Enhanced luminescence of Mo3+-doped β-NaREF4 nanowires prepared via coprecipitation–solvothermal ion-exchange method and their application in upconversion polyurethane composite

A variety of 0–20 mol% of molybdenum ions (Mo3+)-doped sodium rare-earth (RE) fluoride upconversion nanowires (UCNW) were prepared by Coprecipitate–Solvothermal Ion-Exchange (CSIE) method. In this study, the Mo3+-doped rare-earth hydroxide [REMo(OH)3] precursors were synthesized by the coprecipitation–solvothermal method. Following, the hexagonal phase of the Mo3+-doped sodium rare-earth fluoride (β-NaGdF4: Yb3+/Tm3+/Mo3+, abbreviated as NaREMoF4) nanowires were successfully prepared by ion-exchange reaction, and checked by XRD data analysis. As shown in the EDS results, Mo3+ was uniformly distributed in the β-NaREMoF4. The controlled diameter (20–50 nm) and aspect ratio (20–500) values of β-NaGdF4: Yb3+/Tm3+/Mo3+ nanowires strongly depend on the amount of Mo doping according to TEM images. The upconversion luminescence intensity (UC) of 10 mol% Mo3+-doped β-NaREMoF4 nanowires was increased by one order of magnitude under the 980 nm near-infrared (NIR) excitation in regard to the undoped sample. One-dimensional (1D) upconversion nanowires (UCNW) with 10 mol% Mo3+ doping gives the upconversion polyurethane (UCPU) excellent luminescent performance and about 99% of enhanced tensile strength.