Project description:The medical applications of carbon nanotubes (CNTs) have garnered much attention. However, evaluating the safety of CNTs remains difficult, and no consensus has been reached. Moreover, assessing the biosafety of multi-walled CNTs (MWCNTs), which can become tangled during manufacturing, is challenging because they do not readily disperse. We studied how the dispersion state of tangled MWCNTs affects their cytotoxicity, using three sonicators. Flotube 9110 (FT9110), tangled MWCNTs, were dispersed in two dispersants (fetal bovine serum and polysorbate 80) using a new type of sonicator (PR-1) and two conventional sonicators. The size and cytotoxicity of the dispersed FT9110 were measured using the BEAS-2B human bronchial epithelial cell line. The PR-1 dispersed the FT9110 to agglomerates <200 nm in diameter; FT9110 dispersed with the PR-1 did not show cytotoxicity regardless of dispersant. The other sonicators dispersed the FT9110 to particles >1000 nm in diameter, and cytotoxicity depended on the dispersant. We found that excluding cells adhered to agglomerated FT9110 before evaluating cytotoxicity can lead to false-positive results. The PR-1 sonicator dispersed tangled FT9110 to many single fibers, which showed lower cytotoxicity than conventionally-sonicated MWCNTs. We suggest that dispersion state should be accounted for when evaluating the cytotoxicity of MWCNTs.
Project description:In this study, complexes composed of poly-l-tyrosine (pLT) and single-walled carbon nanotubes (SWCNTs) were produced and the dispersibility of the pLT/SWCNT complexes in water by measuring the ? potential of the complexes and the turbidity of the solution were investigated. It is found that the absolute value of the ? potential of the pLT/SWCNT complexes is as high as that of SWCNTs modified with double-stranded DNA (dsDNA) and that the complexes remain stably dispersed in the water at least for two weeks. Thermogravimetry analysis (TGA) and visualization of the surface structures of pLT/SWCNT complexes using an atomic force microscope (AFM) were also carried out.
Project description:Excitement surrounding the attractive physical and chemical characteristics of single walled carbon nanotubes (SWCNTs) has been tempered by concerns regarding their potential health risks. Here we consider the lung toxicity of nanoscale dispersed SWCNTs (mean diameter approximately 1 nm). Because dispersion of the SWCNTs increases their aspect ratio relative to as-produced aggregates, we directly test the prevailing hypothesis that lung toxicity associated with SWCNTs compared with other carbon structures is attributable to the large aspect ratio of the individual particles. Thirty days after their intratracheal administration to mice, the granuloma-like structures with mild fibrosis in the large airways observed in mice treated with aggregated SWCNTs were absent in mice treated with nanoscale dispersed SWCNTs. Examination of lung sections from mice treated with nanoscale dispersed SWCNTs revealed uptake of the SWCNTs by macrophages and gradual clearance over time. We conclude that the toxicity of SWCNTs in vivo is attributable to aggregation of the nanomaterial rather than the large aspect ratio of the individual nanotubes. Biocompatible nanoscale dispersion provides a scalable method to generate purified preparations of SWCNTs with minimal toxicity, thus allowing them to be used safely in commercial and biomedical applications.
Project description:Homogenously dispersing single-walled carbon nanotubes (SWNTs) in solvents has been one critical step towards exploiting their exceptional properties in high-performance components. However, the solubility of SWNTs is severely limited by the inert tube surfaces and strong tube-tube van der Waals attractions. Starting with carbon nanotubides, i.e., negatively charged SWNTs reduced by alkali metals, we herein propose a sonication-free approach to prepare an aqueous dispersion of SWNTs. The approach combines the spontaneous dissolution of nanotubides in polar aprotic solvents with polyvinylpyrrolidone wrapping and dialysis in deionized H2O, which results in well-dispersed, neutralized SWNTs. The gelation of concentrated SWNT dispersion leads to the formation of hydrogels, which is subsequently transformed into SWNT aerogels through lyophilization. The prepared SWNT aerogels exhibit high-mass-sorption capacities for organic solvent absorption, paving the way towards harvesting the extraordinary properties of SWNTs.
Project description:Carbon nanotube-based donor-acceptor devices are used in applications ranging from photovoltaics and sensors to environmental remediation. Non-covalent contacts between donor dyes and nanotubes are often used to optimize sensitization and scalability. However, inconsistency is often observed despite donor dye studies reporting strong donor-acceptor interactions. Here, we demonstrate that the dye binding location is an important factor in this process: we used coated-acceptor chromatic responses and find that dye binding is affected by the coating layer. The emission response to free- and protein-sequestered porphyrin was tested to compare direct and indirect dye contact. An acceptor complex that preferentially red-shifts in response to sequestered porphyrin was identified. We observe inconsistent optical signals that suggest porphyrin-dye interactions are best described as coating-centric; therefore, the coating interface must be considered in application and assay design.
Project description:The formation of discrete macrocycles wrapped around single-walled carbon nanotubes (SWCNTs) has recently emerged as an appealing strategy to functionalize these carbon nanomaterials and modify their properties. Here, we demonstrate that the reversible disulfide exchange reaction, which proceeds under mild conditions, can install relatively large amounts of mechanically interlocked disulfide macrocycles on the one-dimensional nanotubes. Size-selective functionalization of a mixture of SWCNTs of different diameters were observed, presumably arising from error correction and the presence of relatively rigid, curved π-systems in the key building blocks. A combination of UV/Vis/NIR, Raman, photoluminescence excitation, and transient absorption spectroscopy indicated that the small (6,4)-SWCNTs were predominantly functionalized by the small macrocycles 12 , whereas the larger (6,5)-SWCNTs were an ideal match for the larger macrocycles 22 . This size selectivity, which was rationalized computationally, could prove useful for the purification of nanotube mixtures, since the disulfide macrocycles can be removed quantitatively under mild reductive conditions.
Project description:SWCNTs were individually dispersed in ethylne glycol (EG) via mild bath-type sonication using quaternized poly(furfuryl methacrylate)-co-(2-(dimethylamino)ethyl methacrylate) p(FMA-co-QDMAEMA) as a dispersing agent. QDMAEMA, which has alkyl groups, was more favorable to the dispersion ability of single walled carbon nanotubes (SWCNTs). The dispersion mechanism of SWCNTs in EG via helical wrapping of polymer chains along their sidewalls was suggested based on transmission electron microscopic observation.
Project description:The assessment of the toxicity of airborne nanofibers is an important task. It relies on toxicological inhalation studies and validated exposure measurement techniques. Both require nanofiber-containing aerosols of known morphological composition and controlled fraction of individual fibers. Here, a dry powder dispersion method is presented that operates with mixtures of nanofibers and microscale beads. Aerosolization experiments of mixtures of multi-walled carbon nanotubes (MWCNTs) and glass beads that were continuously fed into a Venturi nozzle enabled high generation rates of aerosols composed of individual and agglomerate nanofiber structures. The aerosol process achieved good stability over more than 2 h with respect to concentration and aerodynamic size distribution. Its operation duration is limited only by the reservoir volume of the cyclone used to separate the beads from the aerosol. The aerosol concentration can be controlled by changing the mass ratio of MWCNTs and glass beads or by adapting the mass feed rate to the nozzle. For two agglomerated MWCNT materials, aerosol concentrations ranged from 1700 to 64,000 nano-objects per cm3. Comprehensive scanning electron microscope analysis of filter samples was performed to categorize and determine the morphological composition of the aerosol, its fiber content as well as fiber length and diameter distributions. High fractions of individual fibers of up to 34% were obtained, which shows the setup to be capable of dispersing also highly tangled MWCNT agglomerates effectively.
Project description:Dispersible multi-walled carbon nanotubes (MWCNTs) in water have been widely applied in the nanotechnology field. This study reports a water-soluble N,O-carboxymethyl chitosan(N,O-CMCS) assisted individual dispersion of oxidized multi-walled carbon nanotubes (oMWCNTs) as a dispersant. First, the dispersing agent N,O-CMCS was successfully synthesized using the nucleophilic substitution of deacetylated chitosan with chloroacetic acid in an alkaline solution. It was further confirmed using Fourier transform infrared spectroscopy (FTIR). Second, after the treatment with the concentrated hydrochloric acid, the prepared oMWCNTs were dispersed in an aqueous solution of N,O-CMCS under ultrasonic vibrations. Finally, the dispersed aqueous solution was subjected to centrifugation to collect the supernatant of individually dispersed N,O-CMCS/oMWCNTs. In addition, transmission electron microscopy (TEM) further confirmed that the purity of oMWCNTs was improved after the acidification progress. Besides, the stability of the dispersion solution was evidenced by digital photos of oMWCNTs dispersed by N,O-CMCS before and after. Moreover, the UV-vis spectrum (the characteristic peak of dispersed oMWCNTs downshifted 13 nm) showed that the supernatant was enriched by the individual oMWCNTs. In particular, the analytical results of FTIR (the -NH2 band of N,O-CMCS downshifted 7 cm-1), resonance Raman spectroscopy (the I D/I G ratio of dispersed oMWCNTs only increased 0.14), and XRD identified the formation of a non-convalent interaction between N,O-CMCS and oMWCNTs. These findings reveal the dispersing nature of N,O-CMCS towards oMWCNTs in water media.
Project description:Individual single-walled carbon nanotubes (SWNTs) with distinct electronic types are crucial for the fabrication of SWNTs-based electronic and magnetic devices. Herein, the water-soluble polymethyl(1-butyric acidyl)silane (BA-PMS) was synthesized via the hydrosilylation reaction between 3-butenoic acid and polymethylsilane catalyzed by 2,2'-azodibutyronitrile. As a new dispersant, BA-PMS displayed a quite good dispersing capacity to arc-discharged SWNTs and moderate selectivity for metallic species. The application of sucrose-DGU, the density gradient ultracentrifugation with sucrose as the gradient medium, to the co-surfactants (BA-PMS and sodium dodecyl sulfonate) individually dispersed SWNTs yielded metallic SWNTs of 85.6% purity and semiconducting SWNTs of 99% purity, respectively. This work paves a path to the DGU separation of the SWNTs dispersed by polymer-based dispersants with hydrophobic alkyl chains.