ZnO nanoflowers were synthesized by the hydrothermal process at an optimized growth temperature of 200 • C and a growth/reaction time of 3 h. As-prepared ZnO nanoflowers were characterized by x-ray diffraction, scanning electron microscopy, UV-visible and Raman spectroscopy. X-ray diffraction and Raman studies reveal that the as-synthesized flower-like ZnO nanostructures are highly crystalline with a hexagonal wurtzite phase preferentially oriented along the (1 0 1 1) plane. The average length (234-347 nm) and diameter (77-106 nm) of the nanorods constituting the flower-like structure are estimated using scanning electron microscopy studies. The band gap of ZnO nanoflowers is estimated as 3.23 eV, the lowering of band gap is attributed to the flower-like surface morphology and microstructure of ZnO. Room temperature photoluminescence spectrum shows a strong UV emission peak at 392 nm, with a suppressed visible emission related to the defect states, indicating the defect free formation of ZnO nanoflowers that can be potentially used for UV light-emitting devices. The suppressed Raman bands at 541 and 583 cm −1 related to defect states in ZnO confirms that the ZnO nanoflowers here obtained have a reduced presence of defects.

a By using the spray pyrolysis methodology in its classical configuration we have grown self-assembled Mg x Zn 12x O quantum dots (size y4-6 nm) in the overall range of compositions 0 ¡ x ¡ 1 on c-sapphire, Si (100) and quartz substrates. Composition of the quantum dots was determined by means of transmission electron microscopy-energy dispersive X-ray analysis (TEM-EDAX) and X-ray photoelectron spectroscopy.

The magnetic properties of Mn‐doped ZnO (ZnO:Mn) nanorods grown by hydrothermal process at a temperature of 200 °C and a growth time of 3 h have been studied. The samples were characterized by using powder X‐ray diffraction with Rietveld refinement, scanning electron microscopy, energy‐dispersive X‐ray analysis and SQUID magnetometry. Mn (3 wt%) and (5 wt%)‐doped ZnO samples exhibit paramagnetic and ferromagnetic behavior, respectively, at room temperature. The spin‐glass behavior is observed from the samples with respect to the decrease of temperature. At 10 K, both samples exhibit a hysteresis loop with relatively low coercivity. The room‐temperature ferromagnetism in 5 wt% Mn‐doped ZnO nanorods is attributed to the increase in the specific area of grain boundaries, interaction between dopant Mn2+ ions substituted at Zn2+ site and the interaction between Mn2+ ions and Zn2+ ions from the ZnO host lattice. M–H curve of hydrothermally grown ZnO:Mn (3 wt%) and ZnO:Mn (5 wt%) nanorods at 10 K.

In this work, the growth of isolated Cd 1−x Mg x O nanoparticles on r-sapphire substrates is extended to the entire range of Mg content (0 ≤ x ≤ 1) using the spray pyrolysis method. The sizes of the Cd 1−x Mg x O nanoparticles were in the ranges 4-6 nm and 15-30 nm (with a nanoparticle density of 10 10 cm −2 ).The composition of the nanoparticles was determined using transmission electron microscopy energy dispersive X-ray analysis (TEM-EDAX), while the compound formation was confirmed using X-ray photoelectron spectroscopy. A systematic decrease in the a lattice parameter of Cd 1−x Mg x O on increasing the Mg content substantiated the successful incorporation of Mg 2+ ions into the cubic CdO lattice. Single-phase cubic Cd 1−x Mg x O nanoparticles were obtained in the range of nominal Mg content 0% to 30% (0 ≤ x ≤ 0.26), whereas a Mg content of about 40% (nominal) forced a phase separation where Cd 1−x Mg x O and Mg 1−x Cd x O co-exist (the Mg nominal content was 40% to 90%), providing experimental evidence of the phase separation that exists in the MgO-CdO system. This phase separation was detected using selected area electron diffraction and X-ray diffraction measurements. Cross-sectional transmission electron microscopy analysis shows the growth of a single layer of isolated and crystalline Cd 1−x Mg x O nanoparticles over the r-sapphire substrate.

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