Abstract：To discuss the uncertainty sources of the particle size measurement by dynamic light scattering (DLS) , and their influence degree on the measurement results, the particles with the nominal value of 20 and 80 nm were mixed and then measured by DLS. The uncertainty sources were analyzed, and the uncertainty of the results were evaluated. The results show that the measured particle sizes are 17.80 and 88.43 nm respectively, and the results are expressed as (17.80±1.02) nm and (88.43±2.48) nm. Among all the uncertainty sources, such as decay rate, temperature, scattering angle, viscosity and repeated measurement, among them the repeated measurement is the main source.

Keywords: dynamic light scattering; nano silica; particle size; uncertainty