The discovery of free radicals in ancient silk textiles

Protection of ancient silk textiles from further deterioration is of vital importance to the investigation and preservation of ancient Chinese culture. Ancient silk textiles from several different ages (more than 2000 years ago) and regions were studied by means of Raman and electron paramagnetic resonance (EPR) spectroscopy in an attempt to unveil the deterioration mechanism of silk. The Raman spectra showed two peaks (D and G), which are indicative of carbonization. The EPR spectra of the ancient samples showed a characteristic sharp absorption centered at g∼2.0037 without a hyperfine structure, and have been identified as those of carbon radicals. These free radicals had not been discovered in ancient silk fabrics before, and the discovery may shed light on the deterioration mechanisms of ancient silk textiles.