Artificial fluorescent proteins as sustainable downshifters for bio-hybrid LEDs: tailoring the emission through modifications of a non-native fluorophore

LED lighting plays a fundamental role in the energy transition, due to its superior energy efficiency, compared to traditional light sources. For this reason, LEDs have now become the standard for indoor and outdoor applications, but their production and disposal still poses concerns in terms of sustainability, due to the need of employing rare-earth based colour down-converting filters. In the search for alternative solutions, fluorescent proteins (FPs), in which an organic fluorophore is embedded into a peptide scaffold, have been proposed as bio-based emitters for sustainable downshifter materials.1 An ideal FP emitter should display high fluorescence quantum yield values and good photo- and thermal stability, to ensure long lifetime, compatible with the required applications. To achieve such features, we studied several classes of fluorescent organic compounds, in order to cover the whole range of the visible light spectrum, by tailoring the absorption and emission properties. In this regard, we selected a well-known fluorescent core based on a photostable thiadiazole molecule as a flexible molecular platform, whose emission wavelength can be extensively modulated from green-yellow to orange-red, with relatively low synthetic effort, through conjugation with different (hetero)aryl moieties.2 Through synthetic modification of the fluorophore scaffold, we investigated the possibility to adapt it for efficient interaction with a properly designed protein scaffold. Finally, we revised the whole synthetic route to improve the overall sustainability of the process.