Reducing Grain Size and Enhancing Luminescence of NaYF₄:Yb³⁺, Er³⁺ Upconversion Materials

Abstract

A variety of NaYF 4 :Yb/Er upconversion materials were successfully synthesized via a facile hydrothermal method by altering the volume ratios (0:1, 1:1, 2:1, 3:1, 4:1, 5:1) of ethanol to water and various alcohols (methanol, n-propyl alcohol, isopropyl alcohol, ethylene glycol, polyethylene glycol, and phemethylol), and the grain size and luminescence of the materials were effectively tailored. The addition of alcohol effectively reduces the grain size of the materials and simultaneously leads to the surprising enhancement of the UC emission. The increase in the volume ratio of EtOH/H 2 O causes the transformation of the crystal structure of the materials from hexagonal to cubic phase. The particle size of the material with the EtOH/H 2 O of 2:1 is almost 1000 times smaller than that of the material without EtOH, and the strongest luminescence is observed at the EtOH/H 2 O of 2:1. The type of alcohol in the solvent exhibits a significant influence on the luminescent properties of the materials. The NaYF 4 :Yb/Er nanocrystals obtained using different alcohols as solvent possess much a smaller grain size and stronger upconversion luminescence than that using water as solvent, and the NaYF 4 :Yb/Er materials with n-propyl alcohol exhibit the strongest luminescence intensity. The mechanism of the reduction of grain size and enhancement in the luminescence of the NaYF 4 :Yb 3+ , Er 3+ upconversion materials has been proposed. This study may suggest a simple method to significantly reduce the grain size and improve the upconversion luminescence properties of NaYF 4 -based fluorescence material.

Controlled Morphology, Improved Photoluminescent Properties, and Application of an Efficient Non-rare Earth Deep Red-Emitting Phosphor

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In Situ Synthesis of Dicarboxylic Acid Functionalized Upconversion Nanoparticles for Bioimaging Applications

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Controllable Synthesis of Upconversion Nanophosphors toward Scale‐Up Productions

“…Also, apart from the ligands, other experimental factors including reaction temperature and time, volume ratios of ethanol to water, alcohol type, and subsequent annealing could also affect the morphology of the particles. [ 84–86 ]…”