Optical properties, Judd-Ofelt analysis and energy transfer processes of Eu3+ doped ZnS quantum dots

Quantum dots (QDs) of ZnS doped with different Eu3+ ion concentrations were synthesized using a chemical method. The X-ray diffraction (XRD) pattern showed that the prepared QDs were crystallized in the Zincblende phase and their size was estimated to be approximately 3 nm. The XRD pattern and XPS spectrum analysis showed that Eu3+ ions replaced Zn2+ ions in the crystal lattice. For the first time, the optical properties of Eu3+ doped ZnS QDs were studied using photoluminescence excitation (PLE), photoluminescence (PL) spectra, and Judd-Ofelt (J-O) theory. Ωλ (λ = 2, 4, 6) parameters were calculated from the PLE spectra of the samples. The luminescence quantum efficiency and properties of the ligand field of the material were calculated and compared with those of other lattice hosts. The energy transfer (ET) processes from the ZnS host to Eu3+ ion and between Eu3+ ions were also discussed in detail. The ET process from the ZnS host to the Eu3+ ion occurred through the exchange interaction. The dominant interaction between Eu3+ ions in the ET process is the dipole-dipole mechanism, which is determined by fitting the decay curve of the 5D0 level to the Inokuti-Hirayama model.