Tuning the electric dipole transitions (5D0 → 7F2, and 5D0 → 7F4) in thin Eu-doped BiOCl nanosheets

The polarization and depolarization of layered ferroelectric materials can be tuned by altering the thickness of nanosheets apart from controlling inter/intra layer distances, doping of ions, surrounding dielectric environments, etc. In two-dimensional (2D) single-crystalline ferroelectric nanosheets, the reduction in the thickness facilitates the internal electric field, which leads to enhanced depolarization. BiOCl is a characteristic layered ferroelectric material that contains [Bi2O2]2+ layers arranged anisotropically along the c-direction. However, the depolarization and polarisation of BiOCl are significantly influenced by the thickness of its nanosheets. In this study, europium (Eu3+)-doped BiOCl nanosheets resembling a 2D-dimensional structure have been synthesized using the solid-state grinding method at ambient temperature. As a result of the depolarization effect, the intensity of the electric dipole (ED) transitions 5D0 → 7F2 and 5D0 → 7F4 increases in Eu3+-doped BiOCl nanosheets. Further, electric force microscopy (EFM) confirms that the electric field is present in close proximity to the surface of Eu3+-doped BiOCl. However, thiol capping helps in synthesizing uniform 2D nanosheets with reduced vertical dimensions (c-direction). It is observed that all the prepared samples with varying Eu ion concentrations show uniform nanosheet-like morphology. As the concentration of Eu ions increases in the BiOCl host lattice, the intensity of electric dipole transitions also increases. Fourier transform infrared spectroscopy (FT-IR) discloses the coating of 1-dodecanthiol on Eu-doped BiOCl molecules. Furthermore, the Eu-doped BiOCl samples demonstrated a prominent far-red emission at 700 nm, corresponding to the 5D0 → 7F4 transition. Moreover, this work emphasizes the synthesis of Eu-doped phosphor at an ambient temperature of 24 + 2 ˚C and generates a deeper understanding of the abnormal electric dipole (5D0 → 7F4) transition.