The fabrications of iron oxides nanoparticles using co-precipitation and gadolinium nanoparticles using water in oil microemulsion method are reported in this paper. Results of detailed phase analysis by XRD and Mössbauer spectroscopy are discussed. XRD analysis revealed that the crystallite size (mean coherence length) of iron oxides (mainly γ-Fe(2)O(3)) in the Fe(2)O(3) sample was 30 nm, while in Fe(2)O(3)/SiO(2) where the ε-Fe(2)O(3) phase dominated it was only 14 nm. Gd/SiO(2) nanoparticles were found to be completely amorphous, according to XRD. The samples showed various shapes of hysteresis loops and different coercivities. Differences in the saturation magnetization (MS) correspond to the chemical and phase composition of the sample materials. However, we observed that MS was not reached in the case of Fe(2)O(3)/SiO(2), while for Gd/SiO(2) sample the MS value was extremely low. Therefore we conclude that only unmodified Fe(2)O(3) nanoparticles are suitable for intended biosensing application in vitro (e.g. detection of viral nucleic acids) and the phase purification of this sample for this purpose is not necessary.
Keywords: Magnetic nanoparticles; gadolinium nanoparticles; iron oxide; silica coating.