Green Synthesis of Cr³⁺ Doped CaIn₂O₄-Carbon Hybrid Nanostructure and Its Light Absorption and Emission Properties

In this research article, we have used a novel route for synthesis of a greenish phosphor C-CaIn₂O₄ doped with Cr³⁺ ions using green plant (aloe vera gel) and measured its light absorption and emission properties. Our main aim was to enhance the light absorption and emission properties of undoped C-CaIn₂O₄ in order to widen its applications. The introduction of CrO₃ ions can produce Cr ion defects that favor charge balance in Cr³⁺:C-CaIn₂O₄ to facilitate its photoluminescence. The effect of doping in core-shell nanostructure can effectively transfer energy from charge-transfer absorption band of optical host material to characteristic transition of Cr³⁺ ions, utilizing more energy from host absorption for the photoluminescence of Cr³⁺ ions. As-prepared Cr³⁺:C-CaIn₂O₄ exhibits two bands at 270 nm and 370 nm, which are shifted to at 265 and 370 nm when it is annealed at higher dosage of Cr³⁺ ions. These are the ligand-to-metal O^2- to Cr³⁺ charge transfer bands. The light-emission is studied in analyzing migration, transfer and recombination processes of light-induced e^--h⁺ pairs. The results are described in correlation to a Cr³⁺:C-CaIn₂O₄ core-shell nanostructure.