Dual mode emissions with enhanced green up-conversion luminescence by Gd3+ doping and down-conversion from Eu3+ in NaMnF3:Yb,Er@NaGdF4:Eu

Abstract

NaMnF₃:Yb,Er and NaMnF₃:Yb,Er@NaGdF₄:xEu (x = 0, 0.3, 0.6, and 0.9) samples were synthesized by a simple hydrothermal method. The as-obtained NaMnF₃:Yb,Er particles show a single red emission under the irradiation of infrared light (980 nm), due to the energy exchange transfer process between Mn²⁺ ions and Er³⁺ ions. Notably, further growth of NaGdF₄:Eu on the basis of NaMnF₃:Yb,Er enhanced the green up-conversion luminescence of Er³⁺ ions, which gradually shifted from red to green with the increase of the Gd³⁺ ion doping amount. In addition, NaMnF₃:Yb,Er@NaGdF₄:Eu exhibits red color under ultraviolet excitation (397 nm). These results provide a possible means for controlling the luminescence properties of the lanthanide doped up-conversion system. The luminescent film synthesized with NaMnF₃:Yb,Er@NaGdF₄:Eu can show different luminescent colors under different light irradiation (near infrared and ultraviolet), which indicates that they have potential applications in multi-mode anti-counterfeiting.