Multimodal luminescence properties of surface-treated ZnSe quantum dots by Eu

Highlights: • ZnSe:Eu QDs were synthesized using the heating-up method by adding a Eu precursor in Zn and Se precursors. • Optical property was investigated based on the change in the multimodal emission caused by increasing the amount of the Eu precursor. • Compared to the diffraction peaks of pristine ZnSe, the corresponding peaks for the ZnSe:Eu QDs are shifted to larger angles, by about 0.43°, because the ionic radius of Eu³⁺ (0.95 Å) is larger than that of Zn²⁺ (0.74 Å). • ZnSe:Eu QDs have Eu²⁺−O and Eu³⁺−O dangling bonds on the surface of Eu³⁺-doped ZnSe QDs. - Abstract: ZnSe:Eu quantum dots (QDs) were synthesized using the heating-up method by adding a Eu precursor in Zn and Se precursors. The optical property was investigated based on the change in the multimodal emission caused by increasing the amount of the Eu precursor. The emission wavelength of ZnSe QDs increased from 398 nm to 405 nm when the reaction was carried out for 30–300 s. The broad spectrum was attributed to the ⁴F₆⁵D₁ → ⁴F₇ transition when the Eu²⁺ emission was increased from 450 to 550 nm. Eu³⁺ shows characteristic red emission peaks at 579, 592, 615, 651, and 700 nm owing to the electronic transition of ⁵D₀ → ⁷F_j (j = 0, 1, 2, 3, 4). The expected structure of the ZnSe:Eu QDs was verified by XRD, TEM, and XPS. Compared to the diffraction peaks of pristine ZnSe, the corresponding peaks for the ZnSe:Eu QDs are shifted, by about 0.43°, to larger angles, because the ionic radius of Eu³⁺ (0.95 Å) is larger than that of Zn²⁺ (0.74 Å). They also have Eu²⁺−O and Eu³⁺−O dangling bonds on the surface of Eu³⁺-doped ZnSe QDs, with an average size of about 3.15 nm. These semiconductor QDs with rare earth elements are promising candidates to fabricate light-converting materials.