Synthesis of Broad Band Violet-Blue Light-Emitting Core-Shell Cr³⁺:C-CaIn₂O₄ Nanowires

We developed a simple, effective and green method for synthesis of broad band violet-blue lightemitting core-shell Cr³⁺:C-CaIn²O⁴ nanowires (1-10 mol% of Cr³⁺) using aloe vera nectar. Calcium indate (CaIn²O⁴) is an important wideband gap semiconductor that could be explored for optical doping such as transition metals and/or rare-earths useful to make light-emitters, optical data storage, and other devices. The nectar embeds the cations in a gel so as it controls an ionic conversion Cr⁶⁺ to Cr³⁺ in ambient air. When grafting a carbon layer on surface of Cr³⁺:CaIn²O⁴ crystallites it yields a core-shell structure of tailored dielectric, optical and other properties. Asprepared Cr³⁺:CaIn²O⁴-C exhibits two bands at 270 nm and 360 nm, which got shifted-to at 265 and 370 nm when annealed at higher dosage of Cr³⁺ ions. These are the ligand-to-metal O^2- to Cr³⁺ charge transfer bands. We studied the light-emission properties in analyzing migration, transfer and recombination processes of light-induced e^--h⁺ pairs in detail in correlation to a Cr³⁺:CaIn²O⁴-C core-shell nanostructure.