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The use of microspectrofluorimetry for the characterization of lake pigments
Claro, Ana; Melo, Maria J.; Schäfer, Stephan; Melo, J. Sérgio Seixas de; Pina, Fernando; Berg, Klaas Jan van den; Burnstock, AvivaIn this paper, the potential of confocal microfluorescence spectroscopy is explored for the characterization of selected red lake pigments and paints based on alizarin, purpurin and eosin (weak, medium and strong emitters). The anthraquinone pigments have been used since ancient times by artists, and eosin lakes were used by impressionist painters. Reconstructions of artists paints based on 19th century recipes...
A Study in Mauve: Unveiling Perkin's Dye in Historic Samples
Sousa, Micaela M.; Melo, Maria J.; Parola, A. Jorge; Morris, Peter J. T.; Rzepa, Henry S.; Melo, J. Sérgio Seixas deThe analysis of different historic mauve samples - mauve salts and dyed textiles - was undertaken to establish the exact nature of the iconic dye produced by W. H. Perkin in the nineteenth century. Fourteen samples from important museum collections were analyzed, and it was determined that, in contrast to the general wisdom that mauveine consists of C26 and C27 structures, Perkin's mauveine is a complex mixture...
A Study in Mauve: Unveiling Perkin's Dye in Historic Samples
Sousa, Micaela M.; Melo, Maria J.; Parola, A. Jorge; Morris, Peter J. T.; Rzepa, Henry S.; Melo, J. Sérgio Seixas deThe analysis of different historic mauve samples - mauve salts and dyed textiles - was undertaken to establish the exact nature of the iconic dye produced by W. H. Perkin in the nineteenth century. Fourteen samples from important museum collections were analyzed, and it was determined that, in contrast to the general wisdom that mauveine consists of C26 and C27 structures, Perkin's mauveine is a complex mixture...
Identification of 7,4prime-Dihydroxy-5-methoxyflavylium in ldquoDragon's Bloodr...
Melo, Maria J.; Sousa, Micaela; Parola, A. Jorge; Melo, J. Sérgio Seixas de; Catarino, Fernando; Marçalo, Joaquim; Pina, FernandoThe compound 7,4prime-dihydroxy-5-methoxyflavylium (dracoflavylium) was identified as the major red colorant in samples of the resin ldquodragon's bloodrdquo, extracted from the tree Dracaena draco. The complex network of reversible chemical reactions that dracoflavylium undergoes in aqueous solution is fully described; for the first time, all the equilibrium constants that enable a complete characterisation of...
Identification of 7,4prime-Dihydroxy-5-methoxyflavylium in ldquoDragon's Bloodr...
Melo, Maria J.; Sousa, Micaela; Parola, A. Jorge; Melo, J. Sérgio Seixas de; Catarino, Fernando; Marçalo, Joaquim; Pina, FernandoThe compound 7,4prime-dihydroxy-5-methoxyflavylium (dracoflavylium) was identified as the major red colorant in samples of the resin ldquodragon's bloodrdquo, extracted from the tree Dracaena draco. The complex network of reversible chemical reactions that dracoflavylium undergoes in aqueous solution is fully described; for the first time, all the equilibrium constants that enable a complete characterisation of...
Spectral and Photophysical Studies of Substituted Indigo Derivatives in Their K...
Melo, J. Sérgio Seixas de; Rondão, Raquel; Burrows, Hugh D.; Melo, Maria J.; Navaratnam, Suppiah; Edge, Ruth; Voss, GundulaThe spectral and photophysical properties of indigo derivatives with di-, tetra-, and hexa-substitution in their neutral (keto) form are investigated in solution. The study comprises absorption and emission spectra, together with quantitative measurements of quantum yields of fluorescence (φF) and singlet oxygen formation (φΔ) and fluorescence lifetimes. The energy difference between the HOMO and LUMO orbitals ...
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