Dynamic ultrasound scattering analysis of highly concentrated and polydisperse nanoparticle suspensions in comparison with dynamic light scattering

Abstract Dynamic ultrasound scattering (DSS) was applied to analyze concentrated silica particle suspensions at volume fractions up to 25 vol% (42 wt%). Transmission electron microscopy (TEM) showed an intensity-weighted mean diameter d Z of 88 nm (coefficient of variation CV Z = 28%). Predicted DSS correlation functions based on TEM data showed excellent agreement with measured values. Without using the predetermined TEM results, DSS analysis evaluated d Z and CV Z as 89 nm and 0.26, respectively. Ion conductivity measurements revealed that in the case of polydisperse, highly concentrated particle suspensions, the influence of electrostatic interactions is significantly stronger compared to monodisperse or dilute systems, even at salt concentrations equivalent to those in the stock solution. The supplementary three-dimensional modulated dynamic light scattering measurements yielded d Z and CV Z values of 76 nm and 0.3, respectively. Although d Z was slightly underestimated, the results supported the findings of electrostatic interactions revealed by DSS.