Time-resolved UV-visible spectroscopy of bodipy-based materials

This spectroscopy study was carried out in Newcastle University, using a time-resolved fluorimeter acquired with fundings from the EPSRC grant "MESO-FRET" (EP/P015395/1) and from the Newcastle SAgE Faculty. The data refer to the optical properties of two set of systems: porous silica of COK-12 type, doped with a bodipy dye, JM, and porous silica of MCM-41 type, doped with a different bodipy derivative, BPJ2. The first set of materials is characterised by green luminescence that, as the dye loading increases from 1% to 50%, shows a decrease in quantum yields from 0.22 to 0.05 and a reduction of the excited state lifetime. We ascribe this effect to an enhanced non-radiative deactivation, due to quenching caused by possible formation of aggregates and excitation energy traps within the silica matrix. On the other hand, the MCM-41 type materials show a multi-chromophoric behaviour: a new blue light-absorbing species formed as a result of aggregation phenomena and its content varies depending on the dye-loading, as indicated by absorption and emission spectra. This species is able to transfer the excitation energy quantitatively to the bodipy monomers, which in turn act as acceptor units, and the migration process is complete in a time range between 20 and 80 ps.