Noncovalent functionalization of carbon nanotubes and graphene with tetraphenylporphyrins: Stability and optical properties from ab-initio calculations

摘要

The stability, electronic and optical properties of single-walled carbonnanotubes (CNTs) and graphene noncovalently functionalized with free-basetetraphenylporphyrin (TPP) molecules is addressed by density functional theorycalculations, including corrections to dispersive interactions. We study theTPP physisorption on 42 CNT species, particularly those with chiral indices($n$,$m$), where $5 \leq n \leq 12$ and $0\leq m\leq n$. Our results show aquite strong $\pi$-$\pi$ interaction between TPP and the CNT surface, withbinding energies ranging from 1.1 to 1.8 eV, where higher energies can beassociated with increasing CNT diameters. We also find that the TPP opticalabsorptions would not be affected by the CNT diameter or chirality. Results forthe TPP physisorption on graphene show a remarkable stability with bindingenergy of 3.2 eV, inducing a small redshift on the $\pi$-stacked TPP absorptionbands. The strong graphene-TPP interaction also induces a charge transfer fromTPP to graphene, indicating a $n$-type doping mechanism without compromisingthe graphene structure.