Amutha Selvi, M2017-02-092017-02-092015https://ir.avinuty.ac.in/handle/avu/1311Spinel Co^Zn,_,Al204 (0 < x < 1) nano-catalysts were synthesized by a simple Aloe vera plant extracted green synthesis route. Powder XRD patterns and Rietveld analysis confirmed the formation of single phase, cubic spinel gahnite structure without other impurities. The lattice parameter increased from 8.089 to 8.125 A with increasing content. The average crystallite sizes were estimated using Scherrer’s method, and it was found to be in the range of 15.72 nm to 26.53 nm. FT-IR spectra showed vibrational stretching frequencies corresponding to the spinel structure. HRSEM and HR-TEM images showed the features of well particle shaped crystals with nano-sized grains. The elemental compositions of Co, Zn, Al and O were quantitatively obtained from EDX analysis. The band gap energy estimated using Kubelka-Munk method by UV-Visible DRS method, and the values are decreased with increasing the Co^^ content (4.12 eV to 3.67 eV), due to the formation of sub bands in between the energy gap. PL spectra showed emission bands in UV as well as in the visible regions for ZnAIjO^ and Co-doped ZnAl204, due to the defect centers acting as the trap levels. VSM measurements revealed that pure ZnAl204 has diamagnetic, while Co doped ZnAl204 samples (x = 0.2 to 0.8) have superparamagnetism, whereas the sample C0AI2O4 has ferromagnetic in nature. Catalytic oxidation of benzyl alcohol to benzaldehyde was found that the sample Coo 6Zno4Al204 showed 93.25% conversion with 99.56% selectivity, whereas for pure ZnAl204, the conversion was only 86.31% with 92.85% selectivity.