Evaluation of the uncertainty in the measurement of nanoparticle size by dynamic light scattering

Abstract

Of paramount importance in the field of nanotechnology is the ability to measure reliably the
properties of nanomaterials, especially their size. In general, just an estimate of size is not
sufficient: a quantitative indication of the quality of the estimate in the form of an assessment of
its uncertainty is necessary, as well. For example, standard ISO/IEC 17025:2017 (General
Requirements for the Competence of Testing and Calibration Laboratories) stipulates that
appropriate methods and procedures shall be used for laboratory activities and for the analysis
of data, including the identification and quantification of all contributions to the measurement
uncertainties.
In order to facilite compliance with requirements such as these, we propose a procedure to
establish an uncertainty budget for the measurement of the size of monodispersed nanoparticles
in liquid suspension by dynamic light scattering (DLS). We take as a reference the general
approach proposed in the Guide to the Expression of Uncertainty in Measurement (GUM). To
our knowledge, this is the first time correlations that exist between the input quantities to the
DLS measurement model are taken into account. An example involving a reference material
consisting of 60 nm-nominal polystyrene nanoparticles suspended in water serves to illustrate
our proposal.