title: Photoinduced charge-transfer interactions on a graphene/block copolymer electrostatically bound to tetracationic porphyrin in aqueous media.
abstract: Stable dispersions of exfoliated graphene in aqueous media with the aid of the amphiphilic block copolymer poly(isoprene-b-acrylic acid) (PI-b-PAA), in the form of its anion, were used to electrostatically bind cationic 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphine tetra(p-toluenesulfonate) (H2P(4+)). A new graphene/PI-b-PAA(-)-H2P(4+) ensemble was formed and examined by dynamic light scattering, UV/Vis and fluorescence emission spectroscopy. The efficient fluorescence quenching of H2P(4+) in the graphene/PI-b-PAA(-)-H2P(4+) ensemble was probed by using steady-state and time-resolved photoluminescence, suggesting that electron/energy-transfer phenomena occur within the nanoensemble. Blank experiments validated the concept of electrostatic interactions that govern the formation of graphene/PI-b-PAA(-)-H2P(4+) ensemble, which signified the importance of graphene as an electron acceptor toward the preparation of some new donor-acceptor systems. Finally, kinetic analysis of the lifetime profiles of the fluorescence emission gave information regarding the quenching rate constant and quantum yield of the singlet excited state of H2P(4+) in the graphene/PI-b-PAA(-)-H2P(4+) ensemble.
authors.affiliation: National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Contantinou Avenue, Athens 11635, Greece.
authors.forename: Theodosis
authors.initials: T
authors.lastname: Skaltsas
authors.forename: Stergios
authors.initials: S
authors.lastname: Pispas
authors.forename: Nikos
authors.initials: N
authors.lastname: Tagmatarchis
keywords: UV/Vis spectroscopy; charge transfer; fluorescence; graphene; porphyrin