Achieving High Temporal Resolution in Single-Molecule Fluorescence Techniques using Plasmonic Nanoantennas

TL;DR

This paper introduces a method using plasmonic horn nanoantennas to significantly increase fluorescence brightness, enabling sub-millisecond temporal resolution in single-molecule studies and advancing biological and chemical sensing applications.

Contribution

The authors demonstrate a novel application of optical horn nanoantennas achieving 90% light collection efficiency and 2 million photons/sec brightness, surpassing previous limitations for high-resolution fluorescence.

Findings

Achieved 90% collection efficiency with plasmonic nanoantennas.

Reached fluorescence brightness of 2 million photons/sec/molecule.

Enabled microsecond binning and fast FCS measurements.

Abstract

Single-molecule fluorescence techniques are essential for investigating the molecular mechanisms in biological processes. However, achieving sub-millisecond temporal resolution to monitor fast molecular dynamics remains a significant challenge. The fluorescence brightness is the key parameter that generally defines the temporal resolution for these techniques. Conventional microscopes and standard fluorescent emitters fall short in achieving the high brightness required for sub-millisecond monitoring. Plasmonic nanoantennas have been proposed as a solution, but despite huge fluorescence enhancement have been obtained with these structures, the brightness generally remains below 1 million photons/s/molecule. Therefore, the improvement of temporal resolution has been overlooked. In this article, we present a method for achieving high temporal resolution in single-molecule fluorescence techniques using plasmonic nanoantennas, specifically optical horn antennas. We demonstrate about 90% collection efficiency of the total emitted light, reaching a high fluorescence brightness of 2 million photons/s/molecule in the saturation regime. This enables observations of single molecules with microsecond binning time and fast fluorescence correlation spectroscopy (FCS) measurements. This work expands the applications of plasmonic antennas and zero-mode waveguides in the fluorescence saturation regime towards brighter single-molecule signal, faster temporal resolutions and improved detection rates to advance fluorescence sensing, DNA sequencing and dynamic studies of molecular interactions.