Browsing by Author "Tohnai, Norimitsu"

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Control of Crystal Polymorph of Glycine by Photon Pressure of a Focused Continuous Wave Near-Infrared Laser Beam
(2010-02-04)
Rungsimanon, Thitiporn
;
Yuyama, Ken-ichi
;
Sugiyama, Teruki
;
Masuhara, Hiroshi
;
Tohnai, Norimitsu
Crystal polymorph of glycine is controlled by tuning the power of a linearly polarized continuous wave 1064-nm laser beam. Upon focusing the beam to the air/solution interface of a supersaturated glycine/D(2)O solution, it single crystal is spatiotemporally formed at a focal spot within a few seconds to a few ten of seconds. Fourier transform infrared measurement and single-crystal X-ray crystallographic analysis of the fabricated single crystal reveal that two polymorphs of alpha- and gamma-forms are prepared depending on the laser power. The probability of gamma-form are prepared depending on the laser power. The probability of gamma-form preparation, which is not available under ambient conditions arises upto 50% at 1.3 W laser power after an objective lens. The mechanism of the polymorph control is discussed in view of both photon pressure and local temperature elevation due to laser irradiation at the focal spot.
Photochemical Reaction of p-hydroxycinnamic-thiophenyl Ester in the Microcrystalline State
(2010-11-18)
Usman, Anwar
;
Asahi, Tsuyoshi
;
Sugiyama, Teruki
;
Masuhara, Hiroshi
;
Tohnai, Norimitsu
We have studied the photochromic reaction of p-hydroxycinnamic-thiophenyl ester in the microcrystalline state We attributed the fluorescence spectral evolution of the microcrystal under UV irradiation to the photoinduced trans-to-cis isomerization The photocyclic behavior of the chromophore was demonstrated by cis-to-trans back reaction under a subsequent visible light irradiation In addition the [2 2] topochemical photocyclodimer was observed as another photoproduct It is considered that the cooperative photoisomerization is initiated at the local lattice distortion and free spaces around the [2 + 2] cyclodimer near the crystal sui lace and the photoisomerization induces larger lattice deformation and further photoisomerization in the interior of the crystal
Photochemical Reaction of p-hydroxycinnamic-thiophenyl Ester in the Microcrystalline State
(2010-11-18)
Usman, Anwar
;
Asahi, Tsuyoshi
;
Sugiyama, Teruki
;
Masuhara, Hiroshi
;
Tohnai, Norimitsu
We have studied the photochromic reaction of p-hydroxycinnamic-thiophenyl ester in the microcrystalline state We attributed the fluorescence spectral evolution of the microcrystal under UV irradiation to the photoinduced trans-to-cis isomerization The photocyclic behavior of the chromophore was demonstrated by cis-to-trans back reaction under a subsequent visible light irradiation In addition the [2 2] topochemical photocyclodimer was observed as another photoproduct It is considered that the cooperative photoisomerization is initiated at the local lattice distortion and free spaces around the [2 + 2] cyclodimer near the crystal sui lace and the photoisomerization induces larger lattice deformation and further photoisomerization in the interior of the crystal