October 29th, 2019 (First published on web site: September 30th, 2019)
Crystal Growth Technique for Formation of Double Roughness Structures Mimicking Lotus Leaf
Ryo Nishimura, Hiroyuki Mayama, Yoshimune Nonomura, Satoshi Yokojima, Shinichiro Nakamura, and Kingo Uchida
Langmuir, 2019, 35 (43), 14124-14132. (Outside back cover picture)

Bio-inspired functional materials have received much attention for their potential to provide sustainable and advanced materials. The lotus effect has proven to be one of the most remarkable biomimetic effects since it was discovered by Barthlott. A superhydrophobic surface with the ability to bounce water droplets is the origin of the self-cleaning mechanism that keeps the surface clean by removing dust using water droplets moving with momentum. We have developed a crystal growth technique (CGT) of photochromic diarylethenes over the past decade, and from this, we fabricated a surface structure that closely resembles the natural lotus leaf’s characteristic of controlling the Laplace pressure and clarified the importance of the double roughness structure of the surface.

September 16th, 2019 (First published on web site: July 15th, 2019)
Object Transportation System Mimicking the Cilia of Paramecium aurelia Making Use of the Light-Controllable Crystal Bending Behavior of a Photochromic Diarylethene
Ryo Nishimura, Ayako Fujimoto, Nobuhiro Yasuda, Masakazu Morimoto, Tatsuhiro Nagasaka, Hikaru Sotome, Syoji Ito, Hiroshi Miyasaka, Satoshi Yokojima, Shinichiro Nakamura, Ben. L. Feringa, and Kingo Uchida
Angew. Chem. Int. Ed., 2019, 58 (38), 13308-13312. (Hot paper and Outside back cover picture)
DOI: 10.1002/anie.201907574

Lights, camera, action! Diarylethene crystals assembled on a surface bend in response to light irradiation from a certain direction. A photoactuated smart surface based on this system can transport polystyrene beads to a desired area upon application of incident light from the appropriate direction. This system demonstrates the remote‐controlled induction of a mechanical motion along a surface.

August 6th, 2019
Dual Wettability on Diarylethene Microcrystalline Surface Mimicking a Termite Wing
Ryo Nishimura, Kengo Hyodo, Hiroyuki Mayama, Satoshi Yokojima, Shinichiro Nakamura, and Kingo Uchida
Communications Chemistry, 2019, 2, Article number: 90.
DOI: 10.1038/s42004-019-0192-6

The termite wing has a specific property of wetting in contact with a water droplet: it adsorbs water mist, whereas larger water droplets are bounced on the surface. This is owing to the survival strategy of termites. Here, we reproduce the termite wing’s dual wettability by a photoinduced crystal growth technique. Upon UV irradiation to a microcrystalline surface of a mixture of two diarylethenes, two types of needle-shaped crystals of distinctly different sizes are observed to grow. The surface shows behavior akin to the termite wing’s dual wettability. The bouncing ability of a water droplet is attributed to the smaller-sized needle crystals, whereas the adhesive property is owing to the larger-sized ones, explaining the microstructures of the termite wing. Considering dissipation energy and adhesion energy, the bouncing ability and dual wettability can be explained theoretically. The surface could potentially be used in water harvesting applications.

April 1st, 2019
Photosalient Effect of Diarylethene Crystals of Thiazoyl and Thienyl Derivatives
Yuma Nakagawa, Masakazu Morimoto, Nobuhiro Yasuda, Kengo Hyodo, Satoshi Yokojima, Shinichiro Nakamura, and Kingo Uchida
Chem. Eur. J., 2019, 25 (33), 7874-7880. (Hot paper and Outside back cover picture)
DOI: 10.1002/chem.201900811

Consequences of expansion: The photoresponse of diarylethene crystals depends on the intensity of UV light: photoinduced bending is switched to photosalient phenomena upon increasing the light intensity. The patterns depend on molecular ordering (see figure). The change in the size of the crystal unit cell upon UV irradiation is larger for asymmetric diarylethenes.

March 30th, 2018
Photochromic Crystalline Systems Mimicking Bio-Functions
Kingo Uchida, Ryo Nishimura, Eri Hatano, Hiroyuki Mayama, and Satoshi Yokojima
Chem. Eur. J, 2018, 24 (34), 8491-8506.
DOI: 10.1002/chem.201705427

Bio-mimetic functions were realized by using the crystal of photochromic diarylethenes. Diarylethenes undergo reversible photochromic reactions even in the crystalline state. Some of them showed reversible topographical changes on the microcrystalline surfaces, that is the key to exhibit reversible changes of super hydrophobicity, superhydrophilicity, and anti-reflection, mimicking lotus leaf, snail shell, and moth-eye. Another biomimetic function of impatiens, scattering included small beads by action of light, was found for hollow crystals of another diarylethene.

September 1st, 2017
Photosalient Phenomena that Mimic Impatiens Are Observed in Hollow Crystals of Diarylethene with a Perfluorocyclohexene Ring (HOT PAPER)
Eri Hatano, Masakazu Morimoto, Takahiro Imai, Kengo Hyodo, Ayako Fujimoto, Ryo Nishimura, Akiko Sekine, Nobuhiro Yasuda, Satoshi Yokojima, Shinichiro Nakamura, and Kingo Uchida
Angew. Chem. Int. Ed., 2017, 56(41), 12576-12580.
DOI: 10.1002/anie.201706684

A diarylethene with a perfluorocyclohexene ring formed hollow crystals by sublimation under normal pressure. Upon UV irradiation of the crystals, they showed remarkable photosalient phenomena and scattered into small pieces. The speed of the flying debris released from the crystal by UV irradiation exceeded several meters per second. To clearly show a photosalient effect resembling the scattering behavior of Impatiens on a smaller scale, small fluorescent beads (1-μm diameter) were inserted into the hollow crystal. Consequently, scattering of the beads was observed as UV irradiation caused deformation and bursting of the hollow structure. This phenomenon is unique to hollow crystals, and the ability to effectively induce remarkable photosalient phenomena is similar to the behavior of hollow-structured Impatiens in nature.

July 28th, 2016
Photosalient Effect of a Diarylethene with a Perfluorocyclohexene Ring
Eri Hatano, Masakazu Morimoto, Kengo Hyodo, Nobuhiro Yasuda, Satoshi Yokojima, Shinichiro Nakamura, and Kingo Uchida
Chem. - Eur. J., 2016, 22 (36), 12680-12683.
DOI: 10.1002/chem.201603020

Crystals of a diarylethene with a perfluorocyclohexene ring exhibit a remarkable photosalient effect upon UV light irradiation that is attributed to the structural changes that occur when going from open- to closed-ring isomers in the crystalline state, together with the existence of two conformers with different photoconversions compared with those of a perfluorocyclopentene derivative. Our current results give a design principle for molecular structures so as to achieve the photosalient effect for photochromic crystals.

July 25th, 2016
Fractal Surfaces of Molecular Crystals Mimicking Lotus Leaf with Phototunable Double Roughness Structures
Ryo Nishimura, Kengo Hyodo, Haruna Sawaguchi, Yoshiaki Yamamoto, Yoshimune Nonomura, Hiroyuki Mayama, Satoshi Yokojima, Shinichiro Nakamura, and Kingo Uchida
J. Am. Chem. Soc., 2016, 138 (32), 10299-10303.

Double roughness structure, the origin of the lotus effect of natural lotus leaf, was successfully reproduced on a diarylethene microcrystalline surface. Static superwater-repellency and dynamic water-drop-bouncing were observed on the surface, in the manner of natural lotus leaves. Double roughness structure was essential for water-drop-bouncing. This ability was not observed on a single roughness microcrystalline surface showing the lotus effect of the same diarylethene derivative. The double roughness structure was reversibly controlled by alternating irradiation with UV and visible light.

April 14th, 2016
Photoinduced reversible formation of a superhydrophilic surface by crystal growth of diarylethene
Kazuki Takase, Kengo Hyodo, Masakazu Morimoto, Yuko Kojima, Hiroyuki Mayama, Satoshi Yokojima, Shinichiro Nakamura and Kingo Uchida
Chem. Commun., 2016, 52 (42), 6885-6887.
DOI: 10.1039/C6CC01638C

When visible light is irradiated onto the melted microcrystalline-surface of a diarylethene having ionic structures by UV irradiation, it induces crystal-growth of the open-ring isomer of the diarylethene; consequently, the surface covered with lumpy crystals shows superhydrophilicity that can be reversibly controlled by alternating irradiation with UV and visible light.

July 11st, 2015
Photoinduced cytotoxicity of a photochromic diarylethene via caspase cascade activation
Jun-ya Okuda, Yukimi Tanaka, Ryuhei Kodama, Kimio Sumaru, Kana Morishita, Toshiyuki Kanamori, Seiji Yamazoe, Kengo Hyodo, Shohei Yamazaki, Tomohiro Miyatake, Satoshi Yokojima, Shinichiro Nakamura, and Kingo Uchida
Chem. Commun., 2015, 51 (54), 10957-10960.
DOI: 10.1039/C5CC02200B

The photo-generated closed-ring isomer of bis(5-methyl-2-phenylthiazoyl)- perfluorocyclopentene shows cytotoxicity to Madin?Darby canine kidney (MDCK) cells through a caspase cascade and induces apoptosis of cells.

January 31st, 2015
A Diarylethene as the SO2 Gas Generator upon UV Irradiation
Ryuhei Kodama, Kimio Sumaru, Kana Morishita, Toshiyuki Kanamori, Kengo Hyodo, Takashi Kamitanaka, Masakazu Morimoto, Satoshi Yokojima, Shinichiro Nakamura, and Kingo Uchida
Chem. Commun., 2015, 51 (9), 1736-1738.

A closed-ring isomer of a diarylethene having a sulfone group works as the reagent for SO2 gas generation with thermal stability even at 70 °C, and it rapidly reverts to the open-ring isomer and generates the SO2 gas to induce cell death upon UV irradiation.

May 18th, 2013
Photoinduced Self-Epitaxial Crystal Growth of a Diarylethene Derivative with Antireflection Moth-Eye and Superhydrophobic Lotus Effects
Naoki Nishikawa, Shingo Sakiyama, Seiji Yamazoe, Yuko Kojima, Ei-ichiro Nishihara, Tsuyoshi Tsujioka, Hiroyuki Mayama, Satoshi Yokojima, Shinichiro Nakamura, and Kingo Uchida
Langmuir, 2013, 29 (25), 8164-8169.
DOI: 10.1021/la4014834

We identified the mechanism of the formation of needle-shaped microcrystals on which the contact angle of a water droplet exceeds 170°. The standing needle-shaped crystal of the closed-ring isomer of a diarylethene grew at a much lower temperature than the eutectic temperature by irradiation of UV light on the thin films of the open-ring isomer, due to the epitaxial growth of the 013 plane of the closed-ring isomer over the 110 plane of the crystal lattice of the open-ring isomer in the subphase. Therefore, the new crystal-growth mechanism triggered by the photoisomerization does not require special inorganic single-crystal substrates and may be called self-epitaxial crystal growth. The needle-shaped crystals appeared well-ordered and stood inclined at an angle of about 60° to the surface. Consequently, the photo-induced rough surface shows not only the superhydrophobic lotus effect, but also the antireflection moth-eye effect, and these effects were switchable by alternate irradiation with UV and visible light.

November 21th, 2012
Thermal and Photoinduced Liquid Crystalline Phase Transitions with a Rod?disc Alternative Change in the Molecular Shape
Daisuke Tanaka, Hisato Ishiguro, Yo Shimizu and Kingo Uchida
J. Mater. Chem., 2012, 22, 25065-25071.
Article first published online: 01 October 2012 | DOI: 10.1039/C2JM35518C

A triphenylene derivative which has six 4-tetradecyloxyazobenzene units connected with propylene?ester linkages (1) was synthesized to study the liquid crystalline phase transitions in both thermotropic and photo-induced manners. It was found that 1 exhibits smectic A (SmA) and rectangular columnar (Colr) mesophases in an enantiotropic way. This means that 1 can behave as both rod- and disc-like molecules depending on the thermal condition. To the best of our knowledge, this is the first case in thermotropic liquid crystals where one compound exhibits both calamitic and discotic mesomorphism with the change of molecular shape in anisotropy. Under the photo-irradiation at 365 nm of wavelength which induces a photoisomerisation of azobenzene units from trans to cis forms, the phase transitions take place in the same manner as in the thermotropic ones with a certain decrease of phase transition temperatures. It is also a new finding that at 202.5 °C at which 1 exhibits a Colr mesophase without photo-irradiation, the successive phase changes are induced by increasing the light intensity to the isotropic liquid (Iso) phase by way of a SmA phase. This means that the isothermal phase transitions among Iso, SmA and Colr phases can be controlled by light intensity. This is also the first example that the isothermal liquid crystalline phase transitions are controlled by photo-irradiation among three phases (Colr, SmA and Iso), which are also accompanied with the shape change of molecules between rod and disc.

April 6th, 2012
Photochromism of a Diarylethene Having an Azulene Ring
Jun-ichiro Kitai, Takao Kobayashi, Waka Uchida, Makoto Hatakeyama, Satoshi Yokojima, Shinichiro Nakamura, and Kingo Uchida
J. Org. Chem., 2012, 77, 3270-3276.
Article first published online: 12 March 2012 | DOI: 10.1021/jo202673z

Diarylethene derivatives incorporating an azulene ring at the ethene moiety were synthesized. One derivative having thiazole rings showed the expected coloration reaction by excitation at 313 nm (to a higher singlet state) but not when excited at 635 nm (S0 to S1 excitation). The system demonstrates that the cyclization reaction can be controlled by selective excitation at different wavelengths of the absorption spectrum. On the other hand, another derivative having thiophene rings did not show any photochromism. The results clearly show the importance of the coplanarity of the system for the photoisomerization.

March 2nd, 2011
Three-photon Cyclization and Two-Photon Cycloreversion by Near IR Femtosecond Laser Pulse at 1.28 μm
Kazuya Mori, Yukihide Ishibashi, Hirohisa Matsuda, Syoji Ito, Yutaka Nagasawa, Hirotomo Nakagawa, Kingo Uchida, Satoshi Yokojima, Shinichiro Nakamura, Masahiro Irie, Hiroshi Miyasaka,
J. Am. Chem. Soc., 2011, 133, 2621-2625.
Article first published online: 4 FEB 2011 | DOI: 10.1021/ja108992t

One-color control of colorization/decolorization reactions of diarylethene moleculeswas attained by using nonresonant high-order multiphoton absorption processes with a near-infrared (NIR) femtosecond laser pulse at 1.28 μm with 35 fs full width at half-maximum (fwhm). The intensity of a rather weak laser pulse (<1 nJ/pulse) can induce the simultaneous three-photon absorption leading to the colorization, while much weaker intensity induces two-photon absorption resulting in the decolorization. The spatial patterning concomitant with higher-order multiphoton absorption processes was also demonstrated.

July 29th, 2010
Phototunable Diarylethene Microcrystalline Surfaces: Lotus and Petal Effects upon Wetting
Kingo Uchida, Naoki Nishikawa, Norikazu Izumi, Seiji Yamazoe, Hiroyuki Mayama, Yuko Kojima, Satoshi Yokojima, Shinichiro Nakamura, Kaoru Tsujii and Masahiro Irie
Angew. Chem. Int. Ed., 2010, 45, 5942-5944.
Article first published online: 13 JUL 2010 | DOI: 10.1002/anie.201000793

Don't get wet! The UV irradiation of a photochromic diarylethene microcrystalline film and its subsequent temperature treatment leads to the formation of water-repellant surfaces with different microstructures. Depending on the microstructure, a water droplet will either roll off the surface (lotus effect) or stay pinned to it (petal effect; see picture).

June 12th, 2009
Photoisomerization of Azobenzene Gel by Pulsed Laser Irradiation
Kingo Uchida, Shintaro Yamaguchi, Hirofumi Yamada, Masako Akazawa, Tetsuro Katayama, Yukihide Ishibashi, and Hiroshi Miyasaka
Chem. Commun., 2009, 4420-4422.
Article first published online: 12 JUN 2009DOI: 10.1039/B908303K

A decalin gel consisting of an azobenzene derivative with H-aggregation showed a photon-density dependent E-Z isomerization, which is attributable to a cooperation effect of adjacent azobenzene moieties, leading to photo-functionality with a threshold of the light intensity.

January 21th, 2008
Photoresponsive rolling and bending of thin crystals of chiral diarylethenes (Hot Article)
Kingo Uchida, Shin-ichiro Sukata, Yuji Matsuzawa, Masako Akazawa, Jaap J. D. de Jong, Nathalie Katsonis, Yuko Kojima, Shinichiro Nakamura, Jetsuda Areephong, Auke Meetsma and Ben L. Feringa
Chem. Commun., 2008, 326-328. DOI: 10.1039/B715251E

Light is used to induce bending and rolling of thin crystals of diarylethenes. Careful molecular design allows control of both the structure of the crystals formed and their bending properties.

October 6th, 2006
Photoinduced Reversible Formation of Microfibrils on a Photochromic Diarylethene Microcrystalline Surface (HOT PAPER and NEWSWORTHY)
Kingo Uchida, Norikazu Izumi, Shinichiro Sukata, Yuko Kojima, Shinichiro Nakamura and Masahiro Irie
Angew. Chem. Int. Ed., 2006, 45, 6470-6473.
Article first published online: 22 AUG 2006 | DOI: 10.1002/anie.200602126

In a different light: A photoinduced change in surface morphology provides reversible changes in the superhydrophobic properties of a photochromic diarylethene film. The effect is achieved by the reversible formation of fine fibril structures on the coated microcrystalline surface upon irradiation by UV or visible light (see picture).

January 7th, 2005
Three Bits Eight States Photochromic Recording and Nondestructive Readout by Using IR Light
Kingo Uchida, Masaaki Saito, Akinori Murakami, Takao Kobayashi, Shinichiro Nakamura and Masahiro Irie
Chem. Eur. J. 2005, 4, 534-542.
Article first published online: 25 NOV 2004 | DOI: 10.1002/chem.200400575

A nondestructive read-out of multi-frequency photochromic recording was performed by using IR light of appropriate wavenumbers for a polymer film containing three different kinds of diarylethene derivatives. The assignments of the IR bands of the derivatives are also reported.

June 18th, 2003
Calamitic and discotic mesophases formed by kinetically controlled rod-disc alternation of molecular shape in a triphenylene-azobenzene mesogenic system
Yo Shimizu, Atsuhiko Kurobe, Hirosato Monobe, Naohiro Terasawa, Kenji Kiyohara and Kingo Uchida
Chem. Commun., 2003, 1676-1677. DOI: 10.1039/B301862H

A triphenylene mesogen with the peripheral azobenzene units was found to show kinetically controlled bimesomorphism, with a metastable smectic and a stable hexagonal columnar (Colh) phases on cooling, which is caused by the rod-disc alternation of the molecular shape.