H. Amyar, C. Byun, M. Besbes, A. Cattoni, et al.

Probing the formation of sol–gel mesoporous films and characterizing them under environmental/in-operando conditions represents an important challenge to optimize their performances. Obtaining a complete picture of the system usually requires a combination of multiple techniques. In this work, we introduce in situ infrared (IR) ellipsometry equipped with an environmental chamber as a tool to follow simultaneously the evolution of structural, optical and chemical properties during the formation of sol–gel derived mesoporous films. As a case study, we investigate the formation of mesoporous TiO2 by comparing a conventional thermal treatment and a low-temperature annealing by UV irradiation. In both cases, the structural optical and chemical evolution could be monitored during the IR ellipsometric experiment. Interestingly, UV-annealing allows the fabrication of mesoporous TiO2 films at low temperatures enabling the formation of plasmonic mesoporous composites. At last, we critically discuss the advantages and drawbacks of IR ellipsometry for in situ investigations compared to conventional UV–visible ellipsometry by providing additional insights for future developments.

K. Simeonidis; C. Martinez-Boubeta; I. Kellartzis; A. Makridis; E. Delli et al.

Minimizing food wastes and finding a second life use for industrial residuals have become some of the top priorities of modern society. This work considers the use of spent eggs and mussels shells, as well as marble dust, as raw sources to develop nanoparticles involving renewable resources in both their preparation and adoption in technological applications. Specifically, Ca/Mg-based nanoparticles were obtained by evaporating such wastes in a physical vapor deposition system using concentrated solar beam and explored as high capacity H2S adsorbents for the purification of biogas. The evaluation of their uptake performance in a fixed-bed configuration indicates that the formation of a thick layer of Ca(OH)2 on very small nanoparticles (<70 nm) inhibits H2S uptake, whereas the presence of Mg phases (dolomite) favors its potentiation. Importantly, the co-evaporation of iron provides an extra amplification of the absorption capacity due to the synergy of the Ca/Mg neutralizing character and the affinity of Fe for sulfur. In the best case, the nanoparticles obtained from mussels and 10 %wt. Fe reached an uptake capacity of 0.92 mg/g. This high yield is attributed to the formation of oxides, such as Ca2Fe2O5, that allow a sulfide to sulfate oxidation-adsorption mechanism.

D. B. Migas, V. A. Turchenko, A. V. Rutkauskas, et al.

We report the observation of a peculiar polarization behavior of BaFe12O19 in electric field where the linear polarization is detected at temperatures below 150 K whereas at higher temperatures a hysteresis-like polarization response is observed. At the same time, the performed neutron diffraction analysis shows no variations in crystal or magnetic structures with temperature. Based on the results of ab initio calculations we suggest the mechanism able to explain the experimentally observed behavior. We show that specific Fe atoms do not occupy the positions formally assigned to them by the conventional centrosymmetric P6(3)/mmc (#194) space group (z = 0.25; 0.75) as these positions correspond to local energy maxima. Instead, these Fe atoms are shifted along the z-axis to positions z = 0.259 (0.241) and z = 0.759 (0.741), which correspond to local energy minima. To an inversion center move between these minima Fe atoms need to overcome an energy barrier. This barrier is rather insignificant for smaller volumes but it becomes larger for expanded volumes due to coupling between the displacements of these Fe atoms. Additionally, our analysis suggests that the non-centrosymmetric and polar P6(3)mc (#186) space group could be appropriate for the description of the BaFe12O19 structure.