Characterization of Colloidal Nanocrystal Surface Structure using Small Angle Neutron Scattering and Efficient Bayesian Parameter Estimation

Published

June 28, 2019

Author(s)

Samuel W. Winslow, Wenbi Shcherbakov-Wu, Yun Liu, William A. Tisdale, James W. Swan

Abstract

Complete structural characterization of colloidal nanocrystals is challenging due to rapid variation in the electronic, vibrational, and elemental properties across the nanocrystal surface. while electron microscopy and X-ray scattering techniques can provide detailed information about the inorganic nanocrystal core, these techniques provide little information about the molecular ligands coating the nanocrystal surface. Moreover, because most models for scattering data are parametrically nonlinear, uncertainty estimates for parameters are challenging to formulate robustly. Here, using oleate-capped PbS quantum dots as a model system, we demonstrate the capability of small angle neutron scattering (SANS) in resolving core, ligand-shell, and solvent structure for well-dispersed nanocrystals using a single technique. SANS scattering data collected at eight separate solvent deuteration fractions were used to characterize the structure of the nanocrystals in reciprocal space. Molecular dynamics simulations were used to develop a coarse-grained form factor describing the scattering length density profile of ligand-stabilized nanocrystals in solution. We introduce an affine invariant Markov chain Monte Carlo method to efficiently perform nonlinear parameter estimation for the form factor describing such dilute solutions. This technique yields robust uncertainty estimates. This experimental design is broadly applicable across colloidal nanocrystal material systems including emergent perovskite nanocrystals and the parameter estimation protocol significantly accelerates characterization and provides new insights into the atomic and molecular structure of colloidal nanomaterials.

Citation

Journal of Chemical Physics

Volume

150

Issue

24

Pub Type

Journals

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Keywords

small angle neutron scattering, nanocrystal, bayesian parameter estimation

Citation

Winslow, S. , Shcherbakov-Wu, W. , Liu, Y. , Tisdale, W. and Swan, J. (2019), Characterization of Colloidal Nanocrystal Surface Structure using Small Angle Neutron Scattering and Efficient Bayesian Parameter Estimation, Journal of Chemical Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=928187 (Accessed April 20, 2024)