Sorting Nanoparticles By Centrifugal Fields in Clean Media

The on-demand availability of nanomaterials with selected size and well-defined chemical/physical properties is of fundamental importance for their widespread application. We report two clean, rapid and non-destructive approaches for nanoparticles (NPs) size selection in centrifugal fields. The first exploits rate zonal separation in a high viscosity gradient. The second exploits selective sedimentation of NPs with different size. These methods are applied to metallic nanoparticles (MNPs) with different compositions and surface chemistry, dispersed either in water or organic solvents, but they can also be exploited for the separation of NPs of any material. We selectively sort both Au and Ag NPs with sizes in the 10-30nm range, achieving chemical-free MNPs with low polydispersivity. We do not use solutes, thus avoiding contamination, and only require low centrifugal fields, easily achievable in bench-top systems.