Encontrados 12 documentos, a visualizar página 1 de 2
Photoacoustic Measurement of Electron Injection Efficiencies and Energies from ...
Serpa, Carlos; Schabauer, Johann; Piedade, Ana P.; Monteiro, Carlos J. P.; Pereira, Mariette M.; Douglas, Peter; Burrows, Hugh D.; Arnaut, Luís G.Time-resolved photoacoustic calorimetry is used to measure the energy released upon injection of an electron from an electronically excited dye adsorbed to nanocrystalline TiO2 into the conduction band of this material. More energy is released when the environment of the dye is made less polar, because the energy of the dye-oxidized state has a more pronounced solvent dependence than the edge of the conduction ...
The Triplet State of Indigo13
Melo, J. Sérgio Seixas de; Burrows, Hugh D.; Serpa, Carlos; Arnaut, Luis G.No Abstract ; http://dx.doi.org/10.1002/ange.200604679
(More) About biphenyl first excited triplet state energy
Gomes, Paulo J. S.; Serpa, Carlos; Arnaut, Luís G.Biphenyl photophysics was extensively studied in the past and much attention was given to the measurement of its first excited triplet state energy. Phosphorescence and the corresponding T1 <-- S0 absorption give triplet energies that differ by 10 kcal mol-1. We revisited biphenyl photophysics using photoacoustic calorimetry (PAC), a technique that directly measures the thermochemistry and kinetics of short...
Spectroscopic properties and photodynamic effects of new lipophilic porphyrin d...
Kramer-Marek, Gabriela; Serpa, Carlos; Szurko, Agnieszka; Widel, Maria; Sochanik, Aleksander; Snietura, Miroslaw; Kus, Piotr; Nunes, Rui M. D.Photodynamic therapy (PDT) and photodynamic diagnostics (PDD) of cancer are based on the use of non-toxic dyes (photosensitisers) in combination with harmless visible light. This paper reports physicochemical properties, cell uptake, localisation as well as photodynamic efficiency of two novel lipophilic porphyrin derivatives, suitable for use as PDT sensitisers. Both compounds are characterised by high quantum...
Temperature Dependence of Ultra-Exothermic Charge Recombinations13
Serpa, Carlos; Gomes, Paulo J. S.; Arnaut, Luis G.; Melo, J. Seixas de; Formosinho, Sebastião J.We measured the temperature dependence (from +32 to -50 °C) of charge-recombination rates between contact radical ion pairs in isopropyl ether. In the systems selected for this study, aromatic hydrocarbon cations are the electron acceptors and the fumaronitrile anion is the electron donor. Nearly quantitative electron transfers occur at all temperatures. The charge recombinations have excess exothermicities of ...
Electron Transfer in Supercritical Carbon Dioxide: Ultraexothermic Charge Recom...
Serpa, Carlos; Gomes, Paulo J. S.; Arnaut, Luis G.; Formosinho, Sebastião J.; Pina, João; Melo, J. Seixas deCharge-recombination rates in contact radical-ion pairs, formed between aromatic hydrocarbons and nitriles in supercritical CO2 and heptane, decrease with the exothermicity of the reactions until they reach -70 kcal mol-1, but from there on an increase is observed. The first decrease in rate is typical of the ldquoinverted regionrdquo of electron-transfer reactions. The change to an increase in the rate for ult...
A comparative study of water soluble 5,10,15,20-tetrakis(2,6-dichloro-3-sulfoph...
Monteiro, Carlos J. P.; Pereira, Mariette M.; Azenha, M. Emilia; Burrows, Hugh D.; Serpa, Carlos; Arnaut, Luís G.; Tapia, M. J.; Sarakha, Mohamed5,10,15,20-Tetrakis(2,6-dichloro-3-chlorosulfophenyl)porphyrin and its tin and zinc complexes were synthesized with high yields and fully characterized. The corresponding water-soluble 5,10,15,20-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrins were obtained by hydrolysis with water. An extensive photophysical study of the new water soluble porphyrinic compounds was carried out including absorption and fluorescen...
Ethical issues of evaluation practice within the brazilian political context
Serpa,Carlos Alberto; Firme,Thereza Penna; Letichevsky,Ana CarolinaThis paper analyzes a conflict frequently encountered by an evaluation professional working in the Brazilian context and its implications to the evaluation process. The challenge is to follow ethical principles that guide a true evaluation, and yet untangle the interaction of all the actors within a complex political context, where: (a) the recognition and regulation of the evaluation profession leaves much to ...
Fluorescence from the second excited singlet state of 3-hydroxyflavone in super...
Chattopadhyay, Nitin; Barroso, Mónica; Serpa, Carlos; Arnaut, Luís G.; Formosinho, Sebastião J.Fluorescence from the second excited singlet state (S2) of 3-hydroxyflavone (3HF) has been observed for the first time in supercritical carbon dioxide (sc-CO2) environment. Steady-state experiments reveal that the intramolecular proton transfer is less effective from the S2 state of 3HF compared to that from the S1 state. ; http://www.sciencedirect.com/science/article/B6TFN-4BVP7G9-5/1/fe6fe6a663b47e1a622241...
Photophysics of 3-hydroxyflavone in supercritical CO2: a probe to study the mic...
Chattopadhyay, Nitin; Barroso, Mónica; Serpa, Carlos; Isilda Silva, M.; Arnaut, Luís G.; Formosinho, Sebastião J.The excitation of 3-hydroxyflavone (3HF) to its second excited singlet state (S2) gives rise to dual fluorescence in supercritical carbon dioxide. The ultraviolet fluorescence originated from the S2 state of 3HF is well separated from the green emission emanating from the tautomeric form, produced via the excited state intramolecular proton transfer. The relative intensity of the S2 to the tautomer fluorescence...
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