title: Preparation and photophysical and photoelectrochemical properties of a covalently fixed porphyrin-chemically converted graphene composite.
abstract: Chemically converted graphene (CCG) covalently linked with porphyrins has been prepared by a Suzuki coupling reaction between iodophenyl-functionalized CCG and porphyrin boronic ester. The covalently linked CCG-porphyrin composite was designed to possess a short, rigid phenylene spacer between the porphyrin and the CCG. The composite material formed stable dispersions in DMF and the structure was characterized by spectroscopic, thermal, and microscopic measurements. In steady-state photoluminescence spectra, the emission from the porphyrin linked to the CCG was quenched strongly relative to that of the porphyrin reference. Fluorescence lifetime and femtosecond transient absorption measurements of the porphyrin-linked CCG revealed a short-lived porphyrin singlet excited state (38 ps) without yielding the porphyrin radical cation, thereby substantiating the occurrence of energy transfer from the porphyrin excited state to the CCG and subsequent rapid decay of the CCG excited state to the ground state. Consistently, the photocurrent action spectrum of a photoelectrochemical device with a SnO(2) electrode coated with the porphyrin-linked CCG exhibited no photocurrent response from the porphyrin absorption. The results obtained here provide deep insight into the interaction between graphenes and π-conjugated systems in the excited and ground states.
authors.affiliation: Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Umeyama
authors.forename: Junya
authors.initials: J
authors.lastname: Mihara
authors.forename: Noriyasu
authors.initials: N
authors.lastname: Tezuka
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Matano
authors.forename: Kati
authors.initials: K
authors.lastname: Stranius
authors.forename: Vladimir
authors.initials: V
authors.lastname: Chukharev
authors.forename: Nikolai V
authors.initials: NV
authors.lastname: Tkachenko
authors.forename: Helge
authors.initials: H
authors.lastname: Lemmetyinen
authors.forename: Kei
authors.initials: K
authors.lastname: Noda
authors.forename: Kazumi
authors.initials: K
authors.lastname: Matsushige
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Shishido
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.forename: Kaori
authors.initials: K
authors.lastname: Hirose-Takai
authors.forename: Kazu
authors.initials: K
authors.lastname: Suenaga
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Imahori