No abstract

In recent years, the presence of numerous xenobiotic substances, such as antibiotics, has been detected in water environments. They can be considered as environmental contaminants, even if their effect on human health has yet to be totally understood. Several approaches have been studied for the removal of these kinds of pollutants. Among these compounds, tetracycline (TC), a broad-spectrum antibiotic, is one of the most commonly found in water due to its widespread use. In the context of reducing the presence of TC in aqueous solution, in this contribution, a composite catalyst based on zinc oxide (ZnO) and iron oxide (γ-Fe2O3) was developed and its photocatalytic properties were investigated. The catalytic materials were synthesized by a microwave-assisted aqueous solution method and characterized by Field Emission Scanning Electron Microscope (FESEM), X-Ray Fluorescence (XRF) and Brunauer−Emmett−Teller (BET) analysis. The TC concentration was evaluated by spectrophotometer measurements at specific time intervals. The performed photocatalytic experiments clearly demonstrated that the ZnO/γ-Fe2O3 composite catalyst presents significant photocatalytic activity, indeed a TC degradation efficiency of 88.52% was registered after 150 min. The presence of iron oxide in the structure of the catalyst enhances both the surface area and the pore volume, facilitating the adsorption of the analyte on the surface of nanostructures, a fundamental phase to optimize a photodegradation process. Moreover, ZnO was found to play the key role in the photocatalytic process assisted by γ-Fe2O3 which enhanced the TC degradation efficiency by 20%.

A mineral silicate paint has been developed for architectural heritage. To enhance durability, any type of organic additive has been avoided. Potassium silicate was the binder agent intended to give strong adherence and durability to stone and concretes. Incorporation of mainly anatase titanium dioxide was intended to act both as a white, bright pigment and as a photocatalyst. Reflectivity analyses on the paint in the visible-to-near infrared wavelength region show high solar heat reflection. The self-cleaning activity of the mineral paint was evaluated by the degradation of organic dyes under solar light irradiation. Anatase titania was effective in decomposing organic and airborne pollutants with the solar radiation. The optical properties and self-cleaning activity were compared with the organic binder-based paints and commercial paints. Developed paints possess high stability: since they contain only inorganic components that do not fade with exposure to solar radiation, photocatalytic self-cleaning capability further enhances such stability.

We report on the Au‐catalysed synthesis of GaAs nanowires on hetero‐structured GaAs/(111)Si substrates by metalorganic vapour phase epitaxy. It is demonstrated that the deposition of a 40‐50 nm thin GaAs epilayer onto Si guarantees a high percentage of straight and vertically‐aligned GaAs nanowires. GaAs epilayers were grown at 400 °C and subsequently annealed at 700 °C. Growth experiments performed on 4°‐miscut and exactly‐oriented (111)Si substrates show that a higher yield (close to 90%) of vertical nanowires is obtained using miscut substrates, an effect ascribed to the smoother surface morphology of GaAs epilayers on these substrates. Comparison between the cross‐sectional shape of nanowires grown on GaAs/(111)Si hetero‐substrates and those on (111)A‐GaAs and (111)B‐GaAs substrates demonstrates that both GaAs epilayers and over‐grown nanowires are (111)B‐oriented. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)