Free flow electrophoresis for the separation of CdTe nanoparticles

Nanoparticles with narrow size distribution are the cornerstones for better quantum electronics and optics, biological applications, and therapeutic devices. In this communication, we present a new and simple means to separate CdTe nanoparticles into more monodispersed size groups by the free-flow electrophoresis (FFE) technique. One of the most significant challenges of the field is fast fractionation of nanoparticle dispersions in aqueous media. We successfully achieved one-step separation of standard CdTe nanoparticles into partitions with different particle diameters and potentially other structural features, while retaining strong fluorescence. As much as 51% reduction in the half-width of the luminescence peak can be achieved after FFE fractionation. Quantum yields found in different partitions agree with the particle growth model suggested earlier which is important for fundamental studies of nanoscale nucleation. XPS analysis indicated the composition of CdTe nanoparticles remained similar before and after separation and suggests that FFE also provides a route for nanoparticle purification by removing excess stabilizer and impurities, which could be extended to other nanoparticle dispersions.