“…In general, downconversion emissions for Er 3+ produce green ( 2 H 11/2 → 4 I 15/2 , 4 S 3/2 → 4 I 15/2 ) and red emissions ( 4 F 9/2 → 4 I 15/2 , 4 I 9/2 → 4 I 15/2 ), and the green emissions were often stronger than the red emissions. [ 38,57–62,64 ] Here, all Er‐MgAl‐LDH‐ n ( n = 1, 2, 3, 4) exhibited strong infrared emissions at 720, 780, and 850 nm under 480, 520, and 565 nm excitations, respectively, along with red emission at 650 nm under 220 nm excitation (seen in Figure 6II and Figure 7). Strong emissions at 720, 780, and 850 nm have been seldom reported in previous downconverted emission spectra for Er 3+ ‐doped materials.…”