Structure design and modulation of dual-wavelength sensitive upconversion luminescence in RE₂MoO₆:Er³⁺/Yb³⁺ materials

A series of RE₂MoO₆: 2%Er³⁺, 15%Yb³⁺ (RE = Y, Pr, Nd, Sm, Eu, Gd, Dy, and Lu) nanoparticles were prepared by citric acid-assisted sol–gel method. The upconversion luminescence (UCL) properties of block-shaped Gd₂MoO₆: 2%Er³⁺, 15%Yb³⁺ were the best among the materials obtained. In addition, the UCL properties of the investigated systems by two strategies could be further improved. Modulation of the crystal structure could be achieved by the substitution of rare earth ions in matrix lattice. The UC emission intensity of Gd₂MoO₆ doped with Y³⁺ (40%) was enhanced about 2.27 (2.52) more times than that of Y³⁺-absent samples excited at 980 nm (1550 nm). Secondly, dual wavelength was used as the excitation wavelength simultaneously: The green UCL intensity of RE₂MoO₆: 2%Er³⁺, 15%Yb³⁺ was almost not changed, while the red UCL intensity was enhanced compared to the sum of the red UCL intensities excited by 980 nm and 1550 nm, respectively. The UCL mechanism excited by dual wavelength was investigated in detail, in which the two co-operative excitation processes were presented.