Comparisons of particle size measurement method for colloidal silica

Several methods have been used to measure the particle size and distribution of colloidal silica. It is an important parameter governing the proper function of many industrial products, for example, organic-inorganic hybrid coatings, ceramic coatings, paints, and inks, etc. Particle size distribution of commercial colloidal silica of eight was measured by TEM (transmission electron microscopy) or DLS (dynamic light scattering). The accuracy of the particle distribution is decreased when the colloidal silica is a mixture of approximately 50 nm particles and 100 nm particles. The particles less than ~50 nm may not be detected by DLS analyzer in the case of mixture sample. In order to investigate the difference in particle size distribution among measurement methods, we have compared and discussed particle size results measured from DLS, TEM, and BET (Brunauer-Emmett-Teller) analysis. In the TEM observation, 16 TEM images from one grid were compared and found out that the particle size distribution may vary based on the positions from which the particles are observed either scattered or agglomerated. We suggest combination of DLS, TEM and BET method to obtain the particle size distribution reflecting the dispersion, which represents the surface properties and aggregation state.