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UBC Theses and Dissertations

Electronic structure and reactivities of the perfect, defected, and doped single-walled carbon nanotubes Liu, Lei

Abstract

In this thesis, the electronic structure and reactivities of the perfect, defected, and doped single-walled carbon nanotubes (SWCNTs) have been studied by various theoretical methods, including density functional theory, semiempirical methods, and force fields. Among different defects of the SWCNTs, we have concentrated our studies on the vacancy defect and substitutional^ doped defect. Of the vacancy defected SWCNTS, we first studied their geometries, energetics, and electronic structures. After comparing the vacancy defected SWCNTs with the perfect SWCNTs, we found that the vacancy defect introduces localized electronic states near the Fermi level, thus enhancing the chemical reactivity of the SWCNTs. We then studied the reaction mechanisms of the vacancy defect on the (5,5) SWNCT with NO and O₃. We have discovered that the reaction between NO and the vacancy defect provides a possible way to fabricate the substitutionally N-doped SWCNTs. We also obtained a microscopic understanding of the ozonization at the vacancy defect site of the SWCNT. To further understand the doping effects, we have studied the precious metal Ptdoped SWCNTs at different positions of the (5,5) SWCNT rod. We found that the doping of Pt in the SWCNT rod results in localized states at Pt, thus rendering Pt as the active center in chemical reactions. We found that the doping of Pt in the middle of the sidewall of the nanorod has a stronger interaction with adsorbates (e.g., H₂ and C₂H₄) than the doping of Pt at the hemispheric caps of the nanorod.

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