Magnetic enhancement of carbon-encapsulated magnetite nanoparticles

In this paper, we report the effect of carbon encapsulation on the magnetic behavior of magnetite (Fe3O4) nanoparticles obtained through chemical coprecipitation. Using starch, Fe3O4/carbon core-shell nanoparticles were produced through a hydrothermal method. Magnetic studies revealed that both the Fe3O4 and Fe3O4/carbon core-shell nanoparticles were nearly superparamagnetic at room temperature; more importantly, carbon encapsulation significantly enhanced the room-temperature ferrimagnetism. Transmitting optical magnetic circular dichroism analysis indicated the existence of interfacial charge transfer in the Fe3O4/carbon heterosystem. The ferrimagnetic enhancement was attributed to the charge transfer to polarized states of the A-site in Fe3O4, which is equivalent to chemical reduction of the A-site irons of Fe3O4. We concluded that Fe3O4/carbon core-shell nanoparticles formed a heterosystem so that the amorphous carbon passivated the magnetic semiconducting Fe3O4 nanoparticles, to which the sp(2) electron was transferred. (C) 2019 Elsevier B.V. All rights reserved.