The sedimentation of colloidal nanoparticles in solution and its study using quantitative digital photography

Sedimentation and diffusion are important aspects of the behaviour of colloidal nanoparticles in solution, and merit attention during the synthesis, characterisation and application of nanoparticles. Here we study the sedimentation of nanoparticles quantitatively using digital photography and a simple model based on the Mason-Weaver equation. Good agreement between experimental time-lapse photography and numerical solutions of the model was found for a series of gold nanoparticles. The new method was extended to study for the first time the gravitational sedimentation of DNA-linked gold nanoparticle dimers as a model system of a higher complexity structure. Additionally we derive simple formulas for estimating suitable parameters for the preparative centrifugation of nanoparticle solutions.