The influence of Cu-doping on aluminum nitride, silicon carbide and boron nitride nanotubes’ ability to detect carbon dioxide; DFT study Zabiollah Mahdavifar n , Nasibeh Abbasi Computational Chemistry Group, Department of Chemistry, Faculty of Science, Shahid Chamran University, Ahvaz, Iran HIGHLIGHTS  Cu strongly bound to the outer sur- faces of AlNNT, BNNT and SiCNT.  Adsorption of CO 2 onto the Cu- functionalized AlNNT, BNNT and SiCNT is studied.  CO 2 tends to be strongly physisorbed onto Cu-decorated AlNNT, BNNT and SiCNT.  A Cu-doped nanotube is a promising candidate for monitoring CO 2 mole- cules.  A considerable charge transfer reduced the energy gap of the nano- tube/Cu–CO 2 system. GRAPHICAL ABSTRACT The potential usage of Cu-functionalized armchair [4,4] silicon carbide (SiC), aluminum nitride (AlN) and boron nitride (BN) single-walled nanotubes as nanodevices for CO 2 monitoring is investigated . article info Article history: Received 26 August 2013 Received in revised form 13 September 2013 Accepted 16 September 2013 Available online 21 September 2013 Keywords: Inorganic nanotubes Cu-functionalized CO 2 adsorption DFT abstract In this research, the potential use of Cu-functionalized [4,4] silicon carbide (SiC), aluminum nitride (AlN) and boron nitride (BN) single-walled nanotubes as nanodevices for CO 2 monitoring is investigated. It is found that Cu-doping the different sites of the considered nanotubes and combining these nanotubes with CO 2 gas molecules are both exothermic processes, and the relaxed geometries are stable. Our results reveal that the CO 2 gas molecules can be strongly physisorbed on the Cu-doped nanotubes, accompanied by large adsorption energy. Compared with the weak adsorption of CO 2 molecule onto pristine BNNT and SiCNT, the CO 2 molecule tends to be strongly physisorbed onto Cu-decorated BNNT and SiCNT with an appreciable adsorption energy. Furthermore, the results indicate that Cu-functionalized SiCNT is more favorable than Cu-doped BNNT and AlNNT structures for CO 2 adsorption. Natural bond orbital analysis indicates that the adsorption of a CO 2 molecule onto Cu-doped nanotubes is influenced by the electronic conductance and mechanical properties of the nanotube, which could serve as a signal for a gas sensor. It appears that the considerable charge transfer from the Cu-doped nanotubes to a CO 2 molecule reduces the energy gap. These observations suggest that the Cu-doped-SiCNT, -BNNT and -AlNNT can be introduced as promising candidates for gas sensor devices that detect CO 2 molecules. & 2013 Elsevier B.V. All rights reserved. 1. Introduction Carbon dioxide, CO 2 , is the focus of much current research activity [1,2]. Detection of CO 2 molecules is very important in environmental, biological, and industrial processes [3–5] because CO 2 molecules are the most readily available renewable, non-toxic, non-flammable, and highly functional carbon resource [6]. On the other hand, CO 2 is the main greenhouse gas that contributes to climate change, which is increasing drastically due to the combus- tion of fossil fuels and chemical processing. The need for CO 2 sensors for medical applications, atmospheric concentration con- trol, and indoor climate monitoring [7–9] is one of the most Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/physe Physica E 1386-9477/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.physe.2013.09.008 n Corresponding author. Tel.: þ98 9163015227; fax: þ98 611 3331042. E-mail addresses: z_mahdavifar@scu.ac.ir, zb_nojini@scu.ac.ir (Z. Mahdavifar). Physica E 56 (2014) 268–276