Eu 3 + complex as an Efficient Luminescent Sensitizer for NIR-Emitting Core–Shell Zn x Mg y SnO 4 :Cr 3 + Persistent Luminescence Materials

This work presents the development of core–shell Zn x Mg y SnO 4:Cr 3+ (40 and 80% Mg) persistent luminescent (PersL) materials prepared by the ceramic method and decorated with the [Eu(tta) 3 (H 2 O) 2 ] complex via microwave-assisted silanization, with promising optical properties in the near-infrared (NIR) range. The crystal structure of the prepared materials showed overlapping Mg 2 SnO 4 and Zn 2 SnO 4 patterns, along with SnO 2, with increasing Mg content. FESEM and TEM microscopy revealed polycrystalline particles with well-defined surfaces and a silica shell in the 5–10 nm range. The optical properties were investigated by UV–vis and synchrotron spectroscopies (VUV, XANES-XEOL, and XRF). The persistent luminescent materials exhibit a noticeable increase in band gap energy with higher Mg content, intense, broadband NIR emission centered at 780 nm from the Cr 3+ ion in a weak crystal-field environment, as well as longer PersL decay time with a higher Mg/Zn ratio. Core–shell materials decorated with the Eu 3+ -complex indicate energy transfer to the Cr 3+ ion, resulting in NIR luminescence sensitization by UV and X-ray excitation. Therefore, we demonstrate an effective strategy to sensitize NIR emission by utilizing a highly efficient Eu 3+ complex in core–shell persistent luminescent materials, which exhibit notable structural and optical properties and hold promise for optical imaging and photonic applications.