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The evolution of the magnetic state, crystal structure and microstructure parameters of nanocrystalline zinc-ferrite, tuned by thermal annealing of ∼4 nm nanoparticles, was systematically studied by complementary characterization methods. Structural analysis of neutron and synchrotron x-ray radiation data revealed a mixed cation distribution in the nanoparticle samples, with the degree of inversion systematically decreasing from 0.25 in an as-prepared nanocrystalline sample to a non-inverted spinel structure with a normal cation distribution in the bulk counterpart. The results of DC magnetization and Mössbauer spectroscopy experiments indicated a superparamagnetic relaxation in ∼4 nm nanoparticles, albeit with different freezing temperatures T(f) of 27.5 K and 46 K, respectively. The quadrupole splitting parameter decreases with the annealing temperature due to cation redistribution between the tetrahedral and octahedral sites of the spinel structure and the associated defects. DC magnetization measurements indicated the existence of significant interparticle interactions among nanoparticles ('superspins'). Additional confirmation for the presence of interparticle interactions was found from the fit of the T(f)(H) dependence to the AT line, from which a value of the anisotropy constant of K(eff) = 5.6 × 10(5) erg cm(-3) was deduced. Further evidence for strong interparticle interactions was found from AC susceptibility measurements, where the frequency dependence of the freezing temperature T(f)(f) was satisfactory described by both Vogel-Fulcher and dynamic scaling theory, both applicable for interacting systems. The parameters obtained from these fits suggest collective freezing of magnetic moments at T(f).

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Highlights TiO 2 catalysts co-doped with La and V were synthesized using microwave-assisted hydrothermal process. Changes in the morphology and photocatalytic activity were observed as amount of both dopants were altered. The catalyst with 2% w/w La and 0.02% w/w V appeared to be the most photoactive. V-La co-doped TiO 2 was easily separable by settling down and showed good stability and reusability.

Elevated concentrations of arsenic in groundwater, which is used as a source for drinking water, is a worldwide problem. Use of TiO 2 and iron doped TiO 2 synthesized by a microwave-assisted hydrothermal method for As(III) and As(V) removal were examined. Synthesized sorbents were characterized with XRD and nitrogen physisorption. Synthesized sorbents have predominantly anatase structure, and no peaks for iron could be observed. Doping of iron increases the surface area of synthesized sorbents. Sorption experiments show that increase of iron in sorbents increases the sorption capacity for As(III) and As(V). Increase of pH from 3 to 11 has no influence on As(III) sorption but decreases the sorption of As(V). Batch isotherm studies were performed to determine the binding capacities of As(III) and As(V). As(III) followed the Freundlich isotherm model, while for As(V) a better fit was with the Langmuir isotherm. The results of competition of SO 4 2− and PO 4 3− anions on adsorption of As(III) indicated that both anions reduced substantially the efficiency of adsorption on both adsorbents while for As(V) only the presence of PO 4 3− anion interfered with adsorption. Testing 10Fe/TiO 2 sorbent with arsenic contaminated natural water showed that this material could be used for removal of arsenic to the level recommended by WHO without pretreatment.

It is well established that gas/humidity-sensing properties of spinels are markedly influenced by their stoichiometry and microstructure. In this work nucleation and spinel phase development in the Zn-Cr-O system were investigated from the viewpoint of structural and morphological phenomena occurred during nanophased particle synthesis through aerosol reaction. The aerosol was generated from nitrates precursor solution using ultrasonic atomizer operated at 1.7 MHz. The influence of different decomposition schedules on the particle chemical content and morphology was determined by adjusting the processing parameters (aerosol droplet density 3.9x10 6 droplets/cm 3 , droplet velocity 0.035m/s, max. temperature 900 o C and residence times 3, 6 and 9s). A composite particle structure comprised of primary crystallites sized from 22 to 44nm is revealed by SEM and TEM analysis. XRD structural analysis (crystallite size, microstrains, unit cell and ionic occupancies) is performed in accordance with procedure based on Koalariet-Xfit program. A certain degree of non-stochiometry is characteristic for all powders. Homogenous distribution of the constituting elements and Zn/Cr ratio of about 0.68 are proved by EDAX

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Zinc-ferrite, nickel-ferrite and mixed nickel-zinc ferrites were successfully synthesized via the thermal decomposition method from acetylacetonate complexes. To control the particle size and enhance dispersibility in an aqueous medium, starch, a natural and biocompatible compound, was used for the first time for coating such magnetic powders. X-ray powder diffraction (XRPD) was performed to study the structural properties of all samples. The presence of a single-phase spinel structure as well as the cation distribution in both sites of all investigated magnetic powders was confirmed. The values of unit cell parameters obtained from the results of the Rietveld analysis decreased, while the average crystallite size increased with increasing Ni 2+ content. The average microstrain parameters unambiguously showed a change in the spinel structure with cation distribution. Scanning electron 2 microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) analyses were also utilized to characterize the synthesized materials, corroborating the XRPD data. The obtained results indicated that functionalization by starch was successfully achieved.