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

TL;DR

This study uses ab-initio calculations to analyze the stability and optical properties of noncovalently functionalized carbon nanotubes and graphene with tetraphenylporphyrins, revealing strong π-π interactions and potential doping effects.

Contribution

It provides detailed insights into the stability and optical behavior of TPP-functionalized CNTs and graphene, highlighting the effects of diameter, chirality, and charge transfer mechanisms.

Findings

Strong π-π interactions with binding energies 1.1-1.8 eV for CNTs

Stable graphene-TPP binding energy of 3.2 eV with redshift in absorption

Charge transfer from TPP to graphene indicating n-type doping

Abstract

The stability, electronic and optical properties of single-walled carbon nanotubes (CNTs) and graphene noncovalently functionalized with free-base tetraphenylporphyrin (TPP) molecules is addressed by density functional theory calculations, including corrections to dispersive interactions. We study the TPP 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 a quite strong $\pi$-$\pi$ interaction between TPP and the CNT surface, with binding energies ranging from 1.1 to 1.8 eV, where higher energies can be associated with increasing CNT diameters. We also find that the TPP optical absorptions would not be affected by the CNT diameter or chirality. Results for the TPP physisorption on graphene show a remarkable stability with binding energy of 3.2 eV, inducing a small redshift on the $\pi$-stacked TPP absorption bands. The strong graphene-TPP interaction also induces a charge transfer from TPP to graphene, indicating a $n$-type doping mechanism without compromising the graphene structure.