Particle size measurements of dark and concentrated dispersions by dynamic light scattering

In this paper, we introduce an innovative device for nanoparticle sizes measurement in dark and concentrated media based on dynamic light scattering (DLS). Conventional DLS is a powerful technique to characterize dilute and transparent dispersions of nanoparticles. However, it becomes ineffective in dark media, since the laser beam is absorbed by sample and can induce an interfering effect. In the case of concentrated sample, the artefact of multiple scattering also biases the measurement. To circumvent these problems, we propose an original optical configuration that combines back-scattered light detection and the capability to control the sample thickness. The benefits of these improvements are discussed through experimental results obtained from measurement on model latex dispersions.