Synthesis of new LnxBi2-xSe3 (Ln: Sm 3+, Eu3+, Gd3+, Tb3+) nanomaterials and investigation of their optical properties

Abstract

New LnxBi2-xSe3 (Ln: Sm3+, Eu3+, Gd3+, Tb3+) based nanomaterials were synthesized by a co-reduction method. Powder XRD patterns indicate that the LnxBi2-xSe3 crystals (Ln = Sm3+, Eu3+, x = 0.00-0.44 and Ln = Gd3+, Tb3+, x = 0.00-0.50) are isostructural with Bi2Se3. The cell parameter c decreases for Ln = Eu3+, Gd3+, Tb3+ upon increasing the dopant content (x), while a slightly increases. Changes in lattice parameters could be related to the radii of cations. SEM images show that doping of the lanthanide ions in the lattice of Bi2Se 3 generally results in nanoflowers. For the terbium compound two kinds of morphologies (nanoflowers and nanobelts) were observed. UV/Vis absorption and emission spectroscopy reveals mainly electronic transitions of the Ln3+ ions. Emission spectra show intense transitions from the excited to the ground state of Ln3+ and energy transfer from the Bi2Se3 lattice. Emission spectra of europium-doped materials, in addition to the characteristic red emission peaks of Eu 3+, show an intense blue emission band centered at 432 nm, originating from the 4f65d1 to 4f7 configuration in Eu2+. EPR measurements confirm the existence of Eu2+ in the materials. Interestingly, for all samples starting at low Ln3+ concentration, the emission intensity rises to a maximum at a Ln3+ concentration of x = 0.2 and falls again steadily to a minimum at x = 0.45. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.