Efficient quantum cutting in hexagonal NaGdF4:Eu3+ nanorods

Abstract

An ionic liquid (IL) assisted solvothermal method is employed to prepare single phase, oxygen free, hexagonal NaGdF₄:Eu³⁺ (2 mol%) nanorods with a visible quantum efficiency of 187%. In contrast, for mixed materials containing cubic and hexagonal NaGdF₄:Eu³⁺, the quantum efficiency is much less (127%). Thus, synthesis parameters have to be carefully chosen in order to get the high performance hexagonal material. Not only the influence of the IL but also of the Gd : F ratio during synthesis as well as the temperature were studied. It is found that the IL stabilizes the formation of hexagonal NaGdF₄:Eu³⁺, likewise a fluoride excess (Gd : F = 1 : 8) and elevated reaction temperatures (200 °C).