Effect of Directional Movement on Dynamic Light Scattering

Abstract

Dynamic light scattering is a standard technique of nano-particle sizing in colloid systems. However, it is difficult to measure the particle size accurately in the flowing dispersion, which is inevitable in many applications, such as on-line measurement. In this paper, we present that the wave vector of the scattered light, which is averaged to a constant in traditional technique, varies with time when the particles undergoing not only the random motion but also the directional movement. This variation results in an additional term of sinc function to the traditional intensity autocorrelation function of the scattered light, thus affect the final particle size determination, especially for large velocity of the directional movement. The experimental results agree well with our derivation. We believe this will facilitate the extension of the technique of the dynamic light scattering to a wider range of application, especially of the on-line measurement in the flowing dispersion.

Keywords

• Dynamic light scattering
• intensity autocorrelation function
• scattering wave vector
• directional movement