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184 results on '"Takizawa, Shin‐ya"'

10. Hydrogen Production from Hydrophobic Ruthenium Dye-Sensitized TiO2 Photocatalyst Assisted by Vesicle Formation

Author

Higashida, Yusuke, Takizawa, Shin-ya, Yoshida, Masaki, Kato, Masako, Kobayashi, Atsushi, Higashida, Yusuke, Takizawa, Shin-ya, Yoshida, Masaki, Kato, Masako, and Kobayashi, Atsushi

Abstract

Dye-sensitizedH(2) evolution photocatalysts have attractedconsiderable attention as promising systems for the photochemicalgeneration of H-2 from water. In this study, to mimic thereaction field of natural photosynthesis artificially, we synthesizeda hydrophobic Ru-(II) dye-sensitized Pt-TiO2 nanoparticlephotocatalyst, RuC ( 9 )@Pt-TiO2 (RuC ( 9 ) = [Ru-(dC(9)bpy)(2)(H(4)dmpbpy)](2+); dC(9)bpy = 4,4 '-dinonyl-2,2 '-bipyridine, H(4)dmpbpy= 4,4 '-dimethyl phosphonic acid-2,2 '-bipyridine), andintegrated it into 1,2-dipalmitoyl-sn-glycero-3-phosphocholine(DPPC) lipid bilayer vesicle membranes. The photocatalytic H-2 production activity in 0.5 M l-ascorbic acid aqueous solutionenhanced by more than three times in the presence of DPPC vesicles(apparent quantum yield = 2.11%), whereas such a significant enhancementwas hardly observed when the vesicle formation was omitted. Theseresults indicate that the highly dispersed state of the hydrophobic RuC ( 9 )@Pt-TiO2 nanoparticlesin the DPPC bilayer vesicles is a key factor in achieving enhancedphotocatalytic H-2 production activity in aqueous solution.

Published
2023

16. Zn(II)‐Dipicolylamine‐Attached Amphiphilic Polythiophene for Quantitative Pattern Recognition of Oxyanions in Mixtures.

Author

Sasaki, Yui, Ohshiro, Kohei, Okabe, Kiyosumi, Lyu, Xiaojun, Tsuchiya, Kazuhiko, Matsumoto, Akira, Takizawa, Shin‐ya, and Minami, Tsuyoshi

Subjects
NANOWIRES, MOLECULAR shapes, POLYTHIOPHENES, ABSORPTION spectra, MIXTURES, FLUORESCENCE spectroscopy, THIOPHENES
Abstract

Herein, we propose a novel amphiphilic polythiophene‐based chemosensor functionalized with a Zn(II)‐dipicolylamine side chain (1poly ⋅ Zn) for the pattern recognition of oxyanions. Optical changes in amphiphilic 1poly ⋅ Zn can be induced by the formation of a random coil from a backbone‐planarized structure upon the addition of target oxyanions, which results in blueshifts in the UV‐vis absorption spectra and turn‐on‐type fluorescence responses. Dynamic behavior in a polythiophene wire and/or among wires could be a driving force for obtaining visible color changes, while the molecular wire effect is dominant in obtaining fluorescence sensor responses. Notably, the magnitude of optical changes in 1poly ⋅ Zn has depended on differences in properties of oxyanions, such as their binding affinity, hydrophilicity, and molecular geometry. Thus, various colorimetric and fluorescence response patterns of 1poly ⋅ Zn to oxyanions were obtained, albeit using a single chemosensor. A constructed information‐rich dataset was applied to pattern recognition for the simultaneous group categorization of phosphate and carboxylate groups and the prediction of similar structural oxyanions at a different order of concentrations in their mixture solutions. [ABSTRACT FROM AUTHOR]

Published
2023
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21. Spontaneous preparation of a fluorescent ratiometric chemosensor for metal ions using off-the-shelf materials.

Author

Sasaki, Yui, Ohshiro, Kohei, Zhou, Qi, Lyu, Xiaojun, Tang, Wei, Okabe, Kiyosumi, Takizawa, Shin-ya, and Minami, Tsuyoshi

Subjects
CHEMORECEPTORS, METAL ions, PATTERN recognition systems, HEAVY metals, WATER analysis
Abstract

A self-assembled chemosensor prepared using off-the-shelf materials has shown various fluorescence responses including ratiometric and simple ON–OFF switching profiles by adding different toxic metal ions. The unique fingerprint-like responses have been applied to pattern recognition of metal ions in river water for environmental analysis. [ABSTRACT FROM AUTHOR]

Published
2023
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26. Ion Pairing of Cationic and Anionic Ir(III) Photosensitizers for Photocatalytic CO2Reduction at Lipid–Membrane Surfaces

Author

Takizawa, Shin-ya, Okuyama, Takahiro, Yamazaki, Suguru, Sato, Kei-ichi, Masai, Hiroshi, Iwai, Tomohiro, Murata, Shigeru, and Terao, Jun

Abstract

We synthesized an ion pair comprising cationic and anionic Ir(III) photosensitizers ([Ir1+][Ir2–]) for photocatalytic CO2reduction and showed that the cationic component imparts stability, while the cyclometalating ligands in the anionic component ensure effective visible-light absorption. The triplet excited state of [Ir1+] is the key photoredox species in this system and is mainly generated through the transfer of triplet excitation energy from the anionic moiety due to Coulombic interactions and appropriate triplet energy alignment between the two ionic components. The positive photosensitization effect of ion pairing was demonstrated by photocatalytic CO2reduction in cooperation with a Re(I) molecular catalyst incorporated into a vesicle membrane.

Published
2023
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29. Hydrogen Production from Hydrophobic Ruthenium Dye-Sensitized TiO2Photocatalyst Assisted by Vesicle Formation

Author

Higashida, Yusuke, Takizawa, Shin-ya, Yoshida, Masaki, Kato, Masako, and Kobayashi, Atsushi

Abstract

Dye-sensitized H2evolution photocatalysts have attracted considerable attention as promising systems for the photochemical generation of H2from water. In this study, to mimic the reaction field of natural photosynthesis artificially, we synthesized a hydrophobic Ru(II) dye-sensitized Pt-TiO2nanoparticle photocatalyst, RuC9@Pt-TiO2(RuC9= [Ru(dC9bpy)2(H4dmpbpy)]2+; dC9bpy = 4,4′-dinonyl-2,2′-bipyridine, H4dmpbpy = 4,4′-dimethyl phosphonic acid-2,2′-bipyridine), and integrated it into 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayer vesicle membranes. The photocatalytic H2production activity in 0.5 M l-ascorbic acid aqueous solution enhanced by more than three times in the presence of DPPC vesicles (apparent quantum yield = 2.11%), whereas such a significant enhancement was hardly observed when the vesicle formation was omitted. These results indicate that the highly dispersed state of the hydrophobic RuC9@Pt-TiO2nanoparticles in the DPPC bilayer vesicles is a key factor in achieving enhanced photocatalytic H2production activity in aqueous solution.

Published
2023
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30. Phosphorescent iridium complexes based on 2-phenylimidazo[1,2-a]pyridine ligands: Tuning of emission color toward the blue region and application to polymer light-emitting devices

Author

Takizawa, Shin-ya, Nishida, Jun-Ichi, Tsuzuki, Toshimitsu, Tokito, Shizuo, and Yamashita, Yoshiro

Subjects
Iridium -- Chemical properties, Ligands -- Research, Electrochemical analysis, Chemistry
Abstract

A series of new blue-phosphorescent iridium(III) complexes with ligands of 2-phenylimidazo[1,2-alpyridine (pip) derivatives were prepared to investigate their electrochemical, photophysical, and electroluminescent (EL) properties. Results found that combination of electron-withdrawing substituents on the phenyl ring with the use of another ancillary ligand enabled further blue shifts.

Published
2007

45. Photoinduced flavin-tryptophan electron transfer across vesicle membranes generates magnetic field sensitive radical pairs.

Author

Antill, Lewis M., Takizawa, Shin-ya, Murata, Shigeru, and Woodward, Jonathan R.

Subjects
*PHOTOINDUCED electron transfer, *OXIDATION-reduction reaction, *GEMINATE pairs (Molecules), *FLAVIN mononucleotide, *MAGNETIC fields, *BILAYER lipid membranes, *CHEMICAL yield
Abstract

Due to the photobiology of the flavoproteins DNA photolyase and cryptochrome, electron transfer reactions between flavins and tryptophan are of significant biological relevance. In addition, electron transfer across vesicle membranes has also seen much attention. In this work, we study the electron transfer reaction between flavins and tryptophan across lipid bilayer membranes in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine small unilamellar vesicles using time-resolved optical absorption microspectroscopy and magnetically affected reaction yield spectroscopy. We demonstrate that riboflavin tetrabutyrate is embedded in the vesicle bilayer and can undergo electron transfer with tryptophan molecules in either the inner water pool or the bulk solution. Remarkably, flavin mononucleotide encapsulated in the inner water pool can undergo electron transfer across the vesicle bilayer to generate a magnetically sensitive radical pair with tryptophan molecules located in the bulk solution. The observed kinetics suggest that back electron transfer occurs between radical pairs generated by diffusive reencounter, either in the vesicle surface water or via electron hopping through degenerate electron exchange. [ABSTRACT FROM AUTHOR]

Published
2019
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49. Front Cover: Zn(II)‐Dipicolylamine‐Attached Amphiphilic Polythiophene for Quantitative Pattern Recognition of Oxyanions in Mixtures (Chem. Asian J. 16/2023).

Author

Sasaki, Yui, Ohshiro, Kohei, Okabe, Kiyosumi, Lyu, Xiaojun, Tsuchiya, Kazuhiko, Matsumoto, Akira, Takizawa, Shin‐ya, and Minami, Tsuyoshi

Subjects
MIXTURES, MOLECULAR recognition
Abstract

The difference in the optical responses to the oxyanions enables pattern recognition-based discrimination in a mixture. Keywords: sensors; anions; molecular recognition; polythiophene; pattern recognition EN sensors anions molecular recognition polythiophene pattern recognition 1 1 1 08/17/23 20230815 NES 230815 B An amphiphilic polythiophene-based chemosensor b shows optical changes accompanied by the formation of random coils (i.e., fireworks) from the backbone-planarized structures upon the addition of target oxyanions such as pyrophosphate and citrate. Sensors, anions, molecular recognition, polythiophene, pattern recognition. [Extracted from the article]

Published
2023
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