New host-guest materials for light conversion

Abstract

The studies reported in this PhD thesis describe the synthesis and optical properties of new lightharvesting materials, built using organic and organometallic chromophores as guests in a rigid host. Mesoporous silica was chosen as host because of its robustness, high chemical and thermal stability. Different dyes were successfully incorporated within specific sites of the host, that is, into micellar templates and inside the silica framework itself. To achieve such specific functionalisation, new self-assembly strategies were developed, and the obtained materials possess ordered structures and emergent optical properties. Zinc and boron dipyrrins were inserted as guest dyes inside the micellar structures used to template the formation of the silica host (Chapters 3 and 5). The combined host-guest materials showed enhanced fluorescence efficiencies at low dye content, whereas at high concentrations in the template structure inner-filter effects are found to prevail. Mesoporous organosilica materials (PMOs) were made for the first time using zinc quinolinolates and BOPHY dyes within the host structure (Chapters 4 and 6). The organometallic complexes undergo a significant increase in fluorescence efficiency at high concentrations in the PMO structure. Incorporation into the solid network also proved to induce charge-recombination fluorescence. The same phenomenon was observed in the BOPHY-based PMOs. Additionally, the latter materials showed fast energy migration between the single units of dye in the network. Such properties make the materials promising for application in light-harvesting and sensitisation technologies, as well as in lightings and the design of new OLEDs.