Realizing intense deep-far-red broadband emission derived from mica ceramics through isomorphic cation substitution/doping for plant cultivation lighting and latent fingerprint identification

The exploration of transition metal Mn2+ activated luminescent materials is gaining increasing interests due to their diverse uses. Herein, the Mn2+ -incorporated fluorphlogopite (KMg3AlSi3O10F2) mica ceramics were successfully prepared by a high-temperature solid state reaction process, in which Mn2+ occupied Mg2+ site through the isomorphic substitution. The fluorphlogopite itself and derived Mn-mica (KMg2.5Mn0.5AlSi3O10F2) possess negligible luminescence under ultraviolet (UV) excitation. However, the doping of rare earth Eu2+ into Mn-mica generates an evident deep-far-red broadband emission around 620–860 nm peaking at 720 nm as excited with 240~360 nm, which is ascribed to the intrinsic 4T1→6A1 transition of Mn2+, and the maximum spectral enhancement reaches about 22-fold as excited with 320 nm. The more dramatic thing is that Na+ complete substitution for K+ in Mn-mica (NaMg2.5Mn0.5AlSi3O10F2), not only results in the enlarged excitation range towards near-UV region, but also extremely enhances the deep-far-red emission (more than 12-fold) under 365 nm excitation. After optimization, the luminescence internal quantum yield is 87.4% and the emission intensity at 423 K retains 78% of that at ambient temperature, manifesting the modified mica ceramics with superior luminescence and thermal stability through the cooperative effects of isomorphic cation substitution and doping, which is applicable for plant cultivation lighting and latent fingerprint identification.