title: Photostability enhancement of anionic natural dye by intercalation into hydrotalcite.
abstract: The aim of this study is the improvement of the photostability of several natural anionic dyes, carmine (CM), carthamus yellow (CY), and annatto dye (ANA), by complexation with hydrotalcite. The composite of the dyes and hydrotalcite is prepared by the coprecipitation method. CM is successfully intercalated in the hydrotalcite layer when the amount of introduced CM is large. The photostability of CM in CM/HT composites is superior to the CM adsorbed on silica surface. The effect of the stability enhancement is larger when the amount of introduced CM exceeds 0.23 g/g-host, or when the layer charge density of the hydrotalcite is larger. CY is also stabilized by complexation with hydrotalcite, whereas ANA is not stabilized by complexation with hydrotalcite. The photostability of an anionic natural dye can be improved by intercalation into the hydrotalcite layer, if the dye has a hydrophilic nature and a rather planar structure. The intercalated dye is stabilized by the protection from the attack of the atmospheric oxygen. In addition, contribution of the electrostatic interaction between the positively charged hydrotalcite layer and the intercalated anionic dye is also proposed.
authors.affiliation: Department of Materials Science and Chemical Engineering, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan. tykouno@ipc.shizuoka.ac.jp
authors.forename: Yoshiumi
authors.initials: Y
authors.lastname: Kohno
authors.forename: Koichi
authors.initials: K
authors.lastname: Totsuka
authors.forename: Shuji
authors.initials: S
authors.lastname: Ikoma
authors.forename: Keiko
authors.initials: K
authors.lastname: Yoda
authors.forename: Masashi
authors.initials: M
authors.lastname: Shibata
authors.forename: Ryoka
authors.initials: R
authors.lastname: Matsushima
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Tomita
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Maeda
authors.forename: Kenkichiro
authors.initials: K
authors.lastname: Kobayashi
mesh_terms: D000536:Aluminum Hydroxide / Q000737:chemistry*; D000838:Anions; D004396:Coloring Agents / Q000737:chemistry*; D007364:Intercalating Agents / Q000737:chemistry*; D008027:Light; D008276:Magnesium Hydroxide / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000838:Anions; D004396:Coloring Agents; D007364:Intercalating Agents; C010467:hydrotalcite; D000536:Aluminum Hydroxide; D008276:Magnesium Hydroxide