Preparation of Water‐Soluble Magnetite Nanocrystals from Hydrated Ferric Salts in 2‐Pyrrolidone: Mechanism Leading to Fe₃O₄

Differently sized and shaped nanocrystals of water-soluble magnetite were prepared by refluxing FeCl3⋅6 H2O in 2-pyrrolidone for different periods of time. The picture (scale bar: 100 nm) shows how first spherical nanoparticles appear (1 h, a), grow (10 h, b), and finally form cubic particles (24 h, c). The mechanism leading to Fe3O4 nanocrystals is discussed.