Surface modification of Fe3O4 nanoparticles with dextran via a coupling reaction between naked Fe3O4 mechano-cation and naked dextran mechano-anion: A new mechanism of covalent bond formation

A surface modified Fe₃O₄ nanoparticle with dextran, possessing a core-shell structure, was synthesized by vibration ball-milling of Fe₃O₄ with dextran in the solid state under vacuum. A combination of experimental results and density functional theory calculations demonstrate that the surface modified Fe₃O₄ nanoparticle with dextran was performed via a coupling reaction between a “naked” Fe⁺ atom of Fe₃O₄ mechano-cation and a “naked” O^? atom of dextran mechano-anion, viz., a “Fe:O” bond-formation. The naked Fe⁺ atom of Fe₃O₄ mechano-cation was produced by ionic scission of FeO bond of Fe₃O₄ and lost an “electron pair” under the ionic scission. The naked :O^? atom of dextran mechano-anion was produced by ionic scission of CO bond comprising the α-1,6 glycosidic linkage of the dextran and gained the electron pair under the ionic scission. The Fe:O bond formation, viz., a novel type covalent bond formation, was achieved via an electron pair donation from the naked :O^? atom and its acceptance by the naked Fe⁺ atom. Consequently, a shared “electron pair” comprising the Fe:O bond was only donated from the naked :O^? atom. Our work demonstrates a novel method to form covalent bond formation between metal oxides and organic polymers, and provides a novel functionalized nanoparticle.