RETRACTED ARTICLE: Enhanced luminescence of Mo³⁺-doped β-NaREF₄ nanowires prepared via coprecipitation–solvothermal ion-exchange method and their application in upconversion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.