Absorption edges 1 Band gap energy 1 Band gap narrowing 1 Combustion method 1 Combustion synthesis 1 Copper 1 Crystallite size 1 Doped materials Energy gap 1 Field emission scanning electron microscopes 1 Magnesia 1 Nano-structured 1 Oxide minerals 1 Scanning electron microscopy 1 Semiconductor materials 1 Triethanolamine 1 UV-VIS-NIR spectrophotometers 1