The single-band red upconversion (UC) emission of lanthanide-doped materials have attracted attention due to its great potential for versatile applications. In this work, YbOCl: x Er 3+ with super pure red UC emission had been successfully synthesized by conventional high temperature solid-state reaction. X-ray powder diffraction (XRD) confirmed the rhombohedral structure with space group R -3 m (166). Scanning electron microscopy (SEM) exhibited agglomeration morphology of smooth sheets with nanometer thickness. The UC emission spectra of YbOCl:Er 3+ manifested intense red emission and much lower green emission when pumped by 980 nm diode laser. The dominating red emission peaking at 670 nm was assigned to the electron transition 4 F 9/2 → 4 I 15/2 . The green emission at 521 nm and 547 nm were corresponding to 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transition of Er 3+ , respectively. The CIE chromaticity coordinates showed the color of samples lain in red region and the purity of red emission could be tuned by the concentration of Er 3+ . The UC luminescence mechanism was proposed based on the relationship of UC intensity versus pump power density and their lifetime. Our research provided a new thought for realizing single-band red emission without any further modification.
MOX (M = Fe, Co, Mn, Cr, Lanthanide, or Actinide metals; O = oxygen, X = F, Cl, Br, I), an emerging type of 2D layered materials, have been theoretically predicted to possess unique electronic and magnetic properties. However, 2D MOX have rarely been investigated. Herein, for the first time, ultrathin high-quality ytterbium oxychloride (YbOCl) single crystals are successfully synthesized via an atmospheric pressure chemical vapor deposition method. Both theoretical simulations and experimental measurements are utilized to systematically investigate the Raman properties of 2D YbOCl nanosheets. The experimentally observed E g mode at 85.53 cm −1 and A 1g mode at 138.17 cm −1 demonstrate a good match to the results from density functional theory calculations. Furthermore, the temperature-dependent and thickness-dependent Raman scattering spectra reveal the adjacent layers in YbOCl nanosheets show a relatively weak van der Waals interaction. Additionally, the polarized-dependent Raman scattering spectra show the intensity of A 1g mode exhibits twofold patterns while the intensity of the E g mode remains constant as the rotation angle changes. These findings could provide the first-hand experimental information about the 2D YbOCl crystals.
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