論文 - 山本　崇史

Photochromism Induced Magnetization Changes in Prussian Blue Ultrathin Films Fabricated into the Langmuir–Blodgett Films Composed of an Amphiphilic Azobenzene and a Deoxyribonucleic Acid

Takashi Yamamoto, Yasushi Umemura, Masaru Nakagawa, Tomokazu Iyoda, Yasuaki Einaga

Thin Solid Films （ELSEVIER SCIENCE SA）  515 （ 13 ） 5476 - 5483 2007年05月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0040-6090

　概要を見る

A photomagnetic ultrathin film consisting of an azobenzene, a deoxyribonucleic acid, and Prussian Blue has been fabricated by the Langmuir-Blodgett method. Prussian Blue layers in the films were a two-dimensional structure with the height of 50 A and the average coherence length of 210 A. Reversible photoisomerization of the azobenzenes was observed even in the films. The films exhibit the long-range ferromagnetic order below 4.2 K and moreover, upon photoillumination at 2 K, reversible changes in the magnetization were realized with the value of ca. 1.0%. This photoswitching in the magnetization is due to changes in the electrostatic field induced by photoisomerization. (C) 2007 Elsevier B.V. All rights reserved.

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Photomagnetic Langmuir–Blodgett Films Consisting Azobenzene and Prussian Blue: Correlation Between the Film Structure and the Photomagnetic Efficiency

Takashi Yamamoto, Yasushi Umemura, Osamu Sato, Yasuaki Einaga

Science and Technology of Advanced Materials （NATL INST MATERIALS SCIENCE）  7 （ 3 ） 134 - 138 2006年03月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  1468-6996

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A photomagnetic organized thin film consisting of an amphiphilic azobenzene, a smectite clay, and Prussian Blue has been prepared by utilizing the Langmuir-Blodgett (LB) method and an ion-exchange reaction. The magnetic LB films were revealed to possess an organized layered structure, and reversible photoisomerization of the azobenzene was observed even in the LB films. Upon photoillumination at 2 K, reversible changes in the magnetization were realized with the value of ca. 11%. This photoswitching in the magnetization is due to changes in the electrostatic field induced by photoisomerization of the azobenzene. A large photoinduced change in the magnetization would be owing to the highly ordered structure of the LB films. In order to verify the correlation between the film structure and photoswitching efficiency, the LB films have been fabricated in other condition. As results, it is confirmed that the packing state of the azobenzene plays an important and crucial role in accomplishment of the highly efficient photomagnetic switching. (c) 2006 Elsevier Ltd. All rights reserved.

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Observation of the Anisotropic Photoinduced Magnetization Effect in Co–Fe Prussian Blue Thin Films Fabricated by Using the Clay Langmuir–Blodgett Films as a Template

Takashi Yamamoto, Yasushi Umemura, Osamu Sato, Yasuaki Einaga

Journal of the American Chemical Society （AMER CHEMICAL SOC）  127 （ 46 ） 16065 - 16073 2005年11月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0002-7863

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Thin films of cobalt-iron cyanide (Co-Fe Prussian blue) have been fabricated by means of the modified Langmuir-Blodgett (LB) method using a smectite clay mineral (montmorillonite). In this combined method, clay LB films play a template role in the formation of the Co-Fe Prussian blue thin layer. The films were revealed to possess a well-organized structure not only in perpendicular directions to the film surface but also in parallel directions to the film surface. The photoinduced electron transfer from the iron ion to the cobalt through the bridging cyanide in the films occurred at low temperature (8 K), similar to that in the bulk Co-Fe Prussian blue. The films clearly exhibited magnetic anisotropy with regards to the direction of the applied magnetic field. Moreover, the photoinduced magnetization effect in the films was also found to be anisotropic.

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Photomagnetic Co–Fe Prussian Blue Thin Films Fabricated by the Modified Langmuir–Blodgett Technique

Takashi Yamamoto, Yasushi Umemura, Osamu Sato, Yasuaki Einaga

Chemistry Letters （CHEMICAL SOC JAPAN）  33 （ 5 ） 500 - 501 2004年05月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0366-7022

　概要を見る

Co-Fe Prussian blue thin films have been prepared by means of a modified Langmuir-Blodgett technique, in which the hybrid monolayer composed of amphiphiles and clay platelets plays a template role for the formation Co-Fe Prussian blue thin films. Photoinduced magnetization was observed in the thin films as observed in the bulk Co-Fe Prussian blue. To the best of our knowledge, this is the first example Of Successful formation of Co-Fe Prussian blue thin films, which possess the ordered structure and, in addition, exhibit photoinduced magnetization.

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Photoswitchable Magnetic Films: Prussian Blue Intercalated in Langmuir-Blodgett Films Consisting of an Amphiphilic Azobenzene and a Clay Mineral

Takashi Yamamoto, Yasushi Umemura, Osamu Sato, Yasuaki Einaga

Chemistry of Materials （AMER CHEMICAL SOC）  16 （ 7 ） 1195 - 1201 2004年04月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0897-4756

　概要を見る

A novel photocontrollable magnetic thin film consisting of amphiphilic azobenzene cations, a smectite clay, and Prussian Blue has been designed and prepared by using the Langmuir-Blodgett method and an ion-exchange reaction. This magnetic thin film possesses a well-organized nanoscale layered structure. Reversible photoisomerization of the azobenzene chromophore realized photoswitching of the magnetization. The changes in the magnetization values were estimated to be ca. 11%. This figure was much larger than our previous system, which contained azobenzene multi-bilayered vesicles in a poly(vinyl alcohol) matrix (J. Am. Chem. Soc. 1999, 121, 3745). These larger changes in the magnetization values are due to the highly ordered structure of the hybrid multilayered films.

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Reversible Photocontrollable Magnetic Vesicles Consisting of Azobenzene

Yasuaki Einaga, Takashi Yamamoto, Takeshi Sugai, Osamu Sato

Chemistry of Materials （AMER CHEMICAL SOC）  14 （ 11 ） 4846 - 4850 2002年11月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0897-4756

　概要を見る

Photochromic magnetic vesicles have been designed by intercalation of Prussian blue into a lipid bilayer membrane which consists of azobenzene. Reversible photoisomerization of the solid system realized reversible photocontrol of the magnetic properties. Here, we have synthesized an amphiphile azo moiety containing a long alkyl chain, and we have prepared photochromic magnetic vesicles consisting of only this azo moiety. As a result, the magnetic property change brought about by visible light illumination was estimated to be ca. 13%, which is much larger than the figure achieved for the similar system that we reported previously (similar to1%), which contained the double-chain ammonium amphiphile.

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