Speaker
Description
Luminescent lanthanide complexes find broad application in UC processes and beyond: in lasers or displays, in solar cells, as anti-counterfeit materials, in photocatalysis and particularly as bioprobes in photodynamic therapy or imaging. Owning the particular nature of the 4f-electrons, the photophysical properties of f-element are uniques (parity-forbidden f-f transition, sharp transition, long lifetime and low absorption coefficient). Due to the abovementioned parity-forbidden transitions, direct population of the lanthanides’ excited state is quite inefficient. As an alternative to the use of very powerful excitation sources this issue can be addressed more elegantly by indirect population of the emitting states using sensitizing chromophores. This so-called “antenna effect” relies on the excitation of the chromophore, followed by an energy transfer from its singlet or triplet state to the lanthanide, which then relaxes back to its ground state by emitting sensitized light.
In this contribution, we will show through selected examples that transient absorption spectroscopy in the ns-µs regime is a powerful tool to shed light on the photophysical pathways beyond the “antenna effect”. Particular attention will be devoted on the role of oxygen as triplet excited state quencher.
