Shape Measurement of Single Gold Nanorods in Water Using Open-access Optical Microcavities

TL;DR

This paper presents a novel optical microcavity technique for real-time, in-situ measurement of the aspect ratio of single rod-shaped nanoparticles in water with approximately 1% resolution.

Contribution

It introduces a new method using polarization analysis in optical microcavities for accurate, real-time shape measurement of individual nanoparticles in solution.

Findings

Achieved ~1% resolution in aspect ratio measurement.

Enabled in-situ, single-particle shape analysis in fluid environments.

Potential applications in nanoparticle characterization and water safety monitoring.

Abstract

Shape measurement of rod-shaped particles in fluids is an outstanding challenge with applications in characterising synthetic functional nanoparticles and in early warning detection of rod-shaped pathogens in water supplies. However, it is challenging to achieve accurate and real-time measurements at a single particle scale in solution with existing methods. Here we introduce a novel technique to measure the aspect ratio of rod-shaped particles by analysing changes in the polarisation state of a laser beam transmitted through an optical microcavity through which the particle diffuses. The resolution in aspect ratio measurement is found to be around 1%. Our work opens the new possibility of in-situ and single-particle shape measurements, which have promising applications in nanoparticle characterisation, water monitoring, and beyond.