Soluble Multi-walled Carbon Nanotubes Research Articles

Partially oxidized polyvinyl alcohol + functionalized water soluble multiwalled carbon nanotubes: A new conductive nanocomposite material with promising implications for neuroregeneration

Carbon nanotubes (CNT) are promising electroconductive nano-scale materials for neuroregeneration. Herein, we report on a new electroconductive composite scaffold made of the polymer 1% oxidized polyvinyl alcohol (OxPVA) combined with functionalized water soluble multiwalled CNT (OxPVA + MWCNT-S) (diazotization reaction). Preliminarily, MWCNT-S were characterized to evaluate the reaction outcome, the degree of functionalization and the dispersibility in water. Thereafter, OxPVA + MWCNT-S nanocomposite membranes were fabricated and analyzed for physicochemical properties (Raman spectroscopy, thermal decomposition, calorimetric properties, electroconductivity), macroscopic appearance and ultrastructure, mechanical behavior, in vitro cytotoxicity and in vivo biocompatibility. In parallel, OxPVA + MWCNT-S membranes with a linear pattern were also developed and analyzed for interaction with SH-SY5Y cells. Compared to OxPVA, the presence of MWCNT-S (only 0.016 wt%) significantly increased polymer conductivity and imparted a certain porosity without altering mechanical behaviour, as corroborated by uniaxial tensile tests. Neither cytotoxicity nor local signs of inflammation were detected in vitro and after subcutaneous implantation (14 and 42 days), proving composite material biocompatibility. OxPVA + MWCNT-S nanocomposite revealed as promising for future electroconductive conduits free from toxic effects amenable to CNT agglomeration within the polymer. Ideally, nerve lesions with wide gaps, may be effectively supported by those “active” devices, overcoming limitations of the available ones. Despite preliminary data, the presence of a linear pattern confirmed to have a beneficial effect over the scaffold/cells interaction.

Environment friendly milling of Inconel-625

Inconel 625, having wide industrial applications, exhibits poor machinability because of rapid work hardening and poor thermal conductivity. Therefore, cutting fluids are utilised to remove heat and provide lubrication in the cutting zone, but their application poses serious environmental and health hazards, calling to minimise their use. Multi-walled carbon nanotube (NMQL) technique provides an effective alternative to flooded cooling-machining of Inconel and stainless steel. Current study evaluates performance of NMQL in terms of tool wear and surface finish during face milling of Inconel 625. To enhance thermal conductivity of MQL, soluble multiwalled carbon nanotubes (1% wt.) were mixed in vegetable oil. Cutting parameters were optimised to minimise tool wear and surface roughness and validation tests were also conducted under flooded and dry conditions to compare their performance with NMQL machining. Performance of cutting tool during NMQL machining was found to be 15.56% and 3.45% better than dry and flooded machining respectively, on the basis of tool wear (VB), and was 14.06% and 59.02% improved over flooded and dry machining respectively, in terms of surface roughness (Ra).

Environment friendly milling of Inconel-625

Inconel 625, having wide industrial applications, exhibits poor machinability because of rapid work hardening and poor thermal conductivity. Therefore, cutting fluids are utilised to remove heat and provide lubrication in the cutting zone, but their application poses serious environmental and health hazards, calling to minimise their use. Multi-walled carbon nanotube (NMQL) technique provides an effective alternative to flooded cooling-machining of Inconel and stainless steel. Current study evaluates performance of NMQL in terms of tool wear and surface finish during face milling of Inconel 625. To enhance thermal conductivity of MQL, soluble multiwalled carbon nanotubes (1% wt.) were mixed in vegetable oil. Cutting parameters were optimised to minimise tool wear and surface roughness and validation tests were also conducted under flooded and dry conditions to compare their performance with NMQL machining. Performance of cutting tool during NMQL machining was found to be 15.56% and 3.45% better than dry and flooded machining respectively, on the basis of tool wear (VB), and was 14.06% and 59.02% improved over flooded and dry machining respectively, in terms of surface roughness (Ra).

Gold Nanoparticle Conjugated Water Soluble Multiwall Carbon Nanotubes

The poor solubility and dispersibility of carbon nanotubes in both aqueous and organic solvents restrict their applications in biological science. Herein, a simple and cheap method for synthesizing and purification of water soluble multiwall carbon nanotubes from coal combustion fly ash and characterization of this water soluble multiwall carbon nanotubes after conjugation with gold nanoparticles has been described.

Radiation induced graft polymerization of multi-walled carbon nanotubes for superhydrophobic composite membrane preparation

Highly soluble multi-walled carbon nanotubes (MWNTs) were prepared by radiation-induced free radical graft polymerization of vinyl acetate (VAc) onto pristine MWNT surfaces. High resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FTIR) spectroscopy, and micro-Raman spectroscopy were used to confirm that poly(vinyl acetate) (PVAc) had been successfully grafted onto the surface of the MWNTs. The effects of experimental parameters on the degree of grafting (DG) of PVAc were also investigated, including adsorbed dose, dose rate, initial monomer concentration, and solvents. The grafted MWNTs (MWNTs-g-PVAc) exhibited good solubility in common organic solvents at high mass fraction. In addition, a superhydrophobic composite membrane could be readily fabricated by vacuum filtration of MWNTs-g-PVAc onto a supporting membrane, as was confirmed by water contact angle testing and visualization by scanning electron microscopy.

ATRP graft copolymerization of poly(N-isopropylacrylamide-co-acrylic acid) on multiwalled carbon nanotubes

The polymer functionalized multiwalled carbon nanotubes (MWCNT) have been prepared by atom transfer radical graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) monomers from their binary mixture at fixed feed molarity and composition (f NIPAAm ). The donor-acceptor interactions between acrylic acid and N-isopropylacrylamide have enhanced the activity of N-isopropylacrylamide for grafting onto MWCNT (52%) in comparison to individual grafting of N-isopropylacrylamide onto MWCNT (38%). The CuBr and N′N′N′N′N′-pentamethyldiethylenetriamine (PMDETA) were used as ATRP catalysts for graft copolymerization of N-isopropylacrylamide and acrylic acid onto multiwalled carbon nanotubes. The copolymers grafted onto MWCNT were of high molecular weight (42×103 g mol−1) with low molecular weight dispersity (1.13) at 0.1 M a feed molarity and feed composition (f NIPAAm ) of 0.6. The graft yield (%G), molecular weight (MW), and sequence length of N-isopropylacrylamide and acrylic acid monomers (mM1 an mM2) in the grafted chains varied significantly with varying feed composition (f NIPAAm ). The grafting produced highly water soluble multiwalled carbon nanotubes in comparison to pristine MWCNT. The grafted copolymer chain dispersity varied with solution temperature and pH due to the temperature and pH sensitivity of the monomers. The poly(N-isopropylacrylamide-co-acrylic acid) grafted chains were characterized by FT-IR and NMR techniques for their structures and thermal stability as determined by TGA.

Enhanced solid-phase photocatalytic degradation of polyethylene by TiO2–MWCNTs nanocomposites

In this work, a novel acid vapor method was introduced to prepare the water soluble multi-walled carbon nanotubes (MWCNTs) and the titanium dioxide (TiO2)–MWCNTs nanocomposites photocatalyst were successfully synthesized by sol–gel solvothermal method. Products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), which revealed that the anatase TiO2 particles were uniform deposited on MWCNTs surface. UV–vis diffuse reflectance spectroscopy (UV–vis) showed that composite photocatalyst had an obviously absorption band which covered the whole range of UV–vis region and exhibited a significant enhancement of optical absorption property. Based on above properties, we used the TiO2–MWCNTs composites as photocatalysts to degrade the polyethylene (PE) plastic. Solid-phase PE film photocatalytic degradation experiments were investigated through monitoring TiO2–MWCNTs–PE composite film's weight loss under mercury lamp irradiation. Results showed that the degradation efficiency could be tuned by changing the concentration of MWCNTs in photocatalyst. The photo-induced degradation of composite film was significantly higher than that of the pure PE film and the Degussa P25-PE film under the same UV irradiation. The weight loss of TiO2–MWCNTs (20 wt%)–PE sample reached 35% under 180 h UV-light irradiation. Our work could be extended to synthesize other MWCNTs based composite with the purpose of enhancing TiO2's activity and inspiring for the practical environmental pollution, especially for degradation of plastics.

Effects of Phosphoryl Choline Grafted Water Soluble Carbon Nanotubes Examined by Different Cytotoxicity Methods in 16-HEB Cells

The widespread explored application of water soluble carbon nanotubes makes it important to understand their potential toxic effects on health. This study investigates the effects of phosphoryl choline grafted water soluble multi-walled carbon nanotubes (MWCNTs-PC) on human bronchial epithelial (16-HBE) cells by different cytotoxicity methods in vitro. Various concentrations of MWCNTs-PC were incubated with 16-HBE cells, the effects of cell proliferation, cell apoptosis, cell cycle and DNA damage were detected by methyl thiazolyl tetrazolium (MTT) assay, flow cytometry, single cell gel electrophoresis assay (SCGE) and micronuclear assay, respectively. Compared with the control group, there were no significant differences in the changes of cell proliferation, cell apoptosis, cell cycle and DNA damage. Within the experimental concentrations of MWCNTs-PC, no obviously cytotoxicity and DNA damage was observed on 16-HBE cells in this study.

Preparation of Conductive Films by <i>In Situ </i>Polymerization of 3-Alkylthiophene with Soluble MWNTs

Conductive films of multi-walled carbon nanotubes (MWCNTs)/Poly3-alkylthiophene (P3TH) composite films were prepared by in-situ polymerization of 3-alkylthiophene at the presence of soluble MWCNTs. The MWCNTs were safely obtained via a two-step process assisted by microwave radiation, which were soluble in organic media. The obtained composites were examined by FTIR. By using UV-vis analysis it was found that there are strong interactions between P3TH and functionalized MWCNT. The TEM images showed the MWCNTs were homogeneously dispersed in P3TH. In addition, the resulting MWCNT/P3TH composites showed an electrical conductivity at the level 10-3 S/cm.

Carbon Nanotubes Containing Metal Nanoparticles-Graft-Hyperbranched Polyglycerols Nanocomposites

New water soluble multiwall carbon nanotubes (MWCNTs) containing silver nanoparticles-grafted-hyperbranched polyglycerols (HPG) nanocomposites were synthesized and characterized successfully. In this work, MWCNTs were opened using HNO3/H2SO4 mixture and filled by metal nanoparticles such as silver nanoparticles through wet chemcial method. Then MWCNTs containing silver nanoparticles (MWCNTs(Ag)) were used as macroinitiator for ring opening polymerization of glycidol and MWCNTs(Ag)-g-HPG nanocomposites were obtained. Structure of nanocomposites was evaluated by TEM, TGA and spectroscopy methods. With the solubility of MWCNTs(Ag)-g-HPG greatly improved, the new nanocomposites exhibit potential application in biomedicine and nanomedicine.

Water Soluble Multi-Walled Carbon Nanotubes Enhance Peritoneal Macrophage Activity <I>In Vivo</I>

Due to their unique physical properties, carbon nanotubes are becoming promising novel materials in diverse areas like information technology, ultrastiff materials, biomedicine etc. The toxicological study of these materials is very imperative for the safety assessment in respect to their wide applications. The objective of the toxicity study was to find out whether water soluble multi-walled carbon nanotubes (S-MWNTs) would impair the phagocytic activity of macrophages, which play an important role in defenses against invading microbioles. The results showed that S-MWNTs did not impair the phagocytosis of macrophages; to our surprise, S-MWNT significantly enhanced this function. Increased activity of enzymes in lysosome also showed that S-MWNTs enhanced the lysosome function of macrophages. However, S-MWNTs can not influence nitric oxide secretion in macrophages and induce inflammation.

Conjugated polymer covalently modified multiwalled carbon nanotubes for optical limiting

A new soluble multiwalled carbon nanotubes (MWNTs) covalently functionalized with conjugated polymer PCBF, in which the wt % of MWNTs is approximately calculated as 7.3%, and the average thickness of PCBF covalently grafted onto MWNTs is 10.4 nm, was synthesized by an amidation reaction. In contrast to the starting polymer PCBF-NH2, grafting of PCBF onto MWNTs led to a 0.3 eV red-shift of the N1s XPS peak at 399.7 eV assigning to N in the unreacted NH2moieties in the resulting copolymer structure and an appearance of new peak at 402 eV corresponding to N bound to the carbonyl C (i.e., NHCO). Unlike PCBF-NH2, which only displayed a weak optical limiting response at 532 nm, Z-scan for MWNT-PCBF exhibited a much broader reduction in transmission and a scattering accompanying on the focus of the lens at both 532 and 1064 nm, indicating a prominent broadband optical limiting response. The thermally induced nonlinear scattering is responsible for the optical limiting. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

Electrochemistry of glucose oxidase immobilized on carbon nanotubes noncovalently functionalized by multihydroxyl and multicarboxyl groups

In this paper we have described that multi-walled carbon nanotubes (MWNTs) can be homogeneously dispersed and solubilized in water using non-covalent functionalization. These soluble MWNTs were then used for the immobilization of glucose oxidase (GOx) on glassy carbon electrode. Scanning electron microscopy is used to investigate the nanoscale structure of the film formed by the functionalized MWNTs. Electrochemical measurements were conducted to reveal the electroactivity of the GOx on the MWNT modified electrode. The functionalized MWNTs served as a network carrier for GOx as well as a conductor, enhancing greatly the response current. The GOx immobilized in this way retained its bioelectrocatalytic activity for the oxidation of glucose.

The splenic toxicity of water soluble multi-walled carbon nanotubes in mice

Spleen is an important immune organ and a constituting part of the reticuloendothelial system (RES). CNTs in vivo can be readily scavenged from blood and mainly entrapped by liver, spleen and lungs. Herein, water soluble multi-walled carbon nanotubes (S-MWCNTs) were used as a model to investigate the possible toxicity of carbon nanotubes (CNTs) to mouse spleen. The toxicity of various doses of S-MWCNTs was examined by carbon clearance measurement, oxidative stress assay, histopathologic and electron-microscopic examination. Compared with the control group, phagocytic activity of RES, activity of reduced glutathione, superoxide dismutase and malondialdehyde in splenic homogenate did not change significantly in 2 months. The histopathologic examination showed no observable sign of damage in spleen; however, the accumulated S-MWCNTs gradually transferred from the red pulp to the white pulp over the exposure time and might initiate the adaptive immune response of spleen.

Uniform bionanomultilayer constructed with soluble multiwall carbon nanotubes and its application as biosensor

A uniform bionanomultilayer constructed with soluble multiwall carbon nanotubes (MWNTs) was developed. The excellent solubility of MWNTs in aqueous solutions was achieved for the first time simply through the function of barbiturates without having recourse to surfactant or polymer. The soluble MWNTs were selected to construct the bionanomultilayer of MWNTs and horseradish peroxidase (MWNTs/HRP) n via layer-by-layer assembly. UV–vis spectra, scanning electron microscopy, Raman spectra and atomic force microscopy reveal the uniform assembly process and the homogeneity of the developed bionanomultilayer. The bionanomultilayer biosensor can be successfully applied to detect hydrogen peroxide, which presented a linear response for hydrogen peroxide from 0.4 to 12.0 μM with a detection limit of 0.08 μM. The MWNTs in the biosensor provided a suitable microenvironment to retain HRP activity and acted as a transducer for improving the electron transfer and amplifying the electrochemical signal of the product of the enzymatic reaction. So the developed bionanomultilayer biosensor exhibited a fast, sensitive and stable response.

A green route to water soluble carbon nanotubes and in situ loading of silvernanoparticles

A green approach has been developed to synthesize water soluble multi-walled carbonnanotubes (MWNTs). Ag nanoparticles have been loaded on the as-synthesized MWNTsvia the in situ solution method. The strategy is based on the introduction of hydroxyl andcarboxyl groups through a mild modification of MWNTs via polycondensation ofcitric acid and D-sorbitol, improving the water solubility of MWNTs, giving riseto preferred sites of Ag nucleation, and providing mild in situ reducing agents.The modification of MWNTs and loading of Ag nanoparticles on MWNTs weredemonstrated by Fourier transform infrared spectroscopy, thermogravimetricanalysis, transmission electron microscopy, and scanning electron microscopy.

Bio-effects of water soluble taurine multi-wall carbon nanotubes on lungs of mice

To track the translocation of water soluble taurine multi-wall carbon nanotubes (14C-tau-MWCNTs) in lungs of the Kunming mice and evaluate the acute lung toxicity of intratracheally instilled tau-MWCNTs in Kunming mice. Healthy adult Kunming mice were randomly grouped by their body weight (5 mice in each group). The lungs of mice were intratracheally instilled with 0.125, 0.25, 0.5 and 1 mg/kg of water soluble tau-MWCNTs and phosphate-buffered saline (PBS) as negative control. After exposure of 1, 7, 14 and 28 days, the blood and lung tissue were collected. Blood were assessed by using biochemical biomarkers of alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and angiotensin converting enzyme (ACE). Lung tissues were assessed by histopathology. The intratracheal instillation of 14C-tau-MWCNTs was conducted in the same way, after 1, 3, 7, 14, 21, 28 days, 14C-activity of the samples was counted in several organs, tissues, blood and feces etc. 14C-activities were detected only in lungs, and with the exposure time proceeding the radioactivity descending from (80 +/- 7.7)% of the 1st day to (22 +/- 6.9)% of the 28th day. Activity of all groups of ALP and LDH went to the highest level on the 7th day postexposure, and back to the control level on the 28th day post-exposure, but LDH of 1 mg/kg group[(14.18 +/- 1.70) micromol x s(-1) x L(-1)] was still higher than that of control [(10.95 +/- 3.51) micromol x s(-1) x L(-1)] after 28 days' exposure. There was no significant changes observed in the activity of ACE. Histopathology found that lungs of all groups presented significant increase in pulmonary inflammation, lung cell proliferation. Many tau-MWCNTs were clearly found in some alveolar macrophages and bronchial epithelial cells. Intratracheal instillation of water soluble tau-MWCNTs could induce slight bio-effects on lungs of Kunming mice.

Highly Functionalized and Soluble Multiwalled Carbon Nanotubes by Reductive Alkylation and Arylation: The Billups Reaction

Single-walled carbon nanotubes (SWNTs) have been directly sidewall functionalized with a variety of organic addends, which renders them organic soluble or water soluble, depending on the precise functionalities used. However, multiwalled carbon nanotubes (MWNTs) are generally less reactive toward organic group functionalizations. Here, we demonstrate the formation of heavily functionalized MWNTs using the Billups reaction, which is a method of reductive alkylation or arylation (using lithium or sodium) of nanotubes in liquid ammonia. The resulting functionalized MWNTs can be soluble in either water or organic solvents. Raman spectroscopy and high-resolution transmission electron microscopy verify the high degrees of sidewall addends on the MWNTs. Making MWNTs soluble can be critical for efficient composite applications.

Broadband optical limiting performance of polymer-wrapped carbon nanotubes in the orange-NIR region

Soluble multi-walled carbon nanotubes (MWNTs) have been obtained by noncovalent modification with poly [2-methoxy,5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV). For the composite MWNT/MEH-PPV, there is π–π interaction between the MEH-PPV and MWNTs in addition to the wrapping of the polymer. The nonlinear optical transmittance was measured using a nanosecond optical parametric oscillator pumped with a Nd:YAG system. Excellent optical limiting performance of the composite MWNT/MEH-PPV was observed both in the visible region of 590–680 nm and at the wavelength of 1064 nm. By means of time-correlated single-photon counting fluorescence measurement, an explanation based on the nonlinear absorption of MWNT dominated by the intermolecular energy transfer was proposed.

Water soluble multi-walled carbon nanotubes prepared via nitroxide-mediated radical polymerization

Nitroxide-mediated radical polymerizations of 4-vinylpyridine and sodium 4-styrenesulfonate were carried out on the surfaces of MWNT to afford poly(4-vinylpyridine)-grafted MWNT (MWNT-P4VP) and poly(sodium 4-styrenesulfonate)-grafted MWNT (MWNT-PSS). The covalent bonding of polymers to the MWNT surface was confirmed by IR and TGA investigations. SEM, TEM and AFM investigations also showed a polymer-wrapped MWNT structure. Due to the presence of basic pyridine units in the structures, MWNT-P4VP exhibited good solubility in acidic aqueous solutions, but tended to aggregate in neutral or basic solutions. In comparison, MWNT-PSS could form stable dispersion solutions in aqueous solutions throughout the pH range from 1 to 14.