Green, Room-Temperature, Fast Route for NH4Yb2F7:Tm3+ Nanoparticles and Their Blue Upconversion Luminescence Properties

A pure ammonium fluorolanthanate NH4Yb2F7 matrix and its derivative doped Tm3+ were successfully synthesized by an ultra-fast solution route at room temperature. The as-prepared nanoparticles (NPs) were about 70 nm in diameter with the uniform size. In addition, NH4 Yb2F7:Tm NPs demonstrated a bright blue upconversion luminescence feature, which can be observed with the naked eye. There are five emission bands in the range of 400-800 nm and the primary blue and red bands derived from the transitions of D-1(2)-> F-3(4) and (1)G(4)-> F-3(4), respectively. The blue emission was populated via a three-photon process based on the relationship between emission intensity and excitation pump power. Our ultra-fast synthesis route presents a green and one-step strategy for the large-scale production. Moreover, the excellent blue upconversion will arouse extensive interest in upconversion studies in ammonium fluorolanthanate based hosts and pave the way for further development of upconversion material family.