What is dynamic light scattering?

Dynamic Light Scattering (DLS), also known as Photon Correlation Spectroscopy (PCS), is a conventional nanoparticle size characterization method with the advantages of accuracy, speed, and good repeatability. With the update of instruments and the development of data processing technology, the current dynamic light scattering instrument not only has the function of measuring particle size, but also has the ability to measure Zeta potential and molecular weight of macromolecules.

When the laser passes through the suspension, the particles in the liquid will scatter the laser. The initial frequency of the scattered light is the same as the frequency of the incident light, but the particles in the liquid are collided with the surrounding medium molecules and perform random Brownian motion. According to the Doppler effect, the scattered light frequency will fluctuate randomly around the frequency of the incident light, and the scattered light intensity will also fluctuate randomly.

Generally, when the particles are small, the Brownian motion is fast, the scattered light frequency changes quickly, and the light intensity fluctuates quickly; when the particles are large, the motion is slow and the light intensity fluctuates slowly. Therefore, by analyzing the fluctuation of scattered light intensity, the speed of the Brownian motion of the particles can be obtained. Then, the nanometer particle size and particle size distribution can be obtained by using the Stokes-Einstein equation.