Study on Light Aging of Silk Fabric by Fourier Transform Infrared Spectroscopy and Principal Component Analysis

Abstract

Abstract To investigate environmental effect on cultural materials, Fourier transform infrared technique (FTIR/ATR) was applied to analyze the silk aging process. Changes in chemical and conformational structures of silk fabric undergoing ultraviolet induced degradation were investigated. The IR spectra provided strong bands of photosensitive amide I, II, and III. For overlapping amide III region, both of the original and second-derivative IR spectra revealed that UV irradiation induced the structural transformation from β-sheet domain to β-turn conformation, which was supported by the increase of β-turn marker band at 1015 cm−1 associated with polyglycine. Additionally the reduced bands associated with (GlyAla)n segment at 1000 and 976 cm−1, and the decreased band at 1070 cm−1 related to β-sheet structure also illustrated the conformational transition. Furthermore, we applied a chemometric method of principal component analysis for the evaluation of silk degradation based on variations in amide I spectral region. The score plot using the first two principal components effectively summarized the general trend of silk-aging and revealed the quick degradation appeared in the initial stages (12 h and 24 h) and the 108-hr stage. This work provides a potential novel application of the infrared spectroscopy in noninvasive qualitative and quantitative investigation of silk degradation. Keywords: DegradationFourier transform infrared spectrometryPrincipal component analysisSilk fabric Acknowledgments This work was supported by the National Natural Science Foundation of China (20975039), Yantai Science and Technology Bureau (2010145), and Science and Technology Commission of Shanghai Municipality (No.10dz2220500).