pH value manipulated phase transition, microstructure evolution and tunable upconversion luminescence in Yb³⁺–Er³⁺ codoped LiYF₄/YF₃ nanoparticles

Abstract

The pH value plays an important role in controlling the crystallization process and microstructure of the final products in the synthesis of nanocrystals with a solvothermal method. This work reported the effect of the mother solution pH value on the precipitation of LiYF4 and YF3 nanoparticles, as well as the microstructure evaluation of YF3 from a bowknot-like to spindle-like shape. Spectroscopy study suggests that there is strong correlation between the upconversion emission properties of the Yb(3+)-Er(3+) couple and the phase and the microstructure of the host. The strongest emissions and lowest red-to-green ratio are observed in the bowknot-like YF3 nanocrystals with the largest open ends. Further spectral investigation indicates that the phase and microstructure dependent upconversion properties are associated with the upconversion efficiency. The present study is of great importance in the design and synthesis of rare earth ion doped nanocrystals with tunable upconversion properties.

Microwave-Assisted Solvothermal Synthesis of Upconverting and Downshifting Rare-Earth-Doped LiYF4 Microparticles

“…To gain control over the phase, size, and morphology of the target product, pH-sensitive ligands with a selective affinity for particular facets of the developing crystalline material were demonstrated to facilitate the synthesis of M­(RE)­F 4 -based materials. ,, Thus, the pH-dependent abundance of such growth-guiding ligands, their intrinsic chemical nature, and solvent compatibility are important physicochemical reaction parameters to consider when a new synthesis method is developed . For this study, the acetic acid (CH 3 COOH)/acetate (CH 3 COO – ) system was selected on the basis of its excellent H 2 O/ethanol solvent compatibility and successful application as a particle-capping ligand in a previously reported microwave-assisted solvothermal M­(RE)­F 4 material synthesis .…”

Enhancement of Luminescence Intensity in Red Emitting NaYF4:Yb/Ho/Mn Upconversion Nanophosphors by Variation of Reaction Parameters

“…Emission color can be tuned as well as intensity can be improved by varying the doping percentage of a sensitizer or activator or other codopants, which eventually lead to change of crystal phase, morphology, and, subsequently, the luminescence properties. , Luminescence properties can be varied not only by changing the dopant proportions but also by changing the experimental conditions employed during the synthesis. Ye et al reported the effect of reaction solution pH on the precipitated nanoparticles’ luminescence properties . Sarakovskis et al and Xu et al examined the effect of temperature on the luminescence properties of UCNPs, , and Ma et al investigated the effect of reaction temperature as well as time on crystal phase, shape, size, and UCL properties .…”

The luminescence thermometry based on analysing of 3P0-3H5 emission band of Pr3+ ions in Pr3+:LiYF4 nanoparticles and microparticles

“…The Pr 3+ :LiYF4 nanoparticles were synthesized via the hydrothermal synthesis method [1]. Microparticles of Pr 3+ :LiYF4 were synthesized by mechanical grinding of a Pr 3+ :LiYF4 crystal grown by the Bridgman method.…”