Theoretical Investigations on the Healing of Monovacancies in Single-Walled Carbon Nanotubes by Adsorption of Carbon Monoxide
journal contributionposted on 16.12.2010 by Francesco Mercuri
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The outstanding properties of single-walled carbon nanotubes (CNTs) are often impaired by the presence of structural defects, such as vacancies, as consequence of peculiar growth techniques or electron irradiation. However, the changes in the electronic structure due to the presence of defects can also induce the formation of sites at the sidewall exhibiting unusual reactive properties. In particular, monovacancies constitute active reaction sites toward the addition of different kinds of adsorbates, which can potentially cure the defects and restore the properties of pristine nanotubes. In this work, the interaction of carbon monoxide with monovacancies on single-walled CNTs is investigated by means of an integrated approach, based on density functional theory, consisting of both static and molecular dynamics calculations for the evaluation of potential-energy minima and free-energy barriers. Our simulations suggest viable reaction routes for the healing of single vacancies on the sidewall by subsequent interaction with two CO molecules, leading to the restoration of a perfect hexagonal carbon-atom network. The outlined results clarify the role of CO as precursor for the growth of nanotubes both as carbon source and as active chemical species for the formation of a defect-free sidewall.