Levitodynamic spectroscopy for single nanoparticle characterisation

TL;DR

This paper introduces levitodynamic spectroscopy, a non-contact optical method for characterizing single nanoparticles by analyzing their motion when optically levitated, enabling high-resolution size and shape detection in situ.

Contribution

The study presents a novel optical levitation technique to characterize single nanoparticles' shape and size through their rotational and oscillatory motion, without requiring substrates or solvents.

Findings

Successfully measured nanoparticle shape and size with nanometer resolution.

Demonstrated agreement between experimental data and simulations.

Achieved detection of size differences as small as a few nanometers.

Abstract

Fast detection and characterization of single nanoparticles such as viruses, airborne aerosols and colloidal particles are considered to be particularly important for medical applications, material science and atmospheric physics. In particular, non-intrusive optical characterization, which can be carried out in isolation from other particles, and without the deleterious effects of a substrate or solvent, is seen to be particularly important. Optical characterization via the scattering of light does not require complicated sample preparation and can in principle be carried out in-situ. We describe the characterization of single nanoparticle shape based on the measurement of their rotational and oscillatory motion when optically levitated within vacuum. Using colloidally grown yttrium lithium fluoride nanocrystals of different sizes, trapped in a single-beam optical tweezer, we demonstrate the utility of this method which is in good agreement with simulations of the dynamics. Size differences as small as a few nanometers could be resolved using this technique offering a new optical spectroscopic tool for non-contact characterization of single nanoparticles in the absence of a substrate.