Uniform, spherical-shaped TiO2:Eu nanoparticles with different doping concentrations have been synthesized through controlled hydrolysis of titanium tetrabutoxide under appropriate pH and temperature in the presence of EuCl3·6H2O. Through air annealing at 500°C for 2 h, the amorphous, as-grown nanoparticles could be converted to a pure anatase phase. The morphology, structural, and optical properties of the annealed nanostructures were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy [EDS], and UV-Visible diffuse reflectance spectroscopy techniques. Optoelectronic behaviors of the nanostructures were studied using micro-Raman and photoluminescence [PL] spectroscopies at room temperature. EDS results confirmed a systematic increase of Eu content in the as-prepared samples with the increase of nominal europium content in the reaction solution. With the increasing dopant concentration, crystallinity and crystallite size of the titania particles decreased gradually. Incorporation of europium in the titania particles induced a structural deformation and a blueshift of their absorption edge. While the room-temperature PL emission of the as-grown samples is dominated by the 5D0 - 7Fj transition of Eu+3 ions, the emission intensity reduced drastically after thermal annealing due to outwards segregation of dopant ions.

Here, we present the low-temperature (∼600 °C) solution combustion method for the fabrication of CoFe₂O₄, NiFe₂O₄, and Co_0.5Ni_0.5Fe₂O₄ nanoparticles (NPs) of 12–64 nm range in pure cubic spinel structure, by adjusting the oxidant (nitrate ions)/reductant (glycine) ratio in the reaction mixture. Although nitrate ions/glycine (N/G) ratios of 3 and 6 were used for the synthesis, phase-pure NPs could be obtained only for the N/G ratio of 6. For the N/G ratio 3, certain amount of Ni²⁺ cations was reduced to metallic nickel. The NH₃ gas generated during the thermal decomposition of the amino acid (glycine, H₂NCH₂COOH) induced the reduction reaction. X-ray diffraction (XRD), Raman spectroscopy, vibrating sample magnetometry, and X-ray photoelectron spectroscopy techniques were utilized to characterize the synthesized materials. XRD analyses of the samples indicate that the Co_0.5Ni_0.5Fe₂O₄ NPs have lattice parameter larger than that of NiFe₂O₄, but smaller than that of CoFe₂O₄ NPs. Although the saturation magnetization (M_s) of Co_0.5Ni_0.5Fe₂O₄ NPs lies in between the saturation magnetization values of CoFe₂O₄ and NiFe₂O₄ NPs, high coercivity (H_c, 875 Oe) of the NPs indicate their hard ferromagnetic behavior. Catalytic behavior of the fabricated spinel NPs revealed that the samples containing metallic Ni are active catalysts for the degradation of 4-nitrophenol in aqueous medium.

Effects of Ag doping on the crystallinity and optical properties of zinc oxide (ZnO) nanoparticles have been studied by x-ray diffraction, diffuse reflectance spectroscopy, micro-Raman, and photoluminescence spectroscopy. It has been observed that while Ag-doping at low concentration improves the optoelectronic properties of ZnO nanostructures, Ag-doping at high concentrations drastically modify the emission behavior and lattice vibrational characteristics of the nanostructures. High Ag content in ZnO nanostructures causes lattice deformation, induces silent vibrational modes in Raman spectra, and reduces excitonic UV emission due to concentration quenching.

Contributions of morphology, surface area, and defect content, on the photocatalytic activity of ZnO nanostructures have been discussed.