Dynamic Light Scattering
Dynamic light scattering (DLS) is a method for measuring the diffusion of an ensemble of particles in solution. From these measurements, it is possible to derive the hydrodynamic size and molecular weight of the particles, as well as the degree of polydispersity. DLS is particularly good at quickly revealing the presence of high-order aggregated material present in a sample.
The instrument measures how quickly the intensity of the scattered light varies with time and presents this as a correlogram. Large particles diffuse more slowly, and hence the intensity of the scattered light varies slowly. Conversely, smaller particles diffuse more quickly, resulting in a faster change in the intensity of the scattered light. Fitting the correlogram to an exponential function reveals the translational diffusion coefficient, which is related to the size of the diffusing material.
Facilities
Dynamic light scattering is measured using a Malvern Instruments Zetasizer Nano S, which has a red laser and measures particle size (0.6 nm – 6 m) and molecular weight (1 kDa – 20 MDa). The instrument automatically optimises the measurement parameters for the best quality data.