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Spectral measurement of organic crystals, powders and solids

The absorption spectra of organic crystals, powder samples, and solids can be easily measured. (However, it is limited to organic.) Normally, for powder samples, the spectrum measured by the diffuse reflection method is converted in Kubelka-Munk to obtain an absorption spectrum. However, if the same molecule, which has crystal polymorphism and is different in color, is ground with another diluent, the targeted spectrum may not be obtained by itself. With Optical Waveguide Spectroscopy, however, the spectrum is obtained by rubbing a very small amount of sample on the waveguide with a spatula without diluting. Since it is not diluted, the sample can be recovered 100% as it is.

Fig11. Differences in the spectra of organic crystals due to differences in molecules. Quoted from Y. Simada, et al., Dyes Pigm., 121,336(2015)

52. “UV-vis Absorption Spectra of Powdered Materials :Direct Measurements by Optical Waveguide Spectroscopy” Keiichiro Ogawa, Jun Harada, Toshikatsu Fujiwara and Hiromi Takahashi, Chem. Lett., 33, 11, 1446 (2004).

53. “Crystal Structure of Light-Induced Colored Species from Photochromic Dimer of 1,4-Bisimidazolyl-tetrafluorobenzen” Azusa Kikuchi and Jiro Abe, Chem. Lett., 34, 11, 1552 (2005).

54. “J-aggregate structure in a chloroform solvate of a 2,3-dicyanopyrazine dye -Separation of two dimensional stacking dye layers by solvate formation” Shinya Matsumoto, Emi Babamoto, Ryohei Eto, Saori Sato, Takashi Kobayashi, Hiroyoshi Naito, Motoo Shiro, Hiromi Takahashi, Dyes Pigm., 95, 431 (2012).

55. “Unexpected photochemical debenzylation of 2,5-bis(dibenzylamino)-3,6-dichloro-

p-benzoquinone” Yuta Shimada, Emi Horiguchi-Babamoto, and Shinya Matsumoto, Dyes Pigm., 121, 336 (2015).

56. “ Optical properties of three differently colored crystal modifications of a 2,3-dicyanopyrazine dye” Naoya Okada, Ryohei Eto, Emi Horiguchi-Babamoto, Takashi Kobayashi, Hiroyoshi Naito, Motoo Shiro , Hiromi Takahashi, and Sinya Matsumoto, Bull. Chem. Soc. Jpn., 88, 716 (2015).