailed adsorption mechanisms were discussed by experimental characterization and density functional theory (DFT) calculation. The adsorption of Pb2+ on CNTs was co-guided by complexation, ion exchange, electrostatic and cation-π interactions. According to the abnormally low release ratio of Pb2+ on both O-CNTs and G-CNTs (<9.03%), the O-containing groups on CNTs surface are not the only key factor affecting the adsorption behavior. The pore filling and complexation are the main mechanisms leading to irreversible adsorption, especially the important role of the inner-cation-π interaction in Pb2+ adsorption into the inner channel of CNTs at the high initial Pb2+ concentration, and DFT calculations further confirmed this result. The adsorption energy of the inner-cation-π interaction between Pb2+ and CNTs can be as high as − 77.851 kJ/mol, which is much higher than other interactions (≤−41.488 kJ/mol). Moreover, the stability of various adsorption mechanisms by HOMO-LUMO energy gap (Egap), electronic chemical potential (µ) and global hardness (η) were quantitatively measured and further revealed the inner-cation-π interaction is more stable. This study provides a deeper understanding of the removal of heavy metals by porous carbon-based nanomaterials.

Electrochemical Performance of Graphitic Multi-walled Carbon Nanotubes with Different Aspect Ratios as Cathode Materials for Aluminum-ion Batteries.

Graphitic multi‐walled carbon nanotubes (MWCNTs) can function as high‐performance cathode materials for rechargeable Al‐ion batteries with well‐defined discharging plateaus and reasonable charge/discharge C‐rates. However, the main intercalation/deintercalation or adsorption/desorption path of AlCl4 − anions into or onto G‐MWCNTs has not been elucidated. Herein, we used battery cells comprised of G‐MWCNTs with different aspect ratios, Al metal, and AlCl3/1‐ethyl‐3‐methylimidazolium chloride ionic liquid as the cathode, anode, and electrolyte, respectively. The electrochemical performance of the Al||G‐MWCNT cell increased as the aspect ratio of the G‐MWCNT cathode increased (i. e., longer and thinner). The degree of defects of the G‐MWCNTs was similar (0.15–0.22); hence, the results confirm that the main and alternate paths for the AlCl4 − intercalation/de‐intercalation or adsorption/desorption into/from or onto/from the G‐MWCNT are the basal and edge planes, respectively. The step‐like structures of defects on the basal plane provide the main reaction site for AlCl4 − anions.

Adsorption, desorption and coadsorption behaviors of sulfamerazine, Pb(II) and benzoic acid on carbon nanotubes and nano-silica

In this study, nano-silica (Nano-SiO2), oxidized (O-CNTs) and graphitized multi-walled carbon nanotubes (G-CNTs) were applied as model adsorbents to study the adsorption, desorption and coadsorption behaviors of sulfamerazine (SMR), Pb(II) and benzoic acid (BA). The results showed that charge assisted H-bond (CAHB) formation played an important role in adsorption of SMR and BA on O-riched nanomaterials. The adsorption capacities of Pb(II) on CNTs were 21.46– 26.77 times higher than that on Nano-SiO2, which was mainly attributed to surface complexation and cation-π interaction. The fraction of Pb2+ adsorbed in the inside channel of CNTs should not be ignored. In coexisting systems, the absolute sorption inhibition of the SMR (ΔQeSMR) was compared with the amount of competitor adsorbed. Competitive sorption was observed as indicated by adding Pb(II) decreased adsorption of SMR on Nano-SiO2 (ΔQeSMR > 0), but hardly affected SMR adsorption on CNTs (ΔQeSMR ≈ 0) which was attributed to cation-π interaction. In addition, CAHB formed between SMR and Nano-SiO2 (ΔpKa ≈ 4.34) was weaker than that formed between SMR and O-CNTs (ΔpKa ≈ 3.15), which also consequently resulted in stronger competition of Pb(II) to SMR on Nano-SiO2 than that on O-CNTs. Moreover, coexisting BA increased adsorption of SMR on Nano-SiO2 and G-CNTs (ΔQeSMR < 0), but did not result in an apparent competition on SMR adsorption by O-CNTs (ΔQeSMR ≈ 0). These results emphasize that the environmental behaviors of a certain pollutant should be assessed carefully by considering the presence of other pollutants.

Unzipping carbon nanotubes to nanoribbons for revealing the mechanism of nonradical oxidation by carbocatalysis

Graphitic multi-walled carbon nanotubes (MWCNTs) are controllably unzipped into edge-rich graphene nanoribbons to reveal the roles of edges and defects in persulfate activation for bisphenol A (BPA) oxidation. Enriched carbon edges remarkably enhance the catalytic performance and can serve as hosting sites for heteroatom (N, S) doping to promote carbocatalysis. A sample (NS-2) presented a complete BPA removal in 20 min at a rate constant of 0.182 min-1. The rate constants were relating to the defect speciation in a negative correlation to an indicator (ID/ID’) from Raman spectra. Excessive edges induce defects and structure transformation of sp2 to sp3, resulting in deterioration of the organic oxidation. Furthermore, unzipped MWCNTs were clarified to follow a nonradical electron transfer pathway by radical screening tests, in situ Raman and electrochemical characterizations. The unveiled mechanism emphasizes the importance of an essential graphitic degree and conductivity in the edge-enriched carbocatalysts for better catalytic performance.

Graphitic multi-walled carbon nanotube cathodes for rechargeable Al-ion batteries with well-defined discharge plateaus

One-dimensional multi-walled carbon nanotubes (MWCNTs) are promising electrode materials for rechargeable batteries. This paper reports that graphitic MWCNT (G-MWCNT) can serve as a cathode material for a rechargeable Al-ion battery and exhibits well-defined discharging plateaus at around 2 V. AlCl4−intercalates and de-intercalates into/from the graphitic MWCNT rather than simply adsorbing on the surfaces. Hence, the Al||G-MWCNT cell exhibits good electrochemical performance with a specific capacity of 64 mA h g−1 at a current density of 200 mA g−1. The discharge capacity is almost unattenuated and maintained at about 58 mA h g−1 (Coulombic efficiency: 99.5%) after 1000 charge/discharge cycles, which indicates that the Al||G-MWCNT cell has excellent cycling stability. In addition, the low self-discharging rate (~0.4% over 72 h of rest) suggests that the intercalated AlCl4− is stable in the spaces between the graphene layers of G-MWCNT. This work reveals that Al||G-MWCNT cells exhibit diffusion-controlled faradaic process rather than capacitor behavior, which may boost the development of aluminum batteries.

Characteristics of Aniline and Nitrobenzene Adsorption on Single-Walled, Multi-Walled and Graphitized Multi-Walled Carbon Nanotubes

Characteristics of Aniline and Nitrobenzene Adsorption on Single-Walled, Multi-Walled and Graphitized Multi-Walled Carbon Nanotubes

Simultaneous determination of 131 pesticides in tea by on-line GPC-GC–MS/MS using graphitized multi-walled carbon nanotubes as dispersive solid phase extraction sorbent

A rapid and sensitive method was developed to determine 131 pesticides in tea by on-line gel permeation chromatography–gas chromatography tandem mass spectrometer (on-line GPC-GC–MS/MS) using graphitized multi-walled carbon nanotubes (MWCNTs) as dispersive solid phase extraction (DSPE) sorbent in sample pretreatment. Sample clean-up performance of various functionalized MWCNTs and their influences to recoveries were investigated. In the method validation, good linearity correlation coefficients (R2) were obtained, which were higher than 0.99 for all pesticides. The percent recoveries were 78.2%–113.9% at the spiked concentration levels of 20, 50 and 200 µg/kg with relative standard deviations (RSDs, n = 6) lower than 15.8%. Limits of detections (LODs) were in the range of 0.5–5.0 µg/kg. This method is simple and fast with relatively high sensitivity and can achieve the requirements of pesticides analysis.

Surface Carbon as a Reactive Intermediate in Dry Reforming of Methane to Syngas on a 5% Ni/MnO Catalyst

A 5% Ni/MnO catalyst has been tested for the dry reforming of methane at different temperatures and reactant partial pressures. Changing the reactant ratio with time on stream results in a decrease in the deactivation rate of the catalyst. Graphitic carbon growth and metal particle sintering have been observed by applying in situ transmission XRD using synchrotron radiation under actual reaction conditions. Both methane and carbon monoxide separately result in graphitic surface carbon, which can then be oxidized by carbon dioxide. The morphology of the surface carbon has been analyzed by TEM, and the reactions of both methane and carbon monoxide result in the same graphitic multiwalled carbon nanotubes. The present combination of catalytic experiments and in situ techniques suggests that surface carbon acts as an intermediate in the formation of CO and that catalyst deactivation happens via metallic particle sintering. These results enable a more rational choice of reaction conditions to ensure high catal...

Determination of 39 veterinary drug residues in Procambarusclarkii by ultra-high performance liquid chromatography-quadrupole-time of flight mass spectrometry

An ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) method was developed for determination of 39 veterinary drugs in Procambarusclarkii. Samples were extracted with acidified acetonitrile and purified with enhanced matrix removal-lipid (EMR-Lipid) adsorbent and graphitized multi-walled carbon nanotubes (GMWNTs). Extracts were analyzed by UHPLC-Q-TOF-MS. Target compounds were screened according to accurate mass, isotopic ratio, and retention time, and confirmed by library search. Target analytes were quantified using the chromatographic peak area of each compound. For each of the drugs of interest, calibration curves were linear in their respective ranges with correlation coefficients greater than 0.99. The limits of quantification (LOQs) were 3-15 μg/kg. The recoveries for target compounds spiked in Procambarusclarkii ranged from 62.4% to 105.8%, with relative standard deviations (RSDs) ranging from 2.5% to 13.5%. This method is simple, rapid, accurate, and suitable for simultaneous determination of 39 veterinary drugs, including sulfonamides, quinolones, and triphenylmethane, extracted from Procambarusclarkii.

Alkaline electrochemical advanced oxidation process for chromium oxidation at graphitized multi-walled carbon nanotubes

Alkaline electrochemical advanced oxidation processes for chromium oxidation and Cr-contaminated waste disposal were reported in this study. The highly graphitized multi-walled carbon nanotubes g-MWCNTs modified electrode was prepared for the in-situ electrochemical generation of HO2−. RRDE test results illustrated that g-MWCNTs exhibited much higher two-electron oxygen reduction activity than other nanocarbon materials with peak current density of 1.24 mA cm−2, %HO2− of 77.0% and onset potential of −0.15 V (vs. Hg/HgO). It was originated from the highly graphitized structure and good electrical conductivity as illustrated from the Raman, XRD and EIS characterizations, respectively. Large amount of reactive oxygen species (HO2− and ·OH) were in-situ electro-generated from the two-electron oxygen reduction and chromium-induced alkaline electro-Fenton-like reaction. The oxidation of Cr(III) was efficiently achieved within 90 min and the conversion ratio maintained more than 95% of the original value after stability test, offering an efficient and green approach for the utilization of Cr-containing wastes.

Interactions between Volatiles and Char during Pyrolysis of Biomass: Reactive Species Determining and Reaction over Functionalized Carbon Nanotubes

This paper investigated the interactions between volatiles and char during pyrolysis of biomass with an emphasis on those between the reactive compounds in volatiles and the oxygen-containing functional groups in char. On the basis of a comparative study on the products from biomass pyrolysis with and without heavy oil (HO) recycling, which represented a maximization and minimization of the volatile–char interactions, respectively, levoglucosan (LG) was selected as the typical reactive compound in the volatiles. The interactions between LG and functionalized graphitized multiwalled carbon nanotubes with hydroxyl and carboxyl groups (HGMCN and CGMCN, respectively) as char models were surveyed at 300, 350, 400, and 450 °C. The results show that temperature plays an important role in the interactions between LG and GMCNs. HGMCN interacted with LG only at 400 °C, while the LG–CGMCN interactions started at 400 °C and intensified at 450 °C with a significant increase in gas yield. The GC–MS analyses indicated t...

Determination of Tetracycline Antibiotic Residues in Honey and Milk by Miniaturized Solid Phase Extraction Using Chitosan-Modified Graphitized Multiwalled Carbon Nanotubes.

A rapid, simple, and strongly selective miniaturized solid phase extraction (SPE) technique, requiring only small amounts of sorbent (24 mg) and elution solvent (600 μL), coupled with ultrahigh-performance liquid chromatography and quadrupole time-of-flight mass spectrometry was developed for detecting tetracycline antibiotics. These analytes were extracted from honey and milk using chitosan-modified graphitized multiwalled carbon nanotubes (G-MWNTs) as the solid sorbent and acetonitrile/acetic acid (8:2, v/v) as the eluent in miniaturized SPE. Under the optimum experimental conditions, a satisfactory linearity (r(2) > 0.992) was obtained, and the limits of detection were in the range of 0.61-10.34 μg/kg for the analytes. The mean recoveries of the five tetracycline antibiotic residues in the real samples were between 81.5 and 101.4%. The results demonstrated that chitosan-modified G-MWNTs comprise a promising material for the enrichment of tetracycline antibiotics from complex food matrices.

Surfactant-coated graphitized multiwalled carbon nanotubes as the pseudostationary phase in electrokinetic chromatography for the analysis of phytochemical compounds in biological fluids.

This report describes the use of surfactant-coated graphitized multiwalled carbon nanotubes (SC-GMWNTs) as a novel pseudostationary phase in CE with diode array detection for the determination of phenolic acids and tanshinones in herbal and urine samples. Several parameters influencing the separation were studied, such as the concentrations of SDS, GMWNTs, and isopropanol; choice of carbon nanotubes; sodium borate content; and buffer pH. The results revealed that the presence of SC-GMWNTs in buffer enhanced the separation efficiency for the target analytes relative to conventional micelles due to the strong interaction between the surface of the GMWNTs and the target compounds. Under the optimum conditions, the method showed good linearity, with correlation coefficients higher than 0.9950. LODs were in the range of 0.71-3.10 μg/mL. Furthermore, satisfactory separations were achieved with good recovery values in the range of 89.97 and 103.30% when 10 mM borate, 30 mM SDS, 10% isopropanol, and 6 μg/mL SC-GMWNTs were introduced into the buffer solution.

Novel cetyltrimethylammonium bromide-functionalized bucky gel nanocomposite for enhancing the electrochemistry of haemoglobin

Graphitized multiwalled carbon nanotubes (GMWNTs) were ground with 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6) containing dissolved cetyltrimethylammonium bromide (CTAB), and a CTAB-[Bmim]PF6-GMWNT nanocomposite was obtained. The nanocomposite had a regular arrangement, and no agglomeration was observed, in contrast with the case of a bucky gel ([Bmim]PF6-GMWNTs). CTAB-[Bmim]PF6-GMWNT showed significantly lower electron impedance toward an [Fe(CN)6]3−/4− anion probe, compared with [Bmim]PF6-GMWNT, and it was shown (using Fourier transform infrared spectroscopy and UV–visible spectroscopy) that CTAB-[Bmim]PF6-GMWNT acted as a biocompatible matrix for the self-assembly of haemoglobin molecules. Furthermore, the faradaic current (31.77 μA) resulting from the direct electron transfer in self-assembled haemoglobin on a CTAB-[Bmim]PF6-GMWNT-modified glass carbon electrode (GCE) was ~35.5 times larger than that measured for haemoglobin on a [Bmim]PF6-GMWNT-modified GCE (0.8941 μA). The haemoglobin anchored on the CTAB-[Bmim]PF6-GMWNTs/GCE showed a more sensitive response to hydrogen peroxide (H2O2) compared with other electrodes reported in the literature. The CTAB-functionalized bucky gel nanocomposite was biocompatible and showed beneficial characteristics that could be useful for applications in biological engineering.

Cu(II)和Ni(IhI)对四环素在官能团化碳纳米管上吸附的影响

The environmental applications and implications of functionalized carbon nanotubes (CNTs) have received much attention. In this study, the adsorption interactions of graphitized multi-walled carbon nanotubes (G-MWCNTs) and functional- ized MWCNTs, including hydroxylated MWCNTs (OH-MWCNTs), carboxylated MWCNTs (COOH-MWCNTs), and aminated MWCNTs (NH2-MWCNTs), for tetracycline in the aqueous solution were systemically investigated, and the effects of Cu(II) and Ni(II) (two metal ions commonly present in aquatic environments) on MWCNTs-tetracycline interactions were examined. Results showed that the adsorption affinities followed an order of G-MWCNTs>OH-MWCNTs>COOH-MWCNTs>NH2-MWCNTs, indicating that the adsorptive interactions between MWCNTs and tetracycline can be largely affected by the types and abundance of functionalities on the MWCNTs surfaces. Both Cu(II) and Ni(II) had a negligible effect on the adsorption of tetracycline to G-MWCNTs, but varied effects of the metal ions were observed for the three functionalized MWCNTs. In general, Cu(II) ex- hibited a more pronounced effect for the adsorption of tetracycline than Ni(II), due to the degree of complexing capability.

Pristine and graphitized-MWCNTs as durable cathode-catalyst supports for PEFCs

Long-term deterioration in the performance of PEFCs is attributed largely to reduction in active area of the platinum catalyst at cathode, usually caused by carbon-support corrosion. Multi-walled carbon-nanotubes (MWCNTs) as cathode-catalyst support are found to enhance long-term stability of platinum catalyst (Pt) in relation to non-graphitic carbon. In addition, highly graphitic MWCNTs (G-MWCNTs) are found to be electrochemically more stable than pristine MWCNTs. This is because graphitic-carbon-supported-Pt (Pt/MWCNTs) cathodes exhibit higher resistance to carbon corrosion in-relation to non-graphitic-carbon-supported-Pt (Pt/C) cathodes in PEFCs during accelerated stress-test (AST) as evidenced by chronoamperometry and carbon dioxide studies. The corresponding change in electrochemical surface area (ESA), cell performance, and charge-transfer resistance are monitored through cyclic voltammetry, cell polarization, and impedance measurements, respectively. The extent of crystallinity, namely amorphous or graphitic nature of the three supports, is examined by Raman spectroscopy. X-ray diffraction and transmission electron microscopy studies both prior and after AST suggest lesser deformation in catalyst layer and catalyst particles for Pt/G-MWCNTs and Pt/MWCNTs cathodes in relation to Pt/C cathodes, reflecting that graphitic carbon-support resists carbon corrosion and helps mitigating aggregation of Pt particles. It is also found that with increasing degree of graphitization, the electrochemical stability for MWCNTs increases due to the lesser surface defects.

ESR, XPS, and thin-film RRDE characterization of nano structured carbon materials for catalyst support in PEM fuel cells

With the aim of investigating possible connections between structural properties and electrocatalytic characteristics in the oxygen reduction reaction (ORR) for carbon materials with prospective use as catalyst support in polymer electrolyte membrane fuel cells (PEMFC), various carbon samples were examined by electron spin resonance (ESR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and rotating ring–disc electrode (RRDE) technique. The investigated materials were raw and heat-treated carbon black (CB), activated few-walled carbon nanotubes (FWCNTs), functionalized and graphitized multi-walled carbon nanotubes (GMWCNTs), and graphitized carbon nanofibres (CNF). ESR spectroscopy using MgO internal reference showed that raw CB has the highest defect concentration; graphitized CB, GMWCNTs, and CNF are structurally much more perfect; and FWCNTs are in between. XPS analyses revealed oxygen contents of 0.5–3.9 at%, with hydroxyl-functionalized GMWCNT having the highest content. Thin-film RRDE experiments showed that the activity towards ORR for this latter material is remarkably high, and that about 75% of the oxygen is reduced by a peroxide pathway. For the other samples this pathway accounts for 25–75%. However, no significant ORR activity occurred above 0.2 V vs. dynamic hydrogen electrode. Peroxide formation on carbon is thus an issue on the hydrogen (anode) side of a fuel cell where crossover oxygen may be present.