In vivo adsorption study of fluoxetine using carbon materials

The in vivo adsorption of fluoxetine by a commercial activated carbon and a laboratory prepared activated carbon fibre were studied. The results show that the carbon materials tested are not toxic to Wistar rats and both materials had a high efficacy in the in vivo adsorption of fluoxetine preventing toxicity of the drug overdose administered to the animals.     

In situ synthesis and characterization of poly(2,5-benzoxazole)/multiwalled carbon nanotubes composites

This article reports the synthesis of poly(2,5-benzoxazole)/multiwalled carbon nanotubes (ABPBO/MWNT) composites by in situ polycondensation and their chemical and physical properties. The functional groups yielded from the surface modification of MWNTs by hydrochloric acids have been demonstrated to participate in the polymerization and thus led to the composites with homogenous dispersion of carbon nanotubes. The chemical structures and morphology of the afforded polymer composites have been fully characterized by FTIR, WAXD, UV-vis, TGA and SEM. The ABPBO/MWNT composites exhibit excellent thermal stability and greatly improved mechanical properties. The tensile modulus and tensile strength of the composites are 47% and 83%, respectively, higher than those of the polymer matrix. The dielectric constant of the composites is also significantly enhanced from 4 of the polymer matrix to 65 with the incorporation of 5 wt% MWNTs.     

In situ nitrogen enriched carbon for carbon dioxide capture

In situ nitrogen enriched carbon was synthesized from locally available low cost soybean as the proteinaceous source. The material was synthesized by chemical activation using zinc chloride followed by physical activation using CO₂. The surface area of synthesized nitrogen enriched carbon was found to be 811 m²/g which is comparable with commercially available activated carbon. The nitrogen enriched carbon was having a breakthrough adsorption capacity of 23 mg/g at 120 °C which was almost three times higher in comparison with the commercially available activated carbon for a gas mixture comprising 15% CO₂ balanced with helium. This high adsorption capacity was attributed to the presence of nitrogen group within the carbon matrix, which was estimated to be about 0.64% as determined using the Kjeldahl’s method. The presence of different nitrogen containing groups assisting the adsorption of CO₂ in the synthesized sample was also confirmed by infrared analysis. For checking the consistent performance of the synthesized carbon, multi-cycle adsorption-desorption studies were carried out at 30 and 75 °C in binary mixture of CO₂/N₂.     

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.     

In situ grafting of carboxylic acid-terminated hyperbranched poly(ether-ketone) to the surface of carbon nanotubes

Carboxylic acid-terminated hyperbranched poly(ether-ketone)s (HPEKs) were successfully grafted onto the surfaces of single-walled carbon nanotube (SWNT) and multi-walled carbon nanotube (MWNT) to afford HPEK-g-SWNT and HPEK-g-MWNT nanocomposites. They were prepared via in situ polymerization of 5-phenoxyisophthalic acid as an AB₂ monomer for the HPEK in the presence of SWNT or MWNT in polyphosphoric acid (PPA)/phosphorous pentoxide (P₂O₅) medium. The resultant nanocomposites were homogeneously dispersed in various common polar aprotic solvents as well as in concentrated ammonium hydroxide. The experimental results from Soxhlet extraction, solubility enhancement, elemental analysis (EA), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) provided clear evidences for grafting of hyperbranched polymers onto the surfaces of corresponding CNT's. Achieving enhanced solubility of CNT's in common organic solvents via the functionalization of CNT's is a key step for CNT's to be used in various application-specific purposes. The results could potentially envision to the area of CNT researches via the efficient introduction of three-dimensional globular dendritic macromolecules as increasing solubility, available multi-functionality, reactivity, processability, and also biocompatibility.     

In situ TEM studies of tribo-induced bonding modifications in near-frictionless carbon films

Direct in situ TEM evidence is presented for a mechanically-induced increase in sp² bond content in the tribolayers formed on near-frictionless carbon (NFC) films. An in situ TEM nanomanipulation holder is used to perform sliding experiments between a nano-sized tungsten probe and electron transparent NFC samples. Electron energy loss spectra (EELS) were acquired between sliding events to show an incremental increase in the 1s-π peak, suggesting that a graphitization-like process occurs which can lead to a change in the tribological performance of a variety of hard carbon films. Presently, this behavior is only observed for one of the two varieties of NFC, while supporting TEM imaging evidence is in qualitative agreement with macroscopic friction and wear behavior.     

In situ mass-suspension polymerisation

In situ mass-suspension polymerisation of MMA was carried out in a single reactor. The mass polymerisation was carried out in a gently agitated monomer layer of a two stratified layers of monomer and water in the reactor. The degree of conversion at which mass polymerisation changed to suspension polymerisation, by increasing the rate of agitation, was altered systematically. The polymer content of the monomer/polymer solution, formed during the mass polymerisation stage, significantly affected the evolution of the particle size distribution. Mass-suspension polymerisation was found to be more vulnerable to drop coalescence and process failure than conventional suspension polymerisation. The results indicate the importance of the transition stage in a typical suspension polymerisation during which the rate of polymerisation is very low and the adsorption of stabiliser on the surface of drops is completed. The polymer beads from the mass-suspension polymerisation had a very broad size distribution with a large contribution from satellite particles.     

In situ ATR-FT-IR study of the thermal decomposition of diethyl peroxydicarbonate in supercritical carbon dioxide

The thermal decomposition of the organic free-radical initiator, diethyl peroxydicarbonate (DEPDC), was monitored by in situ ATR-FT-IR in heptane, and in the green solvent supercritical carbon dioxide (scCO₂) both with and without supercritical ethylene. It was observed that the characteristic peaks of DEPDC at 1802-1803 and 1194-1203 cm⁻¹ decreased significantly upon heating corresponding to the decomposition of DEPDC, while two new intense peaks simultaneously appeared at 1747 and 1262 cm⁻¹ in heptane, and similarly at 1756 and 1250 cm⁻¹ in scCO₂. The changes in the absorbance intensity of the characteristic peaks of the initiator during the decomposition were used for the measurement of the decomposition rate constant (k_d) of DEPDC. It was found that the thermal decomposition of DEPDC at low concentration in either heptane under atmospheric N₂ or scCO₂ under high pressure was via the first-order kinetics of unimolecular decomposition. The activation energy of the thermal decomposition of DEPDC was found to be 115 kJ/mol in heptane from 40 to 74 °C and 118 kJ/mol in scCO₂ from 40 to 60 °C. These new peaks revealed the formation of carboxyl groups contained in the decomposed products, indicating incomplete decarboxylation. During removal of CO₂ after the reaction in scCO₂, the instable intermediate monoethyl carbonate was decarboxylated and converted into the major end product, ethanol.     

Coating carbon nanotubes with a polystyrene-based polymer protects against pulmonary toxicity

Background

Multi-walled carbon nanotubes (MWCNTs) are widely used in many disciplines due to their unique physical and chemical properties. Therefore, some concerns about the possible human health and environmental impacts of manufactured MWCNTs are rising. We hypothesized that instillation of MWCNTs impairs pulmonary function in C57BL/6 mice due to development of lung inflammation and fibrosis.

Methods

MWCNTs were administered to C57BL/6 mice by oropharyngeal aspiration (1, 2, and 4 mg/kg) and we assessed lung inflammation and fibrosis by inflammatory cell infiltration, collagen content, and histological assessment. Pulmonary function was assessed using a FlexiVent system and levels of Ccl3, Ccl11, Mmp13 and IL-33 were measured by RT-PCR and ELISA.

Results

Mice administered MWCNTs exhibited increased inflammatory cell infiltration, collagen deposition and granuloma formation in lung tissue, which correlated with impaired pulmonary function as assessed by increased resistance, tissue damping, and decreased lung compliance. Pulmonary exposure to MWCNTs induced an inflammatory signature marked by cytokine (IL-33), chemokine (Ccl3 and Ccl11), and protease production (Mmp13) that promoted the inflammatory and fibrotic changes observed within the lung.

Conclusions

These results further highlight the potential adverse health effects that may occur following MWCNT exposure and therefore we suggest these materials may pose a significant risk leading to impaired lung function following environmental and occupational exposures.     

Coating carbon nanotubes with a polystyrene-based polymer protects against pulmonary toxicity

Background  

carbon nanotubes (CNT) can have adverse effects on health. Therefore, minimizing the risk associated with CNT exposure is of crucial importance. The aim of this work was to evaluate if coating multi-walled CNT (MWCNT) with polymers could modify their toxicity, thus representing a useful strategy to decrease adverse health effects of CNT. We used industrially-produced MWCNT uncoated (NT1) or coated (50/50 wt%) with acid-based (NT2) or polystyrene-based (NT3) polymer, and exposed murine macrophages (RAW 264.7 cell line) or Balb/c mice by intratracheal administration. Biological experiments were performed both in vitro and in vivo, examining time- and dose-dependent effects of CNT, in terms of cytotoxicity, expression of genes and proteins related to oxidative stress, inflammation and tissue remodeling, cell and lung tissue morphology (optical and transmission electron microscopy), and bronchoalveolar lavage fluid content analysis.     

Formation of graphitic rods in carbon/carbon composites reinforced with carbon nanotubes

The formation of graphitic rods with a carbon nanotube (CNT) in the center was observed in CNT-reinforced phenolic resin-based carbon/carbon composites heat treated at 2000 °C. TEM characterization indicated that the carbon surrounding the CNT has a much better degree of graphitization compared to the carbon in most of the matrix. The formation temperature (2000 °C) of the graphitic rod is lower than for stress graphitization and normal graphitization of phenolic resin.     

Fabrication of carbon nanotubes/polypyrrole/carbon nanotubes/melamine foam for supercapacitor

The carbon nanotubes (CNTs) have been loaded on the melamine foam (MF) to form the composite (CNTs/MF) by dip‐dry process, then polypyrrole (PPy) is coated on CNTs/MF (PPy/CNTs/MF) through chemical oxidation polymerization by using FeCl₃·6H₂O adsorbed on CNTs/MF as oxidant to polymerize the pyrrole vapor. Finally, CNTs are coated on the surface of PPy/CNTs/MF to increase the conductivity of the composite (CNTs/PPy/CNTs/MF) by dip‐dry process again. The composites have been characterized by X‐ray diffraction spectroscopy, scanning electron microscopy and electrochemical method. The results show that the structure of the composites has obvious influence on their capacitive properties. According to the galvanostatic charge/discharge test, the specific capacitance of CNTs/PPy/CNTs/MF is about 184 F g^?1 based on the total mass of the composite and 262 F g^?1 based on the mass of PPy (70.2 wt % in the composite) at the current density of 0.4 A g^?1, which is higher than that of PPy/CNTs/MF (120 F g^?1 based on the total mass of the composite and 167 F g^?1 based on the mass of the PPy). Furthermore, the capacitor assembled by CNTs/PPy/CNTs/MF shows excellent cyclic stability. The capacitance of the cell assembled by CNTs/PPy/CNTs/MF retains 96.3% over 450 scan cycles at scan rate of 20 mV s^?1, which is larger than that assembled by CNTs/PPy/MF (72.5%). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39779.     

Nebulization of single-walled carbon nanotubes for respiratory toxicity studies

An ultrafine aerosol consisting of airborne single-walled carbon nanotubes (SWCNTs) was produced by nebulizing functionalized SWCNTs in methanol. Prior to atomization, purified SWCNTs were functionalized with aryl sulfonate groups via a Birch reaction. The functionalized SWCNTs were then dispersed in methanol and nebulized using a TSI-3076 constant output atomizer. Atomic force microscopy of a mica plate placed in the flow revealed both individual and bundled SWCNTs. We anticipate that this method for producing ultrafine mists of SWCNTs will enable respiratory toxicity studies of inhaled ultrafine SWCNT particulate.     

Nitrogen-doped carbon nanotubes synthesized with carbon nanotubes as catalyst

Nitrogen-doped carbon (CN_x) nanotubes were synthesized with carbon nanotubes (CNTs) as catalyst by detonation-assisted chemical vapor deposition. CN_x nanotubes exhibited compartmentalized bamboo-like structure. Electron energy loss spectroscopy and elemental mapping studies indicated that the synthesized tubes contained high concentration of nitrogen (ca. 17.3 at.%), inhomogeneously distributed with an enrichment of nitrogen within the compartments. X-ray photoelectron spectroscopy analysis revealed the presence of pyridine-like N and graphitic N incorporated into the graphitic network. The catalytic activity of CNTs for CN_x nanotube growth was ascribed to the nanocurvature and opening edges of CNT tips, which adsorbed C_n/CN species and assembled them into CN_x nanotubes.     

Quartz-crystal microbalance for in situ monitoring of laser cleaning of carbon nanotubes

Photochemical changes of single-walled carbon nanotubes, graphite and amorphous carbon have been investigated with a quartz-crystal microbalance (QCM). The method of in situ measurements reduces our uncertainty that is attributable to environmental variables, such as relative humidity and temperature. At 248 nm, near the resonance of the π-plasmon we expect the interaction of laser light and carbon nanotube material to exhibit relatively high absorptivity. We discuss the importance of the single-walled carbon nanotube surface plasmon in the reduction of carbon impurities. The QCM is a means to quantify laser damage with respect to irradiance, pulse width and exposure time.     

Microstructures and mechanical properties of carbon/carbon composites reinforced with carbon nanofibers/nanotubes produced in situ

Using ferrocene as catalyst and toluene as the liquid precursor, carbon/carbon (C/C) composites were prepared by chemical liquid-vapor infiltration at 850-1100 °C. The microstructures and properties of C/C composites obtained with different ferrocene contents were studied. The results show smooth laminar and isotropic pyrocarbon are obtained after adding ferrocene to the precursor. Carbon nanofibers can be formed as the catalyst content is 0.3-1 wt.%. When the ferrocene content is 2 wt.%, multi-walled carbon nanotubes with the diameter about 20-90 nm are obtained together with carbon-encapsulated iron nanoparticles. After adding ferrocene to the precursor, the fracture modes of the composites change from brittle facture to tough fracture. The flexural strength of the composites is a maximum for 0.3 wt.% ferrocene in the precursor, higher than for ferrocene contents of 0, 0.5, 1 and 2 wt.%. The flexural modulus of the composites decreases after adding ferrocene to the precursor.     

In situ observation of dynamic elastic modulus in polypyrrole actuators

Polypyrrole is a leading conducting polymer actuator, but the factors that influence its performance when actuated under load in devices (such as the polymer stiffness) are not yet fully understood. To this end, we have probed the dynamic elastic modulus of polypyrrole in situ during actuation in a variety of electrolytes. As part of this study, we demonstrate that the electroactive response in dilute 1-butyl-3-methylimidazolium hexafluorophosphate can be changed from cation- to anion-dominated by adjusting the applied potential waveform. We observe that when conservative electrochemical conditions are applied in order to avoid dual ion movement or significant transfer of neutral solvent, the stiffness is determined by level of counterion swelling. The elastic modulus decreases during the net influx of ions into the bulk polymer and increases as these ions are expelled, regardless of whether the electroactive response is cation- or anion-dominated or whether there is a neutral solvent present in the electrolyte. This effect is quite significant, and we have observed up to a 3× increase in elastic modulus upon actuation in neat 1-butyl-3-methylimidazolium hexafluorophosphate.     

In situ high-temperature phase transformation studies on pyrite

Oil shales and coal have considerable amount of pyrite which undergoes various thermal transformations during their processing or combustion. Reactions and changes in pyrite chemistry vary considerably under different environmental conditions. In this paper, we report an in situ high-temperature X-ray diffraction study of phase transformations in pyrite under variable environmental conditions (atmospheric pressure (1 atm.), low air pressure (<0.001 atm.), inert and carbon dioxide atmosphere). We observe that while heating of pyrite in air promotes the formation of hematite (α-Fe₂O₃), magnetite (Fe₃O₄) is a major product in low pressure environment. On the other hand, in the inert environments (nitrogen and argon) pyrrhotite, a non-stoichiometric iron sulphide, is the most dominant product. However, in carbon dioxide (CO₂) environment, pyrrhotite is an intermediate low temperature product which further transforms into magnetite and hematite, attributed to the dissociation of the CO₂ into O₂ and CO providing conducive conditions for the oxidation. We also propose the possible reaction pathways including self-dissociation of CO₂.     

Studies on toxicity of multi-walled carbon nanotubes on suspension rice cells

Possible toxic effects of multi-walled carbon nanotubes (MWCNTs) on plant cells were investigated. Suspension rice cells (Oryza sativa L.) were cultured with MWCNTs; reactive oxygen species (ROS) increased and cell viability decreased were observed. When ascorbic acid, a primary antioxidant, was introduced into the culture suspension, the ROS content decreased and cell viability increased. Transmission electron microscopy revealed individual tubes in contact with the cell walls. The suspension rice cells with individual MWCNTs at their cell wall seemed to undergo a hypersensitive response, namely the ROS defense response cascade, which is sufficient to prevent microbial pathogens from completing their life cycle.     

Post-spinning modification of electrospun nanofiber nanocomposite from Bombyx mori silk and carbon nanotubes

Electrospinning is an effective procedure for fabricating submicron to nanoscale fibers from synthetic polymer as well as natural proteins. We successfully electrospun regenerated silk protein from cocoons of Bombyx mori to produce random as well as aligned fibers with diameter less than 100 nm. The fibers were characterized using field emission environmental scanning electron microscope (ESEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and wide angle X-ray diffraction (WAXD) studies. Post-spinning treatment with methanol and/or stretching and co-electrospinning with single walled carbon nanotubes (CNT) were carried out to alter the strength, toughness, crystallinity and conductivity of silk nanofibers. Addition of just 1% CNT along with post-spinning treatments resulted in 7-fold increase in the strength and 35-fold increase in the modulus of silk nanofibers. Raman spectroscopy confirmed that CNTs were incorporated in the silk fibers. FT-IR spectroscopy and WAXD studies proved that silk-CNT nanofibers had more crystallinity compared to silk nanofibers without CNT. Four-probe method demonstrated that silk-CNT nanofibers had 4 times higher electrical conductivity compared to silk nanofibers without CNT.