Enhanced Luminescence and Photocatalytic Activity in Highly Inverted Spinel ZnGa₂O₄ Nanoplates

Zinc gallate (ZnGa 2 O 4 ) 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 ZnGa 2 O 4 . High-quality nanoplates of ZnGa 2 O 4 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 Ga 3+ ions occupy tetrahedral sites (Ga Zn ) and Zn 2+ 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 ZnGa 2 O 4 nanoplates demonstrate superior photocatalytic efficiency in degrading Rhodamine B (RhB) under ultraviolet A (UVA) irradiation compared to Ga 2 O 3 . Band structure analysis reveals strong tail states extending the valence and conduction band edges of Ga 2 O 3, reducing the band gap to 3.9 eV, and facilitating hydroxyl radical production for enhanced photocatalysis.