Surface Of MWCNTs Research Articles

Poly(3-hydroxyalkanoate)-grafted carbon nanotube nanofillers as reinforcing agent for PHAs-based electrospun mats

Poly(3-hydroxyalkanoate)s, PHAs, have been covalently grafted onto the surface of multi-walled carbon nanotubes, MWCNTs, providing nanofillers (MWCNT-graft-PHAs) with enhanced compatibility and reinforcement effect towards PHAs. MWCNTs were first modified by in-situ generated diazonium cations obtained from a hydroxyl-containing aniline derivative, yielding MWCNTs with reactive hydroxyl surface groups, MWCNT-OH. Then, MWCNT-graft-PHAs were obtained by direct, i.e. without using any catalyst, transesterification approach. The successful chemical modification of MWCNTs surface was evidenced by Raman spectroscopy and XPS analysis confirming the covalent grafting of PHA on MWCNT. 3-Dimension mats were further produced through electrospinning of a PHA/MWCNT-graft-PHA solution providing nanocomposites with well-defined nanofibrous morphology. No aggregation of the MWCNTs was evidenced by SEM attesting that the grafting of PHA onto MWCNT improved their dispersion within the PHA matrix and consequently, the properties of the corresponding nanomaterials. Indeed, mechanical analysis results have shown that nanofibers loaded with MWCNT-graft-PHA (3wt%) displayed excellent properties with an increase (+41%) of the tensile strain at break without any decrease of the high elastic modulus as compared to pristine PHA (131MPa).

Sonochemical production and characterization of d-fructose functionalized MWCNTs/alanine-based poly(amide-imide) nanocomposites

This study presents the preparation of d-fructose covalently functionalized multiwalled carbon nanotube (MWCNT-Fr) and its application in the synthesis of polymer nanocomposites (NCs). Poly(amide-imide) (PAI) as matrix of NCs was synthesized from polycondensation reaction between N-trimellitylimido-l-alanine diacid and 4,4′-diamino diphenyl methane under green conditions. Different percents of functionalized multiwalled carbon nanotube (MWCNT-Fr) were dispersed in the PAI using a solution mixing technique. Increased outer diameter and rough surface of the MWCNT-Fr showed the coating of fructose on the surface of MWCNTs. X-ray diffraction analysis was performed in order to confirm the presence of MWCNT-Fr in the PAI matrix. Surface morphology examination showed that the MWCNT-Fr was very well dispersed in the PAI matrix. The thermal properties of the blends were also evaluated. Our results demonstrated according to the limited oxygen index values that these NCs could be classified as self-extinguishing materials.

Thermal Analysis of NR Composite with MWCNTs Aligned in a Magnetic Field

We got the aligned carbon tube in the rubber matrix through magnetic field. TEM shows that Fe3O4is symmetrically coated on the outer surface of MWCNTs. Diffraction peaks corresponding to Fe3O4cubic crystal also appeared in the X-ray diffraction spectra. Thermal conductivity of composites increases by filling the appropriate content of carbon tube. If the magnetic field is larger and the direction time is longer, a greater thermal conductivity of composites can be obtained.

Fabrication of Fe3O4 Nanoparticles Decorated Multi-Walled Carbon Nanotubes Magnetic Nanocomposite

In this paper, Fe3O4magnetite nanoparticles decorated multi-walled carbon nanotubes (MWCNTs-Fe3O4) nanocomposite was successfully prepared. Firstly, carboxyl-functionalized MWCNTs were obtained after acid oxidization. Then, Fe3O4 nanoparticles were attached onto the surface of MWCNTs through chemical reaction between hydroxyl groups on the surface of Fe3O4 nanoparticles and carboxyl groups on the surface of MWCNTs.

Enhanced methanol oxidation activity of Au@Pd nanoparticles supported on MWCNTs functionalized by MB under ultraviolet irradiation

A successful approach to assemble Au core Pd shell (Au@Pd) nanoparticles on the surface of multi-walled carbon nanotubes functionalized by methylene blue (MB) (Au@Pd/fuv-MWCNTs) was reported. In this method, MWCNTs were functionalized under ultraviolet irradiation. UV–Vis analysis and high-angle annular dark-field transmission electron microscope (HAADF-TEM) image prove that core–shell structure of Au@Pd nanoparticles forms. TEM results indicate that Au@Pd nanoparticles (~5.2 nm) are well-dispersed on the surface of fuv-MWCNTs. X-ray photoelectron spectroscopy (XPS) reveals that ultraviolet irradiation can promote the interaction between Au@Pd nanoparticles and the functional groups on the surface of MWCNTs. Cyclic voltammograms (CV), chronoamperograms (CA), and electrochemical impedance spectroscopy (EIS) results demonstrate that the Au@Pd/fuv-MWCNTs catalysts show excellent electrocatalytic performance for methanol oxidation in alkaline media. The catalytic activity of the Au@Pd/fuv-MWCNTs is ~2 times higher than that of the commercial Pd/C catalysts. This is mostly attributed to that ultraviolet irradiation can make the moieties of MB provide a uniform surface with active and anchoring sites, and improves the functional effect of MB on the surface of MWCNTs. Especially, ultraviolet irradiation modifies electronic structure of Pd and is beneficial for the enhancement of catalytic activity.

Microwave absorbing properties of multi-walled carbon nanotubes/polyaniline nanocomposites

Multi-walled carbon nanotubes/polyaniline (MWCNTs/PANI) nanocomposites with high absorbing properties were successfully prepared through in situ chemical polymerization. The corresponding morphologies, microstructures, thermal stabilities and microwave absorbing properties were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, Ultraviolet–Visible spectroscopy (UV–Vis), X-ray diffraction spectroscopy, thermogravimetric analysis and vector network analyzer. Results indicated that there were strong interactions between π-bonded surface of MWCNTs and quinoid rings of PANI. In addition, the thermal stabilities and the microwave absorbing properties showed significant improvement due to the synergistic effect of MWCNTs and PANI. The reflection loss (R) of MWCNTs/PANI nanocomposites was lower than −10 dB between 8.2 and 10.2 GHz, and the minimum loss value was −49.6 dB at 8.8 GHz. The improved microwave absorbing properties suggested promising application of MWCNTs/PANI nanocomposites in high-performance microwave absorber.

Carboxylated or aminated polyaniline-multiwalled carbon nanotubes nanohybrids for immobilization of cellobiose dehydrogenase on gold electrodes.

Polymer-multiwalled carbon nanotube (MWCNT) nanohybrids, which differ in surface charge have been synthesized to study the bioelectrocatalysis of adsorbed cellobiose dehydrogenase (CDH) from Phanerochaete sordida on gold electrodes. To obtain negatively charged nanohybrids, poly(3-amino-4-methoxybenzoic acid-co-aniline) (P(AMB-A)) was covalently linked to the surface of MWCNTs while modification with p-phenylenediamine (PDA) converted the COOH-groups to positively charged amino groups. Fourier transform infrared spectroscopy (FTIR) measurements verified the p-phenylenediamine (PDA) modification of the polymer-CNT nanohybrids. The positively charged nanohybrid MWCNT-P(AMB-A)-PDA promoted direct electron transfer (DET) of CDH to the electrode and bioelectrocatalysis of lactose was observed. Amperometric measurements gave an electrochemical response with KMapp = 8.89 mM and a current density of 410 nA/cm2 (15 mM lactose). The catalytic response was tested at pH 3.5 and 4.5. Interference by ascorbic acid was not observed. The study proves that DET between the MWCNT-P(AMB-A)-PDA nanohybrids and CDH is efficient and allows the sensorial detection of lactose.

Synthesis of multi-walled carbon nanotube-Ag-nanoparticles composite nanomaterials using proton beam irradiation.

A new synthetic route for decorating carbon nanotubes (MWCNTs) with silver nanoparticles by proton beam irradiation at room temperature is presented. Pristine- and surface-modified MWCNTs were comparatively utilized for the preparation of MWCNT-Ag-nanoparticles nanohybrid. Silver nanoparticles on the surfaces of MWCNTs were produced in situ without any additional reducing reagents, and more importantly, all the solutions were aqueous phase-based. The surfaces of MWCNTs were functionalized with thiol groups using several steps, which included an oxidation step. The silver nanocrystals on the surface-modified MWCNTs were spherical and -4 nm in diameter. Thiolated MWCNTs were well decorated with Ag nanoparticles, whereas pristine MWCNTs were not.

Modification and dispersion of multi-walled carbon nanotubes in water

In the present work, the decorated purified raw multi-walled carbon nanotubes (R-MWCNTs) were obtained by chemical modification (CM) by treatment with concentrated sulfuric acid and concentrated nitric acid mixture with a certain volume ratio of 1: 3. The R-MWCNTs and CM-MWCNTs samples were investigated by X-ray Diffraction (XRD) analysis and Fourier transform infrared spectroscopy (FT-IR). The prepared MWCNTs were homogeneously dispersed in water using a commercial surfactant (Polyvinyl pyrrolidone, (PVP)) and ultra-sonication. The dispersion of MWCNTs was obtained by UV-Vis analysis. The results show that chemical modification purified MWCNTs and more effective functional groups were attached on the surface of MWCNTs. Meanwhile, R-MWCNTs and CM-MWCNTs were uniformly distributed in aqueous PVP solution and the dispersion of CM-MWCNTs in water was better.

Controllable synthesis of multi-walled carbon nanotubes/poly(3,4-ethylenedioxythiophene) core-shell nanofibers with enhanced electrocatalytic activity

Core-shell structured poly(3,4-ethylenedioxythiophene)/multi-walled carbon nanotubes (PEDOT/MWCNTs) nanofibers were synthesized through an interfacial polymerization technique. The interfacial polymerization at a liquid-liquid interface allowed PEDOT to grow uniformly on the surface of MWCNTs due to the presence of π-π interactions between PEDOT and MWCNTs walls. The morphology, structure and composition of the as-prepared PEDOT/MWCNTs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR). In addition, the electrocatalytic properties of PEDOT/MWCNTs toward redox reactions of magnolol, a widely used traditional Chinese medicine, were systematically investigated. The results showed that the PEDOT/MWCNTs nanofibers exhibited a distinctly higher activity for the detection of magnolol compared with those of pure MWCNTs and PEDOT. The remarkably enhanced activity for the nanofibers can be attributed to the unique configuration and synergistic contribution between PEDOT and MWCNTs. The presented method is a general, facile and green approach for the synthesis of polymer/CNTs nanofibers, which is significant for the development of high performance electrocatalysts for biosensing and fuel cell applications.

Redox targeting of DNA anchored to MWCNTs and TiO2 nanoparticles dispersed in poly dialyldimethylammonium chloride and chitosan

A key issue associated with electrochemical DNA-based biosensors is how to enhance DNA immobilization on the substrates. In order to improve the immobilization of DNA and to optimize DNA interaction efficiency, different kinds of strategies have been developed. In this regard, nanomaterials have attracted a great deal of attention in electrode surface modification for DNA biosensor fabrication. In this study, nanostructured films were deposited at the surface of a pencil graphite electrode (PGE) as a working electrode. For the present purpose, common polyelectrolytes are used for surface modification with double-stranded DNA. Two positively charged polyelectrolyte, namely poly dialyldimethylammonium chloride (PDDA) and chitosan, are initially compared for DNA immobilization at the surface of MWCNTs and TiO2 nanoparticles (TiO2NPs). In a second step, the basic electrochemical properties of the sensors are investigated using voltammetric methods. The modified electrodes are also characterized by scanning electron microscopy and electrochemical impedance measurements. It will be shown that electrode modification with DNA and the nanostructure that disperses in PDDA leads to an enhanced sensitivity of the DNA voltammetric detection mechanism. In a previous study, a comparison was done between MWCNTs and TiO2NPs for determining the effect of nanoparticle effect on DNA immobilization on the electrode surface. In order to compare the efficiency of the prepared DNA-based biosensors, methylene blue is chosen as an electroactive probe. It will be shown that the stability of the immobilized DNA within several days will be much higher when MWCNTs rather than TiO2NPs are used.

Effect of Electrostatic Interaction on Electrodeposition of Nickel Hexacyanoferrate with Functional MWCNTs and Their Application for the Determination of Persulfate and Tannic Acid

AbstractA nanocomposite film of NiHCF electrodeposited onto AFCNT was modified on GCE by the electrostatic interaction of multiple scan cyclic voltammetry. Amino groups have been introduced with a positive charge onto the surface of MWCNTs. The presence of NiHCF‐AFCNT/GCE was characterized by using FE‐SEM, EDS, EIS, and XRD studies. The nanocomposite film of NiHCF‐AFCNT was further utilized to determine persulfate and tannic acid, respectively. The nanocomposite film modified electrode displays linear response from 0.1 to 19 mM and 10 to 170 µM for persulfate and tannic acid with a correlation coefficient of 0.9921 and 0.9869. The detection limits were found to be 0.1 mM and 1 µM, respectively. As results, the electrostatic interaction between positively charged metal ions, amino functionalized CNT and negatively charged hexacyanoferrate can be a new subject for many interesting applications.

Influence of multiwalled carbon nanotube addition on the magnetic and reflection-loss characteristics of Mn–Sn–Ti substituted strontium ferrite nanoparticles

In this work, Mn–Sn–Ti substituted strontium ferrite (Sr-ferrite:SrM) nanoparticles were attached on the outer surface of varied multi-walled carbon nanotubes volume fraction with the amount of 10, 15, 20, 25 and 30, by employing of the sol–gel method. The phase identification and morphologies of the nanocomposites were characterized by X-ray diffraction and field emission scanning microscopy respectively. The obtained results showed that the single phase SrFe9.5 (Mn1.25Sn0.625Ti0.625) O19 nanoparticles were decorated on MWCNTs can be obtained at 900°C. Fourier transform infrared revealed that both the stretching and the bending modes are formed in the citrate complex in the ferrite and hydroxyl and carboxyl groups on the external surface of MWCNTs. The Magnetic properties were measured by a vibrating sample magnetometer. It was found that saturation magnetization, remanent magnetization and coercivity decrease by an increase in the MWCNTs content from 10 to 30vol%. The reflection loss measurement of the prepared absorber which contain the ratio of 70–30mass% for the nanocomposite to the polyvinyl chloride, done by the vector network analyzer, proved that the prepared nanocomposites have the maximum reflection loss of −28dB at the frequency of 8.8GHz for Mn–Ti–Sn substituted strontium ferrite −30vol% MWCNT nanocomposite with a bandwidth of 4GHz (RL>−10dB).

Synthesis of highly dispersed platinum particles on carbon nanotubes by an in situ vapor-phase method

Highly dispersed Pt nanoparticles were prepared on functionalized multi-walled carbon nanotubes (f-MWCNTs) using a simple in situ vapor-phase method. The method consisted in two-step procedure in which an initial mixture of Pt precursor (Pt-acac) and f-MWCNTs was heated in a quartz tube reactor, first at 180°C and then at 400°C. Fourier transform infrared spectroscopy (FTIR–ATR), thermal gravimetric analysis (TGA) and X-ray diffraction (XRD) were used to follow the chemical and structural transformations of mixture components during heating steps. The functionalization of MWCNTs with HNO3/H2SO4 solution resulted in formation of surface carbonyl groups. The FTIR–ATR and XRD results indicated that individual Pt-acac withstood heating at 180°C, whereas it was dissociated when heated in contact with f-MWCNTs at the same temperature. Thus, the functional carbonyl groups were found to be responsible for assisted decomposition of Pt-acac at 180°C. Since carbonyl groups served as reaction sites for decomposition of Pt-acac, the resulting particles were highly and homogeneously dispersed on the surface of MWCNTs even the relatively high metallic loading of 27wt%. TEM observations revealed that crystalline Pt particles exhibit narrow size distribution with a mean size of 2.3nm.

Self-assembly of carbon nanotubes modified by hydropropylcellulose in aqueous solution

Hydropropylcellulose (HPC)-modified multi-wall carbon nanotubes (HPC-MWCNTs) were prepared by physical adsorption of HPC on the surface of MWCNTs. The modification decreased the contact angle of water on HPC-MWCNTs and increased their water dispersion ability. However, HPC-MWCNTs dispersed in water were not stable and precipitated on the bottom of the container after 2 days as cylindrical bundles with a diameter of 4–8 μm and a length of 25–35 μm. The cylindrical bundles were formed by self-assembly of HPC-MWCNTs by hydrophilic and hydrophobic interactions. [New Carbon Materials 2013, 29(1): 26–33]

Immobilization and molecular rearrangement of ionic liquids on the surface of carbon nanotubes

Two kinds of imidazolium ionic liquids with different weight ratios were absorbed on the outer surface of MWCNTs. The orientational order and properties of ILs immobilized on the MWCNTs' surfaces were analyzed.

Dual nature, self oxidized poly(o-anisidine) functionalized multiwall carbon nanotubes composite: Preparation, thermal and electrical studies

Poly(o-anisidine) (POAS)/silverized multiwall carbon nanotubes (POAS–MWCNTs/Ag) composite was prepared by adsorption of POAS on the surface of MWCNTs by solution method. This research demonstrated that it was possible to metalized MWCNTs and uses a polymer as a substitute for polyaniline (PANI) to synthesize MWCNTs/conducting polymer nanocomposites by one-step easy mixing of solutions. The resulting composite was characterized using SEM; TGA and fourier transform infrared spectroscopy (FTIR), X-ray spectroscopy. The electrical resistivity of the composites was studies and it was found unusually higher conductivity than that of pure POAS and MWCNTs and it was 5S/cm. All the results demonstrated a facile route to the synthesis of POAS–MWCNTs/Ag composites, possessing good electrical conductivity and outstanding thermal stability at high temperature.

Microwave-assisted synthesis of ZnO/MWCNT hybrid nanocomposites and their alcohol-sensing properties

Zinc oxide and multi-walled carbon nanotube (ZnO/MWCNT) hybrid nanocomposites were synthesised by microwave-assisted method using the mixed solution of zinc acetate dehydrate (Zn(CH3COO)2·2H2O) and treated MWCNTs. The syntheses were carried out at various microwave irradiation powers. The characterisation of the as-synthesised nanocomposites was conducted by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results revealed that the composites were composed of two phases of MWCNTs and hexagonal wurzite ZnO. The SEM results showed that the ZnO nanoparticles were well decorated on the surface of MWCNTs. The amount of ZnO nanoparticles and their size increased with increasing irradiation power. Thick-film sensors were fabricated onto interdigitated conducting electrodes using as-synthesised hybrid composites as sensing materials. The alcohol-sensing behaviour of the hybrid composite films was investigated. The results indicated that the irradiation power had significant influence on the sensing response of the sensors toward alcohol. The sensor fabricated from the composite synthesised at higher irradiation power exhibited an enhanced alcohol-sensing performance.

Preparation of SnO2 -TiO2 /MWCNT nanocomposite photocatalysts with different synthesis parameters

Photocatalytic activity of TiO2 can be further improved by coupling it with other semiconductors and/or carbon nanotubes (CNTs) and create a composite material. SnO2–TiO2/multiwall carbon nanotube (MWCNT) composite catalysts with different molar ratios were prepared and the photocatalytic activities of these samples were evaluated with methylene blue decomposition. The catalysts were synthesized by acid-catalysed sol–gel method. Two series of catalysts were made, one with co-precipitation and the other one with consecutive precipitation method. The samples were characterized by TEM, XRD, BET techniques, respectively. These investigations revealed that some crystalline oxide nanoparticles were successfully bound onto the surface of MWCNTs. Mainly, the MWCNT containing catalysts showed higher photocatalytic activity, and addition of SnO2 enhances the efficiency of photocatalysts. The composites with the ratio of 25–75 (SnO2–TiO2 mol%) with 10 wt% of MWCNTs showed the best performance in photocatalytic test reactions.

Synthesis of silver nanoparticles decorated MWCNTs and their application in antistatic polyetherimide matrix nanocomposite

A facile approach for fabricating antistatic polyetherimide (PEI) had been carried out by introducing poly(sodium acrylate) bonded multi-walled carbon nanotubes and silver nanoparticles (MWCNTs@PSA@Ag). The electrostatic discharge channel was well constructed through homogenously dispersed MWCNTs with polar PSA layer and enhanced by Ag nanoparticles. Chemical structures of MWCNTs@PSA@Ag were characterized by FTIR, XPS, Raman, TGA, UV–vis and TEM. Results revealed that PSA was covalently bonded onto the surface of MWCNTs. Thereby, the ester bond in PSA could improve the dispersion of MWCNT in PEI matrix, and assemble size controlled Ag nanoparticles through coordination bond. Thus, the percolation volume conductivity of MWCNTs@PSA@Ag/PEI nanocomposite was increased to 8.3×10−8S/cm at 0.75wt% concentration. Moreover, the percolation threshold was further declined to 0.5wt% concentration because ionic conduction of PSA could be formed after moisture absorption of MWCNTs@PSA@Ag/PEI nanocomposite in environment.