Singlet Oxygen Generation Mediated By Silicon Nanocrystal Assemblies

摘要

The purpose of this project was investigation and exploitation of the unique role of silicon nanocrystals as activators for photoexcitation of oxygen molecules. At first sight, one might expect the interaction between silicon and oxygen to be no more than a simple oxidation process (producing SiO2). However, we have discovered that, at the nanoscale, the interaction becomes much more interesting and controllable. Silicon (Si) nanostructures have the extraordinary property of acting as facilitators for the photoexcitation of adsorbed oxygen molecules. Incident light creates excitons in Si nanostructures and these transfer energy to the adsorbed oxygen molecules. We focused on the development of nanosilicon-based materials having required morphological and optical properties for the efficient generation of reactive singlet oxygen. Photosensitizing properties of silicon (Si) nanocrystal assemblies in different forms: porosified Si wafers and powders, freestanding spherical Si nanopowders etc have been studied. All relevant parameters of the system: singlet oxygen generation efficiency, stability of these systems under illumination, ageing effects and the influence of nanocrystal surface termination were investigated in detail. Chemical reactivity of singlet oxygen generated in gaseous and liquid phases has been studied using various organic molecules. Finally, prototypes of photochemical flow reactors utilizing porosified Si powders and microreactors based on porosified channels of etched Si wafers have been developed.