Acknowledgments This work was supported by grant number DEC-2021/41/B/ST5/03792: Phosphors for UVC LEDs: Self-Disinfecting Surfaces, and by the Polish Academy of Sciences by the Program of support scientist from Ukraine (PAS and NASU). The authors acknowledge DESY (Hamburg, Germany), Beamtime was allocated for proposal I-20250525 EC. The research leading to this result has been co-funded by the project NEPHEWS under Grant Agreement No 101131414 from the EU Framework Programme for Research and Innovation Horizon Europe. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the Granting Authorities can be held responsible for them.