Investigating the influence of internal electric field on electric dipole transitions (5D0 → 7F2 and 5D0 →7F4) in lithium-incorporated Eu-doped BiOF: Insights beyond the nanoscale

In the previous study (https://doi.org/10.26434/chemrxiv-2025-8q8jd), we have synthesized europium-doped BiOCl phosphors at the nanoscale and examined their photoluminescence behaviour. Furthermore, the impact of the internal electric field (IEF) on the electric dipole transition at the nanoscale has also been examined. However, we were more interested in investigating how the internal electric field affects the electric dipole transitions in bulk materials or above the nanoscale. We have synthesized Eu-doped BiOF in place of BiOCl, as fabricating thick nanosheets (over 150 nm) with BiOCl is quite challenging due to the lower electronegativity of chlorine and its larger size compared to fluorine. The increased electronegativity and reduced fluorine size lead to a stronger structure (F-Bi-O-Bi-F) along the c-direction, accompanied by a shorter distance between van der Waals bonds. In this work, the europium-doped bismuth oxyfluoride (Eu-doped BiOF) has been synthesized using the facile solvothermal method. Further, the lithium ions intercalated in BiOF interlayers (to boost the internal electric field). As synthesized lithium intercalated Eu-doped BiOF phosphor have vertical thicknesses of more than 300 nm as confirmed by FESEM (Field emission electron microscopy). In addition, the effect of the internal electric field (IEF) on electric dipole (ED) transitions in Eu-doped BiOF has been studied which, suggests that the internal electric field does not affect hardly above the nanoscale (bulk). In contrast, the magnetic dipole (MD) transition intensity has been highest in comparison to electric dipole transitions. As discussed in a previous study (https://doi.org/10.26434/chemrxiv-2025-8q8jd), the BiOCl ultrathin nanosheets significantly influence the electric dipole transitions in comparison to the magnetic dipole transition that is due to the internal electric field (IEF). Further, these results suggest that the internal electric field may not significantly affect the electric dipole transitions in bulk materials.