Stepwise Quenching of Exciton Fluorescence in Carbon Nanotubes by Single Molecule Reactions

TL;DR

This study demonstrates that single-molecule reactions can cause stepwise quenching of exciton fluorescence in carbon nanotubes, enabling nanoscale chemical sensing through near-infrared photoluminescence microscopy.

Contribution

It reveals the discrete, localized effects of chemical reactions on exciton fluorescence in individual nanotubes, with insights into exciton diffusion and sensing capabilities.

Findings

Discrete fluorescence steps correspond to localized chemical reactions.

Exciton diffusional range is approximately 90 nanometers.

Each exciton interacts with about 10,000 atomic sites during its lifetime.

Abstract

Single-molecule chemical reactions with individual single-walled carbon nanotubes were observed through near-infrared photoluminescence microscopy. The emission intensity within distinct submicrometer segments of single nanotubes changes in discrete steps after exposure to acid, base, or diazonium reactants. The steps are uncorrelated in space and time, and reflect the quenching of mobile excitons at localized sites of reversible or irreversible chemical attack. Analysis of step amplitudes reveals an exciton diffusional range of about 90 nanometers, independent of nanotube structure. Each exciton visits approximately 104 atomic sites during its lifetime, providing highly efficient sensing of local chemical and physical perturbations.