Efficient Ultraviolet Upconversion in Ca2Al2SiO7:Pr3+ Phosphors under 444 nm Excitation for Antibacterial Applications

Acknowledgements This work was supported by the National Science Centre (NCN) under the OPUS 21 Project (Grant UMO-2021/41/ B/ST5/03792), which is gratefully acknowledged

Abstract

Since Auzel’s discovery of the upconversion effect in rare earth-doped materials in 1966, these materials have received significant attention for their potential applications in optical anticounterfeiting, bioimaging, and optical temperature measurement. More recently, researchers have shown growing interest in developing phosphors capable of converting visible light into ultraviolet radiation for potential antibacterial applications. In this work, we present the results of upconversion luminescence from Ca₂Al₂SiO₇:Pr³⁺ in the 230–320 nm range under 444 nm excitation. The effect of Pr³⁺ concentration on the intensity and lifetime of the upconversion emission was systematically studied. It was established that the primary upconversion mechanism under pulsed laser excitation is excited-state absorption, with the ¹D₂ level acting as the intermediate state. The synthesized crystallites exhibited significantly higher upconversion efficiency compared to the reference material Y₂SiO₅:Pr³⁺, positioning this aluminosilicate as one of the most efficient known matrices for visible-to-ultraviolet upconversion to date.