論文発表
Feng Xu, Takanori Nishida, Kenta Shinohara, Lifen Peng, Makoto Takezaki, Takahiro Kamada, Haruo Akashi, Hiromu Nakamura, Kouki Sugiyama, Kazuchika Ohta, Akihiro Orita, Junzo Otera, Trimethylsilyl Group Assisted Stimuli Response: Self-Assembly of 1,3,6,8-Tetrakis((trimethysilyl)ethynyl)pyrene, ORGANOMETALLICS, 36, 556-563, 2017.
Substitution of 1,3,6,8-tetraethynylpyrene with sterically bulky trimethylsilyl groups enabled four modes of molecular packing, two polymorphs (triclinic system (Y-form) and “loose” crystal Colho (OK-form)), a ”rigid” liquid crystalline phase Colho (OC-form), and an amorphous phase (OA-form), which emitted fluorescence at different wavelengths under UV light. The four phases could be interconverted by physical stimuli such as heating, grinding by mortar and pestle, and exposing to the vapor of organic solvents.
Andrew D. Scully, Hiroyasu Ohtaka, Makoto Takezaki, and Toshihiro Tominaga, Diffusion-Facilitated Direct Determination of Intrinsic Parameters for Rapid Photoinduced Bimolecular Electron-Transfer Reactions in Nonpolar Solvents, J. Phys. Chem. A, 119, 2770–2779, 2015.
Bimolecular fluorescence-quenching reactions involving electron-transfer between electronically excited 5,10,15,20-tetraphenyl-21H,23H-porphine (TPP*) and 1,4-benzoquinone (BQ) or 1,4-naphthoquinone (NQ) were investigated using a set of alkane solvents that enabled the rapid reaction kinetics to be probed over a wide viscosity range, while minimizing changes in other relevant solvent parameters. Relative diffusion coefficients and reaction distances were recovered directly from analysis of fluorescence decay curves measured on a nanosecond time scale. The electron transfer from TPP* to BQ requires reactant contact, consistent with tightly associated exciplex formation in these nonpolar solvents. In contrast, electron transfer from TPP* to NQ displays a clear distance dependence, indicative of reaction via a much looser noncontact exciplex. This difference is attributed to the greater steric hindrance associated with contact between the TPP*/NQ pair. The diffusion coefficients recovered from fluorescence decay curve analysis are markedly smaller than the corresponding measured bulk relative diffusion coefficients. Classical hydrodynamics theory was found to provide a satisfactory resolution of this apparent discrepancy. The calculated hydrodynamic radii of TPP and NQ correlate very well with the van der Waals values. The hydrodynamic radius obtained for BQ is a factor of 6 times smaller than the van der Waals value, indicative of a possible tight cofacial geometry in the (TPP+/BQ–)* exciplex. The present work demonstrates the utility of a straightforward methodology, based on widely available instrumentation and data analysis, that is broadly applicable for direct determination of kinetic parameter values for a wide variety of rapid bimolecular fluorescence quenching reactions in fluid solution.
Makoto Takezaki, Toshihiro Tominaga, Bimolecular Fluorescence Quenching Reactions in Didodecyldimethylammonium Bromide and Chloride Vesicles and Micelles, J. Sol. Chem. 43, 2014, 1732-1745.
Fluorescence decays have been measured for pyrenesulfonate (PyS−) in the presence of anthraquinone-1-sulfonate (AQ1S−), for pyrene (Py) at various concentrations, and Py in the presence of AQ1S− in 5 mmol·dm−3 didodecyldimethylammonium bromide (DDABr) vesicle solutions. Reaction rate constants were found to increase in the order Py*–Py < PyS−*–AQ1S− < Py*–AQ1S−. Fluorescence decays have also been measured in 5 mmol·dm−3 didodecyldimethylammonium chloride (DDACl) solutions; the results showed micellar solution behavior, and micellar aggregation numbers and quenching rate constants were obtained. The quenching rate constants in vesicles and micelles were converted to the two dimensional rate constants having the same units. Two dimensional diffusion coefficient and reaction distance were obtained for the PyS−*–AQ1S− system on the DDABr vesicle surface.
Takezaki Makoto, Shibata Masahiro, Tominaga Toshihiro, Effects of the Ag+ and Cu2+ ions on the shape of triangular gold nanoparticles、Chem. Lett., 41, 1166-1167, 2012.
Triangular gold nanoplates were prepared by the tartaric acid reduction of HAuCl4 in cationic surfactant solutions, in the absence and the presence of small amounts of AgNO3 and CuSO4. With increasing concentration of AgNO3, the particle shape changes from triangular to spherical. In the presence of CuSO4, triangular plates with side lengths and tips that are longer and sharper, respectively, than those of the nanoplates prepared in the absence of CuSO4, are obtained.
学会発表
竹崎 誠, 橋本章裕, 藤沢拓也、陽イオン性界面活性剤保護金ナノ粒子のナノセルロースへの吸着効果、第72回コロイドおよび界面化学討論会(つくば)、 2021年9月
Makoto Takezaki, Takumi Zaima and Tatsuki Katayama、Fluorescence Quenching of Pyrene Sulfonate by Bromide Ions on Surfaces of idodecyldimethylammonium Bromide Aggregates 、Okinawa Colloids 2019(Nago, Okinawa), 2019, Nov.
Hiroki Muraai, Tatsuya Obata, and Makoto Takezaki、pH Dependence of Snowflake Gold Nanoparticles Prepared by Gallic Acid Reduction 、Okinawa Colloids 2019(Nago, Okinawa), 2019, Nov.
Makoto Takezaki and Tatsuki Katayama、Fluorescence quenching of pyrene sulfonate by bromide ions on alkyltrimethylammonium bromide micellar surfaces、Joint conference of EMLG/JMLG Meeting 2018 and 41st Symposium on Solution Chemistry of Japan (Nagoya), 2018, Nov.
村合大輝, 小幡辰哉, 竹崎誠、アルキルトリメチルアンモニウム臭化物存在下での塩化金酸ナトリウムの没食子酸還元、第６９回コロイドおよび界面化学討論会(つくば)、2018年9月
竹崎 誠,多和義弘、イオン性ミセル表面でのピレンメチルアンモニウム蛍光のメチルピリジニウムによる消光反応、第40回溶液化学シンポジウム(姫路)、2017年11月
竹崎 誠,中谷 真生、種々の金属イオン添加による酒石酸還元三角板状金ナノ粒子の形状への効果、第68回コロイドおよび界面化学討論会(神戸) 、2018年９月