White Paper: Particle Size Measurements Of Dark And Concentrated Dispersion By Dynamic Light Scattering

Research on nanoparticles covers a wide range of interests in the fields of physics, chemistry and material science. In particular, the characterization of particle sizes and aggregates formation is a key issue in some processes of mesoporous materials preparation since they will affect the final network and micropore structures.

In this proceeding, we introduce an innovative device for nanoparticle size measurement in dark and concentrated media. The "Vasco" is issued from a mature technology6 transferred from the Institut Français du Pétrole (IFP) to Cordouan Technologies and was initially developed to study the kinetics of asphaltene aggregation in toluene– heptane mixtures1.

Dynamic light scattering is a suited technique for nanoparticles size measurement in dilute and transparent dispersions. Nevertheless, conventional DLS techniques become ineffective in opaque media, since no light is transmitted through the sample. Moreover, low heat capacity solvents or organic components can be extremely sensitive to the thermal effects induced by the absorption of the incident laser beam. We show, for instance, that simply adding black ink to a latex dispersion can bias the measurement by 25%. In the case of concentrated sample, results obtained by conventional DLS are also affected by the artefact of multiple scattering. In comparison with the hydrodynamic diameter measured in the dilute state, we actually observe an error of 27% on a latex standard measurement when its concentration is raised to 0.1wt%.