Multifunctional, luminescent and magnetic systems were synthesised by a co-precipitation method and broadly investigated. In our studies down- and visible up-conversion of Yb³⁺ and Tb³⁺ doped GdPO₄ nanocrystals were observed. The synthesised nanomaterials were analysed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Spectroscopic properties were determined from excitation and emission spectra together with a subsequent analysis. The build-up characteristics of luminescence decays showed the energy transfer processes that occurred. Magnetic measurements were performed by means of vibrating sample magnetometry (VSM). These nanomaterials showed intense green emission under ultraviolet (UV), 272 nm, and near infrared (NIR), 980 nm, laser excitation. The mechanism lying behind the observed spectroscopic properties was proposed. Energy transfer between Gd³⁺ and Tb³⁺ ions, as well as cooperative energy transfer from Yb³⁺ to Tb³⁺, was found to give a dual-mode luminescence. Also, quenching processes by cross-relaxation and phonon-assisted energy transfer were observed. The presence of different lanthanide ions and the influence of the finite-size effect underlie the complex behaviour observed.

A series of the highly crystalline MFe₂O₄ ferrite spinel nanoparticles were synthesized via a modified Bradley reaction using microwave stimulation. Particle size was estimated using theoretical calculations from the X-ray data (Scherrer and Rietveld methods) as well as by direct experimental techniques such as TEM, DLS and NTA. The calculated average grain size for dry powders is in the range 10 to 23 nm. Hydrodynamic size was measured using DLS on non-modified, surfactant free particles of the whole MFe₂O₄ series. Raman spectra used for additional verification of the structure features of the produced spinel phases showed strong asymmetric behavior of the A_1g mode, which was deconvoluted revealing additional components. Among all the products the lowest site inversion was found for the manganese ferrite (MnFe₂O₄). The oxidation of Fe₃O₄ leading to the formation of the Fe₂O₃ hematite phase induced by laser irradiation was observed. Magnetic characterization of the MFe₂O₄ family was carried out, showing that superparamagnetic blocking temperatures and calculated anisotropy constants K are in good agreement with the data for similar fine-particle systems.