Encontrados 6 documentos, a visualizar página 1 de 1
Síntese de fotoprotetores e sua imobilização em poli(metacrilato de metilo): um...
Murtinho,Dina Maria B.; Serra,Maria Elisa S.; Pineiro,MartaDibenzalacetone and other aldol condensation products are known sunscreens commonly used in cosmetics. This type of compounds can easily be prepared in an Organic Chemistry Lab by reaction of aldehydes with ketones in basic medium. These compounds can be incorporated in poly(methyl methacrylate) and used as UV light absorbers, for example in sunglasses. This project has the advantage of using inexpensive reagen...
Photoacid for Extremely Long-Lived and Reversible pH-Jumps
Nunes, Rui M. D.; Pineiro, Marta; Arnaut, Luís G.The ability to change the acidity of an aqueous solution within the time of a short laser pulse and use the resulting low pH to drive acid-catalyzed reactions in the irradiated volume opens news perspectives for the spatial and temporal control of a variety of processes. Persistent and reversible acidification of an aqueous solution is achieved with a new molecule, 1-(2-nitroethyl)-2-naphthol, that combines the...
Heavy-atom effects on metalloporphyrins and polyhalogenated porphyrins
Azenha, Emília G.; Serra, Arménio C.; Pineiro, Marta; Pereira, Mariette M.; Seixas de Melo, J.; Arnaut, Luis G.; Formosinho, Sebastião J.http://www.sciencedirect.com/science/article/B6TFM-45PTWJX-J/1/69780b458d5289db997df5735c97350c
New Halogenated Phenylbacteriochlorins and Their Efficiency in Singlet-Oxygen S...
Pineiro, Marta; Gonçalves, A. M. d'A. Rocha; Pereira, Mariette M.; Formosinho, Sebastião J.; Arnaut, Luís G.Halogenated phenylbacteriochlorins are synthesized with high yields in a two-step procedure. They have strong absorbances in the red and are very stable to air and light at room temperature. Flash photolysis measurements show that the triplet states of these bacteriochlorins have 30 μs lifetimes in deaerated toluene, that are quenched with diffusion-controlled rate constants by molecular oxygen. Time-resolved p...
Singlet oxygen quantum yields from halogenated chlorins: potential new photodyn...
Pineiro, Marta; Pereira, Mariette M.; Rocha Gonsalves, A. M. d'A.; Arnaut, Luis G.; Formosinho, Sebastião J.Flash photolysis and photoacoustic calorimetry were used to measure the energy-transfer rates and singlet oxygen quantum yields originated by the triplet states of halogenated tetrakisphenylporphyrins and related chlorins in aerated toluene. The chlorins ([lambda]max[approximate]660 nm, [var epsilon][approximate]3×104 M-1 cm-1) have long-lived triplet states (>12 [mu]s) in the absence of molecular oxygen, and i...
Photoacoustic Measurements of Porphyrin Triplet-State Quantum Yields and Single...
Pineiro, Marta; Carvalho, Ana L.; Pereira, Mariette M.; Gonsalves, A. M. d'A. Rocha; Arnaut, Luís G.; Formosinho, Sebastião J.Photoacoustic calorimetry and luminescence techniques were used to measure singlet oxygen quantum yields (PhiDelta) of selected 5,10,15,20-tetrakis(aryl)porphyrins and of the novel chlorin shown. The use of validated photoacoustic references removes some inconsistencies existing in the literature. Excitation of halogenated porphyrins produces high yields of long-lived triplet states that efficiently transfer th...
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