Theoretical Studies on the Adsorption of 5-Aminotetrazole on Single-walled Carbon Nanotubes

In the present study, the adsorption of different isomers of 5-aminotetrazole as an important precursor of high energetic materials on single walled carbon nanotubes (SWCNTs) with different sizes including (5,5), (6,6) and (7,7) chiralities using density functional theory calculations is investigated. Different adsorption modes including edge, parallel and perpendicular to carbon nanotubes have been investigated. It was found that three different isomers of 5-aminotetrazole named 1H, 2H and imino forms physically adsorbed on sidewall and end of nanotubes. The adsorption energies for the parallel and perpendicular modes found in the range of -8.25 to -13.16 and -3.74 to -9.42 kcal/mol, respectively. In addition, for the edge mode the adsorption energies are found in the range of -13.01 to -24.5 kcal/mol. On the other hands, from the HOMO/LUMO gap changes, it can be concluded that the SWCNT with (5,5) chirality might sensitively detect the different isomers of 5-aminotetrazole molecule in comparison with other carbon nanotubes. The global reactivity descriptors, before and after functionalization of 5-AT tautomers onto the SWCNTs are compared and the results analyzed. Based on calculated results, the SWCNTs are expected to be a potential adsorbent as well as sensors for the adsorption of 5-AT in environmental and military systems.