Photoelectrocatalytic Performances of Nanostructured/Decorated TiO 2

The behaviour of TiO2 based electrodes was investigated during the photoelectrocatalytic water splitting process. TiO2 nanotubes and compact oxide structures were obtained by electrochemical oxidation of Ti foils. A subsequent hydrothermal process carried out at both the nanotubular and compact oxide structures allowed decorating the structure by TiO2 nanoparticles. The synthesized TiO2 samples worked as photoanodes both in a bulk three electrode cell and in a thin gap cell. The results from measurements of the photocurrent and from electrochemical impedance spectroscopy were used to highlight a combined effect of the wavelength of the incident light and the kind of cell configuration, on the global performance of the systems. The results indicate that the decoration process does not result only in a simple increase of the specific surface, but it also determines a different concentration of the bulk and superficial sites in the electrode. The different response of the sites at different wavelengths, along with the accessibility of the electrolyte to the porous structure are evocated to justify the experimental behaviour observed

ZrO2-doped ZnO-PDMS nanocomposites as protective coatings for the stone materials

ZnO is a semiconductor that has found wide application in the optics and electronics areas. Moreover, it is widely used in different technological areas due to its beneficial qualities (high chemical stability, non-toxicity, high photo-reactivity, and cheapness). Based on its antibacterial activity, recently it has found also application to prevent bio-deterioration of cultural heritage buildings. As many authors suggested, doped ZnO nano-structures exhibit better antibacterial properties than undoped analogues. In the present work, ZnO nanoparticles doped with ZrO2 have been prepared by a sol-gel method in order to enhance the photocatalytic properties as well as the antibacterial activity of ZnO. Then, ZrO2-ZnO-PDMS nanocomposite (PDMS, polydimethylsiloxane used as the binder) was synthesized by in-situ reaction. The resulting nanocomposite has been investigated as a possible protective material for cultural heritage building substrates. The performances of newly prepared coating were evaluated in three different stones (Lecce stone, Carrara Marble and Brick) and compared with Plain PDMS as a reference coating. </p

Dependence of the Ce(III)/Ce(IV) ratio on intracellular localization in ceria nanoparticles internalized by human cells

CeO2 nanoparticles (CNPs) have been investigated as promising antioxidant agents with significant activity in the therapy of diseases involving free radicals or oxidative stress. However, the exact mechanism responsible for CNP activity has not been completely elucidated. In particular, in situ evidence of modification of the oxidative state of CNPs in human cells and their evolution during cell internalization and subsequent intracellular distribution has never been presented. In this study we investigated modification of the Ce(iii)/Ce(iv) ratio following internalization in human cells by X-ray absorption near edge spectroscopy (XANES). From this analysis on cell pellets, we observed that CNPs incubated for 24 h showed a significant increase in Ce(iii). By coupling on individual cells synchrotron micro-X-ray fluorescence (μXRF) with micro-XANES (μXANES) we demonstrated that the Ce(iii)/Ce(iv) ratio is also dependent on CNP intracellular localization. The regions with the highest CNP concentrations, suggested to be endolysosomes by transmission electron microscopy, were characterized by Ce atoms in the Ce(iv) oxidation state, while a higher Ce(iii) content was observed in regions surrounding these areas. These observations suggest that the interaction of CNPs with cells involves a complex mechanism in which different cellular areas play different roles

α-cyclodextrins chemically modified gold electrode for the determination of nitroaromatic compounds.

The preparation, characterization and analytical application of a chemically modified gold electrode (CME), based on thiolated α-cyclodextrin self assembled monolayer (SAM), have been described. The CME was effective for the determination of nitroaromatic explosive compounds; 2,4,6-trinitrotoluene (TNT) was determined with satisfactory results (LOQ = 30 μm/L). The analytical response in contaminated water and in presence of other nitroaromatic compounds, such as 2,4-dinitrotoluene (DNT) and Picric Acid (PA), has been evaluated

Transport properties in bulk nanocrystalline Sm-doped ceria with doping content between 2 and 30at.%

Fully dense Sm-doped ceria powders, with doping content between 2 and 30 at.% and grain size below 20 nm, were consolidated using a High-Pressure Field Assisted Sintering (HP-FAST) apparatus. Using a uniaxial pressure of 600 MPa relative densities above 95% were achieved at temperatures as low as 600 °C with sintering times of only 5 min. Thanks to these exceptionally mild sintering conditions, grain growth during densification was very limited. The samples were characterized using impedance spectroscopy and the results showed a single semicircle, due to an overwhelming contribution of the grain boundary resistance. Thanks to the brick layer model, the present results were compared to literature data on microcrystalline materials and revealed that, contrary to what previously reported by several authors, negligible modification of the specific grain boundary conductivity can be produced through the reduction of the grain size in Sm-doped ceria in the considered doping interval

Enantioselective catalytic allylation of carbonyl groups by umpolung of π-allyl palladium complexes

Diethylzinc mediates the asymmetric allylation of aldehydes through Umpolung of a π-allyl palladium complex. An investigation of the palladium source and the chiral monophosphane ligands have shown that the leaving group has a dramatic effect on the enantioselectivity of the reaction. The procedure furnished products in satisfactory yields and up to 70% ee