Investigating the role of amides on the textural and optical properties of mesoporous-nanostructured θ-Al₂O₃

Mesoporous-nanostructured θ-Al₂O₃ was synthesized by an autoclaving technique using different amidesi.e., formamide (F), dimethyl formamide (DMF) and diethyl formamide (DEF) at 150℃C/24 h followed by calcination at 1000℃C. Crystallization and structural behaviour of the as-synthesized materials were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The porosity study was carried out by N2 adsorption-desorption (BET) technique. Microstructural features were measured by transmission electron microscopy (TEM). The amide based solvents played a deliberate role in microstructural and textural features of θ-Al₂O₃. The DMF-based solvent showed an enhanced surface area of 158 m2^g-1. The as-prepared θ-Al₂O₃ rendered a nano-sheet, nano-rod and nano-flake like morphology for F, DMF and DEF derived products, respectively. From the UV–Vis spectroscopic measurement, the estimated band-gap of θ-Al₂O₃ was found to be 5.16–5.40 eV. Photoluminescence investigation further revealed blue emission particularly for excitation at a wavelength of 252 nm. A DMF-derived sample rendered the lowest band gap due to its smaller crystallite size and higher surface area compared to that of F- and DEF-derived samples. (author)