Alberto Strini

Photocatalytic bacterial inactivation by TiO2-coated surfaces

The aim of this study was the evaluation of the photoactivated antibacterial activity of titanium dioxide (TiO2)-coated surfaces. Bacterial inactivation was evaluated using TiO2-coated Petri dishes. The experimental conditions optimized with Petri dishes were used to test the antibacterial effect of TiO2-coated ceramic tiles. The best antibacterial effect with Petri dishes was observed at 180, 60, 30 and 20 min of exposure for Escherichia coli, Staphylococcus aureus, Pseudomonas putida and Listeria innocua, respectively. The ceramic tiles demonstrated a photoactivated bactericidal effect at the same exposure time. In general, no differences were observed between the antibacterial effect obtained with Petri dishes and tiles. However, the photochemical activity of Petri dishes was greater than the activity of the tiles.Results obtained indicates that the TiO2-coated surfaces showed a photoactivated bactericidal effect with all bacteria tested highlighting that the titania could be used in the ceramic and building industry for the production of coated surfaces to be placed in microbiologically sensitive environments, such as the hospital and food industry.

The effect of absorbing resins on substrate concentration and enantiomeric excess in yeast reduction

Abstract The correlation between the enantiomeric excess (e.e.) of the ( S )-(+)-ethyl-3-hydroxybutanoate 2 , obtained in the bakers yeast reduction of ethyl acetoacetate 1 , and the concentration of the substrates in the fermentation mixture has been studied by the use of two different techniques (absorbing resins and organic solvents) The presence of resins undoubtedly influences the enantiomeric excess of the product.

Preparative transformation of natural phospholipids catalysed by phospholipase D from Streptomyces

Phospholipase D from Stretomyces sp. catalyses the transphosphatidylation reaction of various primary and secondary alcohols with natural phosphatidylcholine in an emulsion system in a preparatively useful manner.

TiO2-Based Photocatalytic Geopolymers for Nitric Oxide Degradation

This study presents an experimental overview for the development of photocatalytic materials based on geopolymer binders as catalyst support matrices. Particularly, geopolymer matrices obtained from different solid precursors (fly ash and metakaolin), composite systems (siloxane-hybrid, foamed hybrid), and curing temperatures (room temperature and 60 °C) were investigated for the same photocatalyst content (i.e., 3% TiO2 by weight of paste). The geopolymer matrices were previously designed for different applications, ranging from insulating (foam) to structural materials. The photocatalytic activity was evaluated as NO degradation in air, and the results were compared with an ordinary Portland cement reference. The studied matrices demonstrated highly variable photocatalytic performance depending on both matrix constituents and the curing temperature, with promising activity revealed by the geopolymers based on fly ash and metakaolin. Furthermore, microstructural features and titania dispersion in the matrices were assessed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) analyses. Particularly, EDS analyses of sample sections indicated segregation effects of titania in the surface layer, with consequent enhancement or depletion of the catalyst concentration in the active sample region, suggesting non-negligible transport phenomena during the curing process. The described results demonstrated that geopolymer binders can be interesting catalyst support matrices for the development of photocatalytic materials and indicated a large potential for the exploitation of their peculiar features.

Enzyme-mediated synthesis of two diastereoisomeric forms of phosphatidylglycerol and of diphosphatidylglycerol (cardiolipin)

3-sn-Phosphatidyl-1′-sn-glycerol and its stereoisomer 3-sn-phosphatidyl-3′-sn-glycerol are prepared through phospholipase D-catalysed transphosphatidylation of natural phosphatidylcholine with the two enantiomeric (R)- and (S)-isopropylideneglycerols and subsequent hydrolysis of the phospholipids obtained. If glycerol is the alcohol donor in the same reaction, a mixture of stereoisomers is obtained. When the enzyme from savoy cabbage is used, the two compounds are obtained as the only products. With PLD from Streptomyces as catalyst, the initially formed phosphatidylglycerols are quantitatively transformed into diphosphatidylglycerol (cardiolipin).

Photocatalytic Activity of Nanotubular TiO2 Films Obtained by Anodic Oxidation: A Comparison in Gas and Liquid Phase

The availability of immobilized nanostructured photocatalysts is of great importance in the purification of both polluted air and liquids (e.g., industrial wastewaters). Metal-supported titanium dioxide films with nanotubular morphology and good photocatalytic efficiency in both environments can be produced by anodic oxidation, which avoids release of nanoscale materials in the environment. Here we evaluate the effect of different anodizing procedures on the photocatalytic activity of TiO2 nanostructures in gas and liquid phases, in order to identify the most efficient and robust technique for the production of TiO2 layers with different morphologies and high photocatalytic activity in both phases. Rhodamine B and toluene were used as model pollutants in the two media, respectively. It was found that the role of the anodizing electrolyte is particularly crucial, as it provides substantial differences in the oxide specific surface area: nanotubular structures show remarkably different activities, especially in gas phase degradation reactions, and within nanotubular structures, those produced by organic electrolytes lead to better photocatalytic activity in both conditions tested.