Infrared to visible upconversion emissions of La1–0.02–xEr0.02YbxOF nanorods

In this work, well-crystallized La1–0.02–xEr0.02YbxOF (x=0, 0.08, 0.06, 0.04, 0.02) nanorods were prepared by annealing the hydrothermally synthesized La1–0.02–xEr0.02YbxF3 nanocrystals at ambient condition. The structural properties of these samples were characterized by XRD and TEM (HRTEM), the results show that the nanorods have a pure tetragonal structure and a preferential growth along the (1 0 1) direction, the average length and cross-section radius are 340nm and 65nm. Excited by 984nm continuous wave laser, strong red (643–677nm), strong green (515–557nm) and weak violet (382–417nm) upconversion emissions have been observed in these nanorods. The influence of Yb3+ concentration on the upconversion emission intensity has been discussed. The possible upconversion mechanisms were proposed through research on pump power dependence of upconversion integrated intensity. Especially, both two-photon process and three-photon process were contributed to the green upconversion in lower Yb3+ concentration doped nanorods.