584
K. Tawa et al.
light and the reaction process was simultaneously observed with the upright-inverted
microscope, i.e., epi-illumination light, transmitted light, and confined light by the
plasmonic field were used for local photoisomerization of 1o and 1c, and optical
images were taken with CCD camera. The needle-shaped crystals studied in the
points of direction dependence of UV irradiation from the bottom side or top side,
and position dependence at center or edge of a film are introduced. From these results,
the growing mechanism of needle-shaped crystals of 1c is discussed. The possibility
of controlling a photoisomerization and a crystallization by the plasmonic chip is
studied [42].
34.2 Cyclization by UV Irradiation on the Glass Slide
Photochromic cyclization from 1o to 1c and crystal growth of 1c were in situ observed
with an upright-inverted microscope (specially made XI71, Olympus) installing an
EM-CCD camera (Luca-r, Andor) and a switchable spectrometer (KNG-CLP-50,
Just Solution) on the upright side, and a halogen and a stabilized Xe lamps on the
inverted side [41, 43]. The observation and irradiation for cyclization were performed
under transmitted light from the inverted side. As an observation light, a yellow light
with ~0.2 mW using a halogen lamp and a long pass filter with cut-on wavelength
(λ cut-on ) of 500 nm were used. On the other hand, for irradiation light to cyclize 1o
with 1 mW, a stabilized Xe lamp and an NUA bandpass filter with a center wavelength
of 365 nm (bandwidth of 5 nm) were used, and for irradiation to reverse to 1o with
~200 mW, a stabilized Xe lamp and the long pass filter with λ cul-on of 500 nm were
used. The objectives of 40× and 10× were used for the upright side and inverted
side, respectively.
Figures 34.2 and 34.3 show the optical images and microscopic spectra, respectively. The mean intensities of transmitted light measured at two positions inside
and outside film shown in Fig. 34.2 were divided by the initial values of Fig. 34.2a,
individually, and they were converted to absorbance by Lambert–Beer law at the two
positions. Figures 34.2a and 34.3a show the optical image and spectra at initial state
of the diarylethene 1 films, which were prepared in the dark. As shown in the optical
image, a transparent film has no absorption of 1c (Fig. 34.3a). It suggests that the
initial state of a dialyrethene 1 films was 1o state and the state immediately converted
to 1c just after UV irradiation as found in Fig. 34.2b. The absorption peak shown at
~600 nm was assigned to the 1c (Fig. 34.3b).
The film thickness of the island-shaped film was evaluated as 7 ± 3 μm by an
absorbance of 1.4 (at wavelength of 600 nm) obtained from microscopic measurement. At 1 h after UV exposure, a needle-shaped crystal was found at the film edge
(Fig. 34.2c), and the absorbance at peak kept constant until 41 h. In previous studies,
randomly growth of needle-shaped crystals from the film surface was shown. Here,
the growth of most microcrystals was observed in the inplane radial direction from
the outline (edge) of island-shaped film. The high mobility of 1c is considered to be
essential for the molecular alignment and for the growth of crystals, and it can be
K. Tawa et al.
light and the reaction process was simultaneously observed with the upright-inverted
microscope, i.e., epi-illumination light, transmitted light, and confined light by the
plasmonic field were used for local photoisomerization of 1o and 1c, and optical
images were taken with CCD camera. The needle-shaped crystals studied in the
points of direction dependence of UV irradiation from the bottom side or top side,
and position dependence at center or edge of a film are introduced. From these results,
the growing mechanism of needle-shaped crystals of 1c is discussed. The possibility
of controlling a photoisomerization and a crystallization by the plasmonic chip is
studied [42].
34.2 Cyclization by UV Irradiation on the Glass Slide
Photochromic cyclization from 1o to 1c and crystal growth of 1c were in situ observed
with an upright-inverted microscope (specially made XI71, Olympus) installing an
EM-CCD camera (Luca-r, Andor) and a switchable spectrometer (KNG-CLP-50,
Just Solution) on the upright side, and a halogen and a stabilized Xe lamps on the
inverted side [41, 43]. The observation and irradiation for cyclization were performed
under transmitted light from the inverted side. As an observation light, a yellow light
with ~0.2 mW using a halogen lamp and a long pass filter with cut-on wavelength
(λ cut-on ) of 500 nm were used. On the other hand, for irradiation light to cyclize 1o
with 1 mW, a stabilized Xe lamp and an NUA bandpass filter with a center wavelength
of 365 nm (bandwidth of 5 nm) were used, and for irradiation to reverse to 1o with
~200 mW, a stabilized Xe lamp and the long pass filter with λ cul-on of 500 nm were
used. The objectives of 40× and 10× were used for the upright side and inverted
side, respectively.
Figures 34.2 and 34.3 show the optical images and microscopic spectra, respectively. The mean intensities of transmitted light measured at two positions inside
and outside film shown in Fig. 34.2 were divided by the initial values of Fig. 34.2a,
individually, and they were converted to absorbance by Lambert–Beer law at the two
positions. Figures 34.2a and 34.3a show the optical image and spectra at initial state
of the diarylethene 1 films, which were prepared in the dark. As shown in the optical
image, a transparent film has no absorption of 1c (Fig. 34.3a). It suggests that the
initial state of a dialyrethene 1 films was 1o state and the state immediately converted
to 1c just after UV irradiation as found in Fig. 34.2b. The absorption peak shown at
~600 nm was assigned to the 1c (Fig. 34.3b).
The film thickness of the island-shaped film was evaluated as 7 ± 3 μm by an
absorbance of 1.4 (at wavelength of 600 nm) obtained from microscopic measurement. At 1 h after UV exposure, a needle-shaped crystal was found at the film edge
(Fig. 34.2c), and the absorbance at peak kept constant until 41 h. In previous studies,
randomly growth of needle-shaped crystals from the film surface was shown. Here,
the growth of most microcrystals was observed in the inplane radial direction from
the outline (edge) of island-shaped film. The high mobility of 1c is considered to be
essential for the molecular alignment and for the growth of crystals, and it can be