Hydrothermal synthesis, growth mechanism and down-shifting/upconversion photoluminescence of single crystal NaGd(MoO4)2 nanocubes doped with Eu3+, Tb3+ and Yb3+/Er3+

•Single crystal NaGd(MoO4)2 nanocubes are synthesized for the first time.•Effect of Na2MoO4 contents on the formation of NaGd(MoO4)2 nanocubes is studied.•Growth mechanism of NaGd(MoO4)2 nanocubes is investigated.•Luminescence and upconversion mechanism of NaGd(MoO4)2: Ln3+ nanocubes are studied.

Uniform and well-crystallized tetragonal NaGd(MoO4)2 nanocrystals with the morphology of nanocubes were synthesized via a modified hydrothermal synthesis method with oleic acid as complexing agent. The as-synthesized NaGd(MoO4)2 nanocubes were characterized by means of powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and selected area electron diffraction respectively. The side-length of the NaGd(MoO4)2 nanocubes is about 100-150 nm. The SAED pattern indicates highly crystalline nature of the NaGd(MoO4)2 nanocubes. The effect of Na2MoO4 contents on the formation of NaGd(MoO4)2 nanocrystals is investigated. A possible growth mechanism of NaGd(MoO4)2 nanocubes is deduced based on time-dependent morphology evolution and XRD analysis. Down-shifting/upconversion photoluminescence properties of NaGd(MoO4)2: Eu3+, Tb3+ and Yb3+/Er3+ nanocubes are investigated in detail. Furthermore, the energy transfer mechanism for upconversion luminescence in NaGd(MoO4)2: Yb3+/Er3+ nanocubes is investigated on the basis of energy level scheme and the excitation power dependence of upconversion luminescence intensities.