Direct synthesis of water-dispersible 2Â nm FePt nanocrystals without ligand exchange

► Water-dispersible 2 nm FePt ultrasmall nanocrystals were directly synthesized in a single-step nanoemulsion process. ► The surface of the nanocrystals was coated by a biocompatible triblock copolymer, rendering the nanocrystals hydrophilic for aqueous dispersion without using conventional ligand exchange and offering proper protection of the nanocrystals from oxidation. ► Revealing both single-crystallinity and high crystallinity of the nanocrystals, with the excellent monosize distribution of 1.95±0.18 nm in diameter. ► Showing well-defined magnetic behavior of the polymer capped nanocrystals. ► Demonstrating the aqueous dispersion-collection process of the nanocrystals for application readiness in an aqueous medium.