|Abstract:||The master’s thesis presents the synthesis of superparamagnetic nanoparticles with the composition Ni67,5Cu32,5, using the sol-gel method, in various functional silica coatings. The purpose of this master’s thesis was to modify the surface or coating on nanoparticles with functional groups, via in situ application of the precursor tetraethyl orthosilicate (TEOS) or its combination with other silica precursors, e.g. (3-aminopropyl)triethoxysilane (APTES), phenyltriethoxysilane (FTES), vinyltriethoxysilane (VTES) and bis-1,2-(triethoxysilyl)ethane (BTSE). The final magnetic nanoparticles were formed after initial sample homogenization in a Bosio furnace, followed by the reduction of the resulting oxides in a tube furnace at 850 °C for 6 h and an Ar/H2 inert atmosphere. Our aim was to assess the impact of the different used functional precursors on the fundamental characteristics of the nanoparticles by studying their structural, morphological and chemical properties, and the surface or coating functionality.
Ni67,5Cu32,5 nanoparticles were characterized by various analytical techniques. The chemical composition of nanoparticles was determined with the X-ray powder diffraction (XRD) and FTIR spectroscopy. We confirmed the absence of nonmagnetic oxides in samples and the presence of the silica coating formed from respective precursors. Using the thermogravimetric analysis (TGA), we determined the Curie temperatures (Tc) and observed the thermal decomposition of the nanoparticles. Variously coated nanoparticles exhibit a deviation in Tc, which have, with further optimization, a high potential to be used in magnetic hyperthermia. Transmission electron microscopy (TEM) has shown that the formed nanoparticles are spherical in shape, monodisperse and homogenously distributed in the silica matrix. The nanoparticles exhibit sizes between 5 nm and 20 nm. Magnetization measurements confirmed an expected magnetization, which was dependent on the particle size and the type, as well as the thickness of the respective coatings. The specific surface area and porosity were studied with the BET analysis, which showed that both parameters varied among the different used precursors. Measurements of contact angles on nanoparticle coating thin film samples indicate the presence of surface functional groups, which lead to changes in hydrophilicity or hydrophobicity of the coating. Synthesized Ni67,5Cu32,5 nanoparticles are potentially useful for therapeutic hyperthermia and nanomedicines development. Based on all mentioned, we concluded that the basic characteristics of NiCu nanoparticles can be varied to a certain extent with the preparation of such functional coatings.|