Quantum chemical characterization of oxide nanoparticles and interactions on their surfaces

Sammanfattning: Titanium dioxide and related oxide materials have been investigated using density functional theory calculations. Nanocrystalline particles were modelled by a finite cluster approach. The studies focus on the characterization of structural and electronic properties of TiO2 and related group-IV materials (SiO2, GeO2, SnO2), as well as, interactions on their surfaces. A set of bare cluster models of oxide nanomaterials with diameters up to 2 nm was first developed and tested with respect to structure, stability, and electronic properties. This set of clusters was further used to study surface interactions and other properties of oxide nanoparticles. The interaction between the surfaces of oxide nanoparticles and water was investigated by saturation of bare clusters with H and OH groups. The water adsorption energy and the change of the structural and electronic properties after addition of water molecules on the cluster surfaces are discussed. Furthermore, the interfacial properties between interacting nanoparticles have been considered by merging two nano-TiO2 clusters with different interacting sides through different orientations. This study provides a detailed understanding of the reactivity of different surfaces, as well as the structural, electronic, and stability changes after the creation of a necking region between clusters. Finally, nano-TiO2 cluster models have been employed to investigate interfaces between dye molecules and TiO2 surfaces with particular focus on the influence of designed spacer groups separating the chromophore from the nano-TiO2 substrate.