G. Chen et al.: Intercalation of rhodamine 6G and oxazine 4 into oriented clay films and their alignment
H-aggregate was calculated to be 52° to LiHT–Ox4 hy-
brid film. In the powder XRD profile, only 1 sharp dif-
fraction peak at 2 ס
4.5° between 2° and 10° suggests
the tilted angle of Ox4 is 47°. Thus, this diffraction peak
mainly results from the oriented high-order H-aggregate
for Ox4 in the LiHT–Ox4 hybrid.
IV. CONCLUSIONS
Two or more states of dyes (monomer, dimer, and
higher-order aggregate) were observed in LiHT-dye hy-
brid films. Based on polarized UV-vis spectroscopy and
XRD, orientations of the monomer, dimer, and higher-
order H-aggregate of R6G and Ox4 in oriented LiHT-dye
hybrid films could be quantitatively clarified. Polarized
UV-vis spectroscopy showed that the high-order H-
aggregates of R6G oriented at 64° and Ox4 at 52° against
silicate layers. Other states of dyes were assumed to be
oriented at 36° or almost randomly on the surface of
LiHT and/or in the interlayer. In both hybrids, the ori-
entation of the higher-order H-aggregate agreed well
with the interlayer distance derived from powder XRD.
This implies that the interlayer distance is mainly deter-
mined by the dimension of the high-order H-aggregate in
the interlayer space.
ACKNOWLEDGMENTS
We thank Professor Dr. Fernando López Arbeloa of
Universidad del Pais Vasco in Bilbao (Spain) for his
suggestions about dye aggregation states, and the Japan
International Science and Technology Exchange Center/
Japan Science and Technology Corporation (JISTEC/
JST) for a Science and Technology Agency (STA)
Fellowship.
FIG. 7. Dependence of incident angle ␣ on dichroic ratios R of LiHT–
dye hybrid films.
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H-aggregate, the absorption band at 461 nm in Fig. 5(a)
intensifies with angle ␣ under Y-pol light, indicating the
higher-order H-aggregate of R6G may have a preferred
orientation in the hybrid film. By least-square fitting of
Eq. (3) to experimental data [Fig.7(a)], angle ␥ was cal-
culated to be about 26°, so the tilted angle of the R6G
high-order H-aggregate (⌰) equals 64°, in good agree-
ment with the value obtained by XRD (60°). The small
discrepancy of 4° may be due to other R6G states in the
interlayer space oriented at a lower angle.
For LiHT-Ox4, absorption intensities of bands at ס
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showed that the angle was 32°. Absorption at 488 nm
ascribed to the higher-order H-aggregate of Ox4 gradu-
ally became intense. The orientation of the higher-order
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