Unusually Effective Blue-to-UVC Upconversion of Pr-Doped SrLu(PO) and BaLu(PO) Phosphors: A Comparative Study.

Many pathogens, including bacteria and viruses, are increasingly developing resistance to conventional disinfectants. As a result, new approaches to disinfection are being explored, such as the use luminophores that convert visible light into ultraviolet C radiation (UVC). In this work, we present novel UVC phosphors, ALu(PO) (A = Sr, Ba), activated by Pr. These phosphates were synthesized by the Pechini method with different activator concentrations and crystallized in a cubic structure with the space group . The emission and excitation spectra, as well as decay times under synchrotron and visible-light excitation, were measured. Both phosphates exhibited efficient and fast 5d-4f emission from 240 to 340 nm, along with a very weak f-f emission line around 600 nm upon ultraviolet excitation. Multiphonon relaxation from the P to D state causes the phosphors to emit weak blue (P → H) and intense orange (D → H) light upon direct excitation of the P level. The upconversion properties of ALu(PO):Pr crystallites were investigated under 444 nm laser excitation, and the effect of Pr concentration on these properties was evaluated. Compared to the YPO:Pr reference material studied earlier, the BaLu(PO):Pr host showed a 20-fold enhancement in UVC upconversion emission, making this phosphate one of the most efficient visible-to-ultraviolet upconversion matrices to date. Thus, the studied phosphates have potential use in sterilization, disinfection, photocatalysis, and phototherapy.