Morphological effects on the photocatalytic properties of SnO<inf>2</inf> nanostructures

The photocatalytic properties of SnO2 nanocrystals are tuned by varying their morphology and microstructure. SnO2 nanoparticles and nanowedges have been synthesised using hydrothermal methods, while microwave irradiation techniques have given nanospheres. Detailed structural and chemical characterization of these different morphologies has been accomplished. The influence of SnO2 morphology on photocatalytic activity has been examined by monitoring the degradation of aqueous methylene blue dye. Results demonstrate that changing the morphology of the SnO2 modulates both surface area and levels of surface defects and that these alterations are reflected in the photocatalytic properties of the materials. The degradation of methylene blue dye (98%) in the presence of SnO2 nanoparticles under simulated solar irradiation is superior to previously reported photocatalyst performance and is comparable to that of standard TiO2 (Degussa P-25). The SnO2 nanoparticles perform better than both the nanowedges and nanospheres and this is attributed to the number of surface defects available to the high surface area material. They also reveal outstanding recyclability and stability

Magnesium Matrix Composite with Open-Celled Carbon Foams Obtained by Powder Metallurgy

The preliminary results of the application of open-celled glassy-carbon foam (Cof) in magnesium matrix composites processed by the powder metallurgy method were presented. For the component consolidation, compaction with vertically-torsional vibration and hot-pressing were applied. For the material characterization, the microstructure examination LM and SEM with EDS was employed and also, the porosity and microhardness were measured. An influence of the carbon foam cells’ size on the composite porosity and microhardness was revealed. Additionally, a generation of a few micrometer thin and differently shaped MgO inclusions was observed. Differences in the oxide phase amount, size and shape in the magnesium matrix measured by the quantitative metallography method in the cross-sectioned composite elements were stated. With an increase of the distance from the composite roller top, an increase of the MgO content and microhardness was noticed

Reducing indium dependence by heterostructure design in SnO<inf>2</inf>–In<inf>2</inf>S<inf>3</inf> nanocomposites

Toxic organics like dyes represent a major and growing source of environmental contamination. A promising method to remedy this uses semiconductors to catalytically photodegrade the stable bonds in these molecules. Heterostructured photocatalysts composed of two different semiconductors can overcome problems of fast electron-hole recombination and inefficient light harvesting whilst reducing dependency on either component individually. In this work, SnO2 nanowedges have been surface-modified with In2S3 nanoparticles to produce mSnO2-nIn2S3 (m:n = 1:2, 1:1, 2:1) heterostructures. The injection, by In2S3, of photoelectrons into the conduction band of SnO2, is argued to enhance charge stabilization and exciton lifetime. The photocatalytic degradation of methyl orange (MO) consequently reveals these nanocomposites to outperform their individual SnO2 and In2S3 components and industry standard TiO2. Sensitization of the SnO2 is explained by a strong type-II effect. The effects of varying SnO2:In2S3 are studied, leading us to propose a charge separation mechanism that explains why the nanocomposite containing the least photosensitizer (2SnO2-In2S3) offers the best photocatalysis per unit mass In.Royal Societ

Polyphenolic profiles in lettuce (Lactuca sativa L.) after CaCl2 treatment and cold storage

Lettuce (Lactuca sativa L.) is a popular vegetable with the health-enhancing properties determined by high levels of antioxidant polyphenols as chlorogenic acids and other derivatives of caffeic acid or flavonoids. In this study, changes in the phenolic compound profiles in the lettuce leaves induced by application of CaCl2 before harvest and cold storage were studied. For the first time quantitative analysis of individual phenolic compounds on the basis of standards isolated from lettuce leaves was performed. Compounds were identified using HPLC, LC-MS, 1H and 13CNMR techniques. The dominant compounds were 2,3-dicaffeoyltartaric (2,3-diCTA), 5-O-caffeoylquinic (5-OCQA) and caffeoyltartaric (CTA) acids, with content of 5.7, 2.5 and 0.981&nbsp;mg/g DM, respectively. The levels of individual phenolic compounds, total phenolics and antioxidant activity (DPPH assay) in plants treated by CaCl2 were determined throughout the storage period (7 and 14&nbsp;days) at 4&nbsp;°C. To ascertain the relationship between the content of individual compounds, total phenols, antioxidant activities and storage time, Pearson’s correlation analysis was used. The best correlation between the storage length and compound concentration was observed for 2,3-diCTA (R2 = 0.866) and caffeoylmalic acid (CMA) (R2 = 0.750). Application of CaCl2 (0.05M) on lettuce resulted in an increase in the levels of CTA, 2.3-diCTA and 5-OCQA about 120, 65 and 57%, respectively, compared to the control stored for 7 days in the same conditions and had a favourable effect on the antioxidant activity (R2 = 0.985). The present paper shows that CaCl2 may be used as an agent that influences the stability of health-promoting compounds of cold-stored lettuce