Research Center for Solar Energy Chemistry

Allenstown Elementary School, United States

Research Center for Solar Energy Chemistry

Allenstown Elementary School, United States
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Shiraishi Y.,Research Center for Solar Energy Chemistry | Sakamoto H.,Research Center for Solar Energy Chemistry | Sugano Y.,Research Center for Solar Energy Chemistry | Ichikawa S.,Osaka University | Hirai T.,Research Center for Solar Energy Chemistry
ACS Nano | Year: 2013

Visible light irradiation (λ > 450 nm) of Pt-Cu bimetallic alloy nanoparticles (∼3-5 nm) supported on anatase TiO2 efficiently promotes aerobic oxidation. This is facilicated via the interband excitation of Pt atoms by visible light followed by the transfer of activated electrons to the anatase conduction band. The positive charges formed on the nanoparticles oxidize substrates, and the conduction band electrons reduce molecular oxygen, promoting photocatalytic cycles. The apparent quantum yield for the reaction on the Pt-Cu alloy catalyst is ∼17% under irradiation of 550 nm monochromatic light, which is much higher than that obtained on the monometallic Pt catalyst (∼7%). Cu alloying with Pt decreases the work function of nanoparticles and decreases the height of the Schottky barrier created at the nanoparticle/anatase heterojunction. This promotes efficient electron transfer from the photoactivated nanoparticles to anatase, resulting in enhanced photocatalytic activity. The Pt-Cu alloy catalyst is successfully activated by sunlight and enables efficient and selective aerobic oxidation of alcohols at ambient temperature. © 2013 American Chemical Society.


Hirakawa H.,Research Center for Solar Energy Chemistry | Katayama M.,Research Center for Solar Energy Chemistry | Shiraishi Y.,Research Center for Solar Energy Chemistry | Sakamoto H.,Research Center for Solar Energy Chemistry | And 5 more authors.
ACS Applied Materials and Interfaces | Year: 2015

Photoirradiation (λ > 300 nm) of Degussa (Evonik) P25 TiO2, a mixture of anatase and rutile particles, in alcohols containing nitroaromatics at room temperature produces the corresponding imines with very high yields (80-96%). Other commercially available anatase or rutile TiO2 particles, however, exhibit very low yields (<30%). The imine formation involves two step reactions on the TiO2 surface: (i) photocatalytic oxidation of alcohols (aldehyde formation) and reduction of nitrobenzene (aniline formation) and (ii) condensation of the formed aldehyde and aniline on the Lewis acid sites (imine formation). The respective anatase and rutile particles were isolated from P25 TiO2 by the H2O2/NH3 and HF treatments to clarify the activity of these two step reactions. Photocatalysis experiments revealed that the active sites for photocatalytic reactions on P25 TiO2 are the rutile particles, promoting efficient reduction of nitrobenzene on the surface defects. In contrast, catalysis experiments showed that the anatase particles isolated from P25 TiO2 exhibit very high activity for condensation of aldehyde and aniline, because the number of Lewis acid sites on the particles (73 μmol g-1) is much higher than that of other commercially available anatase or rutile particles (<15 μmol g-1). The P25 TiO2 particles therefore successfully promote tandem photocatalytic and catalytic reactions on the respective rutile and anatase particles, thus producing imines with very high yields. © 2015 American Chemical Society.


Shiraishi Y.,Research Center for Solar Energy Chemistry | Suzuki T.,Research Center for Solar Energy Chemistry | Hirai T.,Research Center for Solar Energy Chemistry
Journal of Photochemistry and Photobiology A: Chemistry | Year: 2010

Two kinds of amphiphilic graft copolymers, PAA-g-P(MMA-co-BP) and P(AA-co-BP)-g-PMMA, consisting of polar poly(acrylic acid) (PAA), less polar poly(methyl methacrylate) (PMMA), and benzophenone (BP) photosensitizing units, have been synthesized. These polymers, when used as a photosensitizer for isomerization of trans-β-methylstyrene, show a sensitization activity controlled by solvents. In benzene and chloroform, P(AA-co-BP)-g-PMMA forms a micelle structure consisting of aggregated P(AA-co-BP) core with dissolved PMMA units at the outer sphere. This suppresses a triplet energy transfer (TET) from the excited state BP units to olefin and, hence, shows lower sensitization activity than a bulk sensitizer (4-methoxybenzophenone: MBP). In methanol, both polymers form a weak aggregate of less polar PMMA units containing dissolved PAA units. The internal cavity of the aggregate is less polar and stabilizes the excited state BP units. This accelerates a TET from the excited state BP units to olefin and shows higher sensitization activity than MBP. © 2010 Elsevier B.V. All rights reserved.


Wang D.,Research Center for Solar Energy Chemistry | Shiraishi Y.,Research Center for Solar Energy Chemistry | Hirai T.,Research Center for Solar Energy Chemistry
Tetrahedron Letters | Year: 2010

A new boradiazaindacene (BODIPY) derivative (1a) bearing simple NO bidentate ligands has been synthesized. The 1a molecule behaves as a fluorescent probe for Cr3+ and shows strong red fluorescence upon coordination with Cr3+, while showing almost no fluorescence for other metal cations. © 2010 Elsevier Ltd. All rights reserved.


Shiraishi Y.,Research Center for Solar Energy Chemistry | Manabe K.,Research Center for Solar Energy Chemistry | Hirai T.,Research Center for Solar Energy Chemistry
Applied Catalysis B: Environmental | Year: 2010

Cross-linked polymer nanocapsules (PC) encapsulating an iron tris(bipyridine) complex, Fe(bpy)32+@PC, have been synthesized by a ship-in-a-bottle method. This was used as a photosensitizer for the decomposition of organic pollutant in water under visible light irradiation with molecular oxygen. The Fe(bpy)32+@PC promotes efficient decomposition of organic pollutant, whereas noncapsulated Fe(bpy)32+ is inactive. The enhanced sensitization activity of Fe(bpy)32+ within PC is due to the interaction with the PC wall. This lengthens the lifetime of the excited state Fe(bpy)32+ and promotes efficient production of hydroxyl radicals. The sensitization activity of Fe(bpy)32+@PC depends on the thickness of the PC wall. The Fe(bpy)32+@PC with an appropriate PC wall thickness allows accumulation of pollutant within the PC and, hence, promotes efficient decomposition of pollutant. © 2009 Elsevier B.V. All rights reserved.

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