Light UpConverting ASsemblies – LUCAS

The LUCAS project aims at developing molecular and supramolecular devices for photonic upconversion (UC) in aqueous solutions at room temperature and to study them by microscopy. In these assemblies, the funneling of energy transfer will optimize the piling up of intermediate excited states to achieve their summation on higher lying excited states able to emit light. LUCAS proposes an innovative approach in which the careful design of the ligands, allows triplets of adequately chosen lanthanide cations, two photo-sensitizers and a central energy acceptor, to be positioned in close proximity, allowing for efficient intramolecular energy transfers. The ligand design is a critical step which must obey drastic rules in order to obtain: a perfectly controlled assembly of the different lanthanide cations within a single molecule, a close spatial proximity of the lanthanides to ensure efficient intermetallic energy transfer processes, and minimization of energy losses through non-radiative transitions.
The project brings together the internationally recognized skills of three French teams in macrocyclic ligand design, lanthanide coordination chemistry, microscopy and advanced spectroscopic technologies to achieve a breakthrough in spectroscopy: the observation of an efficient energy up conversion at the molecular level in aqueous solutions. LUCAS will further strengthen the existing collaboration between the different partners by fostering this highly ambitious research program. The project proposes an innovative approach through molecular and supramolecular systems to favor intramolecular energy transfer phenomena within lanthanide cations. To achieve this ambitious goal, the project relies on three major axis : i) a strictly controlled organization (molecular or supramolecular) of the lanthanide cations to obtain convergence of the energy inputs to a central lanthanide emitter; ii) to decrease losses due to non-radiative primary excited state quenching; and iii) to optimize the energy transfer by a drastic shortening of the intermetallic distances. By a careful design of the ligands, triplets of adequately chosen lanthanide cations, two sensitizers and an activator acting respectively as energy donors and energy acceptor, will be placed in close proximity, allowing for successful intramolecular energy transfers to occur efficiently within the molecular devices. The ligand design is a critical step which must obey drastic rules in order to obtain: a perfectly controlled assembly of different lanthanide elements within a single molecule, a close spatial proximity of the lanthanide cations, and minimal losses of energy through non-radiative transitions.
The breakthrough will be to bring the up conversion at the molecular level in aqueous solution with an efficient energy transfer conversion. Although the project is targeted towards the very fundamental aspects of research in coordination chemistry and spectroscopy, long term potential applications of such a new technology should be found in numerous societal or scientific fields. As examples, UC may be used to improve solar cell efficiency, to develop anti-counterfeiting inks, to create new bio-labels with anti-Stokes emission, or to improve background free fluorescence resonance energy transfer (FRET) bio-analytical tools.