Influences of spinel type and polymeric surfactants on the size evolution of colloidal magnetic nanocrystals (MFeO, M= Fe, Mn).

Two types of polymeric surfactants, PEG and PVP, were used for the preparation of magnetic ferrite MFeO (M = Mn, Fe) colloidal nanocrystals using a solvothermal reaction method. The effect of spinel type effect on the size evolution of various nanoparticles was investigated. It was found that FeO nanoparticles exhibited higher crystalinity and size evolution than MnFeO nanoparticles with use of the two surfactants. It is proposed that this observation is due to fewer tendencies of surfactants on the surface of FeO building blocks nanoparticles than MnFeO. Less amounts of surfactant or capping agent on the surface of nanoparticles lead to the higher crystalibity and larger size. It is also suggested that the type of spinel (normal or inverted spinel) plays a key role on the affinity of the polymeric surfactant on the surface of building blocks. [ABSTRACT FROM AUTHOR]