| 1. |
- Duan, Haiming, et al.
(author)
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Computational studies of small carbon and iron-carbon systems relevant to carbon nanotube growth
- 2008
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In: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 8:11, s. 6170-6177
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Journal article (peer-reviewed)abstract
- Density functional theory (DFT) calculations show that dimers and longer carbon strings are more stable than individual atoms on Fe(111) surfaces. It is therefore necessary to consider the formation of these species on the metal surfaces and their effect on the mechanism of single-walled nanotube (SWNT) growth. The good agreement between the trends (energies and structures) obtained using DFT and those based on the Brenner and AIREBO models indicate that these analytic models provide adequate descriptions of the supported carbon systems needed for valid molecular dynamics simulations of SWNT growth. In contrast, the AIREBO model provides a better description of the relative energies for isolated carbon species, and this model is preferred over the Brenner potential when simulating SWNT growth in the absence of metal particles. However, the PM3 semiempirical model appears to provide an even better description for these systems and, given sufficient computer resources, direct dynamics methods based on this model may be preferred.
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| 2. |
- Li, Junxin, et al.
(author)
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Rapid Acid-Mediated Purification of Single-Walled Carbon Nanotubes with Homogenization of Bulk Properties
- 2007
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In: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 7:4-5, s. 1525-1529
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Journal article (peer-reviewed)abstract
- A rapid, mild and readily scaleable method for purification and isolation of single-walled nanotubes (SWNTs) using aqueous nitric acid that, in only 1-2 hours at reflux temperature, not only decrease the content of residual metal particles but also the relative ratio of small diameter and metallic NTs. The acid-treated SWNTs have been characterised by TEM, FT-IR, and Raman spectroscopy (514 and 783 cm-1). The results are discussed in relation to observations from other acid-mediated treatments and the reactive chemical species involved at different conditions.
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| 3. |
- Li, Song, et al.
(author)
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Electrochemical Performances of Nanocomposite Solid Oxide Fuel Cells Using Nano-Size Material LaNi0.2Fe0.65Cu0.15O3 as Cathode
- 2009
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In: Journal of Nanoscience and Nanotechnology. - 1533-4880 .- 1533-4899. ; 9:6, s. 3824-3827
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Journal article (peer-reviewed)abstract
- In order to develop nanocomposite solid oxide fuel cells (NANOCOFCs) at the range of intermediate temperature (500-700 degrees C), the new cathode materials LaNi0.2Fe0.8-xCuxO3 (x = 0.0-0-2) (LNFCu) powders were prepared using coprecipitation method. It was found that the orthorhombic structure could be formed after being calcined at 900 degrees C for 4 h, and the powders were mainly composed of nano-size particles. The lattice volume of LNFCu decreased with increasing x, and the second phase La2CuO4 appeared when x = 0.15. Fuel cells based on the nano-ceramic composite electrolyte were fabricated to evaluate the electrochemical properties of the LNFCu materials as cathodes at different operating temperatures. The peak power density of the fuel cell with LaFe0.65Ni0.2Cu0.15O3 cathode reached 635.2 mW/cm(2) and 762.7 mW/cm(2) at 580 degrees C and 650 degrees C respectively, which were much higher than that of LaFe0.8Ni0.2O3 under the same condition. The results indicate doping with copper improves evidently electrochemical properties of the cathode compared with the LaFe0.8Ni0.2O3 cathode. The excellent performance of fuel cells makes LaNi0.2Fe0.8-xCuxO3 material as the candidate electrode for NANOCOFCs.
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| 4. |
- Li, Shanghua, et al.
(author)
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Template electrodeposition of ordered bismuth telluride nanowire arrays
- 2009
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In: Journal of Nanoscience and Nanotechnology. - 1533-4880 .- 1533-4899. ; 9:2, s. 1543-1547
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Journal article (peer-reviewed)abstract
- Thermoelectric bismuth telluride nanowire arrays have been synthesized by direct-current electrodeposition into porous anodic alumina membranes both galvanostatically and potentiostatically. The as-synthesized Bi2Te3 nanowire arrays are highly ordered in large area, stoichiometric, uniform, with high aspect ratio (above 100) and high filling ratio (>90%) of the membrane. The effects of different electrochemical deposition parameters on crystal structures, morphology and composition have been investigated. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) have been used to characterize the physical and chemical properties of the nanowires.
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| 5. |
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| 6. |
- Sharma, Hari Shanker, et al.
(author)
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Chronic Treatment with Nanoparticles Exacerbate Hyperthermia Induced Blood-Brain Barrier Breakdown, Cognitive Dysfunction and Brain Pathology in the Rat : Neuroprotective Effects of Nanowired-Antioxidant Compound H-290/51
- 2009
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In: Journal of Nanoscience and Nanotechnology. - 1533-4880 .- 1533-4899. ; 9:8, s. 5073-5090
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Journal article (peer-reviewed)abstract
- The possibility that chronic exposure of nanoparticles may alter stress reaction and brain pathology following hyperthermia was examined in a rat model. Engineered nanoparticles from Ag or M Cu (approximate to 50-60 nm) were administered (30 mg/kg, i.p.) once daily for 1 week in young male rats. M On the 8th day these animals were subjected to 4 h heat stress at 38 degrees C in a BOD incubator. In these animals stress symptoms, blood-brain barrier (BBB) permeability, cognitive and motor functions and brain pathology were examined. Subjection of nanoparticle treated rats to heat stress showed exacerbation of stress symptoms i.e., hyperthermia, salivation and prostration and exhibited greater BBB disruption, brain edema formation, impairment of cognitive and motor functions M and brain damage compared to normal animals. This enhanced brain pathology in heat stress was most marked in animals that received Ag nanoparticles compared to Cu treatment. Treatment with antioxidant compound H-290/51 either 30 min or 60 min after heat stress did not alter hyperthermia M induce brain pathology in nanoparticle treated rats. Whereas, administration of nanowired-H-290/51 after 30 min or 60 min heat stress markedly attenuated BBB disruption, sensory motor function and brain pathology. These results suggest that chronic nanoparticles treatment exacerbate hyperthermia induced brain pathology that is significantly attenuated by nanowired but not normal H-290/51 compound. Taken together, our observations suggest that nano-wired drug delivery of H-290/51 is a promising approach to induce neuroprotection in hyperthermia induced brain pathology, not reported earlier.
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| 7. |
- Sharma, Hari S., et al.
(author)
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Influence of Engineered Nanoparticles from Metals on the Blood-Brain Barrier Permeability, Cerebral Blood Flow, Brain Edema and Neurotoxicity : An Experimental Study in the Rat and Mice Using Biochemical and Morphological Approaches
- 2009
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In: Journal of Nanoscience and Nanotechnology. - 1533-4880 .- 1533-4899. ; 9:8, s. 5055-5072
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Journal article (peer-reviewed)abstract
- Influence of nanoparticles on brain function following in vivo exposures is not well known. Depending on the magnitude and intensity of nanoparticle exposure from the environment, food and/or water source, neuronal function could be affected and may lead to neurotoxicity and neuropathology. This hypothesis was examined in present investigation using systemic or intracerebroventricular administration of engineered nanoparticles from metals, i.e., Al, Ag and Cu (approximate to 50 to 60 nm) on neurotoxicity in rats and mice. Intraperitoneal (50 mg/kg), intravenous (30 mg/kg), intracarotid (2.5 mg/kg) or intracerebroventricular administration (20 mu g) of nanoparticles significantly altered the blood-brain barrier (BBB) function to Evans blue and radioiodine in several regions of the brain and spinal cord at 24 h after their administration. Marked decreases in local cerebral blood flow (CBF) and pronounced brain edema was seen in regional areas associated with BBB leakage. Neuronal cell injuries, glial cell activation, heat shock protein (HSP) upregulation and loss of myelinated fibers are quite common in effected brain areas. The observed pathological changes were most pronounced in mice compared to rats. Exposures to Cu and Ag nanoparticles showed most marked effects on brain pathology when administered into systemic circulation or into the brain ventricular spaces as compared to Al nanoparticles. Our results are the first to show that nanoparticles from metals are able to induce selective and specific neurotoxicity that depends on the type of metals, route of administration and the species used.
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| 8. |
- Sharma, Hari S., et al.
(author)
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Nano-Drug Delivery and Neuroprotection in Spinal Cord Injury
- 2009
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In: Journal of Nanoscience and Nanotechnology. - 1533-4880 .- 1533-4899. ; 9:8, s. 5014-5037
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Journal article (peer-reviewed)abstract
- Recently nano-drug delivery to the central nervous system (CNS) has been shown to be more effective than the parent compound by itself. An increased availability of the drug for longer periods to the brain or spinal cord and/or a decrease in the drug metabolism altogether could lead to potentiation of the pharmacological activity of the nano-delivered compounds. However, it is still unclear whether the nanocarriers used to deliver the drugs may itself has any potential neurotoxic activity. Although, nanodrug-delivery appears to be a quite promising therapeutic tool for the future clinical therapy, its advantages and limitations for the routine use of patients still needs to be elucidated. Our laboratory is engaged to study a plethora of potential neuroprotective novel compounds delivered to the CNS using nanowiring techniques following brain or spinal cord trauma. Our investigations show that nanowired drugs, if delivered locally following spinal cord injury achieve better neuroprotection than the parent compounds. This effect of nano-drug delivery appears to be very selective in nature. Thus, a clear differentiation based on the compounds used for nano-drug delivery can be seen on various pathological parameters in spinal cord injury. These observations suggest that nanowiring may itself do not induce neuroprotection, but enhance the neuroprotective ability of compounds after trauma. This review describes some recent advances in nano-drug delivery to the CNS in relation to novel neuroprotective strategies with special emphasis on spinal cord trauma based on our own observations and recent findings from our laboratory investigations.
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| 9. |
- Sharma, Hari Shanker, et al.
(author)
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Silicon dioxide nanoparticles (SiO2, 40-50 nm) exacerbate pathophysiology of traumatic spinal cord injury and deteriorate functional outcome in the rat : An experimental study using pharmacological and morphological approaches
- 2009
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In: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 9:8, s. 4970-4980
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Journal article (peer-reviewed)abstract
- Silicon (SiO2) nanoparticles or silica dust is quite common form of exposure to soldiers engaged in gulf war that may influence their health and brain function. It is quite likely that traumatic injuries to the CNS may be influenced by exposure to these nanoparticles. However, the details of silicon nanoparticles on human health functions are still unknown. In this investigation we examined the effects of chronic silicon dioxide nanoparticles (SiO2, 40-50 nm) exposure on spinal cord injury (SCI) induced alterations on the functional outcome and the cord pathology in a rat model. Since nanoparticles induce oxidative stress, the influence of an antioxidant compound H-290/51 was also examined in these nanoparticles treated injured rats as well. Rats treated with SiO2 for 7 days did not show any significant alteration in behaviour on rota rod performances or on capacity angle tests. However, subjection of these nanoparticles exposed rats to SCI resulted in a profound deterioration in motor functions compared to normal rats with SCI. The magnitude of blood-spinal cord barrier (BSCB) disruption to Evans blue and radioiodine tracers and edema formation was much more aggravated following SCI in nanoparticles treated animals compared to untreated traumatized rats. Pretreatment with H-290/51 (50 mg/kg, p.o.) 30 min before SCI in nanoparticle treated rats did not alter spinal cord pathology or functional outcome, however, this dose of the compound was very effective in reducing pathophysiology of SCI in normal animals. These observations are the first to suggest that exposure of nanoparticles enhances the sensitivity of CNS to injuries and alter the effect of neuroprotective drugs.
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| 10. |
- Zhu, Wuming, et al.
(author)
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Diameter and Chirality Changes of Single-Walled Carbon nanotubes During Growth : An ab-inition Study
- 2009
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In: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 9:2, s. 1222-1225
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Journal article (peer-reviewed)abstract
- We use density functional theory to investigate possible changes of the diameter and chirality of single-walled carbon nanotubes (SWNTs) during catalyzed growth on a nickel cluster. The interplay of nanotube curvature, defects, and carbon-metal interaction dictates if a change is energetically favorable. We found that, given a sufficiently large Ni cluster, both zigzag and armchair nanotubes tend to increase their diameters during growth. This increase leads to a larger increase in energetic stability for smaller diameter nanotubes. Chirality changes are also demonstrated. Our findings impact on the possibility of using the recently proposed nanotube-seeded continued growth of SWNTs to control their chirality.
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