Modification Of Multi-walled Carbon Nanotubes Research Articles

New definition of sepsis and septic shock: What does it give us?

This research focused on the nanosecond (Nd: YAG-1064 nm) laser pulse effect on the optical and morphological properties of chemically modified multi-walled carbon nanotubes (MWCNT). Two suspensions of MWCNT in tetrahydrofuran (THF) were prepared, one was submitted to laser pulses for 10 min while the other (blank) was only mechanically homogenized during the same time. Following the laser irradiation, the suspension acquired a yellow-amber color, in contrast to the black translucent appearance of the blank. UV-vis spectroscopy confirmed this observation, showing the blank a higher absorption. Additionally, photoluminescence measurements exhibited a broad blue-green emission band both in the blank and irradiated suspension when excited at 369 nm, showing the blank a lower intensity. However, a modification in the excitation wavelength produced a violet to green tuning in the irradiated suspension, which did not occur in the blank. Lastly, the electron microscopy analysis of the treated nanotubes showed the abundant formation of amorphous carbon, nanocages, and nanotube unzipping, exhibiting the intense surface modification produced by the laser pulse. Nanotube surface modification and the coexistence with the new carbon nanostructures were considered as the conductive conditions for optical properties modification.

Investigation of Different Pre-Treated Multi-Walled Carbon Nanotubes by Raman Spectroscopy

Raman spectroscopy is a common method of studying carbon-based materials such as multi-walled carbon nanotubes (MWCNT). However, the analysis of this technique is non-trivial since recorded spectra may be a convolution of both molecular vibrations and phonon resonances. The energies of these physical processes may occur in the same energy regime, and hence several analytical approaches can be necessary for a full analysis. Due to the negligible quantities of non-graphitic carbon in MWCNT, the present fitting procedure focuses on understanding phonon resonances to elucidate how varying modifications of MWCNT ultimately influence their graphitic bulk structure. We have found this approach to provide greater insight into the structure of MWCNT when low quantities of amorphous carbon are present, when compared with methods which try to interpret both phonon scattering and molecular vibrations simultaneously. Different pre-treatments for the modification of the graphitic structure of MWCNT are compared, including aqueous acidic and gas phase methods, and statistically evaluated. Focusing on phonon resonances enables one to analyze the reaction process of nitrosulfuric acid pre-treatment at different temperatures. Thereby, it is possible to control the ratio between defects and graphitic structures in MWCNT samples and prepare samples with reproducible D/G ratios.

Oxygen Electroreduction on Zinc and Dilithium Phthalocyanine Modified Multiwalled Carbon Nanotubes in Alkaline Media

Dilithium and zinc phthalocyanine derived catalysts supported on multiwalled carbon nanotubes (MWCNTs) have been studied as non-precious metal catalysts for oxygen electroreduction. The electrocatalysts were prepared by simple pyrolysis by varying the pyrolysis temperature and metal phthalocyanine-to-MWCNT ratio. The surface morphology of the catalyst materials was characterized by scanning electron microscopy (SEM) and surface composition by X-ray photoelectron spectroscopy (XPS). The rotating disk electrode (RDE) method was used to determine the electrocatalytic activity of these materials in 0.1 M KOH solution. The oxygen reduction reaction (ORR) activities achieved are comparable to well-studied Fe and Co phthalocyanine based catalysts in alkaline media, showing the great potential of non-redox-active metal phthalocyanine-derived catalysts as cathode materials for metal-air batteries and fuel cells. The number of electrons transferred per O2 molecule was determined by the Koutecky-Levich analysis, which indicated that at high negative potentials the ORR process followed a four-electron pathway. The O2 reduction results obtained in this study show clearly the important role of non-redox-active metal ion in the formation of active sites for ORR on pyrolyzed and carbon supported Li and Zn metallomacrocyclic compounds.

Inducing structural defects in multi-walled carbon nanotubes by biological oxidation

In this study, carbon-nanotubes (CNTs) resistant soil bacteria were utilized to induce biotransformation in engineered multiwalled-carbon nanotubes (MWCNTs). It was observed that the CNTs-resistant bacteria upon interaction with engineered MWCNTs lead to their partial degradation. Raman spectra of bio-transformed-MWCNTs revealed increased intensity ratio of ID/IG with subsequent formation of C−O−H, C=O and COOH groups on the outer walls of nanotubes. Our results demonstrate a low-cost modification of MWCNTs by resistant bacteria to induce structural defects that potentially useful for industrial applications.

Multiwalled Carbon Nanotube Modified Electrodes for the Adsorptive Stripping Voltammetric Determination and Quantification of Curcumin in Turmeric

AbstractA sensitive electrochemical method for the determination and quantification of curcumin using adsorptive stripping voltammetry (AdsSV) at a multiwalled carbon nanotube modified basal plane pyrolytic graphite electrode (MWCNT‐BPPG electrode) is presented exploiting the high surface area of the latter. Next the voltammetric behaviour of curcumin on the modified electrode is examined and AdsSV shown to be a sensitive method for quantifying curcumin. The adsorption of curcumin on the electrode surface is evidenced to follow a Langmuir adsorption isotherm. Linear calibration for curcumin in the range of 2–100 μM was obtained with a detection limit of 0.45 μM and a limit of quantification of 1.49 μM. For application to real samples of turmeric, a one‐step sample preparation in ethanol has developed providing a simple and rapid extraction procedure. The MWCNT‐BPPG electrode with AdsSV allowed the determination of curcumin equivalent in turmeric powder sample with recoveries in the range of 92–108 %. This facile and fast method will be useful for monitoring the quality of curcumin containing in commercial turmeric products.

Synthesis of non-destructive amido group functionalized multi-walled carbon nanotubes and their application in antistatic and thermal conductive polyetherimide matrix nanocomposites

Thermal conductive and antistatic polyetherimide (PEI) nanocomposites were fabricated by encapsulating non-destructive amido group functionalized multi-walled carbon nanotubes (MWCNTs) into the PEI matrix. Briefly, nearly half of acyl chloride groups in poly (acryloyl chloride) reacted with sodium azide and formed acyl azide groups, which could conjunct with MWCNTs via non-destruction nitrenes addition reaction. The remaining acyl chloride groups in poly (acryloyl chloride) hydrolyzed into carboxyl groups, therefore COOH-rich MWCNTs (MWCNTs@azide polyacrylic acid) were synthesized without serious damage to the MWCNTs. Then, MWCNTs@azide polyacrylic acid were then reacted with p-Phenylene diamine (PPD) and transformed to amido group functionalized MWCNTs (MWCNTs@PPD). MWCNTs@PPD could participate into the in situ polymerization of PEI matrix, where the conjunction between bisphenol A dianhydride and amido groups on MWCNTs@PPD guaranteed the strong covalent bonding at the PEI/MWCNTs interface, which directly avoided the aggregation of MWCNTs. Owing to the non-destructive modification of MWCNTs and tight matrix/filler interface, the volume electric and thermal conductivity of as-prepared nanocomposites was up to 6.4 × 10−8 S/cm (1.0 wt%, MWCNTs@PPD) and 0.43 W/(m · K) (4.0 wt%, MWCNTs@PPD), respectively. Copyright © 2016 John Wiley & Sons, Ltd.

Honeycomb structured porous films prepared from arborescent graft polystyrenes via the breath figures method

Highly ordered honeycomb films were produced from arborescent graft polystyrene (AGPS) solutions using breath figures (BF). The structure of the BF pattern (whether single layered or multilayered) of pores depended on several factors such as the type of solvent used (CS2 or CHCl3), the length of the side chains, the generation number and the concentration of the polymer. When solutions of AGPS with shorter side chains (Mw ∼ 5000 g/mol) were used for the BF process, arborescent polymers generated a multilayer pore structure. However, when polymers with longer side chains (Mw ∼ 30,000 g/mol) were used, monolayer pore structures were mostly generated. The regularity and surface quality of the honeycomb pattern became worsened as the multilayered structures formed. The polymer concentration (ϕ) also played a critical role in determining the morphology of the BF films. Higher ϕ led to a multilayer pore structure while lower ϕ resulted in a monolayer pore structure. In general, the regularity of top layer pores was found to decrease with increasing generation number. The introduction of multiwall carbon nanotubes (MWCNTs) into AGPS solutions and application of the BF process using the solution blends yielded patterned hybrid films. SEM images showed that some CNTs were loaded into the honeycomb pattern of AGPS, but that most MWCNTs precipitated to form the bottom layer. In this work, the influence of concentration and surface modification of MWCNTs on the BF patterns obtained is discussed.

Facile preparation of carbon nanotubes based carboxymethyl chitosan nanocomposites through combination of mussel inspired chemistry and Michael addition reaction: Characterization and improved Cu2+ removal capability

The adsorption removal of heavy metal ions from aqueous solution using polymer nanocomposites has attracted great interest because of their advantages from both nanomaterials and polymers. In this work, a facile and novel method has been developed for surface modification of multiwalled carbon nanotubes (CNT) with carboxymethyl chitosan via combination of mussel inspired chemistry and Michael addition reaction. To obtain resultant CNT based chitosan nanocomposites (CNT-PDA-CS), pristine CNT were first coated with polydopamine (PDA) thin films through self polymerization of dopamine under alkaline aqueous solution. Then PDA modified CNT were further functionalized with carboxymethyl chitosan (CS) via Michael addition reaction. The successful preparation of CNT-PDA-CS nanocomposites was ascertained by a series of characterization techniques including transmission electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis and X-ray photoelectron spectrometry. The utilization of the resultant CNT-PDA-CS for removal of Cu2+ from aqueous solution was also examined in this work. The results showed that CNT-PDA-CS exhibited obviously enhanced Cu2+ removal capability as compared with the unmodified CNT. Considered the versatility of mussel inspired chemistry, the method described in this work should be a general route for fabricating highly efficient adsorbents, which should be of great interest for environmental applications.

Dispergation and modification of multi-walled carbon nanotubes in aqueous solution

Multi-walled carbon nanotubes (MWCNTs) are widely applied in development of composite materials. However, their properties are directly influenced by the degree of uniformity of dispersion of MWCNTs in the material’s matrix. In this paper, the dispersing of raw MWCNTs (R-MWCNTs) and decorated MWCNTs (D-MWCNTs) was studied in aqueous solution. The D-MWCNTs were obtained by chemical modification method by treatment of initial MWCNTs with the mixture of concentrated nitric and sulfuric acids (3: 1 vol/vol). To achieve a good dispersion of the MWCNTs, a method utilizing ultrasonic processing and surfactant (polyvinylpyrrolidone, PVP) was employed. MWCNTs were characterized by Fourier transform infrared spectroscopy (FT–IR) and X-ray diffraction (XRD). The prepared MWCNTs suspensions were investigated by UV spectroscopy, zeta potential measurements, surface tension and transmission electron microscopy (TEM). The D-MWCNTs have better dispersibility in aqueous solution; this attributed to the functional groups formed on their surface during chemical modification. The PVP surfactant in a certain concentration of 0.6 g/L has the maximum dispersing effect on MWCNTs in aqueous solution, the optimum concentration ratio of PVP and MWCNTs was 3: 1.

MHDA-Functionalized Multiwall Carbon Nanotubes for detecting non-aromatic VOCs.

The chemical modification of multiwalled carbon nanotubes (MWCNTs) with a long chain mercapto acid is reported as a way to improve sensitivity and response time of gas sensors for detecting alcohols, acetone and toxic gases such as DMMP. We have developed sensors employing MWCNTs decorated with gold nanoparticles and modified with a 16-mercaptohexadecanoic acid (MHDA) monolayer. Morphological and compositional analysis by Transmission Electron Microscopy (TEM), Fourier Transform Infra-red Spectroscopy (FTIR) and X-ray photoelectron spectroscopy were performed to characterize the gold nanoparticles and to check the bonding of the thiol monolayer. The detection of aromatic and non-aromatic volatiles and DMMP vapors by MWCNT/Au and MWCNT/Au/MHDA shows that the presence of the self-assembled layer increases sensitivity and selectivity towards non-aromatics. Furthermore, it ameliorates response dynamics, and significantly reduces nitrogen dioxide and moisture cross-sensitivity.

Morphological and structural modifications of multiwalled carbon nanotubes by electron beam irradiation

Effects of electron beam irradiation on a morphology and structure of multiwalled carbon nanotubes sample in a normal imaging regime of a scanning electron microscope (SEM) were investigated. Direct SEM observations give evidence that irradiation by electron beam in SEM eliminates morphological unevenness, in the form of round spots of white contrast, on the surface of carbon nanotubes (CNTs) and makes the tubes thinner. Electron dispersive analysis and Raman spectroscopy are used to explore the origin and nature of these spots. From this analysis we found that e-beam irradiation improves the CNTs graphitization. The synergy of thermal heating and ionization produced by the irradiation are discussed as possible mechanisms of the observed effects.

Enhanced interfacial interaction for effective reinforcement of chitosan nanocomposites at different loading of modified multiwalled carbon nanotubes with vitamin C

Chitosan-based nanocomposites (NCs) at different modified multiwalled carbon nanotubes (MWCNTs) loadings were produced by solvent casting method. The effective dispersion of the MWCNT in polymer matrix is an important factor while making its NCs. The MWCNTs intrinsically tend to bundle and/or aggregate. For this reason, the MWCNT is modified to improve the dispersibility when incorporated into polymer matrix. In this study, the MWCNTs were modified with ascorbic acid or vitamin C (VC). The combined effect of MWCNT-VC and chitosan on the structural, crystallinity, interfacial interactions, and mechanical and thermal properties of the obtained NCs was investigated. Scanning electron micrographs showed that in the NC films, MWCNTs were dispersed homogeneously throughout the chitosan matrix. The tensile strength of chitosan film increased significantly with increasing the MWCNT-VC content.

Effect of the vinyl modification of multi-walled carbon nanotubes on the performances of waste poly(ethylene terephthalate)-based nanocomposites

Production of high-performance nanocomposite materials obtained from unsaturated polyester resin, based on products of the waste poly(ethylene terephthalate) recycling, and modified multi-walled carbon nanotubes is presented. Di-hydroxy functional glycolysates, synthesized by catalytic depolymerization of poly(ethylene terephthalate) with propylene glycol, were used for the unsaturated polyester resin synthesis. The structure of the obtained glycolysis product and unsaturated polyester resin were characterized by using FTIR and NMR spectroscopy, and by acid, iodine, and hydroxyl value. Nanofillers were prepared by direct and two-step amidation of oxidized multi-walled carbon nanotubes. Direct amidation with diallylamine produced multi-walled carbon nanotube-diallylamine reactive nanofiller. Two-step modification with diamines: hexamethylenediamine and p-phenylenediamine gave multi-walled carbon nanotube-hexamethylenediamine and multi-walled carbon nanotube- p-phenylenediamine nanofiller, respectively, whose amidation with methyl ester of linseed oil fatty acids gave multi-walled carbon nanotube-hexamethylenediamine/methyl ester of linseed oil fatty acid and multi-walled carbon nanotube- p-phenylenediamine/methyl ester of linseed oil fatty acid nanofiller, respectively. Influences of vinyl functionalities on mechanical properties of nanocomposite were analyzed from tensile strength ( σb), elongation ( ɛb) and Young’s modulus ( E) determination. An increase of 97.4, 119 and 139% of σb was obtained for nanocomposites with addition of 0.25 wt.% of diallylamine, p-phenylenediamine/methyl ester of linseed oil fatty acid and hexamethylenediamine/methyl ester of linseed oil fatty acid multi-walled carbon nanotubes, respectively. Short techno-economic analysis, performed on the basis of fixed and variable unsaturated polyester resin production costs, showed satisfactory potential profit, which could be realized by the implementation of the presented technology.

Simple Process for Sidewall Modification of Multi-Walled Carbon Nanotubes with Polymer Side Chain Radicals Generated by Ultraviolet-Induced C–Cl Bond Dissociation of Polystyrene Derivatives

In this work, we investigated a simple one-step process for the formation of chemical bonds between multi-walled carbon nanotubes (MWCNTs) and benzyl-type side chain radicals generated by UV photolysis of polystyrene derivatives containing the chloromethyl (–CH2Cl) group. Poly(4-chloromethyl)styrene, or styrene/4-(chloromethyl)styrene random copolymer, was mixed with MWCNTs in 1-methyl-2-pyrrolidone and irradiated with ultraviolet (UV) light. Films of polymer/MWCNT mixtures before and after UV irradiation were fabricated, and then examined by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. According to the XPS analysis, the amount of Cl atoms in the mixture was found to decrease upon UV irradiation, indicating that the Cl atoms generated by photolysis of chloromethyl groups escaped from the reaction system in the form of gaseous Cl2. The structural change of CNTs after UV irradiation was also observed by comparing the G/D ratios (the intensity ratio of the G to D bands) of the Raman spectra obtained before and after UV irradiation. Similar phenomena were also confirmed in the case of the polymer/MWCNT mixture containing hydroxylammonium chloride as a dispersant of MWCNTs. These results confirmed the UV-induced covalent bond formation between polymer side chains and MWCNTs.

The impact of immobilization process on the electrochemical performance, bioactivity and conformation of glucose oxidase enzyme

Our research focuses on the electrochemical performance and influence of conformation on the bioactivity of glucose oxidase (GOx) immobilized on 4-(pyrrole-1-yl) benzoic acid (PyBA) modified multiwalled carbon nanotubes (MWCNT). The presence of PyBA in the nanostructured network introduces carboxylic groups participating in the enzyme immobilization on the electrode surface.In order to study the influence of GOx immobilization process the crosslinking and covalent binding has been applied. The electrochemical characteristics of both GOx modified electrodes were investigated by voltammetric, amperometric and potentiostatic methods. The electronic transfer properties of immobilized enzyme onto MWCNT/PyBA were monitored by electrochemical impedance spectroscopy (EIS). FTIR spectroscopy was used to explore how the immobilization process affected conformational changes in the structure of GOx. The electrochemical measurements revealed that for crosslinked enzyme the heterogeneous electron transfer (ET) rate constant ks was calculated to be 3.2s−1 and confirmed by spectroscopic investigation on the structure of enzyme. A great number of unordered structures in the GOx immobilized by covalent binding, which were not found in the native and crosslinked GOx, indicate that there is a definite change in the tertiary structure of the protein. Such change suggests a partial denaturation of the enzyme molecule and definitely lower ks=0.4s−1. The distinct features of the bioelectrocatalytic systems were the long stability, reproducibility, repeatability and ability to reject or minimize most interferents. These observations provide a promising platform for the development of biofuel cells and biosensing devices.

Influence of MWCNTs modified by silane coupling agent KH570 on the properties and structure of MWCNTs/PLA composite film

Composite films based on poly(lactic acid)(PLA) filled with modified multiwalled carbon nanotubes (MWCNTs) were prepared by casting/solvent evaporation technique and investigated for their properties and structures. MWCNTs were modified by coupling agent KH570 which can improve the dispersion of MWCNTs and then enhance the comprehensive properties of PLA. The influences of modified conditions, including the amounts of KH570, the reaction temperature and time, were analyzed. And also the structures and properties of composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared (FTIR) and thermogravimetric analysis (TG). The two components of the composite films, WMCNTs and PLA, had excellent compatibility. The addition of MWCNTs modified by coupling agents KH570 was beneficial for the crystallization of PLA, and the toughness of composite films was also improved. When the reaction temperature was 70 °C, reaction time was 6 h, and the amount of KH570 was 3 % respectively, the obtained composite films had the perfect comprehensive properties.

Surface Modification of Multi-Walled Carbon Nanotube Using Double-Chained Quartenary Ammonium Bromide

Modification of multi-walled carbon nanotube (MWCNT) plays an important role to produce MWCNT crossbreeds that may be useful for exploration of new materials. In this report, characterization of dimethyl dioctadecylammonium bromide (DDOAB) modified multi-walled carbon nanotube (Mo-MWCNT) using Fourier Transform Infrared (FTIR) spectroscopy and Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) is described. FTIR shows the presence of both aliphatic (CH stretching and CH bending) and ammonium (CN stretching) groups from DDOAB and the existence of C=C aromatic functional group from the structure of MWCNT in Mo-MWCNT spectra. This result was supported by TGA result which suggests that there are weight losses due to the degradation of DDOAB (between 250 °C to 500 °C) in the product. In addition, XRD pattern remain after modification suggesting attachment of MWCNT and DDOAB occurs at the surface of MWCNT.

Aramid–multiwalled carbon nanotube nanocomposites: effect of compatibilization through oligomer wrapping of the nanotubes

AbstractAramid–multiwalled carbon nanotube (MWCNT) nanocomposites with different CNT loadings were prepared by the solution‐blending technique. Aramid oligomeric chains having reactive amine end‐groups were covalently grafted and wrapped over the surface of acid‐functionalized MWCNTs. The presence of functional groups and surface modification of MWCNTs were studied using Raman, Fourier transform infrared and X‐ray photoelectron spectroscopic and transmission/scanning electron microscopic techniques. Addition of these MWCNTs resulted in a homogeneous dispersion throughout the aramid matrix. Dynamic mechanical thermal analysis showed an increase in the storage modulus and the glass transition temperature involved with α‐relaxations on CNT loading. The coefficient of thermal expansion (CTE) of aramid was reduced on loading with such CNTs. Strong interfacial interactions of the matrix with the surface‐modified CNTs reduced the stress‐transfer problem in the composite material and resulted in higher modulus of 4.26 GPa and a glass transition temperature of 338.5 °C, whereas the CTE was reduced to 101.8 ppm °C−1 on addition of only 2.5 wt% CNTs in the aramid matrix. © 2016 Society of Chemical Industry

Electrochemical Modification of Multi-walled Carbon Nanotubes

Electrochemical Modification of Multi-walled Carbon Nanotubes

Reinforcing effect of surface‐modified multiwalled carbon nanotubes on flexural response of E‐glass/epoxy isogrid‐stiffened composite panels

The lack of scientific information about the utilization of nanoparticles on grid‐stiffened composite (GSC) fabrication was the driving force for the selection of this study. In the present work, GSC panels reinforced with various amounts of surface modified multi‐walled carbon nanotubes (MWCNTs) (0–0.5 wt% at a step of 0.1 wt%) have been investigated in terms of their capability to improve the mechanical properties under three‐point flexural condition. Out of these specimens, the maximum value of improvement in the flexural stiffness, load bearing capacity, and specific energy absorption was related to the specimen with 0.4 wt% MWCNTs. It would be worth mentioning that in these structures, a considerable energy absorption was observed after the primary failure related to the load peak. The field‐emission scanning electron microscopy observations of the fracture surfaces of the nanocomposites clearly indicated that the enhancement in the flexural properties was due to the improvement in the interfacial adhesion between the E‐glass fibers and MWCNTs‐enhanced epoxy matrix. POLYM. COMPOS., 39:E677–E686, 2018. © 2016 Society of Plastics Engineers