关键词: 丝织品, 清洗, 红外光谱, 二级结构, 稳定同位素

Abstract: Silk fabrics have a long history in China. They are also an important part of Chinese civilization. Silk fabrics are natural polymer compounds, which are easily damaged by light, temperature, humidity, microorganisms and so on. It is different to preserve cultural relics permanently. Therefore, studies on the protection of ancient silk are particularly crucial. Among them, the origin of ancient silk has always been hotly discussed. As a new technology in modern ecological research, stable isotope technique has become a powerful tool for the traceability of silk fabrics with its advantages of tracing, indication, fast detection and accurate results. During the preservation process of ancient silk, the original pollutants may cause significant changes in the structure and isotopic information of silk fabrics, thereby affecting the accuracy of provenance tracing. Therefore, in order to use isotope technology to trace the origin of ancient silk, it is necessary to figure out how the isotopic information of silk has changed during the cleaning process,.
To explore the influence of cleaning treatment on the morphology, structure, and stable isotope of the ancient silk from the Ming Dynasty, silk fabric samples were simply cleaned by four gentle cleaning methods (deionized water cleaning, ethyl alcohol cleaning, deionized water/ethyl alcohol cleaning, and steam cleaning). The surface morphology, structure and stable isotope ratios of silk samples before and after cleaning were examined by using scanning electron microscope (SEM), fourier transform infrared spectrometer (FTIR), thermal gravimetric analyzer (TGA) and isotope mass spectrometer. The results indicate that deionized water and ethyl alcohol had certain cleaning effects, while steam cleaning caused secondary pollution on the surface of the silk, requiring further removal of contaminants. The relative content of β-sheet in the fibroin decreases after steam cleaning. After cleaning treatment, the hydrogen stable isotope ratio of silk samples decreased, the oxygen stable isotope ratio increased, the carbon stable isotope ratio had little change within 0.30‰, while the variation of nitrogen stable isotope ratio showed no clear appearance. The research results provide certain reference for eliminating external interference and conducting data correction in tracing the origin of ancient silk. 

Key words: silk fabric, cleaning, FTIR, secondary structure, stable isotope