Narrowing size distribution widths of small α-Al2O3 nanoparticles by addition of large nanoparticles in coagulation separation

Abstract α -Al 2 O 3 nanoparticles separated by fractionated coagulation still have broad size distributions which limit their wider applications. By adding 20-time mass of large α -Al 2 O 3 (40.5 nm) into α -Al 2 O 3 nanoparticles to be separated in coagulation separation, the average size of separated α -Al 2 O 3 nanoparticles decrease from 6.6 nm without addition of large α -Al 2 O 3 NPs to 4.4 nm, and the size distribution changes from 3–10 nm without addition of large α -Al 2 O 3 NPs to 3–6 nm. With increasing amount of large α -Al 2 O 3 NPs added, separated α -Al 2 O 3 NPs exhibit smaller average sizes and narrower size distribution widths at the same separation concentrations. This approach may be applied to narrow size distribution widths in large-scale size-selective separations of other nanoparticles.