Synthesis of nanostructured pirochromite magnesium chromate with egg shell membrane template

Abstract

In this work, we report on the use of fresh and boiled egg shell membrane as bio-templates in the co-precipitation of pirochromite. The structure evolution, microstructure and optical properties of the ESM templated MgCr2O4 nanomaterial were studied by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, Energy dispersive X-ray spectroscopy, elemental mapping and UV–Vis–NIR spectrophotometry. The annealing of the untemplated and templated co-precipitated MgCr2O4 powders at 1000 °C for 4 h produced single phased nanostructured material with spinel cubic crystal structure. The FTIR results showed slight variations in the band positions ν 1 and ν 2 which are attributed to the change in the microstructure due to the introduction of ESM in the preparation of MgCr2O4. The morphologies and average crystallite size of the annealed MgCr2O4 nanocrystalline powders depended on the type of the template. 3D hierarchical flake-like and mesh like structures were observed. The annealed MgCr2O4 nanocrystalline powders have shown excitonic absorptions in the visible range 300–500 nm due to the transitions that took place from the O-2p level to the Cr-3d level. The optical band gap energies were found to be 3.68–3.71 eV for the direct band gap and 3.30–3.37 eV for the indirect band gap. This could make these MgCr2O4 nanocrystalline powders possible photocatalysts in the visible range 300–500 nm.