A Comparative Study on the Photophysics and Photochemistry of Xanthene Dyes in the Presence of Polyamidoamine (PAMAM) Dendrimers

Ernesto Maximiliano Arbeloa; Carlos Mario Previtali; Sonia Graciela Bertolotti

doi:10.1002/cphc.201701295

A Comparative Study on the Photophysics and Photochemistry of Xanthene Dyes in the Presence of Polyamidoamine (PAMAM) Dendrimers

Chemphyschem. 2018 Apr 17;19(8):934-942. doi: 10.1002/cphc.201701295. Epub 2018 Feb 19.

Authors

Ernesto Maximiliano Arbeloa¹, Carlos Mario Previtali¹, Sonia Graciela Bertolotti¹

Affiliation

¹ Grupo de Fotoquímica, Departmento de Química, Universidad Nacional de Río Cuarto, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 5800 Río Cuarto, Córdoba, Argentina.

PMID: 29316109
DOI: 10.1002/cphc.201701295

Abstract

The photophysical and photochemical properties of the xanthene dyes Eosin Y, Erythrosin B, and Rose Bengal are evaluated in the presence of amino-terminated polyamidoamine (PAMAM) dendrimers of relatively high generation (G3-G5) in alkaline aqueous solution. UV/Vis absorption and fluorescence spectra of the dyes show bathochromic shifts, which correlate with the size of the dendrimer. Binding constants (K_bind ) are calculated from absorption data. The resulting high K_bind values indicate strong interactions between both molecules. Triplet-triplet absorption spectra of the dyes are recorded by laser flash photolysis, and a decrease in the triplet lifetimes is observed in the presence of dendrimers. At the same time, an increase in the absorption of the semireduced form of the dyes is observed. Rate constants for triplet quenching (³ k_q ) and radical quantum yields (Φ_R ) are obtained. The results are explained by a very efficient electron-transfer process from PAMAM to xanthene dyes for all of the dye/dendrimer couples that are evaluated.

Keywords: dendrimers; dyes/pigments; photochemistry; photophysics; time-resolved spectroscopy.

Publication types

Research Support, Non-U.S. Gov't