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 340 nm and 65 nm. Excited by 984 nm continuous wave laser, strong red (643-677 nm), strong green (515-557 nm) and weak violet (382-417 nm) 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.