Nucleotide-mediated size fractionation of gold nanoparticles in aqueous solutions.

It is well-known that the applications of nanoparticles are highly dependent on their size-related physical and chemical properties. Size fractionation, therefore, is important for the successful application of nanoparticles. In this study, we present a method for the size fractionation of gold nanoparticles (Au-nps) in aqueous solution, which combines the nucleotide-mediated stabilization and the size-dependent salt-induced aggregation of nanoparticles. With a coating layer of nucleotide, Au-nps undergo reversible salt-induced aggregation in aqueous solutions where the critical salt concentration (CSC) for the transition of monodispersed Au-nps to aggregated form is dependent on the size of nanoparticles; i.e., the smaller the particle, the higher is the CSC. Successful fractionations of a solution containing Au-nps of different sizes (10, 20, and 40 nm) were demonstrated with final purity of each fraction higher than 90%. Taking advantages of the rapidness of the nucleotide-mediated stabilization of Au-nps, the whole fractionation process can be completed within 1 h.