Single-Particle Dynamic Light Scattering: Shapes of Individual Nanoparticles

Abstract

Metallic nanoparticles (MNPs) are prevalent in modern nanotechnologies due to their unique optical properties, chemical and photostability, and ease of manipulation. In particular, many recent advances have highlighted the importance of fundamentally understanding dynamic reconfiguration in MNP morphologies and compositions. Techniques to measure the shape of a single particle are lacking, however, often requiring immobilization, extensive numerical simulations, and irreversible alterations of the particle or its environment. In this work, we introduce “single-particle dynamic light scattering” (SP-DLS) as a far-field technique capable of analyzing the shape of individual, freely diffusing MNPs. Assuming symmetric-top rotors for MNPs and passively confining them to the focal volume of a dark-field microscope for long-term observation, we directly relate polarization dynamic fluctuations in the scattered light to the relative difference between the nondegenerate axes of individual particles. Our results show remarkable agreement with transmission electron microscopy analyses of the same population and allow for unprecedented measurements of the extent of prolate or oblate asphericity of nominally spherical MNPs in solution where the current implementation affords an asphericity detection limit of ∼2.5% assuming a 10% relative error. SP-DLS should serve as a powerful, nondestructive technique for characterizing the shapes of individual MNPs and other nanostructures.

Determining the Spheroid Geometry of Individual Metallic Nanoparticles by Two-Dimensional Single-Particle Dynamic Light Scattering

“…Finally, we studied the precision with which ξ could be determined after assignment of prolate or oblate geometry; specifically, by investigating the behavior of the relative error σ ξ /ξ (see ref 19 for calculation of σ ξ ) as a function of the SNR (Figure 5g−i). Unlike the spheroid assignment, the relationship between σ ξ /ξ and the SNR was insensitive toward the metallic identity of the MNP: For each element, high-precision (i.e., σ ξ /ξ < 0.05) estimates of the shape parameter were possible at low SNR for almost all probed prolate and oblate shape parameters.…”

“…In the first experimental realization of SP-DLS shape analysis, 19 only information from polarization measurements was utilized, where the polarization contrast fluctuation function to be used in the autocorrelation calculation is defined as…”

Sub-millisecond Translational and Orientational Dynamics of a Freely Moving Single Nanoprobe

“…This is accomplished by a new instrument that combines division-of-amplitude polarimetry 21 and realtime 3D single-particle tracking (RT-3DSPT). 30 We further use the division-of-amplitude polarimeter to, at the same time as the position and orientation are determined, perform singleparticle dynamic light scattering (SP-DLS) 31 for determination of the shape of gold nanorods (AuNRs). The setup and experimental geometry at the particle are shown in Figure 1.…”

Approaches to Understanding the Solution-State Organization of Spray-Dried Dispersion Feed Solutions and Its Translation to the Solid State

“…DLS is a powerful technique with broad applications in polymer, nanoparticle, and biomedical sciences as evidenced by its widespread utilization to provide rich sample information including particle size, shape, − particle–particle interactions, − colloidal stability, − aggregation, ,, phase separation, − and translational and rotational diffusion coefficients. − …”