Investigating the role of amides on the textural and optical properties of mesoporous-nanostructured $$\uptheta $$-$$\hbox {Al}_{{2}}\hbox {O}_{{3}}$$

Abstract

Mesoporous-nanostructured $$\uptheta $$-$$\hbox {Al}_{{2}}\hbox {O}_{{3}}$$ was synthesized by an autoclaving technique using different amides i.e., formamide (F), dimethyl formamide (DMF) and diethyl formamide (DEF) at $$150^{\circ }\hbox {C}/24\,\hbox {h}$$ followed by calcination at $$1000^{\circ }\hbox {C}$$. 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 $$\hbox {N}_{{2}}$$ 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 $$\uptheta $$-$$\hbox {Al}_{{2}}\hbox {O}_{{3}}$$. The DMF-based solvent showed an enhanced surface area of $$158\,\hbox {m}^{2}\,\hbox {g}^{-1}$$. The as-prepared $$\uptheta $$-$$\hbox {Al}_{{2}}\hbox {O}_{{3}}$$ 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 $$\uptheta $$-$$\hbox {Al}_{{2}}\hbox {O}_{{3}}$$ 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.