Hierachical Ni@Fe₂O₃ superparticles through epitaxial growth of γ-Fe₂O₃ nanorods on: In situ formed Ni nanoplates

One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Niatγ-Fe₂O₃ superparticles containing Ni cores densely covered with highly oriented γ-Fe₂O₃ (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)₂) and Fe(CO)₅. Automated diffraction tomography (ADT) of the Ni-Fe₂O₃ interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe₂O₃ nanorods on the Ni core is facilitated through the formation of a Fe_0.05Ni_0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe₂O₃ interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Niatγ-Fe₂O₃ superparticles were dispersible in water.