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Molecules 2012, 17(2), 1602-1616; doi:10.3390/molecules17021602

Phloxine B as a Probe for Entrapment in Microcrystalline Cellulose

Centro de Química-Física Molecular, and IN-Institute of Nanoscience and Nanotechnology Complexo Interdisciplinar, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
Escola Superior de Tecnologia e Gestão, Instituto Politécnico de Portalegre, Lugar da Abadessa, Apt 148, 7301-901, Portalegre, Portugal
INQUIMAE / DQIAyQF, Facultad de Ciencias Exactas y Naturales, UBA, Ciudad Universitaria, Pab. II, C1428EHA, Buenos Aires, Argentina
Authors to whom correspondence should be addressed.
Received: 11 November 2011 / Revised: 26 January 2012 / Accepted: 2 February 2012 / Published: 7 February 2012
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The photophysical behaviour of phloxine B adsorbed onto microcrystalline cellulose was evaluated by reflectance spectroscopy and laser induced time-resolved luminescence in the picosecond-nanosecond and microsecond-millisecond ranges. Analysis of the absorption spectral changes with concentration points to a small tendency of the dye to aggregate in the range of concentrations under study. Prompt fluorescence, phosphorescence and delayed fluorescence spectral decays were measured at room temperature and 77 K, without the need of sample degassing because cellulose protects triplet states from oxygen quenching. In all cases, spectral changes with time and lifetime distribution analysis were consistent with the dye coexisting in two different environments: dyes tightly entrapped between polymer chains in crystalline regions of cellulose showed longer fluorescence and phosphorescence lifetimes and more energetic triplet states, while dyes adsorbed in more amorphous regions of the support showed shorter lifetimes and less energetic triplet states. This behaviour is discussed in terms of the different dye-support interactions in both kinds of adsorption sites.
Keywords: phloxine B; heterogeneous systems prompt fluorescence; phosphorescence; delayed fluorescence; microenvironmental effects phloxine B; heterogeneous systems prompt fluorescence; phosphorescence; delayed fluorescence; microenvironmental effects

This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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MDPI and ACS Style

Duarte, P.; Ferreira, D.P.; Ferreira Machado, I.; Vieira Ferreira, L.F.; Rodríguez, H.B.; San Román, E. Phloxine B as a Probe for Entrapment in Microcrystalline Cellulose. Molecules 2012, 17, 1602-1616.

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