Treatment Of Single-walled Carbon Nanotubes Research Articles

Isoflavones-functionalized single-walled and multi-walled carbon nanotubes: Synthesis and characterization of new nanoarchitetonics for biomedical uses

In this work, we describe the functionalization of single-walled carbon nanotubes (SWCNTs) and multiple-walled carbon nanotubes (MWCNTs) with two selected isoflavones (biochanin A and formononetin), and compare the physicochemical properties of the obtained assemblies. The selection of isoflavones was based on the preliminary assessment of bibliometric maps generated from Scopus core collection. Acidic treatment of SWCNTs and MWCNTs improved the samples’ dispersibility in water. Regardless the pH environment, SWCNTs remained aggregated in aqueous solution, even after functionalization. The dispersibility of MWCNT increased after acidic treatment (MWCNTA) in both tested pH values (4 and 7). Functionalization was confirmed by the improved dispersibility of CNTs with both isoflavones. MWNCTA and isoflavone 1:1 (w/w) was used for both molecules. Biochanin A showed improved anchoring in MWNCTA when compared to formononetin. Our results corroborate the interest on the use of these new biomaterials based on carbon nanotubes for a range of biomedical applications.

Tapered Optical Fiber Sensor Coated with Single-Walled Carbon Nanotubes for Dye Sensing Application

The present study aimed to improve the optical sensing performance of tapered optical fiber sensors toward aqueous Rhodamine B solution of different concentrations by applying single-walled carbon nanotubes (SWCNTs). The functional coating was formed on the surface of the tapered optical fiber sensor using an aerosol layer-by-layer deposition method. Before deposition, the SWCNTs were processed with multistage liquid-phase treatment in order to form a stable dispersion. The effect of SWCNT treatment was investigated through Raman spectroscopy. The deposition of 220 layers caused a reduction of up to 60% of the initial optical power of radiation propagating through the optical fiber core. The optical fiber sensor coated with SWCNTs demonstrated significantly higher sensitivity compared to a non-coated sensor in the range of 2-32 mg/L of Rhodamine B concentration in an aqueous solution. The experimental results demonstrated that the sensitivity was increased 10 times from 32 (mg/L)-1, for the non-coated sensor, up to 317 (mg/L)-1 after SWCNT coating deposition. Moreover, the SWCNT-coated sensor demonstrated high repeatability that allowed for the evaluation of the concentration regardless of the previously analyzed dye concentration.

Exposure of carbon nanotubes affects testis and brain of common carp

Carbon nanotubes production has been rapidly increasing for many potential applications, however, the environmental impact of this nanomaterial needs to be comprehended. The present work focused on unraveling the effects of single-walled carbon nanotubes (SWCNT) in the common carp, Cyprinus carpio. The physicochemical properties of SWCNT were analyzed with X-ray diffraction, Fourier transforms infra-red, UV-Vis absorption, transmission electron microscopy (TEM), and Raman spectroscopy before testing for exposure impact. The effects of SWCNT, were investigated by exposing to two doses viz., 10 and 50 μg/L, for 7 days in adult common carp, in vivo. Expression of key steroidogenic and transcription factor genes related to testis and brain were downregulated after the treatment. The concomitant decreases in serum testosterone and 11-ketotestosterone levels revealed the impact of SWCNT after exposure. Further, SWCNT exposure induced antioxidant enzymes namely glutathione-S-transferases, superoxide dismutase, and catalase in both testis and brain. Concurrently, histological and TEM analysis of testis revealed structural disarray. In addition, SWCNT treatment, in testicular and brain primary cell cultures decreased cell viability with an increase of reactive oxygen species levels, leading to a significant elevation of apoptotic cells. In line with this, low mitochondrial membrane potential and DNA damage were also observed during post SWCNT treatment. Taken together, transient exposure of SWCNT causes toxic effects and alters testicular and brain function in the common carp. Thus, the discharge of carbon nanotubes poses a greater risk to the aquatic environment warranting regulatory measures.

Superwetting TiO2-decorated single-walled carbon nanotube composite membrane for highly efficient oil-in-water emulsion separation

With the advantages of one-dimensional hollow structure, high porosity and prominent mechanical strength, single-walled carbon nanotubes (SWCNTs) have been extensively utilized to improve conventional filtration membranes for oil/water separation. Their intrinsic hydrophobicity, however, adversely affects the anti-fouling performance of the SWCNT membrane. Herein, a super-hydrophilic and underwater super-oleophobic hierarchical modified membrane with enhanced permeability and anti-fouling property was fabricated using the vacuum-assisted filtration technique by synergistically assembling SWCNTs and titanium dioxide (TiO2) nanoparticles on a cellulose acetate membrane. Highly dispersed SWCNTs were obtained by carboxylating treatment of agglomerate SWCNTs. The controlled stacking of SWCNTs fibers and a controllable amount of TiO2 rendered a modified membrane with high porosity and hierarchical structure, leading to an ultrahigh water flux up to 4,777.07 L·m−2·h−1, and excellent separation performance with efficiency greater than 99.47%. Most importantly, the membrane exhibited excellent anti-fouling ability during ten cycles with the aid of the super-wetting property of TiO2 nanoparticles. The results indicated that coating TiO2 nanoparticles on SWCNTs modified the surface topography of the obtained SWCNT/TiO2 membrane, which improved hydrophilicity, permeability and anti-fouling property, manifesting attractive potential applications in oil/water separation.

Photo-sensing and photo-conversion investigation of single walled carbon nanotube-silicon interface: role of acid stimulation

Single walled carbon nanotubes (SWCNTs) are emerging as potential candidate in solar applications because of their remarkable structural, electrical and optical properties. In this work, we have reported simple and effective approach for the fabrication of SWCNTs/Si interface which play important role in photo-sensing and photo conversation applications. It is observed that, controlled acid treatment of SWCNTs at room temperature conditions proved helpful for the removal of amorphous carbon and significantly enhanced their photo-sensing response from 4% to 40%, respectively. In addition, it is found that open circuit voltage and current density of SWCNT/Si interface is become increased due to the presence of functional groups. However, Raman analysis also confirms that, acid stimulation significantly affect their crystalline structure. These results are important and compatible with the existing silicon technology without adopting any complex technique.

Effect of Liquid-Phase Oxidative Treatments on the Purity, Hydrophilicity, and Structure of Single-Wall Carbon Nanotubes and on the Electrical Conductivity of Their Arrays

A study using a set of physicochemical methods has shown that treatment of single-wall carbon nanotubes synthesized by the electric arc method with an aqueous solution of hydrogen peroxide (followed by treatment with hydrochloric acid) and with a mixture of concentrated nitric and sulfuric acids leads to a decrease in the content of inorganic impurities in the bulk of the finished materials. The acid oxidizing mixture shows the highest performance in the process, causing splitting of the bundles of single-wall carbon nanotubes into separate nanotubes and formation of stable concentrated suspensions of the nanotubes in water and in an isopropanol–water mixture. Both kinds of liquid-phase oxidative treatment enhance the electrical conductivity of the nanotube arrays and exert no pronounced selective effect on single-walled carbon nanotubes depending on the electronic conductivity of molecules of this material.

Influence of process conditions and effect of functionalization in inducing time dependent polymorphic states in single walled carbon nanotube incorporated poly(vinylidene fluoride)

Poly(vinylidene fluoride) (PVDF) based composites were prepared using the compatibilizing properties of optimally functionalized single walled carbon nanotubes (SWCNTs). Our previous studies revealed that acid treatment of SWCNTs for 4 h (FSWCNT-4) incorporates maximum concentration of –COOH functional groups on nanotube surface with least defects. Therefore, PVDF-SWCNT composites were prepared by dispersing FSWCNT-4 in PVDF through ultrasonication. Here time of ultrasonication controls the crystallization of the polymer either in the electroactive γ phase or in the non-electroactive α phase. γ polymorphic state is easily obtained with very low concentration of FSWCNT-4 followed by ultrasonication for just 5 min. The chemical composition of the composites is studied using X-ray photoelectron spectroscopy confirming the inclusion of nanotubes in PVDF. Computational analysis explained the role of ultrasonication in providing the required energy for the transformation from α phase to γ phase apart from establishing the favourable site of interaction of PVDF with FSWCNT-4. The micrographs of the composite showed scrolled lamellar features of γ phase morphology. PVDF-FSWCNT-4 composites showed 54% higher capacitance compared to its unfilled counterpart with significant improvement in mechanical properties due to stronger interactions between H atom with positive charge in PVDF and “O” atom with π orbital in FSWCNT-4.

Reaction kinetics and temperature effects in syngas photo-initiated chemical vapor deposition on single-walled carbon nanotubes

Photo-initiated chemical vapor deposition (PICVD) is a solvent-free process that can be used to produce thin films on a variety of substrates, with applications in fields ranging from biomedicine to optics and microelectronics. This study presents a kinetic analysis for this process using syngas (CO + H2) as a precursor for the surface treatment of single-walled carbon nanotubes (SWCNT) with average dimensions of 1.5 × 100 nm (diameter × length), and addresses the role of iron pentacarbonyl (Fe(CO)5), a photo-active contaminant found in CO. This work builds upon previously developed reaction schemes for PICVD, based mainly on surface characterizations, by coupling these analyses with gas-phase monitoring. This allows us to propose two separate reaction schemes for the gas and surface phase reactions and consider temperature effects. Online FTIR, offline GC-MS, and online GC characterized the gas phase, while for surface characterizations, XPS and TGA were used. Characterizations showed that a coating with a general formula of CnO3nFen was deposited, corresponding to 0.29 ± 0.04 mg carbon and 0.49 ± 0.03 mg iron on the SWCNT substrate over the course of treatment. The Fe(CO)5 was identified as the key reactant in syngas/PICVD reactions and was nearly completely consumed (94%). Mass balances derived from the gas phase characterization showed that Fe(CO)5 inputted to the plug flow reactor could potentially contribute all the amount of 0.49 ± 0.03 mg of Fe and 0.29 ± 0.04 mg of C to the coating on the SWCNT, indicating that syngas/PICVD can be optimized in the future to decrease gas throughput. Temperature did not show a significant effect in the case of PICVD. However, in the absence of ultraviolet light, its role becomes determinant, with rising temperatures causing more Fe deposition.

Adsorption of Plasma Proteins on Single-Walled Carbon Nanotubes Reduced Cytotoxicity and Modulated Neutrophil Activation.

Proteins in the bloodstream bind to carbon nanotubes (CNTs) through noncovalent interactions to form a protein corona, thereby effectively influencing the biological properties and blood biocompatibility of the CNTs. Here, we investigated the binding of common plasma proteins (i.e., human immunoglobulin G (IgG), human serum albumin (HSA), and fibrinogen (FG)) to carboxylated single-walled CNTs (SWCNTs), and evaluated the effects of these different protein coronas on cytotoxicity to endothelial cells and immune response to neutrophils in the bloodstream. Measurements of adsorption parameters revealed tight binding of proteins to SWCNTs, and the SWCNTs adsorption capacities followed the order FG > HSA > IgG. In addition, the basic residues (Arg, Lys, His) were found to play an important role in the formation of protein-SWCNTs corona complexes and determine their adsorption capacity. Consistent with the higher protein adsorption capacity, FG more significantly reduced the cytotoxicity of CNTs to human umbilical vein endothelial cells than the other two proteins. However, only treatment of SWCNTs with IgG resulted in the enhancement of CNT-induced myeloperoxidase (MPO) release (i.e., neutrophil activation) in neutrophils, while MPO-dependent degradation of CNTs induced less cytotoxicity than initial nanomaterials. Consistent with these effects of protein coronas, the presence of serum attenuated the cytotoxicity of CNTs and CNTs could induce neutrophil activation in human blood plasma. Our study demonstrates the ability of adsorbed plasma proteins to influence cytotoxicity and neutrophil response caused by CNTs in the bloodstream.

Investigation of Physicochemical and Electrochemical Properties of Single-Walled Carbon Nanotubes Modified with Nitrogen

Composites of the type “nitrogen-containing carbon coating – single-walled carbon nanotubes” were obtained by the treatment of single-walled carbon nanotubes (SWCNT) in a gaseous 40%NH3-1%C2H2-C2H4 mixture at temperatures 600–750 °C. Single-walled carbon nanotubes etched in aqua regia (SWCNTet) and doped with nitrogen (N-SWCNT) were studied by XPS, electron microscopy and IR spectroscopy. Various oxygen-containing functional groups were found to reside on the surface of initial SWCNTet. Upon treatment of SWCNTet in 40%NH3-1%С2Н2-C2H4, polymerization and condensation of hydrocarbons resulted in the formation of a thin nitrogen-containing carbon coating. Specific capacitance per a weight of initial and nitrogen-doped carbon nanotubes in an aqueous electrolyte with 1 M H2SO4 was measured. Specific capacitance of carbon electrodes was found to change symbately with the content of nitrogen-containing functional groups on the SWCNT surface.

Surface modification of single-walled carbon nanotubes by functional nitrogen-containing groups and study of their properties

Treatment of single-walled carbon nanotubes (SWCNT) in a gaseous 40%NH3–1%С2Н2–C2H4 mixture at 600 and 700°С led to “nitrogen-containing carbon coating–single-wall carbon nanotubes” composites. Single-walled carbon nanotubes after etching in aqua regia (SWCNTetch) and doped with nitrogen (N-SWCNT) were studied by XPS, electron microscopy, and IR spectroscopy. It was found that the initial SWCNTetch surface contains various oxygen-containing functional groups. Treatment of SWCNTetch in a 40%NH3–1%С2Н2–C2H4 mixture led to the formation of a thin carbon coating on the carbon nanotube surface due to polymerization and condensation of hydrocarbons. After treatment at 600°C, the formation of nitrogen-containing functional groups is insignificant; however, when the treatment temperature is increased to 700°C, the nitrogen content reaches 0.5 at % of the weight of the N-SWCNT sample.

Single-walled carbon nanotube: One specific inhibitor of cancer stem cells in osteosarcoma upon downregulation of the TGFβ1 signaling

Cancer stem cells (CSCs) are believed to have a critical role in tumorigenesis, metastasis, therapeutic resistance or recurrence. Therefore, strategies designed to specifically target and eliminate CSCs have become one of the most promising and desirable ways for tumor treatment. Osteosarcoma stem cells (OSCs), the CSCs in osteosarcoma (OS), are critically associated with OS progression. Here, we show that single-walled carbon nanotubes (SWCNTs), including unmodified SWCNT (SWCNT-Raw) and SWCNT-COOH, have the ability to specifically inhibit the process of TGFβ1-induced OS cells dedifferentiation, prevent the stem cell phenotypes acquisition in OS cells and reduce the OSC viability under conditions which mimic the OS microenvironment. Concurrently, SWCNT treatment significantly down-regulates the expression of OSC markers in OS, and markedly reduces the tumor microvessel density and tumor growth. Furthermore, we found that SWCNT could suppress the TGFβ1-induced activation of TGFβ type I receptor and downstream signaling, which are key for the OSC formation and maintenance. Our results reveal an unexpected function of SWCNT in negative modulation of OSCs, and provide significant implications for the potential CSCs-targeted therapeutic applications of SWCNT.

A simple chemical treatment for easy dispersion of carbon nanotubes in epoxy matrix for improving mechanical properties

Carbon nanotubes have considerable potential for use as reinforcements in high-performance polymer composites, but their large-scale application has been hindered by their poor processability. Here, we report an extremely simple and scalable method for the chemical treatment of single-wall carbon nanotubes (SWNTs) to enable easy dispersion in an epoxy matrix. The treatment involves stirring SWNTs in a concentrated solution of sodium hydroxide in ethanol. The chemicals used can be recovered and re-used. The treated SWNTs show greater ease of exfoliation into organic solvents without the need for high-intensity ultrasonic probe treatment. Raman spectroscopy shows that the treatment does not create any noticeable defects or functional groups on the SWNT walls. As a result of the treatment, the SWNTs could be dispersed in epoxy with minimal, low-power ultrasonic treatment. The resulting composites showed increased fracture toughness and tensile strength at SWNT loadings as low as 0.5 weight percent, when compared with neat epoxy. The enhancement in properties of the composites does not decrease with increased SWNT loading, implying that the SWNTs do not re-aggregate.

Pulmonary Inflammation Induced by Single Walled Carbon Nanotubes in Golden Syrian Hamsters

Single-walled carbon nanotubes (SWCNTs) have a broad range of applications; however, they may present a potential health hazard. The current study was undertaken to evaluate the effects of inhalation exposure of aerosolized SWCNTs on hamster lungs. Golden Syrian Hamsters were divided in to 2 groups: a control group that was exposed to an aerosol of distilled water, and a treated group exposed to aerosolized SWCNTs at concentrations of 1, 2 or 4mg/m3 for 2hrs/day for 4 consecutive days. Additional groups were used to investigate longer inhalation periods (8 and 14 days) with exposures of 4hrs/day to 2mg/m3 SWCNTs. One day post exposure, hamsters were euthanized. Tissue sections were evaluated by TUNEL assay to determine apoptosis and tissue homogenates were used to measure endothelin-1 (ET-1) levels. Bronchoalveolar lavage fluid (BALF) was used to determine total leukocyte cell numbers, tumor necrosis factor receptor type 1 (TNFR1) counts and endothelin receptor subtypes A (ETA) levels on alveolar macrophages. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were carried out on lung tissue sections. The current study demonstrates inhalation exposures to SWCNTs in hamster induce pulmonary inflammation. Results from histological analysis of tissue sections indicated increase in inflammatory cells predominantly macrophages in airways and hyperplasia of airway epithelial cells. SWCNTs treatment significantly increased total BAL leukocyte counts, TNFR1 and lung ET-1 levels. SWCNTs treatment caused an increase in ETA levels and evidence of lung toxicity was demonstrated by apoptosis. SWCNTs deposition in alveolar airspaces along with changes to alveolar epithelium was observed in tissue sections examined by TEM.

Microwave pumped high-efficient thermoacoustic tumor therapy with single wall carbon nanotubes

The ultra-short pulse microwave could excite to the strong thermoacoustic (TA) shock wave and deeply penetrate in the biological tissues. Based on this, we developed a novel deep-seated tumor therapy modality with mitochondria-targeting single wall carbon nanotubes (SWNTs) as microwave absorbing agents, which act efficiently to convert ultra-short microwave energy into TA shock wave and selectively destroy the targeted mitochondria, thereby inducing apoptosis in cancer cells. After the treatment of SWNTs (40 μg/mL) and ultra-short microwave (40 Hz, 1 min), 77.5% of cancer cells were killed and the vast majority were caused by apoptosis that initiates from mitochondrial damage. The orthotopic liver cancer mice were established as deep-seated tumor model to investigate the anti-tumor effect of mitochondria-targeting TA therapy. The results suggested that TA therapy could effectively inhibit the tumor growth without any observable side effects, while it was difficult to achieve with photothermal or photoacoustic therapy. These discoveries implied the potential application of TA therapy in deep-seated tumor models and should be further tested for development into a promising therapeutic modality for cancer treatment.

Coculture with Low-Dose SWCNT Attenuates Bacterial Invasion and Inflammation in Human Enterocyte-like Caco-2 Cells.

Single walled carbon nanotubes (SWCNTs) have been shown to be highly effective against a wide range of bacteria. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) infection is a well-known mediator to prolong hospitalization and initiate chronic inflammation, yet the biological effects of SWCNTs on the pathogen-infected enterocytes remain unclear. Herein, it is shown that the low-dose SWCNT treatment attenuates the human enterocyte-like Caco-2 cells from the damage of E. coli and S. aureus infection by suppressing NLRP3 inflammasome activation. The relatively low-dose (1 and 10 μg mL(-1) ) SWCNT treatments reduce the adhesion and invasion of E. coli and S. aureus to Caco-2 cells, increase the cell viability and proliferation, reduce the tight junction permeability, and restitute the integrity of cell surface microvilli structure, meanwhile has low cytotoxicity to the host cells. The low-dose SWCNT treatment further reduces the NLRP3-mediated IL-1β secretion in the infected cells. The results identify that a low-dose SWCNT treatment serves a protective function for the E. coli- and S. aureus-infected Caco-2 cells by negatively regulating mitochondrial reactive oxygen species-mediated NLRP3 inflammasome activation.

Scalability of the Heat and Current Treatment on SWCNTs to Improve their Crystallinity and Thermal and Electrical Conductivities.

We have investigated the scalability of our post-synthesis graphitization process for single-walled carbon nanotubes (SWCNTs), which applies heat and current to SWCNTs to improve the thermal and electrical conductivities. This investigation was performed by examining the relationship between the processing conditions and the amount of treated SWCNTs. Characterization of all cases of treated SWCNTs showed the same level of improvement of ~3 times to both the thermal and electrical conductivities and that the SWCNTs remained SWCNTs, i.e., no change in diameter or wall number. These results provided evidence that the ability to improve the crystallinity of the SWCNTs was independent of the treatment amount. Further, our results showed that an increase in SWCNT amount required increased applied current density or increased in applied temperature to achieve optimum property improvement. Finally, we found a trade-off between the current density and temperature indicating that either a high current or high temperature was required to achieve the optimum process conditions. These results demonstrated that our heat and current SWCNT treatment was fundamentally scalable and applied towards larger scale (i.e., gram-level or more) amounts of SWCNT.

Commercial single-walled carbon nanotubes effects in fibrinolysis of human umbilical vein endothelial cells

Recent studies have demonstrated that carbon nanotubes (CNTs) induce platelet aggregation, endothelial dysfunction and vascular thrombosis. However, there is little information on the effects of CNTs on fibrinolysis. We investigated the role of pristine-commercial single-walled carbon nanotubes (SWCNTs) with <3% Co content in fibrinolysis and their contribution to the induction of pro-thrombotic processes in human vein endothelial cells (HUVEC). SWCNTs alone produced concentration-dependent oxidation, as measured by a dithiothreitol oxidation assay. Internalized SWCNTs were located in HUVEC treated with 25μg/ml using transmission electron microscopy, whereas treatment with 50μg/ml compromised cell viability, and oxidative stress increased significantly at 5μg/ml. The study showed that in HUVEC treated with 25μg SWCNT/ml, fibrinolysis-related gene expression and protein levels had increased by 3–12h after treatment (serpine-1: 13-fold; PLAT: 11-fold and PLAU: 2-fold), but only the PAI-1 protein was increased (1.5-fold), whereas tissue and urokinase plasminogen activator proteins (tPA and uPA, respectively) tended to decrease. In summary, pristine SWCNTs treatment resulted in evident HUVEC damage caused by cell fiber contact, internalization, and oxidative stress due to contaminant metals. The generation of endothelial dysfunction, as shown by the altered expression of genes and proteins involved in fibrinolysis, suggest that SWCNTs display pro-thrombotic effects.

Inhibitory effects of single-walled carbon nanotubes on biofilm formation from Bacillus anthracis spores

This study reports the inhibitory effect of single walled carbon nanotubes (SWCNTs) on biofilm formation from Bacillus anthracis spores. Although the presence of 50 to 100 μg ml−1 of SWCNTs in the suspension increased spore attachment in the wells of 96-well plates, the presence of 200 μg ml−1 of SWCNTs in the germination solution decreased the germination percentage of the attached spores by 93.14%, completely inhibiting subsequent biofilm formation. The inhibition kinetics of 50 μg ml−1 SWCNTs on biofilm formation showed that this concentration inhibited biofilm formation by 81.2% after incubation for 48 h. SWCNT treatment in the earlier stages of biofilm formation was more effective compared to treatment at later stages. Mature biofilms were highly resistant to SWCNT treatment.

Etching single-wall carbon nanotubes into green and yellow single-layer graphene quantum dots

Single-walled carbon nanotubes (SWCNTs) have been used to prepare single-layered graphene quantum dots (GQDs) through a simple and green hydrothermal etching method. After the characterization of products and intermediates with scanning electronic microscopy, Raman and FTIR, a possible mechanism has been proposed for the formation of GQDs. The treatment of SWCNTs has resulted in two kinds of GQDs (i.e. GQD1 and GQD2), both of which are monodisperse and single-layered nanosheets with an average lateral dimension of 8nm and an average height of 0.5nm. Excited with 365nm UV light, aqueous solutions of GQDs1 and GQDs2 give green and yellow luminescence, respectively. The differences in optical property between GQDs1 and GQDs2 mainly results from their differences in degree of oxidation.