title: Tuning the concentration of dye loaded polymer films for maximum photosensitization efficiency: phloxine B in poly(2-hydroxyethyl methacrylate).
abstract: Fluorescence and singlet molecular oxygen ((1)O2) quantum yields for phloxine B loaded poly(2-hydroxyethyl methacrylate) thin films are determined at dye concentrations from 0.015 to 22 wt%. Fluorescence self-quenching and the fall off of the (1)O2 quantum yield observed above 0.1 wt% are attributed to very weakly 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 concentrations around 2 wt%, where fluorescence self quenching amounts to more than 80%. Data are fitted quantitatively 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 photosensitizers in general and, particularly, for applications in which the antimicrobial activity of singlet oxygen is central.
authors.affiliation: INQUIMAE (UBA-CONICET)/DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, Buenos Aires, Argentina. esr@qi.fcen.uba.ar.
authors.forename: Yair
authors.initials: Y
authors.lastname: Litman
authors.forename: Hernán B
authors.initials: HB
authors.lastname: Rodríguez
authors.forename: Enrique
authors.initials: E
authors.lastname: San Román