Browsing by Subject "Carbon nanotube"
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Item Open Access Chemically uracil-functionalized carbon and silicon carbide nanotubes: computational studies(Elsevier, 2018) Harismah, K.; Mirzaei, M.; Sahebi, H.; Gülseren, Oğuz; Rad, A. S.Chemical additions of uracil (U) nucleobase to sidewall of each of representative (4,4) armchair carbon and silicon carbide nanotubes (CNT and SiCNT) were investigated based on density functional theory (DFT) calculations. All singular and hybrid models were optimized to obtain the minimum-energy structures. The evaluated molecular properties indicated the effects of U-attachment on properties of both of U and NT counterparts, in which additional evaluated atomic-scale chemical shifts indicated the role of atomic sites in the U-attachment processes. Both of U-CNT and U-SiCNT hybrids could be considered as achievable compounds; however, the aim of application could organize the achievement of which hybrid. There was one possibility of U-attachment for the homo-atomic system of CNT whereas there were two possibilities of U-attachment for the hetero-atomic system of SiCNT. Interestingly, the evaluated atomic and molecular properties indicated differences between the characteristics of U-SiCNT-1 and U-SiCNT-2 as an advantage of computational chemistry methodologies, in which the results were very much interesting for the water-solvated systems.Item Open Access DFT studies of CNT-functionalized uracil-acetate hybrids(Elsevier, 2015) Mirzaei, M.; Gulseren, O.Calculations based on density functional theory (DFT) have been performed to investigate the stabilities and properties of hybrid structures consisting of a molecular carbon nanotube (CNT) and uracil acetate (UA) counterparts. The investigated models have been relaxed to minimum energy structures and then various physical properties and nuclear magnetic resonance (NMR) properties have been evaluated. The results indicated the effects of functionalized CNT on the properties of hybrids through comparing the results of hybrids and individual structures. The oxygen atoms of uracil counterparts have been seen as the detection points of properties for the CNT-UA hybrids.Item Open Access Dielectrophoresis in microfluidics technology(2011) Çetin B.; Li, D.Dielectrophoresis (DEP) is the movement of a particle in a non-uniform electric field due to the interaction of the particle's dipole and spatial gradient of the electric field. DEP is a subtle solution to manipulate particles and cells at microscale due to its favorable scaling for the reduced size of the system. DEP has been utilized for many applications in microfluidic systems. In this review, a detailed analysis of the modeling of DEP-based manipulation of the particles is provided, and the recent applications regarding the particle manipulation in microfluidic systems (mainly the published works between 2007 and 2010) are presented. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Item Open Access Enhancing oxygen evolution catalytic performance of nickel borate with cobalt dopingand carbon nanotubes(Wiley, 2023-02-16) Enez, S.; Karani Konuksever, V.; Samuei, S.; Karadaş, Ferdi; Ülker, E.Item Open Access Growth of vertically aligned carbon nanotubes over self-ordered nano-porous alumina films and their surface properties(Elsevier, 2012) Rana, K.; Kucukayan-Dogu, G.; Bengu, E.Nanoporous anodic aluminum oxide (AAO) with self-organized arrays of uniform nanopores have been used for various applications in the fields of sensing, storage, separation and template-based fabrication of metal nanowires, carbon nanotubes, oxides and polymers. The work presented here involves the production and use of AAO templates for growth of aligned multi walled carbon nanotube arrays. AAO templates were formed by electrochemical oxidation of aluminum in different electrolyte solutions containing sulfuric, oxalic and phosphoric acid. SEM was used for the analysis of the surface morphology of the AAO films. The porous structures with pore size in the range of 25–120 nm were observed. Pore sizes were correlated with the type of acidic solutions used as the electrolyte. Finally, AAO surfaces have been used as substrates for the growth of vertically aligned carbon nanotubes through chemical vapor deposition technique, which showed super-hydrophobic behavior as confirmed by contact angle measurements.Item Open Access High conducting nanowires obtained from uniform titanium covered carbon nanotubes(2005) Daǧ, Sefa; Durgun, Engin; Çıracı, SalimWe have shown that Ti atoms can form continuous coating of carbon nanotubes at different amount of coverage. The circular cross section changes to a square-like form, and the semiconducting tube becomes ferromagnetic metal with high quantum ballistic conductance. Metallicity is induced not only by the metal-metal coupling, but also by the band gap closing of SWNT at the corners of the square. The magnetic properties of Ti coated tubes depend strongly on the geometry, amount of Ti coverage and also on the elastic deformation of the tube. While the magnetic moment can be pronounced significantly by the positive axial strain, it can decrease dramatically upon the adsorption of additional Ti atoms to those already covering the nanotube. Besides, electronic structure and spin-polarization near the Fermi level can also be modified by radial strain. Our results have been obtained by the first-principles, spin-relaxed pseudopotential plane wave calculations within the density functional theory. © TÜBİTAK.Item Open Access A new tool for differentiating hepatocellular cancer cells: patterned carbon nanotube arrays(Elsevier, 2015) Kucukayan-Dogu, G.; Gozen, D.; Bitirim, V.; Akcali, K. C.; Bengu, E.We aimed to develop a new approach to detect the invasiveness and metastatic degree of hepatocellular carcinoma cells (HCC) based on their epithelial mesenchymal transition (EMT) status by using patterned carbon nanotubes (CNT) without any further surface functionalization. We used well differentiated HUH7 and poorly differentiated SNU182 cells to examine and compare their adhesive features on patterned CNTs. We found that the well differentiated HUH7 cells attached significantly more on the patterned CNTs than the poorly differentiated SNU182 cells due to the difference in epithelial and mesenchymal phenotypes of these cells. Collagen coated patterned CNTs having less roughness resulted in a decrease in the number of attached cells compared to non-coated patterned surfaces indicating that surface topography playing also a vital role on the cell attachment. LDH testing indicated no adverse, or thereof toxic effect of collagen coated or non-coated patterned surfaces on the HCC cells. The results of this study clearly suggest that patterned CNT surfaces can be used as a diagnostic tool to determine the invasiveness and metastatic level of HCCs. Hence, CNTs could be considered as a promising diagnostic tool for the detection of differentiation and invasiveness of the HCC cells. © 2015 Elsevier B.V. All rights reserved.Item Open Access Non-covalent functionalized SWNTs as delivery agents for novel Bodipy-based potential PDT sensitizers(2009) Erbas, S.; Gorgulu, A.; Kocakusakogullari, M.; Akkaya, E. U.Pyrenyl-functionalized distyryl-Bodipy sensitizer attached non-covalently to SWNTs was shown to generate singlet oxygen when excited at 660 nm with a red LED array; this work emphasizes the potential of SWNT as a viable alternative carrier of bioactive agents, including photodynamic therapy sensitizers. © 2009 The Royal Society of Chemistry.Item Open Access Persistent currents in helical structures(American Physical Society, 2004) Iskin, M.; Kulik, I. O.The recent discovery of mesoscopic electronic structures, in particular the carbon nanotubes, made necessary an investigation of what effect a helical symmetry of the conductor (metal or semiconductor) may have on the persistent current oscillations, We investigate persistent currents in helical structures which are nondecaying in time, not requiring a voltage bias, dissipationless stationary flow of electrons in a normal-metallic or semiconducting cylinder or circular wire of mesoscopic dimension. In the presence of magnetic flux along the toroidal structure, helical symmetry couples circular and longitudinal currents to each other. Our calculations suggest that circular persistent currents in these structures have two components with periods Φ0 and Φ0/s (s is an integer specific to any geometry). However, resultant circular persistent current oscillations have Φ0 period.Item Open Access Recent advances in bioactive 1D and 2D carbon nanomaterials for biomedical applications(Elsevier, 2018) Erol, Özlem; Uyan, İdil; Hatip, Meyem; Yılmaz, Canelif; Tekinay, Ayse B.; Güler, Mustafa O.One-dimensional (1D) carbon nanotubes (CNTs) and the two-dimensional (2D) graphene represent the most widely studied allotropes of carbon. Due to their unique structural, electrical, mechanical and optical properties, 1D and 2D carbon nanostructures are considered to be leading candidates for numerous applications in biomedical fields, including tissue engineering, drug delivery, bioimaging and biosensors. The biocompatibility and toxicity issues associated with these nanostructures have been a critical impediment for their use in biomedical applications. In this review, we present an overview of the various materials types, properties, functionalization strategies and characterization methods of 1D and 2D carbon nanomaterials and their derivatives in terms of their biomedical applications. In addition, we discuss various factors and mechanisms affecting their toxicity and biocompatibility.Item Open Access Theoretical study of Ga-based nanowires and the interaction of Ga with single-wall carbon nanotubes(American Physical Society, 2004) Durgun, Engin; Dag, S.; Çıracı, SalimGallium displays physical properties which can make it a potential element to produce metallic nanowires and high-conducting interconnects in nanoelectronics. Using first-principles pseudopotential plane method we showed that Ga can form stable metallic linear and zigzag monatomic chain structures. The interaction between individual Ga atom and single-wall carbon nanotube (SWNT) leads to a chemisorption bond involving charge transfer. Doping of SWNT with Ga atom gives rise to donor states. Owing to a significant interaction between individual Ga atom and SWNT, continuous Ga coverage of the tube can be achieved. Ga nanowires produced by the coating of carbon nanotube templates are found to be stable and high conducting.