Papers by Keyword: Nanotube

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Authors: Yan Li Wang, Ke He Su, Xin Wang
Abstract: The single walled armchair (3,3) (BN)xCy nanotubes with different ratios of B, C and N atoms were studied with density functional theory of B3LYP/3-21G(d) combined with the periodic boundary conditions in simulating the ultra long tube model. Different types of twelve models were examined and the diameter, energy, energy gaps and the band structures were obtained. The energy gaps were within 0.203eV to 2.620eV showing semiconductor conductivity. Results show that the energy gap and the band structure depend on both the atom ratio and arrangement.
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Authors: K.Eric Drexler
Abstract: Proposed advanced mechanosynthetic systems [1] require molecular tools able to bind and transfer reactive moieties with high reliability at 300 K (failure rates << 10–10 per transfer operation). Screening of a large number of candidate tools at the AM1 level enabled the identification of a structure, DC10c, that is calculated (at the B3LYP/6- 31G(d,p) level) to meet these stringent requirements when used to transfer carbon dimers to any of a target class of graphene-, nanotube-, and diamond-like structures [2]. The favorable energy of transfer (exoergic by a mean energy ≥ 0.261 aJ per dimer) results from avoidance of the generation of high-energy radical sites during dimer release by means of π-delocalization to form a strained aromatic ring on the binding face of the empty structure. These energies are compatible with transfer-failure rates ~ 10–24 per operation at 300 K, and overall failure rates << 10–10.
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Authors: Habibollah Faraji, Reza Nedaeinia, Esmaeil Nourmohammadi, Bizan Malaekeh-Nikouei, Hamid Reza Sadeghnia, Seyyed Payman Ziapour, Hoda Khoshdel Sarkarizi, Reza Kazemi Oskuee
Abstract: Nanotechnology as a multidisciplinary and scientific innovation plays an important role in numerous biomedical applications, such as molecular imaging, biomarkers and biosensors and also drug delivery. A wide range of studies have been conducted on using of nanoparticles for early diagnosis and targeted drug therapy of various diseases. In fact, the small size, customized surface, upgraded solubility, or multi-functionality of nanoparticles enabled them to interact with complex cellular functions in new ways which opened many doors and created new biomedical applications. These studies demonstrated that nanotechnology vehicles can formulate biological products effectively, and this nano-formulated products with a potent ability against different diseases, were represented to have better biocompatibility, bioaccessibility and efficacy, under in vitro and in vivo conditions.
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Authors: Jian Wei Wei, Hui Zeng, Li Chun Pu, Nan Hu
Abstract: In this paper, we have investigated the geometries and electronic structures of B-N co-doped carbon nanotube with inside adsorption of water molecules. The charge distributions, band structures and local density of states are calculated by using the first-principles theory in detail. The results show that the water molecules can adsorb stably on the inside surface of the doped nanotube with slight deformation. The π and π* subbands shift upward depending on the sites of the adoptions. The investigations will be beneficial to the biological application of B-N co-doped nanotube.
132
Authors: G.R. Ahmed Jamal, M. Asraf Siddique, Sawon, Khalid Hasan, M. Jane Alam
Abstract: In this work, an improved technique for chirality assignment of single wall carbon nanotubes (SWCNT) is proposed which work for both isolated and bundles SWCNTs. The technique exploits the (2n+m) family pattern both in optical transitions vs diameter plot and Raman G-mode frequency vs diameter plot of SWCNTs. Using two different plots can give accurate value of the family of unknown SWCNTs that can be used to find chiral index (n, m) of unknown SWCNT unambiguously in most of the cases. Unlike existing methods, graphical comparison or pattern recognition with an existing Kataura plot is not required here. Chirality of 13 SWCNTs are assigned here using this technique. Validity of assigned chirality is cross checked from previous experimental reports. The technique is especially useful for determining chirality of isolated SWCNT.
253
Authors: P. Bocchetta, M. Santamaria, F. Di Quarto
Abstract: Anodic alumina membranes with highly ordered cylindrical pores and tuneable geometry have been prepared (pore diameters=20−200 nm; pore density 1012-1014 pores/m2; thickness: 20-100 mm) by controlling the anodizing process of aluminum in phosphoric, oxalic and sulphuric acid. The influence of different parameters (initial treatment of aluminium surface, composition of electrolyte, temperature and applied potential) on the final characteristics of the membranes have been investigated. The use anodic alumina membranes as template for the electrosynthesis of some metal hydroxides and oxides 1-D nanostructures (nanowires and nanotubes) will be also proved.
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Authors: Natthaphol Chomsaeng, Bralee Chayasombat, Inthiraporn Insura, Kritsana Narkdee, Chanchana Thanachayanont
Abstract: Titanium dioxide nanotubes on titanium surface were prepared by electrolytic anodization in aqueous solution at constant voltages at room temperature for 2, 4 and 6 hours. Anodized titanium was heat treated in a furnace at 450 °C for 4 hours to convert amorphous structure to anatase and rutile crystalline structure. A scanning electron microscope was utilized for morphology investigation of the anodized titanium surfaces. For HF containing water media, porous surface on titanium was revealed after anodizing for 2 hours. Nanotubes (NT) were formed in this media at 4 and 6 hours anodizing time, the diameters of the tubes were approximately 70 to 100 nm. For HF/Na2SO4 aqueous solution, fine NTs, approximately 50 nm in diameter, were grown after 2 hours. However, the NTs obtained at anodizing time 4 and 6 hours were the same size, ranging from 100 to 120 nm. Anatase and rutile phases of TiO2 were formed in the anodized samples after annealing at 450 °C for 4 hours. The anodized samples were tested for their abilities to degrade Rhodamine B, to demonstrate their application as a material for waste water treatment. The Rhodamine B was degraded up to 41% in annealed sample anodized by electrolyte contained HF.
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Authors: Yutaka Ito, Nikolay Djourelov, Takenori Suzuki, Kenjiro Kondo, Yasuo Ito, Victor P. Shantarovich, Jun Onoe
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Authors: Yoshitaka Umeno, Masanobu Sato, Hiroyuki Shima, Motohiro Sato
Abstract: We carried out the atomistic structural instability (ASI) analysis with an empirical interatomic potential for carbon nanotubes (CNTs) under axial compression with the aim to reveal the mechanism of buckling. We investigated how ‘latent’ instability modes develop until one of them is activated at the structural instability. For pristine single-walled carbon nanotubes (SWCNTs), Euler-type buckling was found in relatively thin nanotubes, while buckling modes corresponding to change in the cross-sectional shape (radial buckling) were found in thick nanotubes. The crossover between the Euler-type buckling and radial buckling modes was clearly seen in the ASI analysis. While the reduction of Hessian eigenvalues in the pristine nanotubes and nanotubes with a vacancy is nearly linear until instability, rapid decrease of eigenvalues just before instability was found in models with Stone-Wales defects. This is due to localization of instability mode vectors around the defects that tends to arise before structural instability.
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