NaYF4: Eu3+ microwires: Synthesis and the mechanism of stark splitting by monitoring time-resolved photoluminescence spectroscopy at high temperature

A new design of NaYF₄: Eu³⁺ microwires (MWs) with a hexagonal structure were synthesized via a facile hydrothermal method assisted with the sodium citrate, and their microstructure and phase structure have been analyzed. The photoluminescence (PL) mechanism of β-NaYF₄: Eu³⁺ MWs was systematically investigated under 532 nm laser excitation through adjusting MW number and excitation environment including the excited position, laser power, and temperature. The strongest emission peak originated from the ⁵D₀→⁷F₂ hypersensitive transition in this system. Furthermore, owing to the special temperature-dependent optical properties of β-NaYF₄: Eu³⁺ MWs, time-resolved PL spectroscopy with high sensitivity is in situ real-time monitored at 1273 K to reveal the underlying mechanism of stark splitting. Therefore, our study should serve as a promising application in optical thermometry.