(132e) Size and Polydispersity of a Nanoparticle Reference Material By Dynamic Light Scattering

Nanotechnology continues to gain importance in both fundamental and applied sciences. A key parameter of anything “nano” is defined by the typical dimensions encountered, and subsequently the need to measure size. Of the various techniques available to characterize nanoparticle size (such as atomic force [AFM], transmission electron [TEM], or scanning electron microscopy [SEM], and also small angle X-ray scattering [SAXS]), we concentrate on dynamic light scattering [DLS] in this study.

The method itself is a relatively quick, cuvette-based ensemble measurement that extracts information about the diffusion coefficient of the nanoparticles from correlation analysis of the underlying signal fluctuations. DLS is also known as photon correlation spectroscopy [PCS] or quasi-elastic light scattering [QELS]. Due to the nature of the technique, the data are “low resolution” with an inherent polydispersity for even perfect standard materials.

We investigate this polydispersity as well as the other key characteristics of the analysis (z-average cumulant size, intensity distribution, volume distribution) at the practical example of a Nanoparticle reference standard from the National Institute of Standards & Technology. The NIST Reference Material RM8011 contains citrate-stabilized colloidal gold nanoparticles of nominal 10nm diameter.

The experimentally determined standard deviations of the key measurement parameters such as mean size and overall polydispersity may serve as guidance for researchers sizing non-standard samples of unknown nanoparticles that tend to be more polydisperse and show larger statistical variances. These results set a bench mark reference point for a ‘best and smallest in class’ reference nano material near 10nm diameter.