A small amount of finely powdered sample was dispersed in acetone medium by ultra-sonication, drop-cast on carboncoated copper grids, and dried. The particle size distribution of the typical pigment samples (Mn 2 and Si 2) were investigated in water medium with calgon as the dispersing agent using the
Laser Scattering Particle Size Distribution Analyzer (CILAS 930 Liquid). The samples were ultrasonically homogenized for180 s during measurement and the signal was evaluated on the
asis of Fraunhofer bending.