Parallel heterodyne detection of dynamic light scattering spectra from gold nanoparticles diffusing in viscous fluids

TL;DR

This paper introduces a parallel heterodyne detection method for analyzing light scattering spectra from gold nanoparticles in viscous fluids, enabling high-frequency, low-light measurements of particle dynamics.

Contribution

The study presents a novel microscopy scheme that allows ensemble-averaged fluctuation measurements over multispeckle recordings at high temporal frequencies.

Findings

Cutoff frequencies scale linearly with viscosity as expected.

Method works across viscosities 1-15 times water.

Enables measurements up to 10 kHz with 12 Hz framerate.

Abstract

We developed a microscope intended to probe, using a parallel heterodyne receiver, the fluctuation spectrum of light quasi-elastically scattered by gold nanoparticles diffusing in viscous fluids. The cutoff frequencies of the recorded spectra scale up linearly with those expected from single scattering formalism in a wide range of dynamic viscosities (1 to 15 times water viscosity at room temperature). Our scheme enables ensemble-averaged optical fluctuations measurements over multispeckle recordings in low light, at temporal frequencies up to 10 kHz, with a 12 Hz framerate array detector.