Figure 5

(a) Normalized PLE spectra of the SPBO_Cl:0.04Eu2+ (0 ≤ x ≤ 0.5) obtained by monitoring the higher-energy emission. (b) Normalized PLE spectra of the SPBO_Cl:0.04Eu2+ (0 ≤ x ≤ 0.5) obtained by monitoring the lower-energy emission. Additionally, the PL spectrum of Sr5(PO4)3Cl:0.04Eu2+ is also shown as a reference.