title: Structure and photophysical properties of porphyrin-modified metal nanoclusters with different chain lengths.
abstract: Three-dimensional porphyrin-monolayer-protected gold clusters with different chain lengths (MPCs) have been prepared to examine the structure and photophysical properties, in comparison with self-assembled monolayers (SAMs) of the porphyrins on a flat gold surface. The three-dimensional porphyrin MPCs exhibit electrochemical and photophysical properties that are much closer to those of a porphyrin reference compound in solution than those of two-dimensional porphyrin SAMs on the flat gold surface. The three-dimensional architectures of porphyrin MPCs with large surface area have improved the light-harvesting efficiency relative to the corresponding porphyrin SAM on the two-dimensional flat gold surface. Time-resolved single photon counting fluorescence and transient absorption spectroscopic studies have demonstrated that undesirable quenching of the porphyrin excited singlet state via energy transfer to the gold surface of the three-dimensional MPCs is much suppressed, as compared to the quenching of the porphyrin SAMs on the two-dimensional flat gold surface. Both the quenching rate constants of the porphyrin excited singlet state by the surfaces of bulk gold and gold nanoclusters reveal weak chain length dependence of the energy transfer quenching.
authors.affiliation: Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, PRESTO, Japan Science and Technology Agency (JST), Katsura, Nishikyo-ku, Kyoto 615-8510, Japan. imahori@scl.kyoto-u.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Imahori
authors.forename: Yukiyasu
authors.initials: Y
authors.lastname: Kashiwagi
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Endo
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hanada
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Iwao
authors.initials: I
authors.lastname: Yamazaki
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Araki
authors.forename: Osamu
authors.initials: O
authors.lastname: Ito
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
mesh_terms: D006046:Gold / Q000737:chemistry / Q000528:radiation effects; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry / Q000528:radiation effects; D009942:Organometallic Compounds / Q000737:chemistry / Q000528:radiation effects; D010316:Particle Size; D010777:Photochemistry; D011166:Porphyrins / Q000737:chemistry / Q000528:radiation effects; D013499:Surface Properties
chemical_list: D009942:Organometallic Compounds; D011166:Porphyrins; D006046:Gold