Mesoporous $\gamma$-alumina was synthesized by the microwave-hydrothermal process with a shorter duration time at 150$^{\circ}$C/2 h followed by calcination at 550$^{\circ}$C/1 h. Ag nanoparticles (AgNPs) were impregnated into $\gamma$-alumina under a reducing atmosphere at 450$^{\circ}$C. The synthesized product was characterized by X-ray diffraction (XRD), thermogravimetric (TG)/differential thermal analysis (DTA), X-ray photoelectron spectroscopy (XPS), N$_2$ adsorption–desorption study, fieldemissionscanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The BET surface area values of $\gamma$-alumina and Ag-impregnated $\gamma$-alumina were found to be 258 and 230 m$^2$ g$^{−1}$, respectively. FESEM images showed the formation of grain-like particles of 50–70 nm in size with a flake-like microstructure. The XRD, XPS and TEM studies confirmed the presence of Ag in the synthesized product. Catalytic properties of the product for CO oxidation was studied with the $T_{50}$ (50% conversion) and $T_{100}$ (100% conversion) values of 118 and 135$^{\circ}$C, respectively; the enhancedvalues were compared with the literature reported values.

Mesoporous-nanostructured $\theta$-Al$_2$O$_3$ was synthesized by an autoclaving technique using different amidesi.e., formamide (F), dimethyl formamide (DMF) and diethyl formamide (DEF) at 150$^{\circ}$C/24 h followed by calcinationat 1000$^{\circ}$C. Crystallization and structural behaviour of the as-synthesized materials were characterized by X-raydiffraction 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 amidebasedsolvents played a deliberate role in microstructural and textural features of $\theta$-Al$_2$O$_3$. The DMF-based solventshowed an enhanced surface area of 158 m$2^$ g$^{−1}$. The as-prepared $\theta$-Al$_2$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 $\theta$-Al$_2$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 thelowest band gap due to its smaller crystallite size and higher surface area compared to that of F- and DEF-derivedsamples.

Preparation of CuO nanostructure was reported by oxalic acid-assisted wet-chemical method in aqueous medium. As-prepared sample was identified as C$_2$CuO$_4$.$n$H$_2$O, which was further transformed into CuO after heat treatment. To enhance the textural property, CTAB was employed as soft-templating agent. DTA–TGA characterization was performed to investigate the thermal stability of as-prepared C$_2$CuO$_4$.$n$H$_2$O sample, whereas Raman and XPS measurements confirmed the presence of CuO. FESEM and TEM studies revealed porous architecture with shelled interior for CuO sample. The formation of porous network could be demonstrated by oxidative decomposition of C$_2$CuO$_4$.$n$H$_2$O due to high temperature calcination. The BET surface area and pore volume were found to be 51 m$^2$ g$^{-1}$ and 0.4492 cc g$^{-1}$, respectively. The catalytic activity of sample was investigated for CO oxidation and achived $T_{50}$ and $T_{100}$ at 133 and 175°C, respectively, which were further compared with commercialized CuO sample and previously reported data.