Orthogonal luminescence properties of a single rare-earth activator ion doped upconversion nanoparticles

Upconversion luminescence nanomaterials have attracted widespread attention owing to their special optical properties, while most of them emit single color luminescence. In order to achieve multicolor orthogonal upconversion luminescence and avoid the synthesis complexity and interference between multiple dopant ions, herein, we reported a novel orthogonal emissive upconversion nanoparticle, NaErF₄:Yb(19.5%)/Tm(0.5%)@NaYF₄:Yb(10%)@NaNdF₄:Yb(10%), through thermal decomposition strategy step by step. This novel nanoparticle can give out green luminescence and red luminescence by the energy level transition of Er³⁺ from ²H_11/2,⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 under the excitation light of 980 nm and 808 nm, respectively. The particles demonstrated uniform size, stable structure and excellent dispersibility. Under the excitation of 980 nm, the emission intensity at 650 nm of red luminescence was approximately 9.46 times more than the emission intensity at 540 nm. Under the excitation of 808 nm, the emission intensity at 540 nm of green luminescence was about 5.39 times more than the emission intensity at 650 nm.