Synthesis, characterization and performance of porous Sr(II)-added ZnAl2O4 nanomaterials for optical and catalytic applications

Strontium(II)-added ZnAl2O4 nanomaterials with spinel structure were prepared by modified sol–gel method using ethylenediamine followed by sintering at 900 °C. The samples were labeled as ZnSA1-900, ZnSA2-900, ZnSA3-900, ZnSA4-900, ZnSA5-900, ZnSA6-900, respectively, where the molar ratios of Zn:Sr was 1.0:0.0, 0.9:0.1, 0.8:0.2, 0.7:0.3, 0.6:0.4 and 0.5:0.5 and aluminum molar ratio was kept constant, 900 refers to the sintering temperature. The effect of Sr addition on the structural, morphological and optical properties of zinc aluminate nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), high resolution scanning electron microscopy (HR-SEM), nitrogen adsorption/desorption isotherms, diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. The addition of Sr improves the performance of the zinc aluminate towards the selective oxidation of alcohols and decreases the grain size. The effect of solvent, oxidant and reaction time on the Sr(II)-added zinc aluminate nanomaterials for the oxidation of benzyl alcohol was studied. Higher activity was obtained for the conversion of benzyl alcohol to benzaldehyde for 0.3 molar percentage Sr(II)-added zinc aluminate (ZnSA4-900) which was used for the selective oxidation of other alcohols. Stability and reusability of the nanomaterials was also investigated.