Mie Voids for Single-Molecule Fluorescence Enhancement in Wavelength-Scale Detection Volumes

Area of Science:

• Nanophotonics
• Optical Sensing
• Biophotonics

Background:

• Mie voids are promising nanophotonic platforms for light manipulation and optical sensing.
• Their large detection volumes are suitable for low-concentration single-molecule fluorescence biosensing.
• Quantifying fluorescence enhancement for diffusing molecules in Mie void optical antennas is not well-understood.

Purpose of the Study:

• To explore the potential of Mie voids to enhance single-molecule fluorescence.
• To quantify the fluorescence enhancement of diffusing fluorophores using Mie void nanoantennas.
• To investigate the factors limiting fluorescence enhancement in Mie void systems.

Main Methods:

• Utilized fluorescence correlation spectroscopy (FCS) to study diffusing AF647 fluorophores.
• Optimized Mie void structure to confine excitation light and enhance intensity.
• Monitored changes in molecular number and single-molecule brightness.

Main Results:

• Demonstrated Mie void ability to enhance single-molecule brightness up to 2.8 times.
• Observed a reduction in the effective detection volume within the Mie void.
• Identified limited fluorescence enhancement due to emission directed away from the optical axis.

Conclusions:

• Mie void nanoantennas show potential for single-molecule fluorescence spectroscopy.
• Optimized Mie voids can enhance excitation intensity and single-molecule brightness.
• Azimuthal emission patterns can limit the overall fluorescence enhancement efficiency.