Characterization of size, anisotropy, and density heterogeneity of nanoparticles by sedimentation velocity
Nguyen, Tich Lam
Gorbet, Gary E.
Schirf, Virgil R.
Brookes, Emre H.
Mulvaney, Paul T.
El-Ballouli, AlA'A O.
Demeler, Aysha K.
Hernandez Uribe, Blanca I.
Whetten, Robert L.
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
KAUST Catalysis Center (KCC)
Materials Science and Engineering Program
KAUST Solar Center (KSC)
Functional Nanomaterials Lab (FuNL)
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AbstractA critical problem in materials science is the accurate characterization of the size dependent properties of colloidal inorganic nanocrystals. Due to the intrinsic polydispersity present during synthesis, dispersions of such materials exhibit simultaneous heterogeneity in density ρ, molar mass M, and particle diameter d. The density increments ∂ρ/∂d and ∂ρ/∂M of these nanoparticles, if known, can then provide important information about crystal growth and particle size distributions. For most classes of nanocrystals, a mixture of surfactants is added during synthesis to control their shape, size, and optical properties. However, it remains a challenge to accurately determine the amount of passivating ligand bound to the particle surface post synthesis. The presence of the ligand shell hampers an accurate determination of the nanocrystal diameter. Using CdSe and PbS semiconductor nanocrystals, and the ultrastable silver nanoparticle (M4Ag 44(p-MBA)30), as model systems, we describe a Custom Grid method implemented in UltraScan-III for the characterization of nanoparticles and macromolecules using sedimentation velocity analytical ultracentrifugation. We show that multiple parametrizations are possible, and that the Custom Grid method can be generalized to provide high resolution composition information for mixtures of solutes that are heterogeneous in two out of three parameters. For such cases, our method can simultaneously resolve arbitrary two-dimensional distributions of hydrodynamic parameters when a third property can be held constant. For example, this method extracts partial specific volume and molar mass from sedimentation velocity data for cases where the anisotropy can be held constant, or provides anisotropy and partial specific volume if the molar mass is known. © 2014 American Chemical Society.
SponsorsB.D. acknowledges support from the National Science Foundation (Grants ACI-1339649, OCI-1032742, and MCB-070039). O.M.B., A.O.E., and J.P. acknowledge the financial support of KAUST's University Research Fund. P.M. acknowledges support through ARC Grant DP130102134. E.H.B. acknowledges support through NIH/K25GM090154 and NSF/CHE-1265821. B.I.H.U. thanks the trustees of the Max and Minnie Tomerlin Voelcker Fund for financial support through the Voelcker Biomedical Research Academy scholar program. N.B. and R.L.W. acknowledge funding from NSF-PREM DMR-0934218. T.-L.N. thanks Prof. Helmut Colfen from University of Konstanz for the use of the multi-wavelength detected AUC and Mr. Johannes Walter from the Institute of Particle Technology at the University of Erlangen, Germany, for his assistance and the development of the data acquisition software for the multi-wavelength detector used in these experiments.
PublisherAmerican Chemical Society (ACS)
PubMed Central IDPMC4144751