Fig. 13

a Schematic illustration for the realization of a time-dependent color variation display [134]. Copyright 2021 Royal Society of Chemistry. b₁ Schematic illustration of the application in 3D optical information storage. b₂-b₃ The original images using NaYF₄:Ln³⁺@NaYF₄ and monochromatic images after passing through 545BP, 570BP and 605LP filters. The scale bars are 100 μm [153]. Copyright 2021 Springer Nature Limited. c Photographs of NaMgF₃:Tb³⁺@NaMgF₃ emission images during X-ray irradiation, at the moment of turning off, with a delay time of 10 min, and heated to 400 K [181]. Copyright 2021 Wiley–VCH