Burst-by-Burst Measurement of Rotational Diffusion at Nanosecond Resolution Reveals Hot-Brownian Motion and Single-Chain Binding.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37352134.
- Also identified by DOI 10.1021/acsnano.3c03392 and PMC identifier 10339794.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
We record dark-field scattering bursts of individual gold nanorods, 52 × 15 nm<sup>2</sup> in average size, freely diffusing in water suspension. We deduce their Brownian rotational diffusion constant from autocorrelation functions on a single-event basis. Due to spectral selection by the plasmonic resonance with the excitation laser, the distribution of rotational diffusion constants is much narrower than expected from the size distribution measured by TEM. As rotational diffusion depends on particle hydrodynamic volume, viscosity, and temperature, it can sense those parameters at the single-particle level. We demonstrate measurements of hot Brownian rotational diffusion of nanorods in temperature and viscosity gradients caused by plasmonic heating. Further, we monitor hydrodynamic volumes of gold nanorods upon addition of very low concentrations of the water-soluble polymer PVA, which binds to the particles, leading to measurable changes in their diffusion constant corresponding to binding of one to a few polymer coils. We propose this analysis technique for very low concentrations of biomolecules in solution.