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Solubilization of Poly1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)] fluoren...
Burrows, Hugh D.; Tapia, María J.; Fonseca, Sofia M.; Pradhan, Swapna; Scherf, Ullrich; Silva, Cláudia L.; Pais, Alberto A. C. C.; Valente, Artur J. M.In the presence of the nonionic alkyloxyethylene surfactant n-dodecylpentaoxyethylene glycol ether (C12E5), the anionic conjugated polyelectrolyte (CPE) poly1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl (PBS-PFP) dissolves in water, leading to a blue shift in fluorescence and dramatic increases in fluorescence quantum yields above the surfactant critical micelle concentration (cmc). No sign...
Synthesis, spectroscopy, photophysics and thermal behaviour of stilbene-based t...
Gigante, Bárbara; Esteves, M. Alexandra; Pires, N.; Davies, Matthew L.; Douglas, Peter; Fonseca, Sofia M.; Burrows, Hugh D.; Pina, JoãoNovel stilbene-based triarylamines with dehydroabietic acid methyl ester moieties have been synthesised by palladium catalysed C–N coupling reactions. The presence of the bulky dehydroabietic acid group increases solubility, hinders crystallisation and permits their sublimation while preserving their electronic and optical characteristics. This makes them good candidates for various molecular electronic applica...
Interactions between hairy rod anionic conjugated polyelectrolytes and nonionic...
Fonseca, Sofia M.; Eusébio, M. Ermelinda; Castro, Ricardo; Burrows, Hugh D.; Tapia, Maria José; Olsson, UlfThe effect of three anionic, hairy-rod fluorene based conjugated polyelectrolytes on the cloud points of the alkyloxyethylene surfactants C10E3, C12E4, C12E5, and C12E6 has been studied in aqueous solution. Although the association behaviour of these rigid polymers with surfactants is different from that of more flexible polyelectrolytes, both types of polymers are seen to increase the cloud points, probably as...
Opto-Electronic Properties of Fluorene-Based Derivatives as Precursors for Ligh...
Fratiloiu, Silvia; Fonseca, Sofia M.; Grozema, Ferdinand C.; Burrows, Hugh D.; Costa, Maria L.; Charas, Ana; Morgado, Jorge; Siebbeles, Laurens D. A.This paper reports optical absorption spectra of oxidized fluorene copolymers obtained by chemical oxidation with Ce(IV) and by pulse radiolysis experiments in chlorinated solvents. Comparison of the results observed by the two techniques is used to provide spectral data on the copolymer radical ions and information on stability of the oxidized species. In addition, a detailed quantum chemical characterization ...
Interplay of Electrostatic and Hydrophobic Effects with Binding of Cationic Gem...
Burrows, Hugh D.; Tapia, María J.; Silva, Cláudia L.; Pais, Alberto A. C. C.; Fonseca, Sofia M.; Pina, João; Melo, J. Seixas de; Wang, YujieUnderstanding factors responsible for the fluorescence behavior of conjugated polyelectrolytes and modulation of their behavior are important for their application as functional materials. The interaction between the anionic poly1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diylcopolymer (PBS−PFP) and cationic gemini surfactants α,ω-(CmH2m+1N+(CH3)2)2(CH2)s(Br-)2 (m-s-m; m = 12, s = 2, 3, 5, 6, ...
On the photophysical behaviour of 4-halo-5-phenylisoxazoles
Fonseca, Sofia M.; Burrows, Hugh D.; Nunes, Cláudio M.; Melo, Teresa M. V. D. Pinho e; Gonsalves, António M. d'A. RochaDetailed spectral and photophysical properties of 4-halo-5-phenylisoxazoles in cyclohexane solutions are presented, including measurements of energies of lowest excited singlet and triplet states, fluorescence quantum yields, lifetimes, phosphorescence and triplet-singlet difference absorption spectra. Upon addition of ethanol, loss of vibrational structure is observed in fluorescence spectra and attributed to ...
Photooxidation of cellulose acetate and cellobiose by the uranyl ion
Fonseca, Sofia M.; Burrows, Hugh D.; Miguel, Maria G.; Sarakha, Mohamed; Bolte, MichèleThe photooxidation of cellulose acetate by uranyl nitrate in acetone solutions has been investigated. Studies of the effect of the polymer on the uranyl luminescence showed an initial increase in intensity, followed by quenching. This is interpreted in terms of competition between complexation of uranyl ions by the polymer and dynamic quenching. In the quenching region, Stern–Volmer kinetics are followed. Upon ...
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