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Novel crystalline tetragonal ZrO 2 : Eu 3+ phosphors were prepared by a facile and efficient low temperature solution combustion method at 400 ± 10 °C using oxalyl dihydrazide (ODH) as fuel. The powder X-ray diffraction patterns and Rietveld confinement of as formed ZrO 2 : Eu 3+ (1–11 mol%) confirmed the presence of body centered tetragonal phase. The crystallite size estimated from Scherrer’s and W–H plots was found to be in the range of 7–17 nm. These results were in good agreement with transmission electron microscopy studies. The calculated microstrain in most of the planes indicated the presence of tensile stress along various planes of the particles. The observed space group ( P4 2 /nmc ) revealed the presence of cations in the 2b positions (0.75, 0.25, 0.25) and the anions in the 4d positions (0.25, 0.25, 0.45). The optical band gap energies estimated from Wood and Tauc’s relation was found to be in the range 4.3–4.7 eV. Photoluminescence (PL) emission was recorded under 394 and 464 nm excitation shows an intense emission peak at 605 nm along with other emission peaks at 537, 592, 605 and 713 nm. These emission peaks were attributed to the transition of 5 D 0 → 7 F J ( J = 0, 1, 2, 3) of Eu 3+ ions. The high ratio of Intensity of ( 5 D 0 → 7 F 2 ) and ( 5 D 0 → 7 F 1 ) infers that Eu 3+ occupies sites with a low symmetry and without an inversion center. CIE color coordinates indicated the red regions which could meet the needs of illumination devices. [ABSTRACT FROM AUTHOR]

Green synthesis of multifunctional Zinc oxide nanoparticles (NPs) with a variety of morphologies were achieved by low temperature solution combustion route employing neem ( Azadirachta indica ) extract as fuel . The nanoparticles were characterized by PXRD, FTIR, XPS, Raman and UV–Visible spectroscopic studies. The Morphologies were studied by SEM and TEM analysis. The NPs were subjected for photoluminescence, photocatalytic, antibacterial and antioxidant activity studies. PXRD pattern confirmed the hexagonal wurtzite structure of the product. SEM images indicated the transformation of mushroom like hexagonal disks to bullets, buds, cones, bundles and closed pine cone structured NPs with increase in the concentration of neem extract in reaction mixture. The NPs exhibited prominent green emission due to the presence of intrinsic defect centers. The as-formed bullet shaped ZnO with 4 ml of neem extract was found to decolorize Methylene blue (MB) under Sunlight and UV light irradiation. The antibacterial studies indicated that ZnO NPs of concentration 500, 750 and 1000 μg resulted in significant antibacterial activity on Klebsiella aerogenes and Staphylococcus aureus but not against Escherichia coli and Pseudomonas aeruginosa in agar well diffusion method. Further, ZnO NPs exhibited significant antioxidant activity against scavenging DPPH free radicals. The current investigation demonstrated green engineering method for the synthesis of multifunctional ZnO NPs with interesting morphologies using neem extract. [ABSTRACT FROM AUTHOR]

For the first time nanoparticles of Tb 3+ doped (1–11 mol%) Mg 2 SiO 4 have been prepared using low temperature (350 °C) solution combustion technique with magnesium nitrate as precursor and oxalyl di-hydrazide (ODH) as fuel. The Powder X-ray diffraction (PXRD) patterns of the sample revealed orthorhombic structure with α-phase. The average crystallite size using Scherer’s formula, W – H plot and Size–strain plot is found to be 28 nm and the same is confirmed by Transmission electron microscopy (TEM) studies. Scanning electron microscopy (SEM) pictures show a porous structure and the crystallites were agglomerated. The effect of Tb 3+ cations on luminescence characteristics of Mg 2 SiO 4 is studied and the results are discussed in detail. The phosphors exhibit bright green emission upon near ultra violet (NUV) 377 nm excitation. The characteristic photoluminescence emission peaks at 417, 436, 458 nm in blue region due to 5 D 3 → 7 F J ( J = 5, 4, 3) of Tb 3+ ions and the emission peaks at 486, 541, 584 and 621 nm in green region corresponds to 5 D 4 → 7 F J ( J = 6, 5, 4, 3) transitions of Tb 3+ ions owing to f–f transitions of Tb 3+ cations in the given host lattice and are due to dipole–quadropole interactions. The CIE chromaticity co-ordinates are calculated from emission spectra and falls in green region. Therefore the present phosphor is highly useful for mercury free solid state lighting (SSL) and also for display applications. [ABSTRACT FROM AUTHOR]