Artifact-Free Dark-Field Scattering Microspectroscopy for Single-Particle Chiral Measurements at the Nanoscale

Area of Science:

• Plasmonics
• Chiral Nanooptics
• Single-Particle Spectroscopy

Background:

• Characterizing single-particle chirality is vital for understanding structure-optochirality relationships in plasmonic nanostructures.
• Conventional dark-field scattering microspectroscopy for circular differential scattering is prone to linear dichroism artifacts, compromising accuracy.

Purpose of the Study:

• To develop an improved dark-field scattering microspectrometer with hyperspectral imaging for accurate single-particle chiral measurements.
• To address and eliminate artifacts caused by linear dichroism in circular differential scattering measurements.

Main Methods:

• Utilized unpolarized excitation and specialized detection optics including a broadband quarter waveplate and Wollaston prism.
• Implemented dual measurements with the waveplate's fast axis rotated ± 45° to cancel linear dichroism artifacts.
• Employed finite element simulations to analyze near-field coupling in chiral nanostructures.

Main Results:

• Successfully eliminated linear dichroism artifacts in circular differential scattering measurements of achiral gold nanorods.
• Preserved and accurately measured the circular differential scattering of chiral nanostructures.
• Confirmed that near-field coupling between nanorods is responsible for the circular differential scattering in dimer structures.

Conclusions:

• The developed method provides a robust solution for accurate chiral measurements of plasmonic nanostructures without instrument modification.
• This technique is well-suited for the advancement of chiral nanooptics and nanoplasmonics research.
• The findings enhance the ability to study structure-optochirality relationships at the single-particle level.