Preparation of NaYF4:,Er3+/TiO2 composite and up-conversion luminescence properties under visible light excitation

The up-conversion luminescence composite NaYF₄:,Er³⁺/TiO₂ is prepared using the sol—gel method. The specimen has good crystallinity and two shapes, i.e., viereck and round, while the sizes of viereck and round particles are both micron-sized. The TiO₂ has an anatase structure, while the NaYF₄ has a hexagonal phase, which can be hardly obtained through the common sol—gel method. Due to the big particle size and the high crystallinity of pure NaYF₄:,Er³⁺, the composite has a small specific surface area that is less than Degussa P25 TiO₂. The NaYF₄:,Er³⁺/TiO₂ composite shows several emission peaks at 211, 237, and 251 nm under the excitation of 388 nm, at 395 nm and 411 nm under the excitation of 500 nm, and at 467, 481, 492, and 508 nm under the excitation of 570 nm.