Thermal behavior of ferromagnetic bio-compatible nanoparticles: A comparative DSC study

Three pairs of ferromagnetic nanoparticle - samples obtained with and without application of d.c. magnetic field during their synthesis in aqua solutions are investigated with differential scanning calorimeter (DSC). In all three cases during first heating, the results show significant difference in the behavior between the samples that are synthesized with application of a d.c. magnetic field versus samples obtained without magnetic field. At second heating run, the difference disappears. Obviously the specific self-organization phenomena induced by a d.c. magnetic field application during borohydride reduction synthesis is destroyed by the first heating to 450 ºC. It was found also that the thermal behavior of samples using monovalent Cl anion of Co salt as precursor is rather different as compared to samples obtained with polyvalent anions such as SO4 and (en)2. While the first gives separated peaks for dehydration and dehydroxlation the second types of samples shows very broad peaks with shoulders. Results show that DSC could be a valuable tool for investigation of the self-organization of ferromagnetic nanoparticles