Characterization of size, anisotropy, and density heterogeneity of nanoparticles by sedimentation velocity


  • Materials science faces a significant obstacle in accurately characterizing the size-dependent properties of colloidal inorganic nanocrystals. These nanocrystals display intrinsic polydispersity during synthesis, resulting in heterogeneity in density (ρ), molar mass (M), and particle diameter (d). The addition of surfactants during synthesis to regulate the shape, size, and optical attributes of these nanocrystals complicates the post-synthesis determination of the amount of passivating ligand bound to the nanocrystal surface. Consequently, accurately gauging the nanocrystal diameter becomes challenging due to the ligand shell's presence


  • The study introduced the Custom Grid method, incorporated in UltraScan-III, as a technique to characterize nanoparticles and macromolecules through sedimentation velocity analytical ultracentrifugation. Using CdSe and PbS semiconductor nanocrystals, along with the ultrastable silver nanoparticle (M4Ag44(p-MBA)30) as model systems, the researchers demonstrated that the Custom Grid method can offer high-resolution compositional information for mixtures of solutes heterogeneous in two of the three parameters. When one property is kept constant, this method can discern arbitrary two-dimensional distributions of hydrodynamic attributes. As instances, the method can derive partial specific volume and molar mass where anisotropy remains constant, or it can pinpoint anisotropy and partial specific volume if the molar mass is predefined.


  • The Custom Grid method presents an innovative and effective solution for the intricate challenge of characterizing heterogeneous nanoparticles, especially in circumstances where traditional methods falter due to the presence of added surfactants and the complexity of the inherent polydispersity of nanocrystals. This approach can unveil crucial high-resolution compositional data for diverse solutes, thereby bolstering the understanding and potential applications of colloidal inorganic nanocrystals in materials science.
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Comparability Studies
Material Science (metal nanoparticles, synthetic polymers, drug compounds)

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