title: Photosensitized hydrogen evolution from water using conjugated polymers wrapped in dendrimeric electrolytes.
abstract: High-efficiency light-driven hydrogen evolution from water was demonstrated by using poly(phenyleneethynylene) bearing negatively charged, [G3] poly(benzyl ether) dendrimeric side groups 3(L4) as photosensitizer. Three-dimensional wrapping of the conjugated backbone suppressed self-quenching of the photoexcited state, while methyl viologen (MV(2+)), a positively charged electron acceptor, was trapped on its negatively charged surface, to form a spatially separated donor-acceptor supramolecular complex. Studies with time-resolved fluorescence spectroscopy showed that the quenching rate constant (k(q) = 1.2 x 10(15) M(-1) s(-1)) is much greater than diffusion control rate constants. Upon excitation of 3(L4) in the presence of a mixture of MV(2+), triethanolamine (TEOA; sacrificial electron donor), and a colloidal PVA-Pt, hydrogen evolution took place with an overall efficiency of 13%, 1 order of magnitude better than precedent examples. Comparative studies with several reference sensitizers showed that spatial isolation of the conjugated backbone and its long-range pi-electronic conjugation, along with electrostatic interactions on the exterior surface, play important roles in achieving the efficient photosensitized water reduction.
authors.affiliation: Aida Nanospace Project, Exploratory Research for Advanced Technology (ERATO), Japan Science and Technology Agency (JST), 2-41 Aomi, Koto-ku, Tokyo 135-0064, Japan. jiang@nanospace.miraikan.jst.go.jp
authors.forename: Dong-Lin
authors.initials: DL
authors.lastname: Jiang
authors.forename: Cheol-Kyu
authors.initials: CK
authors.lastname: Choi
authors.forename: Kayoko
authors.initials: K
authors.lastname: Honda
authors.forename: Wei-Shi
authors.initials: WS
authors.lastname: Li
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Yuzawa
authors.forename: Takuzo
authors.initials: T
authors.lastname: Aida