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Theoretical studies on physical and chemical properties of tubular nanostructures of boron, boron nitride, gold and zinc oxide

Wei An, University of Nebraska - Lincoln

Abstract

The physical and chemical properties of tubular nanostructures of boron, boron nitride, gold, and zinc oxide have been theoretically studied. First, calculations using high-level ab initio methods suggest that double-ring tubular isomer of B20 is likely the global minimum of neutral B20 cluster. The planar-to-tubular structural transition starts at n=20 for neutral Bn clusters but should occur beyond n=20 for anion Bn - clusters. Second, adsorption of chemical species H, O, CO, H 2, O2, H2O and NH3 at a perfect site (PS) and near a Stone-Wales (SW) defect on the sidewall of zigzag (8,0) and armchair (5,5) boron nitride (BN) single-walled nanotubes (SWNTs) was studied using density-functional theory (DFT) method. Reactivity near SW defect is generally higher than that at the PS due to the formation of frustrated B-B and N-N bonds and the local strain caused by pentagonal and heptagonal pairs. Third, a systematic DFT study on field-emission performance of prototype BN nanocones has shown that two 120°-BN nanocones are the promising candidates for the field-emission electron source based on their ionization potential and electron affinity. The doping/adsorption of an impurity atom is unfavorable to the field emission. Fourth, a DFT study of CO oxidation on Au helical (5,3) nanotubes suggests that CO oxidation is initiated by CO+O2→OOCO→CO 2+O reaction, where a low activation barrier of 0.29eV and peroxo-type O-O-CO intermediate along the reaction pathway exist, and followed by CO +O→CO 2 reaction with a barrier of 0.03eV. Fifth, a DFT study on the potential application of a prototype ZnO (6,0) zigzag SWNT as gas sensor for H 2, O2, CO, NH3 and NO2 shows that the electron-donor molecules (CO and NH3) tend to enhance the concentration of major carriers (electrons), whereas the electron-acceptor molecules (O 2 and NO2) tend to reduce the concentration. O2 and NO2 can dissociate at the oxygen vacancy (VO) sites through filling the VO with one atomic O originated from the adsorbates. The dissociation of O2 is exothermic and barrierless while the dissociation of NO 2 is also exothermic but entails a small activation barrier (0.49eV). ^

Subject Area

Chemistry, Physical

Recommended Citation

An, Wei, "Theoretical studies on physical and chemical properties of tubular nanostructures of boron, boron nitride, gold and zinc oxide" (2008). ETD collection for University of Nebraska - Lincoln. AAI3291922.
http://digitalcommons.unl.edu/dissertations/AAI3291922

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