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

NaMnF₃:Yb,Er shows single band red emissions of Er³⁺at 980 nm, while NaMnF₃:Yb,Er@NaGdF₄:Eu shows green up-conversion emission due to the presence of Gd³⁺, and red down-conversion emission of Eu³⁺.