Huygens-Kamerlingh Onnes Laboratory, Leiden University, Postbus 9504, 2300 RA Leiden, The Netherlands.
Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany.
ACS Nano. 2023 Jul 11;17(13):12684-12692. doi: 10.1021/acsnano.3c03392. Epub 2023 Jun 23.
We record dark-field scattering bursts of individual gold nanorods, 52 × 15 nm 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.
我们记录了在水中自由扩散的单个金纳米棒的暗场散射爆发，平均尺寸为 52×15nm。我们从单事件的自相关函数推导出它们的布朗旋转扩散常数。由于等离子体共振与激发激光的光谱选择，旋转扩散常数的分布比通过 TEM 测量的尺寸分布窄得多。由于旋转扩散取决于颗粒的流体力学体积、粘度和温度，因此它可以在单粒子水平上感知这些参数。我们展示了在由等离子体加热引起的温度和粘度梯度下纳米棒的热布朗旋转扩散的测量。此外，我们在添加极低浓度的水溶性聚合物 PVA 时监测金纳米棒的流体力学体积，该聚合物与颗粒结合，导致其扩散常数发生可测量的变化，对应于一个或几个聚合物线圈的结合。我们提出了这种分析技术，用于溶液中非常低浓度的生物分子。
