Photodynamics and surface characterization of TiO2 and Fe2O3 photocatalysts immobilized on modified polyethylene films

Polyethylene block-copolymer films containing negative anhydride groups were used to immobilize TiO2, Fe2O3, and Fe3+ photocatalysts. The kinetics of the mineralization of azo-dye Orange II and chlorophenols on copolymer−TiO2, copolymer−Fe2O3, and copolymer−Fe3+ have been tested under optimized experimental conditions. In the case of copolymer−TiO2, the degradation kinetics for the model organic compounds were about the same as those observed with TiO2 suspensions containing about a 27 times higher amount of TiO2 per unit volume. The surface of the derivatized copolymer semiconductor catalysts was studied by infrared attenuated total reflection spectroscopy. The spectroscopic data provided evidence for a TiO2 interaction with the negatively charged conjugated carboxylic groups of the copolymer, leading to an asymmetric-stretching band of −COO−Ti4+ at the position expected for metal carboxylates. In the case of Fe2O3 and Fe3+, the asymmetric-stretching carboxylate bands are ascribed to the carboxylate bands of −COO−Fe2O3 and −COOO−Fe3+. Evidence is presented by X-ray photoelectron spectroscopy for the existence of two oxidation states of Ti and Fe after the photocatalytic degradation of Orange II. This observation is consistent with light-induced interfacial charge transfer (redox processes) taking place at the metal−oxide copolymer surface. The nature of the latter processes is presented in detail during this study

Magnetron-Sputtered Ag Surfaces. New Evidence for the Nature of the Ag Ions Intervening in Bacterial Inactivation

DC-magnetron sputtering with an Ag target on textile surfaces produced Ag particles with sizes similar to 4.7 nm (+/- 15%). Sputtering for 15 s led to Ag layers of 15-20 nm. The threshold sputtering time precluding airborne bacterial growth was about 60 s. In this case, the coating was similar to 40-50 nm thick and the cotton Ag loading was 0.0026 wt %. The Ag particle size did not vary significantly with sputtering time between 15 and 600 s. Only coatings above this thickness lead to bacterial inactivation. Ag/Pt targets with sputtering times <60 s did not increase the bactericide performance of the Ag cotton samples with respect to sputtering from an Ag target alone, as expected from the position of Pt respect to Ag in the electrochemical series (Galvanic effect). The Ag cotton deposition led to very thin metallic semitransparent gray color coatings. X-ray of the Ag cotton suggested the presence of amorphous and crystalline Ag species. By X-ray photoelectron spectroscopy (XPS), it was found that the amount of oxidized silver species on the cotton was similar for sputtering times of 60 and 600 s, but the total amount of Ag deposited was almost two times higher after 600 s sputtering. This suggests chat the positive silver-ions were located mainly at the silver interface. The type of silver ions produced using the Ag/Pt sputtering was determined to be very similar at 15, 60, and 600 s with the silver ions produced with the Ag target. This explains the lack of an increased inhibitory effect of Pt during the inactivation of airborne bacteria when present in the Pt/Ag target with respect to the Ag target, because in both cases similar silver ionic species were found

Sorption of uranium (VI) species on zircon: structural investigation of the solid/solution interface

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