Enhancing the reactivity of carbon-nanotube for carbon monoxide detection by mono- and co-doping of boron and nitrogen heteroatoms: A DFT and TD-DFT study

Abstract

Carbon nanotube (CNT) doped with boron (p-type) and nitrogen (n-type) atoms (BxNy@CNT) have attracted the attention of many experimental and theoretical researchers for variety of industrial applications such as catalytic processes in fuel cells and detection of environmental pollutants. BxNy@CNTs can be synthesized with different concentrations (i.e. x/y ratios) and various configurations (i.e. relative position of B to N atoms), and therefore, BxNy@CNTs show an unpredictable reactivity in physical and chemical reactions. Hence, the selection of an appropriate BxNy@CNTs combination to achieve the most efficiency for a specific application is a challenge for experimentalists. In this regard, herein, we investigated theoretically different combinations of BxNy@CNT (x, y = 0, 1), i.e. single doped boron (B@CNT) and nitrogen (N@CNT) along with multi-doped boron and nitrogen BN@CNT, in three ortho, meta and para-BN@CNT configurations for detection and removing of monoxide carbon (CO) as a diatomic toxic gas. Theoretical calculations were done based on the quantum calculations in DFT and TD-DFT levels of theory using M06-2X (and B3LYP-D3)/6-31+G(d,p) functional/basis set. We focused on variations in electrical (useable for electronic based nano-sensor devices) and optical (useable for optical based nano-sensor devices) properties after adsorption of CO gas. Results indicate that, compared to the other combinations, co-doping of boron in para position relative to nitrogen (para-BN@CNT) can significantly activate the inert-CNT toward CO sensing. Theoretical results of this work can help experimental scientists in the synthesis and selection of the appropriate BxNy@CNT combinations for applying in nanotube based nano-sensors.