Modeling super-resolution SERS using a T-matrix method to elucidate molecule-nanoparticle coupling and the origins of...

Area of Science:

• Plasmonics
• Super-resolution microscopy
• Computational modeling

Background:

• Significant experimental progress has been made in plasmon-based super-resolution imaging.
• Theoretical prediction of diffraction-limited images in these systems remains a challenge.

Purpose of the Study:

• To introduce a computational method for modeling diffraction-limited images from super-resolution surface-enhanced Raman scattering (SERS) microscopy.
• To calculate localization errors and image intensities for nanoparticle-molecule systems.

Main Methods:

• Utilized a modified generalized Mie (T-matrix) theory with a point dipole source to calculate light scattering.
• Employed vectorial diffraction theory to compute diffraction-limited images.
• Calculated multipole expansion for each emitter and their coherent superposition.

Main Results:

• The method reveals anisotropic excitation distorts the nanoparticle center by ~50% of its radius towards the molecule.
• This distortion arises from a weak quadrupole resonance interfering with the dipole field.
• Image intensity and distortion depend on the phase relationship between nanoparticle and molecule fields.

Conclusions:

• The developed computational method offers new insights into strong coupling between molecules and nanoparticles in SERS.
• It accurately predicts image distortions and localization errors, aiding in understanding plasmon-enhanced super-resolution experiments.
• The method's applicability to various wavelengths and particle sizes highlights its versatility.