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For the first time, different morphologies of zinc oxide (ZnO) superstructures are synthesized by a simple and environmental friendly route using Nerium oleander leaf extract as fuel. Powder X-ray diffraction, scanning electron microscopy, UV−visible spectroscopy, and photoluminescence studies are performed to ascertain the formation and characterization of ZnO. X-ray diffraction confirmed the crystalline nature of the compound with hexagonal Wurtzite structure. When the concentration of the leaf extract is varied, different morphologies are formed. ZnO are tested for antifungal using soybean seed-borne fungi by food-poison method and antibacterial activity against bacterial human pathogens by a broth microplate dilution method using 96-well plates. Among the screened soybean seed-borne fungi, Fusarium equisiti was found to be more susceptible, which was followed by Macrophomina phaseolina for ZnO nanoparticles (NPs) prepared using 0.2188 mol/dm 3 N. oleander leaf extract. It was observed that NPs exhibited pronounced antifungal activity in a dose-dependent manner with a relatively high percentage of mycelial inhibition. ZnO obtained with the concentration of 0.2188 mol/dm 3 leaf extract showed both minimum inhibitory concentration and minimum bactericidal concentration effectiveness compared to other synthesized compounds. It is observed that the samples with small crystallite size show greater antibacterial activity than those of larger crystallite size. Further, we found that crystallite size and morphology significantly affects the antibacterial activity of ZnO. Prepared compounds showed significant inhibition against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeurginosa. Among the tested bacteria, P. aeurginosa is more susceptible and E. coli is the least effective against bacterial pathogens. The antibacterial activities of the as-formed ZnO are preliminarily studied against Gram-positive (B. subtilis and S. aureus) and Gram-negative (E. coli and P. aeruginosa) bacteria and are found to be dependent on the shape of the nanostructures.

Nanocrystalline meta-zinc titanate (ZnTiO 3 ) ceramic was prepared using a self-propagating solution combustion synthesis (SCS) for the first time using urea as fuel. The product was calcined at 800 • C for 2 h to improve the crystallinity. Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), high resolution transmission electron microscopy (HR-TEM) and UV-vis absorption spectroscopy were used to characterize the final product. PXRD results show that the ilmenite type rhombohedral structure was formed when the sample was calcined at 800 • C for 2 h. Adsorption experiments were performed with cationic malachite green (MG) dye. ∼96% dye was adsorbed onto nanocrystalline ZnTiO 3 ceramic at pH 9 for 30 min of the contact time. The optimum adsorbent dose was found to be 0.45 g/L of dye. Langmuir-Hinshelwood model was used to study adsorption kinetics and first order kinetic model best describes the MG adsorption on ZnTiO 3 . Antibacterial activity was investigated against gram negative Klebsiella aerogenes, Pseudomonas desmolyticum, Escherichia coli, and gram positive Staphylococcus aureus bacteria by agar well diffusion method. Nanocrystalline ZnTiO 3 ceramic showed significant effect on all the four bacterial strains at the concentration of 1000 and 1500 g per well.

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