Functionalization of single-walled (n,0) carbon and boron nitride nanotubes by carbonyl derivatives (n=5, 6): a DFT study

By using density functional theory calculations, the chemical functionalization of finite-sized (5,0) and (6,0) carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) by different carbonyl derivatives -COX (X = H, CH3, OCH3, OH, and NH2) is studied in terms of geometrical and electronic structure properties. Also, the benefits of local reactivity descriptors is studied to characterize the reactive sites of the external surface of the tubes. These local reactivity descriptors include the electrostatic potential V-S(r) and average local ionization energy (I) over bar (S)(r) on the surfaces of these nanotubes. The estimated (I) over bar (S)(r) values show that the functionalized CNTs tend to activate the surface toward electrophilic/radical attack. Results show that the chemical functionalization of CNTs leads to the reduction of V-S(r) values and therefore enhances the surface reactivity. On the other hand, BNNTs resist chemical functionalization due to the negligible decrease in the V-S,V-min and (I) over bar (S, min) values. Generally, in contrast to BNNTs, the chemical functionalization of CNTs can considerably improve their surface reactivity. To verify the surface reactivity pattern based on the chosen reactivity descriptors, the reaction energies for the interaction of an H+ ion or hydrogen radical with external surface of the functionalized CNTs and BNNTs are calculated. A general feature of all studied systems is that stronger potentials are associated with regions of higher curvature.