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Photodegradation of atrazine and ametryn with visible light using water soluble...
Rebelo, Susana; Melo, A.; Coimbra, R.; Azenha, M.; Pereira, Mariette; Burrows, Hugh; Sarakha, MohamedAbstract The photodegradation of the herbicides atrazine and ametryn with visible light in aerated neutral aqueous solutions and 5, 10, 15, 20-tetrakis (2,6-dichloro-3-sulfophenyl) porphyrin or 5, 10, 15, 20-tetrakis (4-sulfophenyl) porphyrin as sensitizers are reported for the first time. Our findings show that the degradation percentage reached 30% for atrazine and 63% for ametryn. The final photoproducts we...
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...
Photooxidation of 4-chlorophenol sensitised by iron meso-tetrakis(2,6-dichloro-...
Silva, Eliana; Pereira, Mariette M.; Burrows, Hugh D.; Azenha, M. E.; Sarakha, Mohamed; Bolte, MichèleThe photosensitised degradation of 4-chlorophenol (4-CP) by iron meso-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrin (FeTDCPPS) has been studied in aerated aqueous solution, and is shown to lead to formation of p-benzoquinone (BQ) and p-hydroquinone (HQ) as main photoproducts. In deaerated solution no p-benzoquinone was formed. The photolysis products were identified by high performance liquid chromatography (HP...
Deactivation processes of the lowest excited state of [UO2(H2O)5]2+ in aqueous ...
Formosinho, Sebastião J.; Burrows, Hugh D.; Miguel, Maria da Graça; Azenha, M. Emília D. G.; Saraiva, Isabel M.; Ribeiro, A. Catarina D. NA detailed analysis of the photophysical behaviour of uranyl ion in aqueous solutions at room temperature is given using literature data, together with results of new experimental and theoretical studies to see whether the decay mechanism of the lowest excited state involves physical deactivation by energy transfer or a chemical process through hydrogen atom abstraction. Comparison of the radiative lifetimes de...
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 ...
Electron-Transfer Oxidation of Chlorophenols by Uranyl Ion Excited State in Aqu...
Sarakha, Mohamed; Bolte, Michèle; Burrows, Hugh D.The oxidation of chlorophenols by photoexcited uranyl ion was studied in aqueous solution at concentrations where the ground-state interactions were negligible. Nanosecond flash photolysis showed that a clean electron-transfer process from the chlorophenols to the excited uranyl ion is involved. This is suggested to lead to the formation of a U(V)/chlorophenoxyl radical pair complex. The efficiency of this char...
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