Enhanced Luminescence and Photocatalytic Activity in Highly Inverted Spinel ZnGa2O4 Nanoplates

Zinc gallate (ZnGa₂O₄) has recently emerged as a promising wide-band-gap material for light-emitting and power electronic devices. This study investigates the impact of cation site inversion on the luminescence and photocatalytic properties of ZnGa₂O₄. High-quality nanoplates of ZnGa₂O₄ with pure spinel phase, lateral dimensions up to 10 μm, and thicknesses around 40 nm are synthesized via hydrothermal reaction. Photoemission and Raman spectroscopies reveal significant cation inversion, where Ga³⁺ ions occupy tetrahedral sites (Ga_Zn) and Zn²⁺ ions occupy octahedral sites (Zn_Ga), forming antisite defects. The cation inversion parameters are measured as 0.36 ± 0.04 for Ga_Zn and 0.25 ± 0.02 for Zn_Ga. The nanoplates exhibit stable, bright broad-band luminescence featuring an ultraviolet (UV) band at 3.2 eV associated with self-trapped holes and three visible bands attributed to defects. Furthermore, the ZnGa₂O₄ nanoplates demonstrate superior photocatalytic efficiency in degrading Rhodamine B (RhB) under ultraviolet A (UVA) irradiation compared to Ga₂O₃. Band structure analysis reveals strong tail states extending the valence and conduction band edges of Ga₂O₃, reducing the band gap to 3.9 eV, and facilitating hydroxyl radical production for enhanced photocatalysis.