Tuning a colloidal synthesis to control Co2+ doping in ferrite nanocrystals

Cobalt-ferrite nanocrystals were synthesized using a high-temperature organometallic decomposition scheme in the presence of surfactant molecules. The influence of the addition of cosurfactant molecules of polyol type on the resulting nanocrystals was examined. The properties of the nanocrystals were studied using electron microscopy, and magneto-optical and Raman spectroscopies. The addition of the cosurfactants was found to influence the growth mechanism of the nanocrystals, resulting in a significant reduction in the concentration of the Co2+ ions incorporated into the ferrite lattice up to a factor of 4 and an increase in the size of the synthesized nanocrystals. In addition, control over the occupation of octahedral versus tetrahedral coordination sites by the cobalt ions was demonstrated.