Tuning the concentration of dye loaded polymer films for maximum photosensitization efficiency: phloxine B in poly(2-hydroxyethyl methacrylate)

ENRIQUA SAN ROMÁN; HERNÁN B. RODRÍGUEZ; YAIR LITMAN

Photochemical and Photobiological Sciences

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2016 vol. 15 p. 80 - 85

1474-905X

Fluorescence and singlet molecular oxygen (1O2) quantum yields for phloxine B loaded poly(2-hydroxyethylmethacrylate) thin films are determined at dye concentrations from 0.015 to 22 wt%. Fluorescenceself-quenching and the fall off of the 1O2 quantum yield observed above 0.1 wt% are attributed to veryweakly interacting close-lying dye molecules acting as energy traps arising from molecular confinement.The maximum singlet oxygen generation efficiency (quantum yield × absorption factor) lies at concentrationsaround 2 wt%, where fluorescence self quenching amounts to more than 80%. Data are fittedquantitatively by using a quenching radius model involving energy migration and trapping with rQ =1.2 nm. The present results constitute a proof of concept for the rational design of heterogeneous photosensitizersin general and, particularly, for applications in which the antimicrobial activity of singlet oxygenis central.