Metal-Enhanced Fluorescence of Carbon Nanotubes

TL;DR

This study demonstrates a significant increase in the photoluminescence efficiency of surfactant-coated carbon nanotubes when placed on nanostructured gold, due to resonance coupling with surface plasmons, revealing potential for enhanced nanotube-based optoelectronic devices.

Contribution

First demonstration of metal-enhanced fluorescence in surfactant-coated carbon nanotubes on gold, elucidating the mechanism involving surface plasmon resonance and distance-dependent effects.

Findings

Photoluminescence quantum yield increased over 10-fold.

Strong MEF observed without quenching at close contact.

Enhancement linked to surface plasmon resonance and radiative lifetime shortening.

Abstract

The photoluminescence (PL) quantum yield of single-walled carbon nanotubes (SWNTs) is relatively low, with various quenching effects by metallic species reported in the literature. Here, we report the first case of metal enhanced fluorescence (MEF) of surfactant-coated carbon nanotubes on nanostructured gold substrates. The photoluminescence quantum yield of SWNTs is observed to be enhanced more than 10-fold. The dependence of fluorescence enhancement on metal-nanotube distance and on surface plasmon resonance (SPR) of the gold substrate for various SWNT chiralities is measured to reveal the mechanism of enhancement. Surfactant-coated SWNTs in direct contact with metal exhibit strong MEF without quenching, suggesting a small quenching distance for SWNTs on the order of the van der Waals distance, beyond which the intrinsically fast non-radiative decay rate in nanotubes is little enhanced by metal. The metal enhanced fluorescence of SWNTs is attributed to radiative lifetime shortening through resonance coupling of SWNT emission to the re-radiating dipolar plasmonic modes in the metal.