3D Spectroscopic Tracking of Individual Brownian Nanoparticles during Galvanic Exchange

TL;DR

This paper introduces a real-time holography-based 3D tracking method for individual nanoparticles, enabling continuous spectroscopic monitoring of chemical reactions at the single-particle level in solution.

Contribution

The study presents a novel real-time 3D tracking technique that dynamically adjusts the confocal volume to monitor single nanoparticles during galvanic exchange reactions.

Findings

Successfully tracked individual nanoparticles in real-time.

Observed composition changes and transformation kinetics at the single-particle level.

Revealed different kinetics for free and tethered particles.

Abstract

Monitoring chemical reactions in solutions at the scale of individual entities is challenging: single particle detection requires small confocal volumes which are hardly compatible with Brownian motion, particularly when long integration times are necessary. Here, we propose a real-time (10 Hz) holography-based nm-precision 3D tracking of single moving nanoparticles. Using this localization, the confocal collection volume is dynamically adjusted to follow the moving nanoparticle and allow continuous spectroscopic monitoring. This concept is applied to the study galvanic exchange in freely-moving collo{\"i}dal silver nanoparticles with gold ions generated in-situ. While the Brownian trajectory reveals particle size, spectral shifts dynamically reveal composition changes and transformation kinetics at the single object level, pointing at different transformation kinetics for free and tethered particles.