Characterization of core-shell oxide nanoparticles

Abstract: The growing amount of applications of nanoparticles (NP) have led to concern for their possible harmful effect on human health and the leakage in the environment. Characterization and quantification of the content of NPs are of prime importance, especially methods to relate size, composition and morphology of the particles with the possibility of their detection and quantification. Magnetic iron oxide core-shell nanoparticles, coated with a protective silica layer have been proven to be successful as adsorbents for water purification and hydromet-allurgy of rare earth elements. Their growing applications in catalysis, medicine and protection of the environment make them highly interesting for further characterization. The goal of this thesis project was to analyze and characterize these NPs for future applications and quantification with single particle ICP-MS (spICP-MS). Instrument difficulties made quantification with spICP-MS impossible, but the particles have been characterized in the solid state using environmental scanning microscopy with energy dispersion X-ray spectroscopy analysis (ESEM-EDS), atomic force micros-copy (AFM), powder X-ray diffraction (PXRD) and Fourier transform infrared spec-troscopy (FTIR). The nanoparticles in solution are also investigated with nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), inductively coupled plasma mass spectroscopy (ICP-MS) and again with ESEM-EDS and AFM. The mean size results of these different methods were compared. It was concluded that the iron oxide core-shell NPs were successfully encapsulated by a silica layer. The core consists mostly of magnetite (Fe3O4), but some oxidation to maghemite (gg-Fe2O3) has taken place. The particles are very polydisperse and the dispersion aggregates quickly, so no 'right' size can be determined. Further research needs to be done for development of applications. External inves-tigation for separation based on magnetic properties to determine the fraction Fe3O4 that has been oxidized to gg-Fe2O3 and method development with single particle ICP-MS is required.