title: Quantitative analysis for a color-change of humidity indicator by microscopic absorption spectrometry.
abstract: A sensitive and easily distinguishable cobalt-free humidity indicator of porphyrin-silica gel-MgCl(2) composite was prepared from pH-induced spectra changeable tetraarylporphyrin, silica gel (SiO(2)), and MgCl(2). The pH change arose from proton release under dry conditions, and proton capture under humid conditions by a reversible reaction between MgCl(2) and a silanol group of SiO(2). A pink-orange porphyrin-Si(OH)(2)-MgCl(2) composite was dried to give a green protonated porphyrin-SiO(2)Mg composite. The optimized concentrations of MgCl(2) to make the concentrations of protonated porphyrin maximum under dry conditions were determined by absorption spectrometry of the green composite using a confocal laser scanning microscope as a microscopic spectrometer. Moreover, the green composite was prepared by heating dichloro(tetraarylporphyrinato)phosphorus chloride with MgCl(2) and SiO(2). The humidity-sensitivity of the green composite was evaluated by the absorption spectra under controlled humidity. A distinguishable color change of the green composite took place below 30% of relative humidity.
authors.affiliation: Technical Center, Faculty of Engineering, University of Miyazaki, Gakuen-Kibanadai, Miyazaki 889-2192, Japan. t-matsu@cc.miyazaki-u.ac.jp
authors.forename: Tomoko
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Yoko
authors.initials: Y
authors.lastname: Mitsumura
authors.forename: Miyuki
authors.initials: M
authors.lastname: Miyamoto
authors.forename: Jin
authors.initials: J
authors.lastname: Matsumoto
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Shiragami
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Fueda
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nobuhara
authors.forename: Masahide
authors.initials: M
authors.lastname: Yasuda