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Nankawa, Takuya; Sekine, Yurina; Matsumura, Daiju; Hiroi, Kosuke; Takata, Shinichi; Kamiya, Yoshimi*; Honda, Takayuki*
Langmuir, 40(11), p.5725 - 5730, 2024/03
Times Cited Count：0 Percentile：0(Chemistry, Multidisciplinary)The chemical reaction between Fe and lacquer has been used to create the black color lacquer since ancient times. Here, the chemical state of Fe ions in black lacquer was investigated by using X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and Fourier transform-infrared (FT-IR) spectroscopy. Fe(II) or Fe(III) was added to the lacquer paste to prepare black lacquer films by air drying, heating, or UV irradiation. The XANES spectral features of all the film samples were similar, meaning that the Fe ions in the samples existed in the trivalent state regardless of the oxidation state of the initially added Fe. The corresponding Fourier transforms of the EXAFS spectra around the Fe K-edge were used to investigate Fe sites in the lacquer films. The spectra of all the film samples were similar shapes, but the peak intensities decreased in the order air dried 
heated UV irradiated films. This result indicates that heating and UV irradiation made the coordination structure of Fe in the lacquer non-uniform, and that heating caused the greatest non-uniformity. The complementary use of XANES, XAFS, and FT-IR spectroscopy is highly effective for non-destructive analysis of black lacquer in precious cultural artifacts.
Nankawa, Takuya
no journal, ,
Urushi, the main component of which is urushiol, is a natural lacquer polymer which has unique characteristics, including high water resistance, chemical resistance, and antibacterial propertiesl. Since ancient times, lacquer has often been used not only in its original brown color, but also in shades such as black and vermilion. Black lacquer is traditionally produced by adding iron to lacquer, but the reaction mechanism both raw and black lacquer (Kiurushi and Kurourushi, respectively) is largely unknown even today. In this study, we investigated the structure of them in order to develop a new coating material that has high durability and antibacterial properties by mimicking urushi coating using various measurement methods (FT-IR, XANES, EXAFS, SAXS, SANS). As a result, the addition of iron ions is thought to catalyze the polymerization and blackening of urushiol using iron as a catalyst, as well as the arrangement of the iron core to form the structure of the lacquer. This is the first observation that the polymer network structure is completely different between raw lacquer and black lacquer, and the structural changes of black lacquer during UV irradiation and heating were also investigated in the same way. It was indicated that the physical properties of the lacquer film could be controlled by controlling the formation reaction of the lacquer film.
