%0 Journal Article
%T Theoretical Studies of Substitutionally Doped Single-Walled Nanotubes
%A Charles See Yeung
%A Ya Kun Chen
%A Yan Alexander Wang
%J Journal of Nanotechnology
%D 2010
%I Hindawi Publishing Corporation
%R 10.1155/2010/801789
%X The rich chemistry of single-walled carbon nanotubes (SWCNTs) is enhanced by substitutional doping, a process in which a single atom of the nanotube sidewall is replaced by a heteroatom. These so-called heteroatom-substituted SWCNTs (HSWCNTs) exhibit unique chemical and physical properties not observed in their corresponding undoped congeners. Herein, we present theoretical studies of both main group element and transition metal-doped HSWCNTs. Within density functional theory (DFT), we discuss mechanistic details of their proposed synthesis from vacancy-defected SWCNTs and describe their geometric and electronic properties. Additionally, we propose applications for these nanomaterials in nanosensing, nanoelectronics, and nanocatalysis. 1. Introduction Iijima＊s pioneering work on carbon nanotubes (CNTs) [1] and single-walled carbon nanotubes (SWCNTs) [2] in the early 1990s sparked a general interest in both fundamental and practical nanotechnology. Over the past 20 years, research efforts have aimed to improve both efficiency and selectivity of nanotube synthesis, as well as understand their chemical reactivity and extraordinary electronic and thermal properties [3每5]. Carbon nanotubes have significant potential for application in molecular electronics [6每15], nanomechanics [16每20], optics [21每24], sensors [6, 25每31], and even catalysis [32]. The molecular structure of SWCNTs can be obtained by rolling up an infinite graphene sheet into a cylinder [33每40]. As illustrated in Figure 1, SWCNTs are characterized by a chiral (or circumferential) vector AB, which is a linear combination of two unit lattice vectors a and b. In other words, where m and n are integers. The pair of indices ( ) determines the diameter and chirality of the tube, as well as the basic electronic character. If , the nanotube is classified as armchair and is metallic in nature (i.e., having a band gap of 0ˋeV). If and both n and m are nonzero, the nanotube is chiral. If , where p is a nonzero integer, the nanotube is semimetallic with a band gap on the order of meV [34, 37]. If , where is a nonzero integer, the nanotube is semiconducting with a band gap on the order of 1ˋeV. Figure 1 also highlights the wrapping direction and translation direction for armchair SWCNTs. Figure 1: A schematic illustrating the wrapping of a graphene sheet to form a SWCNT. The (5,5) SWCNT is shown on the left [ 35]. While carbon nanotubes can be considered a seamless graphene cylinder, the sidewall curvature has a strong influence on electronic structure. Importantly, this leads to a pyramidalization of the
%U http://www.hindawi.com/journals/jnt/2010/801789/