Single-walled carbon nanotubes alleviate autophagic/lysosomal defects in primary glia from a mouse model of Alzheimer's disease.
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ABSTRACT:
SUBMITTER: Xue X
PROVIDER: S-EPMC4160261 | biostudies-literature | 2014 Sep
REPOSITORIES: biostudies-literature
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Project description:Recently, evidence was presented that certain single-walled carbon nanotubes (SWNTs) possess helical defective traces, exhibiting distinct cleaved lines, yet their mechanical characterization remains a challenge. On the basis of the spiral growth model of SWNTs, here we present atomic details of helical defects and investigate how the tensile behaviors of SWNTs change with their presence using molecular dynamics simulations. SWNTs have exhibited substantially lower tensile strength and strain than theoretical results obtained from a seamless tubular structure, whose physical origin cannot be explained either by any known SWNT defects so far. We find that this long-lasting puzzle could be explained by assuming helical defects in SWNTs, exhibiting excellent agreement with experimental observation. The mechanism of this tensile process is elucidated by analyzing atomic stress distribution and evolution, and the effects of the chirality and diameter of SWNTs on this phenomenon are examined based on linear elastic fracture mechanics. This work contributes significantly to our understanding of the growth mechanism, defect hierarchies, and mechanical properties of SWNTs.
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Project description:Oxygen defects in semiconducting single-walled carbon nanotubes (SWCNTs) are localized disruptions in the carbon lattice caused by the formation of epoxy or ether groups, commonly through wet-chemical reactions. The associated modifications of the electronic structure can result in luminescent states with emission energies below those of pristine SWCNTs in the near-infrared range, which makes them promising candidates for applications in biosensing and as single-photon emitters. Here, we demonstrate the controlled introduction of luminescent oxygen defects into networks of monochiral (6,5) SWCNTs using a solid-state photocatalytic approach. UV irradiation of SWCNTs on the photoreactive surfaces of the transition metal oxides TiOx and ZnOx in the presence of trace amounts of water and oxygen results in the creation of reactive oxygen species that initiate radical reactions with the carbon lattice and the formation of oxygen defects. The created ether-d and epoxide-l defect configurations give rise to two distinct red-shifted emissive features. The chemical and dielectric properties of the photoactive oxides influence the final defect emission properties, with oxygen-functionalized SWCNTs on TiOx substrates being brighter than those on ZnOx or pristine SWCNTs on glass. The photoinduced functionalization of nanotubes is further employed to create lateral patterns of oxygen defects in (6,5) SWCNT networks with micrometer resolution and thus spatially controlled defect emission.
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Project description:Long carbon nanotubes (CNTs) resemble asbestos fibers due to their high length to diameter ratio and they thus have genotoxic effects. Another parameter that might explain their genotoxic effects is contamination with heavy metal ions. On the other hand, short (1-2 µm) CNTs do not resemble asbestos fibers, and, once purified from contaminations, they might be suitable for medical applications. To identify the role of fiber thickness and surface properties on genotoxicity, well-characterized short pristine and carboxylated single-walled (SCNTs) and multi-walled (MCNTs) CNTs of different diameters were studied for cytotoxicity, the cell's response to oxidative stress (immunoreactivity against hemoxygenase 1 and glutathione levels), and in a hypoxanthine guanine phosphoribosyltransferase (HPRT) assay using V79 chinese hamster fibroblasts and human lung adenocarcinoma A549 cells. DNA repair was demonstrated by measuring immunoreactivity against activated histone H2AX protein. The number of micronuclei as well as the number of multinucleated cells was determined. CNTs acted more cytotoxic in V79 than in A549 cells. Plain and carboxylated thin (<8 nm) SCNTs and MCNTs showed greater cytotoxic potential and carboxylated CNTs showed indication for generating oxidative stress. Multi-walled CNTs did not cause HPRT mutation, micronucleus formation, DNA damage, interference with cell division, and oxidative stress. Carboxylated, but not plain, SCNTs showed indication for in vitro DNA damage according to increase of H2AX-immunoreactive cells and HPRT mutation. Although short CNTs presented a low in vitro genotoxicity, functionalization of short SCNTs can render these particles genotoxic.
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Project description:While several approaches have been developed for sorting metallic (m) or semiconducting (s) single-walled carbon nanotubes (SWCNTs), the length of SWCNTs is limited within a micrometer, which restricts excellent electrical performances of SWCNTs for macro-scale applications. Here, we demonstrate a simple sorting method of centimetre-long aligned m- and s-SWCNTs. Ni particles were selectively and uniformly coated along the 1-cm-long m-SWCNTs by applying positive gate bias during electrochemical deposition with continuous electrolyte injection. To sort s-SWCNTs, the Ni coating was oxidized to form insulator outer for blocking of current flow through inner m-SWCNTs. Sorting of m-SWCNTs were demonstrated by selective etching of s-SWCNTs via oxygen plasma, while the protected m-SWCNTs by Ni coating remained intact. The series of source-drain pairs were patterned along the 1-cm-long sorted SWCNTs, which confirmed high on/off ratio of 10(4)-10(8) for s-SWCNTs and nearly 1 for m-SWCNTs.
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Project description:High-pressure carbon monoxide (HiPCO) single-walled carbon nanotubes (SWCNTs) were heat treated at high temperatures from 1700 to 3000 °C. During the heating below 2500 °C, the diameters of the SWCNTs gradually increase from ∼1.0 to >1.5 nm, and at the temperatures higher than 2500 °C, double-, triple-, multiwalled carbon nanotubes (MWCNTs) appear as a consequence of the coalescence of SWCNT bundles. It is surprising that most MWCNTs have odd number of walls, such as 3 or 5. The even-odd number effect agrees well with the mechanism of SWCNT bundle coalescence proposed by López M. J. [Phys. Rev. Lett.2002, 89, 255501], in which an SWCNT that templated the layer by layer coalescence of surrounding SWCNTs is responsible for the enrichment of MWCNTs with odd number of walls. This study confirms the mechanism of SWCNT bundle coalescence, discovers an interesting odd-even number of walls effect in the consequent MWCNTs, and suggests that it is possible to obtain structure-controllable MWCNTs via SWCNT bundle coalescence.
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Project description:Inorganic nanotubes are morphological counterparts of carbon nanotubes (CNTs). Yet, only graphene-like BN layer has been readily organized into single walled nanotubes so far. In this study, we present a simple route to obtain inorganic single walled nanotubes - a novel ultrathin morphology for bismuth iodide (BiI3), embedded within CNTs. The synthesis involves the capillary filling of BiI3 into CNT, which acts as a nanotemplate, by annealing the BiI3-CNT mixture above the melting point of BiI3. Aberration corrected scanning/transmission electron microscopy is used in characterizing the novel morphology of BiI3. A critical diameter which enables the formation of BiI3 nanotubes, against BiI3 nanorods is identified. The relative stability of these phases is investigated with the density functional theory calculations. Remarkably, the calculations reveal that the single walled BiI3 nanotubes are semiconductors with a direct band gap, which remain stable even without the host CNTs.
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Project description:Control of single-walled carbon nanotube dispersion properties is of substantial interest to the scientific community. In this work, we sought to investigate the effect of a macrocycle, pillar[5]arene, on the dispersion properties of a polymer-nanotube complex. Pillar[5]arenes are a class of electron-rich macrocyclic hosts capable of forming inclusion complexes with electron-poor guests, such as alkyl nitriles. A hydroxyl-functionalized pillar[5]arene derivative was coupled to the alkyl bromide side chains of a polyfluorene, which was then used to coat the surface of single-walled carbon nanotubes. Noncovalent functionalization of carbon nanotubes with the macrocycle-containing conjugated polymer significantly enhanced nanotube solubility, resulting in dark and concentrated nanotube dispersions (600 ?g mL-1), as evidenced by UV-vis-NIR spectroscopy and thermogravimetric analysis. Differentiation of semiconducting and metallic single-walled carbon nanotube species was analyzed by a combination of UV-vis-NIR, Raman, and fluorescence spectroscopy. Raman spectroscopy confirmed that the concentrated nanotube dispersion produced by the macrocycle-containing polymer was due to well-exfoliated nanotubes, rather than bundle formation. The polymer-nanotube dispersion was investigated using 1H NMR spectroscopy, and it was found that host-guest chemistry between pillar[5]arene and 1,6-dicyanohexane occurred in the presence of the polymer-nanotube complex. Utilizing the host-guest capability of pillar[5]arene, the polymer-nanotube complex was incorporated into a supramolecular organogel.
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Project description:Carbon nanotubes could accumulate in organism and have a negative impact on the structure and function of the ecosystem when they were discharged into environment. Furthermore, it will affect the migration and fate of pollutants in the water body. The study is mainly to explore the adsorption behavior and mechanism of beta-blocker on multi-walled carbon nanotubes (MWCNTs). Propranolol (PRO) was selected as the representative of beta-blocker. The effects of different environmental factors such as pH, ionic strength and humic acid (HA) on the adsorption process were investigated. The adsorption results were characterized by Zeta potential. At the same time, the effects of different types of drugs on the adsorption process were explored and the possible adsorption mechanisms were analyzed. The experimental results showed that the adsorption behavior was significantly different under different pH conditions. ?-? EDA interaction, hydrophobic interaction and hydrogen bonding were speculated to be the main adsorption mechanisms for PRO adsorption on MWCNTs.
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Project description:The controlled functionalization of single-walled carbon nanotubes with luminescent sp3-defects has created the potential to employ them as quantum-light sources in the near-infrared. For that, it is crucial to control their spectral diversity. The emission wavelength is determined by the binding configuration of the defects rather than the molecular structure of the attached groups. However, current functionalization methods produce a variety of binding configurations and thus emission wavelengths. We introduce a simple reaction protocol for the creation of only one type of luminescent defect in polymer-sorted (6,5) nanotubes, which is more red-shifted and exhibits longer photoluminescence lifetimes than the commonly obtained binding configurations. We demonstrate single-photon emission at room temperature and expand this functionalization to other polymer-wrapped nanotubes with emission further in the near-infrared. As the selectivity of the reaction with various aniline derivatives depends on the presence of an organic base we propose nucleophilic addition as the reaction mechanism.
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