Sidewalls Of Multiwalled Carbon Nanotubes Research Articles

N8 (-) polynitrogen stabilized on multi-wall carbon nanotubes for oxygen-reduction reactions at ambient conditions.

Polynitrogen (PN) species (Nn , n from 3 to 8) as highly energetic materials have attracted many theoretical calculations and predictions. N3 , N4 , N5 or their ions were experimentally detected under high-pressure and high-temperature conditions. Herein, a N8 (-) PN stabilized on the positively charged sidewalls of multi-walled carbon nanotubes (MWNTs) has been synthesized using cyclic voltammetry (CV) under ambient conditions. ATR-FTIR and Raman spectroscopic data assigned on the basis of density functional theory (DFT) calculations support the successful synthesis of a C2h symmetry chain structure of the N8 anion stabilized as MWNT(+) N8 (-) . Temperature programmed desorption (TPD) data show that MWNT(+) N8 (-) is thermally stable up to 400 °C. Oxygen-reduction reaction (ORR) experiments carried out using MWNT(+) N8 (-) as the cathodic catalyst shows that it is very active for ORR with an even higher current density than that of a commercial Pt/carbon catalyst.

Fabrication and Properties of Composites of Linear Polyacrylamide and Functionalized Carbon Nanotubes

Polyacrylamide (PAM) was chemically anchored to the surface of multi-walled carbon nanotubes (MWCNTs) by atom transfer radical polymerization (ATRP) of acrylamide (AM). It started from the functional groups such as –COOH on the sidewall of MWCNTs, which derived from the oxidation of carbon nanotubes. FT-IR and 1H NMR results shown that the multi-walled carbon nanotubes grafted PAM (MWCNT-g-PAM) have been successfully carried out. The MWCNT-g-PAM showed different relative weight loss kinetics with PAM determined by thermal gravimetric analysis (TGA). The transmission electron microscopy (TEM) shown that the PAM grafted polymer was wrapped on the surface of carbon nanotubes.

Carbon Nanotube-Loaded Nafion Film Electrochemical Sensor for Metal Ions: Europium

A Nafion film loaded with novel catalyst-free multiwalled carbon nanotubes (MWCNTs) was used to modify a glassy carbon (GC) electrode to detect trace concentrations of metal ions, with europium ion (Eu(3+)) as a model. The interaction between the sidewalls of MWCNTs and the hydrophobic backbone of Nafion allows the MWCNTs to be dispersed in Nafion, which was then coated as a thin film on the GC electrode surface. The electrochemical response to Eu(3+) was found to be ∼10 times improved by MWCNT concentrations between 0.5 and 2 mg/mL, which effectively expanded the electrode surface into the Nafion film and thereby reduced the diffusion distance of Eu(3+) to the electrode surface. At low MWCNT concentrations of 0.25 and 0.5 mg/mL, no significant improvement in signal was obtained compared with Nafion alone. Scanning electron microscopy and electrochemical impedance spectroscopy were used to characterize the structure of the MWCNT-Nafion film, followed by electrochemical characterization with Eu(3+) via cyclic voltammetry and preconcentration voltammetry. Under the optimized conditions, a linear range of 1-100 nM with a calculated detection limit of 0.37 nM (signal/noise = 3) was obtained for determination of Eu(3+) by Osteryoung square-wave voltammetry after a preconcentration time of 480 s.

A layer-nanostructured assembly of PbS quantum dot/multiwalled carbon nanotube for a high-performance photoswitch

A layered nanostructure of a lead sulfide (PbS) quantum dot (QD)/multi-walled carbon nanotube (MWNT) hybrid was prepared by the electrostatic assembly after the phase transfer of PbS QDs from an organic to an aqueous phase. Well-crystallized PbS QDs with a narrow diameter (5.5 nm) was mono-dispersed on the sidewalls of MWNT by the electrostatic adsorption. Near-infrared absorption of PbS/MWNT nanostructures was improved and controlled by the packing density of PbS QDs. Efficient charge transfer between PbS and MWNT at the interface resulted in a remarkable quenching of photoluminescence up to 28.6% and a blue-shift of emission band by 300 nm. This feature was facilitated by band energy levels based on the intimate contact through the electrostatic interaction. Two-terminal devices using PbS/MWNT nanostructures showed an excellent on/off switching photocurrent and good stability during 20 cycles under light illumination due to electron transfer from PbS to MWNT. The photoswitch exhibited a high photo sensitivity up to 31.3% with the photocurrent of 18.3 μA under the light of 3.85 mW/cm2, which outperformed many QD/carbon-based nanocomposites. Results indicate that the electrostatic layered assembly of QD/MWNT nanostructure is an excellent platform for the fabrication of high-performance optoelectronic devices.

Preparation and adsorption properties of a novel superabsorbent based on multiwalled carbon nanotubes-xylan composite and poly(methacrylic acid) for methylene blue from aqueous solution

A novel superabsorbent was prepared by the copolymerization reaction between multiwalled carbon nanotubes (MWCNTs)–xylan composite and poly(methacrylic acid) (PMAA) in the presence of N,N′-methylenebisacrylamide as cross-linker and the redox initiation system (NH)4S2O8-anhydrous Na2SO3 as initiator for adsorbing methylene blue (MB) from aqueous solution. First, covalent modification of MWCNTs with a natural polymer xylan was achieved by the nucleophilic substitution reaction. The obtained xylan modified MWCNTs–xylan composite was characterized by transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometer, and thermal gravimetric analysis. The results indicated that the hydroxyl groups of xylan participated in the formation of MWCNTs–xylan composite, and MWCNTs–xylan composite contained 32% xylan and about four molecule chains of xylan were grafted onto 5,000 carbon atoms of MWCNTs sidewalls. Subsequently, a novel superabsorbent based on MWCNTs–xylan composite and PMAA was prepared and characterized by Fourier transform infrared spectroscopy, scanning electron microscope, and swelling test. The results proved that superabsorbent was successfully prepared by copolymerization reaction and found that the superabsorbent evidently presented three-dimensional network structure. Swelling process of superabsorbent complied with the Fick's law. Adsorption property of superabsorbent for MB was also systematically studied by investigating these parameters, such as superabsorbent dosage, initial MB concentration, contact time, ion strength, and pH. The superabsorbent presented a higher adsorption capacity and removal rate for MB. The adsorption data were fitted by Langmuir, Freundlich isotherm models, and four adsorption kinetic models. Freundlich isotherm model better fitted the equilibrium data than Langmuir, and adsorption kinetics could be well described by pseudo-second-order kinetic and intraparticle diffusion. These results indicated that the superabsorbent can be used as an efficient absorbent for removal of MB from aqueous solution. POLYM. COMPOS., 35:1516–1528, 2014. © 2013 Society of Plastics Engineers

Raman, EELS and XPS studies of maghemite decorated multi-walled carbon nanotubes

Iron oxide particles with the diameter being 5–10nm were attached onto the sidewalls of multi-walled carbon nanotubes (MWCNTs) by the thermal decomposition of cyclopentadieny iron (II) dicarbonyl dimmer. The red shift of G-mode from 1579cm−1 to 1571cm−1 in the Raman profile of the decorated MWCNTs is indicative of the attachment of nanoparticles. Electron energy loss spectroscopy and X-ray photoelectron spectroscopy analyses reveals that the attached nanoparticles are composed of a maghemite phase. Transmission electron microscopy suggests the maghemite particles are covered with amorphous carbon materials and form a core–shell structure.

Improved Polymer Encapsulation on Multiwalled Carbon Nanotubes by Selective Plasma Induced Controlled Polymer Grafting

Surface graft polymerization on multiwalled carbon nanotubes (MWCNTs) with several grafting mechanisms is nowadays a demanding field of nanocomposites in order to enhance the load carrying capacity, thus improving the overall performance of the composites. Here, we demonstrate the covalent grafting of a sulfonic acid terminated monomer, 2-acrylamido-2-methylpropane sulfonic acid onto sidewalls of MWCNTs via a comparative study between oxygen plasma induced grafting (OPIG), nitrogen plasma induced grafting (NPIG), and nitrogen + oxygen plasma induced grafting (NOPIG) with the aim to identify the most effective process for the preparation of polymer encapsulated carbon nanotubes. From the detail surface analysis, it has been noticed that NOPIG offered much better surface grafting than that of the OPIG and NPIG. The transmission electron microscopy (TEM) images showed that MWCNTs modified by NOPIG possess much thicker and uniform polymer coatings throughout. From thermogravimetric analysis (TGA), the grafting degree was found to be ~80 wt % for the NOPIG sample.

Synthesis of Phosphorus Included Multiwalled Carbon Nanotubes by Pyrolysis of Sucrose

Multiwalled carbon nanotubes (MWCNT) were synthesized by a pyrolysis route which involves a dehydration step using phosphoric acid. The resultants were found to be mostly containing amorphous carbon with scattered MWCNTs using scanning electron and transmission electron microscopy techniques. These MWCNTs were smaller in size and limited in quantity compared to the ones synthesized using other common precursors. Energy dispersive X-ray and electron energy loss spectroscopy analysis indicated the presence of phosphorus both at the MWCNT sidewalls and in the catalyst particles encapsulated inside the MWCNTs. In addition, a comparative investigation for sulfur and phosphorus inclusion to the sidewalls of MWCNTs was carried out using density functional theory calculations. The results of the computational study showed that both phosphorus and sulfur atoms prefer to bind among themselves rather than adsorbing directly on carbon nanotubes (CNT). Furthermore, cluster calculations revealed that phosphorus atoms m...

Enhanced Photoluminescence Effect of Poly(L-lactide) Biodegradable Polymer with Functionalized Carbon Nanotubes

Functionalization of Multiwalled Carbon Nanotubes (MWCNTs) for biological applications was considered. For this purpose, the pristine MWCNTs (pMWCNTs) are covalently aminated using p-amino benzoic acid and phosphoric acid without shortening of pMWCNTs. The grafted amine groups on the sidewall of pMWCNTs are useful as initiator for grafting of polymer chains on the sidewall of aminated MWCNTs (MWCNT-NH2). The PLLA homopolymer chains grafted covalently from the sidewall of aminated MWCNTs successfully. The FT-IR spectra revealed that the amine groups and the PLLA chains grafted form the sidewall of pMWCNTs strongly. The fluoroscopy test results shows that the pMWCNTs and aminated MWCNTs have not any significant photoluminescence (PL) effect at 350 nm excitation. The MWCNT-g-PLLAs exhibit an extremely strong visible emission at 404 nm and 429 nm. These results may be ascribed to the contribution of oxygen vacancies and defects at the end chain of grafted PLLA chains on the sidewall of MWCNTs that created by Sn atoms of initiator during polymerization on the sidewall of MWCNTs. The oxygen vacancies usually act as radiative centers in the PL process. In addition, The MWCNT-g-PLLAs enhance the PL of neat PLLA. The PL of composites slightly diminishes with blue shift during in-vitro degradation. As mentioned above, the MWCNT-g-PLLAs are the functionalized MWCNTs that applicable in the field of medicine. Due to biocompatible and biodegradable molecular groups on the sidewall of MWCNTs, it is predictable that the MWCNT-g-PLLAs will pass all exams for its application in medicine.

Effect of functionalized multiwalled carbon nanotubes on thermal stability of poly (L-LACTIDE) biodegradable polymer

The thermal stability of Poly (L-lactide) PLLA biocompatible and biodegradable polymer reinforced with functionalized Multiwalled carbon nanotubes (MWCNTs) was investigated. For improvement of MWCNTs, the pristine MWCNTs (pMWCNTs) were functionalized, at first, by Friedel Crafts acylation, which introduced the aromatic amine groups on the side wall of MWCNTs (MWCNT- NH2) without shortening or cutting of pMWCNTs. Then, the PLLA chains were covalently grafted from the sidewall of MWCNT- NH2 by in situ ring-opening polymerization of L-lactide oligomers (LA), using stannous octanoate as the initiating system (MWCNT-g-PLLA). The FT-IR and XPS spectra revealed that the PLLA chains grafted strongly from the sidewall of MWCNTs. The thermo-gravimetric analysis of prepared composites with various concentrations of MWCNT-g-PLLAs shows a significant increment in the thermal stability of composites, by increasing the concentration of MWCNT-g-PLLAs in composites. The XRD analysis revealed that the MWCNT-g-PLLAs increased the crystallinity of PLLA, indicating that the composites with PLLA grafted MWCNTs were more thermally stable than those of neat PLLA.

BIOMIMETIC SYNTHESIS OF FePt NANOPARTICLES ON MULTI-WALLED CARBON NANOTUBES FOR FUNCTIONAL NANOMATERIALS

We present a facile green biomimetic synthesis of FePt nanoparticles (NPs) on the sidewalls of multi-walled carbon nanotubes (CNTs). A core-shell globular protein, ferritin (Fr), was bound onto Z-glycine N-succinimidyl ester (Z-Gly-OSu) modified CNTs and served as precursor to create FePt NPs at the core part of Fr. Biomimetic synthesis of FePt NPs was carried out by chemical reducing of Fe2+ and [Formula: see text] ions that transferred into the core part of Fr molecules. The created one-dimensional CNT- FePt nanohybrids were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The synthesized CNT- FePt nanohybrids show multi-properties of high water-solubility, ferromagnetism, and electrocatalytic activity.

Dispersion of Multiwalled Carbon Nanotubes in Water Using Ionic-Complementary Peptides

We demonstrate the noncovalent modification of multiwalled carbon nanotubes (MWNTs) immersed in aqueous solution using the ionic-complementary peptide EFK16-II. This modification presumably arises through the interaction between the hydrophobic side of the EFK16-II and MWNT sidewalls and orients hydrophilic functional groups toward the solution phase and enables them to form highly stable dispersions in water. This stability can be attributed to the electrostatic repulsion between self-assembled peptides on the MWNTs. This repulsion as determined by ζ potential measurements increases as the pH diverges from the isoelectric point of ~6.7 for EFK16-II. This trend is confirmed by dynamic light scattering measurements of the suspensions showing a decrease in their particle size as the ζ potential increases. These EFK16-II-MWNT suspensions have been used to modify mica surfaces. Atomic force microscopy and scanning electron microscopy images show that this leads to a uniform distribution of individual modified MWNTs on the mica surfaces. Transmission electron microscopy reveals images of well-dispersed fibers with dimensions similar to those of individual MWNTs. Tissue culture plates previously contacted with EFK16-II-modified MWNTs have been shown to have enough biocompatibility for growth and attachment of cells. The biocompatibility and enhanced electrical conductivity that should result from the modification with these EFK16-II-MWNT suspensions opens up their use in a number of potential biomedical applications such as the design of bioelectrode interfaces and fabrication of biosensors with high sensitivity.

Solvothermal synthesis and optical limiting properties of carbon nanotube-based hybrids containing ternary chalcogenides

Two or three types of semiconductor nanoparticles (NPs) have been deposited on the sidewalls of multi-wall carbon nanotubes (MWCNTs) by a solvothermal treatment of a mixture containing poly(sodium 4-styrenesulfonate) (PSS) wrapped MWCNTs, metal chloride (CuCl2 and SnCl2), and thiourea. Changing the ratio of Cu2+ to Sn2+ alters the composition of the resultant MWCNT–PSS–NP hybrids. Under Cu/Sn ratios of 3:1 and 2:1, MWCNTs can be simultaneously decorated with Cu2S and Cu3SnS4 NPs. When the ratio is reduced to 1:1, Cu3SnS4, Cu2S and SnO2 NPs would be formed at the same time. Further decreasing the ratio results in the formation of Cu2SnS3 and SnO2 instead of Cu3SnS4 and Cu2S. Open-aperture z-scan measurements have been carried out on three typical MWCNT–PSS–NP samples to study their optical limiting (OL) properties. The addition of semiconductor NPs can improve the OL performance of MWCNTs, and the composition of the NPs has a significant effect on the OL behavior of the hybrids.

Noncovalent Modification of Carbon Nanotubes with Proteins via Biotinylated Peptides Having a Binary Pattern within the Sequences

Abstract We describe peptide-based solubilization and functionalization of multiwalled carbon nanotubes (MWNTs), in which biotinylated peptides that are physically adsorbed onto the sidewalls of MWNTs can anchor proteins of interest via specific interactions.

Enhanced mechanical and photoluminescence effect of poly(l-lactide) reinforced with functionalized multiwalled carbon nanotubes

The poly(l-lactide) (PLLA) biocompatible and biodegradable polymer was reinforced with functionalized Multiwalled carbon nanotubes (MWCNTs) to overcome on insufficient mechanical properties of this polymer for high load bearing applications. To fully realize the potential of MWCNTs for this purpose, they have to be homogeneously dispersed in polymer matrix and have efficient load transfer across the MWCNTs/polymer interface. The pristine MWCNTs (pMWCNTs) were functionalized, at first, by Friedel–Crafts acylation, which introduced the aromatic amine groups on the sidewall of MWCNTs (MWCNT–NH2) without shortening or cutting of pMWCNTs. And then, the PLLA chains covalently grafted from the sidewall of MWCNT–NH2 by in situ ring-opening polymerization of l-lactide oligomers using stannous octanoate as the initiating system. The Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy spectra revealed that the PLLA chains grafted form the sidewall of MWCNTs strongly. The surface morphology of pristine and PLLA-grafted MWCNTs (MWCNT-g-PLLAs) was characterized by scanning electron microscopy and transmission electron microscopy. The tensile test of prepared composites of PLLA with various concentrations of MWCNT-g-PLLAs show a significant increment in tensile strength and elongation at failure of composites with increasing the concentration of MWCNT-g-PLLAs in composites. Also, it is found that the MWCNT-g-PLLAs increased the photoluminescence effect of PLLA and widened the luminescence region of PLLA.

Effects of Surface Modification of MWCNT on the Mechanical and Electrical Properties of Fluoro Elastomer/MWCNT Nanocomposites

Surface modification is a good way to improve the surface activity and interfacial strength of multiwalled carbon nanotubes (MWCNTs) when used as fillers in the polymer composites. Among the reported methods for nanotube modification, mixed acid oxidation and plasma treatment is often used by introducing polar groups to the sidewall of MWCNT successfully. The purpose of this study is to evaluate the effect of different surface modification of MWCNT on the mechanical property and electrical conductivity of Fluoro‐elastomer (FE)/MWCNT nanocomposites. MWCNTs were surface modified by mixed oxidation and CF4 plasma treatment and then used to reinforce the fluoro elastomer (FE, a copolymer of trifluorochloroethylene and polyvinylidene fluoride). FE/MWCNT composite films were prepared from mixture solutions of ethylacetate and butylacetate, using untreated CNTs (UCNTs), acid‐modified CNTs (ACNTs), and CF4 plasma‐modified CNT (FCNTs). In each case, MWCNT content was 0.01 wt%, 0.05 wt%, 0.1 wt%, and 0.2 wt% with respect to the polymer. Morphology and mechanical properties were characterized by using scanning electron microscopy (SEM), Raman spectroscopy, as well as dynamic mechanical tests. The SEM results indicated that dispersion of ACNTs and especially FCNTs in FE was better than that of UCNTs. DMA indicated mechanical properties of FCNT composites were improved over ACNT and UCNT filled FE. The resulting electrical properties of the composites ranged from dielectric behavior to bulk conductivities of 10−2 Sm−1 and were found to depend strongly on the surface modification methods of MWCNTs.

Electroless preparation and characterization of Ni–B nanoparticles supported on multi-walled carbon nanotubes and their catalytic activity towards hydrogenation of styrene

Nickel–boron (Ni–B) nanoparticles supported on multi-walled carbon nanotubes (MWCNTs) were successfully synthesized through an electroless deposition process using the plating bath with sodium borohydride as a reducing agent. The structural and morphological analyses using field-emission scanning electron microscopy, X-ray diffractometry and high-resolution transmission electron microscopy have shown that the Ni–B nanoparticles deposited on the sidewalls of MWCNTs are fine spheres comprised of amorphous structure with the morphologically unique fine-structure like flowers, and homogenously dispersed with a narrow particle size distribution centered at around 60 nm diameter. The catalytic activity of MWCNT/Ni–B nanoparticles was evaluated with respect to hydrogenation of styrene. The hydrogenation catalyzed by MWCNT-supported Ni–B nanoparticles has been found to make styrene selectively converted into ethylbenzene. The highest conversion reaches 99.8% under proper reaction conditions, which demonstrates the high catalytic activity of MWCNT/Ni–B nanoparticles.

Magnetic field-guided orientation of carbon nanotubes through their conjugation with magnetic nanoparticles

Low intensity magnetic fields (22mT) rendered by a pair of bar magnets have been used to achieve in situ precise orientation of multiwalled carbon nanotubes (MWCNTs) and their directional deposition on solid substrates. The nanotubes were imparted magnetic characteristics through Fe3O4 (magnetite) nanoparticles covalently attached to their surface. The side walls of nanotubes were first acid oxidized with H2SO4/HNO3 (3:1 v/v) mixture and amine-functionalized magnetic nanoparticles were then interfaced to ends and side walls of the nanotubes through covalent linkages in the presence of a zero length cross linker, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide. Fourier transformed infrared spectroscopic investigations affirmed the functionalization of nanostructures and formation of a magnetic nanohybrid. Transmission electron microscopy results revealed the attachment of nanoparticles along the side walls of MWCNTs. A flow cell was utilized to orient magnetic nanohybrid in the desired direction and also to create thin films of aligned MWCNTs. Further, directional assembly of magnetic MWCNTs at different orientation angles on solid substrates was studied by field emission scanning electron microscopy and optical microscopy. The procedure can be scaled to align CNTs on large surface areas for numerous applications, e.g., nanosensors, field emitters, and composites.

Dispersion Stability of Fluorinated Multi-Walled Carbon Nanotubes in FC-27 Refrigerant

In order to achieve the dispersion stability of multi-walled carbon nanotubes (MWCNT) in a fluorinated refrigerant (FC-72) used in various cooling purposes, fluorinated MWCNT (MWCNT-F) was prepared by a combined process of oxidation and fluorination. As a fluorine source, (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane was used to react with hydroxyl groups on MWCNT (MWCNT-OH) generated by chemical oxidation. Pristine MWCNT, MWCNT-OH, and MWCNT-F were dispersed in FC-72 and MWCNT-F was also dispersed in polar and nonpolar solvents. The MWCNT-F has excellent colloidal stability in FC-72 because of the chemical affinity between FC-72 and functional groups (-CFn) on the side walls of MWCNT. Through surface modifications, we could obtain the enhanced dispersion stability of MWCNT in a refrigerant. This homogenous MWCNT solution in FC-72 may be used to increase the heat transfer in FC-72 based nanofluids.

Synthesis of multi-walled carbon nanotube supported nickel catalysts by hydrazine reduction and their electrocatalytic activity on ethanol electro-oxidation

Multi-walled carbon nanotube (MWCNT) supported nickel (Ni) catalysts were chemically synthesized via a hydrazine reduction process with addition of cetyltrimethylammonium bromide (CTAB) as a special additive. As evidenced by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and high-revolution transmission electron microscope (HR-TEM), the Ni nanoparticles (NPs) deposited on the sidewalls of MWCNTs were found to be face-centric cubic (fcc) crystal structure, and dispersed homogenously with a sharp particle size distribution centered at around 20 nm of diameter. Electro-oxidation of ethanol on MWCNT/Ni catalysts was investigated by cyclic voltammetry (CV) measurement. The MWCNT/Ni catalysts showed excellent electro-catalytic activity for the oxidation of ethanol in alkaline solution.