DETERMINATION OF PARTICLE-SIZE DISTRIBUTIONS WITH ANGSTROM RESOLUTION

An analytical ultracentrifugation technique for the determination of p article-size distributions is used which applies an ultracentrifuge wi th a scanning absorption optical system. Radial scans during a sedimen tation velocity experiment yield the particle-size distribution. If th e particles consist of several defined monodisperse species, we show t hat for dense inorganic colloids the resolution of the particle-size d istribution is in the angstrom range. This is demonstrated for a Pt co lloid (0.4-2 nm) and unstabilized ZnO (4-9 nm) during particle growth. Such highly resolved particle-size distributions show that the analyt ical ultracentrifuge is an excellent and rapid tool for the study of p article growth mechanisms as no other fractionating analytical techniq ue with almost atomar resolution is known up to now. Some potential ap plications arising from the applied ultracentrifuge technique are sugg ested.