Metallic nanoparticles (MNPs) are prevalent in modern nanotechnologies due to their unique optical properties, chemical and photostabilities, and ease of manipulation. In particular, many recent advances have highlighted the importance… Click to show full abstract
Metallic nanoparticles (MNPs) are prevalent in modern nanotechnologies due to their unique optical properties, chemical and photostabilities, 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 non-degenerate 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, non-destructive technique for characterizing the shapes of individual MNPs and other nanostructures.
               
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