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

ARBELOA, ERNESTO MAXIMILIANO; PREVITALI, CARLOS MARIO; BERTOLOTTI, SONIA GRACIELA

Chemphyschem

WILEY-V C H VERLAG GMBH

Año: 2018 vol. 19 p. 934 - 942

1439-4235

The photophysical and photochemical properties of the xanthene dyes Eosin-Y (Eos), Erythrosin-B (Ery) and Rose Bengal (RB) were evaluated in the presence of amino-terminated polyamido-amine (PAMAM) dendrimers of relatively high generations (G3-G5), in alkaline aqueous solution. UV-Vis absorption and fluorescence spectra of the dyes showed bathochromic shifts, which correlated with the size of the dendrimer. From absorption data binding constant (Kbind) were calculated. High Kbind values resulted, indicating a strong interaction between both molecules. Triplet-triplet absorption spectra of the dyes were recorded by laser flash photolysis, and a decrease of the triplet lifetimes was observed in the presence of dendrimers. At the same time, an increase in the absorption of the semireduced form of the dyes was observed. Rate constants for the triplet quenching (3kq) and radical quantum yields were obtained. The results were explained by a very efficient electron-transfer process from PAMAM to xanthene dyes, for all dye/dendrimer couples evaluated.