Heavy rare-earth-doped ZBLAN glasses for UV–blue up-conversion and white light generation

Noticeable UV–vis up-conversion luminescence of Er3+ and Tm3+ ions sensitised by Yb3+ ions in ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) fluoride glasses have been obtained under near-infrared excitation at 980 nm. Red, green and blue simultaneous emissions were observed yielding to a white-balanced overall colour. Moreover significant UV up-conversion emissions observed can contribute to enhance spectral response of semiconductor electrode, such as TiO2 and Fe2O3, for sustainable production of hydrogen via water photolysis by harvesting of long wavelength solar irradiation, emerging as an interesting solely luminescent approach for improving water-splitting. Total infrared to UV–vis up-conversion efficiency has been calculated to be at around 46%. Laboratory tests prove the improvement in the photocatalytic action of a commercial benchmark photocatalyst (TiO2 Degussa P25) in the decomposition of methylene blue in water under sun-like irradiation, by a factor of 16% driven by up-conversion effects due to the inclusion of RE-doped ZBLAN powders into a slurry-type photo-reactor.