Upconversion luminescence of NaYF_4:Yb,Er nanocrystals with high uniformity

The NaYF4:Yb,Er nanocrystals were synthesized via the thermal decomposition of metal oleate precursors. The nanocrystals in hexagonal structure were highly uniform and in size of 25 nm. The bright upconversion luminescence was observed under the excitation of 980 nm laser and the upconversion emission spectra were investigated at different pump powers. The emission intensity ratio of red light to green light linearly increased with pump power increasing. This result indicated that there existed a large threshold power of saturation pump for the first excitation state in NaYF4:Yb,Er nanocrystals comparing to that in bulk material.

The NaYF4：Yb,Er nanocrystals were synthesized via the thermal decomposition ot metal oleate precursors, lhe nanocrys- tals in hexagonal structure were highly uniform and in size of 25 nm. The bright upconversion luminescence was observed under the excitation of 980 nm laser and the upeonversion emission spectra were investigated at different pump powers. The emission intensity ratio of red light to green light linearly increased with pump power increasing. This result indicated that there existed a large threshold power of saturation pump for the first excitation state in NaYFa：Yb,Er nanocrystals comparing to that in bulk material.