Eu3+ doped KYF4nanocrystals: synthesis, electronic structure, and optical properties

Abstract

Monodisperse cubic-phase KYF₄ : Eu³⁺ nanocrystals (NCs) were synthesized via a modified thermal decomposition method. The optical properties of Eu³⁺ in KYF₄ NCs including multiple luminescence centers, site symmetry, luminescence dynamics, as well as crystal-field levels of Eu³⁺ were investigated in detail based on high-resolution photoluminescence (PL) spectroscopy at low temperature (10 K). Different from Eu³⁺ in bulk counterparts, multiple sites of Eu³⁺ in KYF₄ NCs were revealed by using the luminescence of Eu³⁺ as a sensitive structural probe. The highest site symmetry of Eu³⁺ at new near-surface site was deduced to be distorted from O_h to D₂ (or C_2v). Due to a small filling factor (0.45) of NCs, the PL lifetime of ⁵D₀ of Eu³⁺ in KYF₄ NCs was much longer than that in bulk counterparts, which was found to be significantly affected by the surrounding medium around the NCs.