In-line Particle Characterization

Holographic video microscopy yields fast and accurate measurements of the size and refractive index of individual colloidal particles. Particle-resolved characterization offers useful insights into the progress of colloidal synthesis without relying on models for the distributions of particle sizes and properties, and can be performed rapidly enough to provide feedback for process control. The measured increase in the most probable radius over the course of the reaction is consistent with the LaMer model for colloidal growth. Uniformity in the measured refractive index suggests that the spheres grow with uniform density. The joint distribution of size and refractive index provides evidence for a low rate of nucleation proceeding after the initial nucleation event. The same analysis reveals that these PDMS particles shrink by compactification in the first few days after their synthesis.