Ordered LiGa5O8 loaded with redox capable Cu2+, Cr3+ ions to manifest interesting optical, magnetic, and catalytic properties

Abstract

The crystal structure and associated property changes brought about by substituting Cu 2? and Cr 3? ions for Li ? and Ga 3? ions, respectively, in ordered LiGa 5 O 8 are probed in the present work. The samples were synthesized by a single-step calcination process of epoxide-mediated xerogels rapidly and characterized extensively. Powder X-ray diffraction patterns revealed the preservation of the superstructure of spinel up to 50 mol % Cu 2? with Li ? , 20 mol % Cr 3? with Ga 3? and coupled substitution of Cu 2? (25 mol %) and Cr 3? (5 mol %) with Li and Ga, respectively. The structural refinements and electron microscopic analysis (high-resolution transmission electron microscopy and selected area electron diffraction) confirmed the samples' ordered spinel structure. Raman and FTIR features confirmed the lower symmetry arising from the cation ordering in the samples. UV-visible and electron paramagnetic resonance spectroscopy measurements on Cu-and Cr-containing samples revealed their oxidation state and site preferences. Reversible peaks in DSC heating and cooling traces showed order/disorder phase transition in Cu 2? (1069 and 1044 °C)-and Cr 3? (1100 and 1038 °C) substituted samples. Photoemission in the red region and antiferromagnetic behavior with a Ne ´el temperature of 8 K were displayed by the Cr-containing LiGa 5 O 8 . The Cu 2? -substituted samples catalyzed the reduction of the nitroaromatics while Cr 3? -containing sample catalyzed the photodegradation of Rh-6G dye solution. The coupled substituted sample (Cu/Cr), being advantageous, could perform both catalytic conversions.

Probing Local Structural Changes by Sharp Luminescent Infrared Nanophosphor for Application in Light-Emitting Diodes

“…As Raman active phonon modes are highly related to the structural symmetry, Raman spectra of LiGa 5(1– x ) Al 5 x O 8 :0.05Cr 3+ with x = 0–1.0 are characterized to understand the discontinuity of the structural evolution between LiGa 5 O 8 and LiAl 5 O 8 , as shown in Figure S6. All of the peaks shift toward the higher wavenumber with the incorporation of Al 3+ ions due to the larger atomic weight of Ga 3+ (69.72 amu) compared to that of Al 3+ (26.98 amu). , For the x = 0 sample, the peak at 272 cm –1 can be attributed to the translational motion of [GaO 4 ] tetrahedrons . Besides, the peaks in the regions of 300–600 cm –1 belong to the deformation of [GaO 4 ] tetrahedrons and [GaO 6 ] octahedrons .…”

“…16,17 For the x = 0 sample, the peak at 272 cm −1 can be attributed to the translational motion of [GaO 4 ] tetrahedrons. 18 Besides, the peaks in the regions of 300−600 cm −1 belong to the deformation of [GaO 4 ] tetrahedrons and [GaO 6 ] octahedrons. 19 The peaks in the region >600 cm −1 belong to the stretching and bending of [GaO 4 ] tetrahedrons.…”

Regulating the trap distribution of ZnGa2O4:Cr3+ by Li+/Ga3+ doping for upconversion-like trap energy transfer NIR persistent luminescence

“…The translational motion of the GaO 4 tetrahedron generates a band in the lower wavenumber region. 39,41 The FWHM of XRD patterns and Raman spectrum are demonstrated in Fig. S3,† which can prove the orderliness of samples.…”

“…Cubic spinel contains 42 vibrational modes in its group theory. The following modes of spinels are predicted by group theory analysis at the Γ point: 18,37–40 where most modes are silent or acoustic modes except for the indicated infrared-active and Raman-active modes. There are only four infrared active modes and five Raman active modes in normal non-defective spinels.…”

Effect of Eu3+ doping on the structural, optical, and photoluminescent properties of LiGa5O8 phosphor

“…These values fall within the range reported in the literature. 31 Meanwhile, Table 4 presents Wyckoff positions and atomic parameters for the synthesized host material.…”