Experimental determination of distance and orientation of metallic nanodimers by polarization dependent plasmon coupling

TL;DR

This paper presents a novel experimental method to measure subdiffraction distances and orientations between metallic nanodimers using polarization-dependent plasmon coupling, enabling detailed tracking of nanoscale biological interactions.

Contribution

The study introduces a new technique combining polarization control and spectral separation to determine distances and orientations of metallic nanodimers with high precision.

Findings

Successfully measured radii, distances, and orientations of nanodimers

Statistical distributions matched theoretical expectations

Demonstrated potential for long-term biological process tracking

Abstract

Live cell imaging using metallic nanoparticles as tags is an emerging technique to visualize long and highly dynamic processes due to the lack of photobleaching and high photon rate. However, the lack of excited states as compared to fluorescent dyes prevents the use of resonance energy transfer and recently developed super resolution methods to measure distances between objects closer that the resolution limit. In this work, we experimentally demonstrate a technique to determine subdiffraction distances based on the near field coupling of metallic nanoparticles. Due to the symmetry breaking in the scattering cross section, not only distances but also relative orientations can be measured. Gold nanoparticles were prepared on glass in such way that a small fraction of dimers was present. The sample was sequentially illuminated with two wavelengths to separate background from nanoparticle scattering based on their spectral properties. A novel total internal reflection illumination scheme in which the polarization can be rotated was used to further minimize background contributions. In this way, radii, distance and orientation were measured for each individual dimer and their statistical distributions were found to be in agreement with the expected ones. We envision that this technique will allow fast and long term tracking of relative distance and orientation in biological processes.