5. Density Gradient Ultracentrifugation of Colloidal Nanostructures

According to the centrifugation theory, various factors, such as the media density (ρ_m), radius (r) and thickness (h) of nanostructures, and solvation shell thickness (t) in different media, will directly influence the particle behavior during the density gradient centrifugation process. Density gradient centrifugation has become a promising tool to purify nanomaterials, such as metal nanostructures, carbon materials (carbon nanotubes and graphene), non-metal nanostructures (e.g., rare-earth nanostructures and oxide nanostructures). For the practical separation, as demonstrated in previous chapters, on the basis of the theoretical analysis of the target nanostructures and the preliminary separation, one can optimize the centrifugation according to the comprehensive consideration. While after all, the optimization direction of nanoseparation should be mainly focused on the net density of nanostructures and media. In this chapter, we will discuss the separation examples according to the dimensional difference of colloidal nanostructures, including 0D, 1D, 2D nanostructures, and assemblies/clusters.