Chirality dependence of the absorption cross-section of carbon nanotubes

TL;DR

This study investigates how the optical absorption cross-section of carbon nanotubes varies with their chirality, revealing a significant dependence that impacts spectroscopic analysis and nanotube characterization.

Contribution

The paper introduces an innovative method using energy transfer in porphyrin/nanotube compounds to measure absorption cross-sections across various chiralities.

Findings

Absorption cross-section varies up to 2.2 times with chiral angle.

Type I nanotubes exhibit higher absorption.

Luminescence quantum yield remains nearly constant.

Abstract

The variation of the optical absorption of carbon nanotubes with their geometry has been a long standing question at the heart of both metrological and applicative issues, in particular because optical spectroscopy is one of the primary tools for the assessment of the chiral species abundance of samples. Here, we tackle the chirality dependence of the optical absorption with an original method involving ultra-efficient energy transfer in porphyrin/nanotube compounds that allows uniform photo-excitation of all chiral species. We measure the absolute absorption cross-section of a wide range of semiconducting nanotubes at their S22 transition and show that it varies by up to a factor of 2.2 with the chiral angle, with type I nanotubes showing a larger absorption. In contrast, the luminescence quantum yield remains almost constant.