Pristine Multi-walled Carbon Nanotubes Research Articles

RUBBER NANOCOMPOSITES REINFORCED WITH SINGLE-WALL AND MULTIWALL CARBON NANOTUBES FOR INDUSTRIAL APPLICATIONS

ABSTRACT Nanofillers of type carbon nanotubes (CNTs) were investigated as reinforcing agents in silicone rubber matrix. Two types of CNT, namely, single-wall CNTs (SWCNTs) and multiwall CNTs (MWCNTs), were tested as reinforcing agents in rubber matrix. These CNTs were characterized with different purity, morphology, and sonication treatment (MWCNTs). Rubber nanocomposites were prepared by mixing room temperature vulcanized (RTV) silicone rubber with CNTs. At a filler loading of 3 phr, the modulus increased by 190% for specimens with MWCNTs and 150% for specimens filled with SWCNTs. Sonication was used to de-bundle the MWCNT aggregates into individual particles and to improve filler dispersion in the rubber matrix. The resistance of the MWCNTs was almost 750 times lower than that of the SWCNTs at 3 phr. The sonicated MWCNTs (2.2 kΩ) show lower electrical resistance than the pristine MWCNTs (3 kΩ) at 2 phr. These improvements could be useful for new devices such as flexible electrodes or actuators.

Adsorption study of bovine serum albumin onto multiwalled carbon nanotubes

Carbon nanotubes (CNTs) exhibit interesting physical and chemical properties that are useful for biomedical applications. In this work, the adsorption of bovine serum albumin by multi-walled carbon nanotubes modified with mixed H2SO4/HNO3 was investigated. The minimum time to reach adsorption equilibrium was determined to be 6 h for pristine MWCNTs and for MWCNTs with a modified surface. The maximum adsorption capacities of BSA on the pristine and treated MWCNTs were 532.56 and 771.87 mg/g, respectively. Both the Langmuir and Freundlich isotherms were well fitted to the adsorption data and could best describe the behavior of the adsorption process. The modified surface of the MWCNTs exhibited higher absorbability than the pristine MWCNTs because the modified MWCNTs possessed a greater surface area and large amounts of oxygen-containing functional groups. Moreover, the release characteristics of BSA with MWCNTs exhibited a relatively rapid initial release phase, followed by a phase involving a sustained release. The study could be used for prolonged drug release model in medical applications.

Parametric Optimization of Surface Roughness and Delamination Damage in End Milling Operation of GFRP Laminate Modified With MWCNT

Abstract In the present investigation, milling operation is carried out on pristine woven GFRP and MWCNT loaded GFRP laminates. The experiments were performed by changing the parameters like depth of cut, spindle speed and feed rate to optimize the machining output. Feed rate and spindle speed were changed in the range of 40 – 100 mm/min and 1000 - 2000 rpm respectively while the depth of slot was varied in the range of 0.5 – 1.5 mm using 4-flute solid carbide end milling tool of 6 mm diameter on a vertical milling machine. Experiments are executed according to orthogonal array of taguchi design and Response table shows the involvement of process parameters on performances. Experimental result shows that the inclusion of MWCNT in GFRP lead to the better surface finish and less delamination damage factor compare to plain GFRP laminates. It was also found that surface quality improves at high spindle speed and low feed rate for both the specimens. Optical microscopy and FESEM were applied to study about extent of delamination, fiber pull-out, micro-cracking and surface finish for both GFRP and MWCNT doped GFRP laminate. FESEM image shows good surface finish and less machining defect at optimal parameter combination for both plain GFRP and MWCNT doped GFRP laminates

Straightforward preparation of highly loaded MWCNT-polyamine hybrids and their application in catalysis.

Multiwalled carbon nanotubes (MWCNTs) were easily and efficiently functionalised with highly cross-linked polyamines. The radical polymerisation of two bis-vinylimidazolium salts in the presence of pristine MWCNTs and azobisisobutyronitrile (AIBN) as a radical initiator led to the formation of materials with a high functionalisation degree. The subsequent treatment with sodium borohydride gave rise to the reduction of imidazolium moieties with the concomitant formation of secondary and tertiary amino groups. The obtained materials were characterised by thermogravimetric analysis (TGA), elemental analysis, solid state 13C-NMR, Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), potentiometric titration, and temperature programmed desorption of carbon dioxide (CO2-TPD). One of the prepared materials was tested as a heterogeneous base catalyst in C–C bond forming reactions such as the Knoevenagel condensation and Henry reaction. Furthermore, two examples concerning a sequential one-pot approach involving two consecutive reactions, namely Knoevenagel and Michael reactions, were reported.

High catalytic performance of laccase wired to naphthylated multiwall carbon nanotubes

The direct electrical connection of laccase on the electrode surface is a key feature in the design of efficient and stable biocathodes. However, laccase can perform a direct electron transfer only when it is in the preferred orientation toward the electrode. Here we report the investigation of the orientation of laccase from white rot fungus on multi-walled carbon nanotube surface modified with a naphthalene group. Naphthylated multi wall carbon nanotubes were synthesized and the kinetics of laccase from white rot fungus adsorption and its direct electro-catalytic activity toward oxygen reduction was investigated by QCM and electrochemical techniques. Compared to pristine multi-walled carbon nanotubes laccase shows a high affinity to be adsorbed onto the surface of naphthylated carbon nanotubes at a very fast rate. The subsequent wiring to the naphthylated multi-walled carbon nanotubes is accompanied by a reorientation and arrangement of adsorbed laccase to create a composite biocathode that exhibits a high-performance for oxygen reduction by direct electron transfer with maximum current densities of 3 mA cm−2.

Effect and mechanism analysis of functionalized multi-walled carbon nanotubes (MWCNTs) on C-S-H gel

The effect and the interaction mechanism of functionalized multi-walled carbon nanotubes (MWCNTs) on C-S-H gel were studied in this paper. Fourier infrared spectroscopy, acid-base titration, Raman spectroscopy and transmission electron microscopy were utilized to analyze the pristine MWCNTs and functionalized MWCNTs, showing that the degree of graphitization of the functionalized MWCNTs reduced. And the surface of the functionalized MWCNTs was grafted with acidic functions which the content was 2.5 × 10−3 mol/g. Afterward, the MWCNTs/C-S-H composite was prepared by well-dispersing the functionalized MWCNTs and the C-S-H. The experimental results showed that for the C-S-H produced with different designed molar ratios of CaO to nanosilica (C/SD), the measured molar ratio of Ca to Si (C/SM) of the C-S-H decreased and the interlayer spacing of the C-S-H increased with the increase of the amount of the functionalized MWCNTs. When C/SD = 0.8, the polymerization degree of the C-S-H decreased and the proportion of the capillary pores increased gradually with increasing the amount of the functionalized MWCNTs. When the values of C/SD were 1.5 and 2.0, the trends the polymerization degree and the proportion of the capillary pores of C-S-H were opposite to those of C/SD = 0.8. The reasons were further analyzed based upon the above experimental results.

Hydrogen bonds leading nanodiamonds performing different thermal conductance enhancement in different MWCNTs epoxy-based nanocomposites

The lack of thermal conductance (TC) remains to be a challenge for epoxy resin. Fortunately, the thermal conductance of epoxy resin can be effectively improved by filler incorporation. Recently, compositing epoxy resin with hybrid filler system has been the direction for the development of next-generation thermal conductive functional materials. In this paper, epoxy-based nanocomposites containing nanodiamonds (DNDs)/pristine multi-walled carbon nanotubes (p-MWCNTs) and DNDs/KH550 functionalized MWCNTs (MWCNTs-KH) as the hybrid filler system were prepared respectively, and the thermal conductance of the nanocomposites was compared. The addition of DNDs was found to play a dominating role in the MWCNTs-KH filler systems (0.2 g, from 0.30 W/mK to 0.34 W/mK), but hardly has any effect on the p-MWCNTs filler system (0.2 g, from 0.24 to 0.26 W/mK only). Furthermore, the TC of the DNDs/MWCNTs-KH (2 g) epoxy-based nanocomposite increased to 0.45 W/mK, displaying an enhancement of 114.2 %. A shift of 5 cm-1 recorded by FTIR and the shift of CO revealed by XPS for DNDs/MWCNTs-KH strongly confirmed the existence of hydrogen bonds. Associating with the characterization results of SEM, TEM and dispersion qualitative experiment, the significant improvement in the TC of DNDs/MWCNTs-KH (2 g) epoxy-based nanocomposite was attributed to the hydrogen bond attachment between DNDs and MWCNTs-KH. The mechanism is that the attachment improves the dispersion of the fillers in epoxy, leading to the formation of a more effective thermal conductive network, thus, the enhanced TC. This work may inspire future studies in hybrid filler recognition and self-assemble technology via hydrogen bonds.

Enhanced tribological performance of alumina composites reinforced with acid-treated carbon nanotubes under water lubrication

Alumina composites reinforced with acid-treated multiwalled carbon nanotubes (MWCNTs) are prepared, and the tribological properties of the composite are investigated under water-lubricated conditions using a ball-on-disk technique against an alumina ball. The coefficient of friction (COF) in the steady-state region of the composite with acid-treated MWCNTs is found to be 0.06, which is 32–37% lower than that of the monolithic alumina and the composite with pristine MWCNTs. Microstructural observations and in-depth Raman spectroscopy analyses of the disk samples and counterparts before and after the friction tests reveal that the MWCNTs located in pits on the disk surface pull-out and that the resultant MWCNT fragments adhere to the friction surface of the counterparts. The enhanced tribological performance shown in the composite with acid-treated MWCNTs is mainly because the negatively charged functional groups adsorbed on the MWCNTs participate in the hydrogen-bond network of the hydrodynamic lubrication film and lead to acceleration of the transformation from a boundary lubrication regime to a mixed lubrication regime.

Electrodeposition of Sn and Sn Composites with Carbon Materials Using Choline Chloride-Based Ionic Liquids

Nano carbons, such as graphene and carbon nanotubes, show very interesting electrochemical properties and are becoming a focus of interest in many areas, including electrodeposition of carbon–metal composites for battery application. The aim of this study was to incorporate carbon materials (namely oxidized multi-walled carbon nanotubes (ox-MWCNT), pristine multi-walled carbon nanotubes (P-MWCNT), and reduced graphene oxide (rGO)) into a metallic tin matrix. Formation of the carbon–tin composite materials was achieved by electrodeposition from a choline chloride-based ionic solvent. The different structures and treatments of the carbon materials will create metallic composites with different characteristics. The electrochemical characterization of Sn and Sn composites was performed using chronoamperometry, potentiometry, electrochemical impedance, and cyclic voltammetry. The initial growth stages of Sn and Sn composites were characterized by a glassy-carbon (GC) electrode surface. Nucleation studies were carried out, and the effect of the carbon materials was characterized using the Scharifker and Hills (SH) and Scharifker and Mostany (SM) models. Through a non-linear fitting method, it was shown that the nucleation of Sn and Sn composites on a GC surface occurred through a 3D instantaneous process with growth controlled by diffusion. According to Raman and XRD analysis, carbon materials were successfully incorporated at the Sn matrix. AFM and SEM images showed that the carbon incorporation influences the coverage of the surface as well as the size and shape of the agglomerate. From the analysis of the corrosion tests, it is possible to say that Sn-composite films exhibit a comparable or slightly better corrosion performance as compared to pure Sn films.

Reinforcing Microwave Absorption Multiwalled Carbon Nanotube–Epoxy Composites Using Glass Fibers for Multifunctional Applications

Herein, the enhancement of the mechanical properties of microwave absorption composites, multiwalled carbon nanotubes (MWCNTs)–epoxy with various MWCNT loadings, using glass fiber (GF) reinforcement is focused upon. The tensile strength, morphologies, dielectric permittivity, and electromagnetic (EM) wave absorption properties (in a frequency range from 1 to 26 GHz) of the composites are investigated. The tensile strength of the composites is enhanced to about 400 MPa, which is comparable with that of commercial aluminum alloy 6061 (about 300 MPa), whereas the tensile strength of the pristine MWCNT–epoxy composite is around 15 MPa. The mass density of the MWCNT–epoxy–GF composites herein is found to be around 1.6 g cm−3, whereas aluminum alloy 6061 has a mass density of ≈2.7 g cm−3. In addition, the MWCNT (9 wt%)–epoxy–GF composite presents a strong EM wave absorption in a wide frequency band from 14 to 26 GHz, whereas aluminum alloys do not have much EM wave absorption. The high microwave absorption together with the enhanced mechanical strength of the composites provides a multifunctional potential for some applications.

Carbon based membranes with modified properties: thermal, morphological, mechanical and antimicrobial

Conjugation of biodegradable cellulose acetate (CA) with high-aspect-ratio carbon nanotubes may increase common properties as well as the specific antibacterial activity of the resulting nanocomposite. Hence, we developed nanocomposite membranes based on pristine-multiwalled carbon nanotubes (p-MWCNTs) and CA. Two air gaps (100 and 200 µm) of a film coating applicator were used for casting the solutions into glass plates, and the membrane precipitation was attained via nonsolvent induced phase separation. The thermal (TGA and DSC), morphological (SEM), and dynamical properties (DMA) of the nanocomposite membranes improved with the increasing content of p-MWCNTs in the nanocomposites. In addition, after 48 h contact there was a reduction of more than 70% and 80% of Staphylococcus aureus and Escherichia coli bacteria, respectively, due to the electrostatic repulsion between the negatively-charged CNTs-loaded nanochannels and the bacterial colonies, as explained by zero charge point measurements. Antibacterial testing confirmed the already discussed antifouling properties of the nanocomposite membranes compared to pristine CA membranes. Membrane performance analysis revealed a rejection of over 24% of E. coli, thus establishing the potential of these nanocomposites for applications in wastewater filtration and biofilm removal.

Experimental investigation of stability and thermal conductivity of phase change materials containing pristine and functionalized multi-walled carbon nanotubes

The biggest challenge in dispersion of nanoparticles in phase change materials (PCMs) is the physical stability of these particles in PCM. Numerous studies have evaluated the effect of different parameters on the stability of nanoparticles in PCM, but the effect of PCM polarity has rarely been investigated. In this study, the stability of functionalized and pristine multi-walled carbon nanotubes (MWCNTs) in three different PCMs with various polarity levels was investigated. The utilized PCMs were paraffin wax (nonpolar), stearic acid (partially polar), and polyethylene glycol (polar). Two different methods of functionalization of MWCNTs, with stearic acid and hexadecyl amine, were used to compare their stability in PCMs. The FTIR analysis and FESEM images reveal that the surface modification reactions were done thoroughly and MWCNTs are well dispersed in PCM. The results showed that pristine MWCNT is more stable in nonpolar PCMs (paraffin and stearic acid), while the samples containing functionalized MWCNT or surfactant had higher stability in polyethylene glycol. The three most stable samples were used to measure their thermal conductivity and heat release/storage capability. The addition of nanoparticles to all kinds of PCMs led to higher rate of heat storage and release. Moreover, the thermal conductivity of all PCMs improved by the introduction of nanoparticles. In both liquid and solid phases, nanoenhanced PCM had higher thermal conductivity compared to pure PCM with stearic acid containing 1 mass% of pristine MWCNT having the highest rate of enhancement at 16.82% for solid phase.

Ultrasonic assisted functionalization of MWCNT and synergistic electrocatalytic effect of nano-hydroxyapatite incorporated MWCNT-chitosan scaffolds for sensing of nitrofurantoin.

In the present work, we report the fabrication of stable composite of chitosan hydrogels (CHI) on multiwalled carbon nanotubes (MWCNT) using a simple ultrasonic-assisted method. Also, rod-like hydroxyapatite nanoparticles (HA NPs) were synthesised using a hydrothermal route and were incorporated into the highly conductive MWCNT-CHI scaffolds using an ultrasonication method. The functionalization of MWCNT and preparation of HA NPs on MWCNT-CHI nanocomposite were done using the sonication over the frequency of 37 kHz with the ultrasonic power capable of 150 W (Elmasonic Easy 60H bath sonicator). The resulting hybrid HA NPs/MWCNT-CHI nanocomposites have an excellent surface area and high surface to volume ratio, which leads to the sensitive detection of nitrofurantoin than pristine MWCNT and HA NPs. The complete elemental and morphological analyses of the HA NPs/MWCNT-CHI nanocomposites were characterised by XRD, FTIR, RAMAN, FESEM, TEM, EDX, and elemental mapping techniques. Electrochemical analysis of the HA NPs/MWCNT-CHI nanocomposites was carried out by cyclic voltammetry, electrochemical impedance spectroscopy and amperometry methods. The modified glassy carbon electrode (GCE) of HA NPs/MWCNT-CHI nanocomposites exhibit the nitrofurantoin detection activity at the linear range of 0.005-982.1 µM with the detection limit of 1.3 nM. The synergistic electrocatalytic activity of HA NPs/MWCNT-CHI nanocomposites modified GCE is correlated to the sensitivity of 0.16 µAµM-1 cm-2 with excellent precision and accuracy towards the sensing of nitrofurantoin.

Hemostatic Effect of Aminated Multiwalled Carbon Nanotubes/Oxidized Regenerated Cellulose Nanocomposites.

We have investigated the covalent conjugation of aminated multiwalled carbon nanotubes (MWCNTNH₂)s with Oxidized Regenerated Cellulose (ORC) in order to enhance the hemostatic effect. The MWCNT-NH₂s were prepared by functionalization of pristine MWCNTs (pMWCNTs) using amine groups. Neat ORC gauze and MWCNT-NH₂s were reacted using glutamic acid as cross linking bridge. We investigated an amination of pMWCNTs as well as the dispersion of MWCNT-NH₂s in the ORC gauze as matrix and their interfacial interactions by SEM and FT-IR. The results revealed that relatively strong interaction exists between aminated MWCNTs and the ORC macromolecules. The hydrophilicity test results in the significant increment of water uptake of MWCNT-NH₂s/ORC composites with increasing the concentration of MWCNT-NH₂s in composite. The in-vitro procoagulation test shows that the MWCNT-NH₂s/ORC gauzes have significant procoagulant activity. The hemostatic evaluation of MWCNT-NH₂s/ORC composites on rabbits shows that the aminated MWCNTs increase the rate of blood stopping and hence they decrease the blood loosing from injured sites. Hemostatic evaluation indicates that the MWCNT-NH₂s/ORC gauze has a valuable hemostatic performance. The products of platelets release reaction, activated platelets glycoprotein and activated clotting enzymes were increased simultaneously. The mechanism of the hemostasis for MWCNT-NH₂s/ORC gauze is discussed.

Covalent grafting of unfunctionalized pristine MWCNT with Nylon-6 by microwave assist in-situ polymerization

Covalent grafting of nylon-6 (Ny-6) and pristine multi-walled carbon nanotubes (MWCNT-P) was performed in-situ via microwave assist polymerization (MAP) of ε-caprolactam and 6-aminocaproic acid at different power and time conditions. The results showed that the microwave dielectric heating of the MWCNT-P activates the nanotube vacancies to react with the amine group of 6-aminocaproic acid at 175 °C. When the reaction temperature reaches 230 °C, Ny-6 polymerization ensues, simultaneously, with insertion of Ny-6 chains on the amine-activated MWCNT to obtain a nanohybrid, MWCNT-Ny, with a grafted Ny-6 coating of 14 nm. The hybridization reaction therein affects the entire polymerization process and the molecular weight and yield of both the hybrid and Ny-6. Raman, XPS and electrical conductivity data for the MWCNT-Ny films show that the nanotube structure remains intact in the films which display an electrical surface conductivity range of 0.47–0.06 S/m. The compatibility and dispersion of the MWCNT-Ny nanohybrid in Ny-6, as observed by crystallization and fusion of the so-formed hybrid polymer nanocomposite, HPNC, exceed those obtained by conventional methods of preparation using ultrasound and functionalized nanotubes.

The influence of treatment time on multi-walled carbon nanotubes functionalized by poly(ethylene glycol)

The paper reports an influence of treatment duration on the characteristics of multi-walled carbon nanotubes (MWCNTs) functionalised by poly(ethylene glycol) (PEG) for the first time. MWCNTs covalently functionalised with PEG (MWCNTs-PEG) are successfully prepared and characterised by several techniques including FE-SEM, EDX, Raman spectroscopy and TGA. The FE-SEM images show that an average tube diameter of the MWCNTs-PEG is increased by 21% in comparison to pristine MWCNTs. According to the TGA analysis and EDX measurements, the highest weight loss of 21.31 wt% and the highest ratio of oxygen to carbon (O/C) of 22.26 % are simultaneously achieved for the treatment time of 6 h. The results allow us to conclude that the optimum time to obtain the best functionalisation result is 6 h.

CO oxidation and the inhibition effects of carboxyl-modification and copper clusters on multi-walled carbon nanotubes

An inhibition of CO oxidation on catalytically active pristine multi-walled carbon nanotubes (MWCNT) in the presence of selected pollutant constituents in flue gas streams was studied. We simulated an interaction between the active MWCNT and the contaminants in CO oxidation atmosphere of: (i) an acidic wet flue gas environment modelled by using MWCNT grafted with carboxyl (COOH) groups; and (ii) a polluted environment formed by trace metal copper particles and other contaminant constituents (e.g. PAHs, VOCs and P) by using a copper cluster of chemical formulae [(PPh3)CuH]6·0.75THF as a model pollutant, doped on the MWCNT. The pristine, unmodified MWCNT were catalytically active from ∼150 °C, whilst the carboxyl-modified MWCNT behaved as an adsorbent of CO molecules without converting them into CO2. The copper cluster was found to have formed CuCO3 during the CO oxidation reaction at temperatures below 330 °C but decomposed above 400 °C to release CO2 product.

Mitsui-7, heat-treated, and nitrogen-doped multi-walled carbon nanotubes elicit genotoxicity in human lung epithelial cells

BackgroundThe unique physicochemical properties of multi-walled carbon nanotubes (MWCNT) have led to many industrial applications. Due to their low density and small size, MWCNT are easily aerosolized in the workplace making respiratory exposures likely in workers. The International Agency for Research on Cancer designated the pristine Mitsui-7 MWCNT (MWCNT-7) as a Group 2B carcinogen, but there was insufficient data to classify all other MWCNT. Previously, MWCNT exposed to high temperature (MWCNT-HT) or synthesized with nitrogen (MWCNT-ND) have been found to elicit attenuated toxicity; however, their genotoxic and carcinogenic potential are not known. Our aim was to measure the genotoxicity of MWCNT-7 compared to these two physicochemically-altered MWCNTs in human lung epithelial cells (BEAS-2B & SAEC).ResultsDose-dependent partitioning of individual nanotubes in the cell nuclei was observed for each MWCNT material and was greatest for MWCNT-7. Exposure to each MWCNT led to significantly increased mitotic aberrations with multi- and monopolar spindle morphologies and fragmented centrosomes. Quantitative analysis of the spindle pole demonstrated significantly increased centrosome fragmentation from 0.024–2.4 μg/mL of each MWCNT. Significant aneuploidy was measured in a dose-response from each MWCNT-7, HT, and ND; the highest dose of 24 μg/mL produced 67, 61, and 55%, respectively. Chromosome analysis demonstrated significantly increased centromere fragmentation and translocations from each MWCNT at each dose. Following 24 h of exposure to MWCNT-7, ND and/or HT in BEAS-2B a significant arrest in the G1/S phase in the cell cycle occurred, whereas the MWCNT-ND also induced a G2 arrest. Primary SAEC exposed for 24 h to each MWCNT elicited a significantly greater arrest in the G1 and G2 phases. However, SAEC arrested in the G1/S phase after 72 h of exposure. Lastly, a significant increase in clonal growth was observed one month after exposure to 0.024 μg/mL MWCNT-HT & ND.ConclusionsAlthough MWCNT-HT & ND cause a lower incidence of genotoxicity, all three MWCNTs cause the same type of mitotic and chromosomal disruptions. Chromosomal fragmentation and translocations have not been observed with other nanomaterials. Because in vitro genotoxicity is correlated with in vivo genotoxic response, these studies in primary human lung cells may predict the genotoxic potency in exposed human populations.

Characterization of functionalized multiwalled carbon nanotubes and comparison of their cellular toxicity between HEK 293 cells and zebra fish in vivo.

Carbon nanotubes (CNTs) hold tremendous potential due to their unique and modifiable properties. Their robust biological applications necessitate minimizing their cytotoxicity and increasing the solubilization. In the present manuscript, we have functionalized multiwalled carbon nanotubes (MWCNTs) using defect functionalization methodology to covalently bind carboxy and amino groups on their walls. This functionalization was reassured through fourier-transform infrared spectroscopy (FTIR), energy dispersive x-ray analysis (EDX), elemental and field emission scanning electron microscopy (FE-SEM) analysis. The observations demonstrated that addition of carboxy as well as amino groups on MWCNTs, besides enabling MWCNTs solubilization also significantly ameliorated the cytotoxicity and the oxidative stress in comparison to pristine MWCNTs. It is envisaged that changes in agglomeration of the functionalized MWCNTs and the acquired surface charge is the reason for the reduction of cytotoxicity. Zebra fish embryo model test system employed for in vivo analysis of the MWCNTs showed no significant toxicity on account of any nanoparticle tested pointing towards intrinsic mechanisms in place for deterring the damage in complex organisms. Overall, the observations besides pointing towards functionalized MWCNTs effectiveness towards weakening the toxicity of pristine MWCNTs also caution for extrapolating in vitro data to in vivo observations. The observations further lend credibility for exploiting the zebra fish as a model system for analyzing the effects of MWCNTs functionalization.

Biotransformation of Pristine and Oxidized Carbon Nanotubes by the White Rot Fungus Phanerochaete chrysosporium.

Carbon nanomaterials are widely studied and applied nowadays, with annual production increasing. After entering the environment, the complete degradation of these carbon nanomaterials by microorganisms is proposed as an effective approach for detoxification and remediation. In this study, we evaluated the degradation of pristine multiwalled carbon nanotubes (p-MWCNTs) and oxidized multiwalled carbon nanotubes (o-MWCNTs) by the white rot fungus Phanerochaete chrysosporium, which is a powerful decomposer in the carbon cycle and environmental remediation. Both p-MWCNTs and o-MWCNTs were partially oxidized by P. chrysosporium as indicated by the addition of oxygen atoms to the carbon skeleton in the forms of C=O and O–H bonds. The fungal oxidation led to the shortening of MWCNTs, where precipitated o-MWCNTs showed more short tubes. During the transformation, the defects on the tubes became detached from the carbon skeleton, resulting in decreases of the ID/IG (intensity of D-band/ intensity of G-band) values in Raman spectra. The transformation mechanism was attributed to the enzymatic degradation by laccase and manganese peroxidase excreted by P. chrysosporium. The results collectively indicated that MWCNTs could be transformed by P. chrysosporium, but complete degradation could not be achieved in a short time period. The implications on the environmental risks of carbon nanomaterials are discussed.