Terahertz spectroscopy can be utilized as an effective nondestructive identification tool for the study of artist's pigments. Consequently, extensive measurements have been conducted on representative pigment species, and a few terahertz spectral databases have been constructed. However, the reported spectra were often acquired from pigment samples mixed with polyethylene at room temperature with low resolution, which often led to low-quality spectra with unresolved overlapping lines further broadened due to thermal effects. Here, we present our study of vermilion (HgS, mercury sulfide) as an illustration of how we can overcome such difficulties by studying free-standing oil-paint samples at room temperature and then by performing low-temperature measurements on polyethylene-mixed samples to minimize line broadening due to thermal effects. Our results identify clearly resolved absorption peaks due to lattice vibrations of vermilion at 40.4, 44.5, and 89.9 cm −1 at 2 K. The temperature dependence of the peak shift and line broadening reveals anharmonic characteristics of these lattice vibrational modes. Our approach will definitely suggest new ways to improve and enhance existing terahertz spectral databases of ancient and modern pigments toward actual analysis, diagnosis, and conservation of heritage artworks.
This study interpreted the chemicals of the pigments and the coloring techniques employed on Youngsan Ritual Ceremony Buddhist Painting through a nondestructive analysis method and a microscopic observation. Based on the interpretation, this study closely examined the chemical properties of the names of the coloring materials specified on the ceremonial writing of the Buddhist painting. It is estimated that lead white was used for the white pigments, orpiment and organic pigment for the yellow pigment, cinnabar/vermilion, minium, red ochre, and red dyes for the red pigments, malachite or atacamite for the green pigments, azurite and indigo for the blue pigments, and ink stick for the black pigments. The pigment names specified on the ceremonial writing are juhong, jungcheong, hayeop, whangdan, and whanggeum, and it was verified that juhong is cinnabar or vermilion, jungcheong is azurite, hayeop is malachite or atacamite, whangdan is minium, and whanggeum is a gold foil.
Electron leakage is one of the most critical factors for the degradation of blue fluorescent organic light‐emitting diodes (FOLEDs), as it occurs when electrons injected from the cathode flow to an electron‐blocking layer (EBL) without being entirely consumed within an emissive layer (EML). To address this issue, this study introduces the concept of an electron leakage‐pathway (ELP). Anthracene core materials, used as hosts for blue FOLEDs were doped in the EBL to prevent its direct damage to the EBL molecules by constructing the ELP. This study shows that using an anthracene core with high bond dissociation energy (BDE) in the anionic state as the ELP is the most effective way to increase the lifetime of the FOLED, demonstrating over 400 h. of LT90 (the time taken for the luminance to decrease to 90% of its initial value), which corresponds to an increase of 33% compared to the lifetime without the ELP. Remarkably, under a commonly used brightness level of 500 cd m−2 in smartphones, an LT50 of over 10 000 h was obtained. Ultimately, this study outlines a strategy for increasing the lifetime of blue FOLEDs through simple modifications to the device structure, without requiring the development of EBL materials or complex device engineering.
We estimated pigments and painting techniques with nondestructive analysis for Yu Eonho's portrait made in the eighteenth century, then compared with 11 portraits and painting characteristics at that time. The pigments used to Yu Eon-ho's portrait include lead white, yellow dye, cinnabar, minium, and pink dye, malachite, azurite, iron oxide red and brown dye, blue and pink dye for purple. In the result compared with painted pigments of 11 portraits, iron oxide red without cinnabar was used on the face part and organic green dye only was used instead of inorganic pigments on the other side of clothing after Yu Eonho's portraits portrait. This study is show the painting techniques on the portraits in the late 18 th century. We expect to use as useful referencing data for the study on the coloring technique of a portrait in the late Joseon Dynasty.
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