A dual-mode strategy combining SERS with MALDI FTICR MS based on core-shell silver nanoparticles for dye identification and semi-quantification in unearthed silks from Tang Dynasty.

Silk, as one of the representative artifacts of China, profoundly affects the communication between eastern and western civilizations, and dyes, as the color support of silks, reflected crucial historical, cultural and technological information. Surface enhanced Raman spectroscopy (SERS) characterized by vibrational information has been extensively employed in dye analysis. However, since natural plants with complex coloring compositions in ancient China were broadly applied in dying textiles, the existing SERS methods often misinterpret results in dye analysis. Besides, semi-quantification of each component was of great difficulty by SERS, limiting the exquisite comparative analyses of different historical samples. For the first time, a dual-mode strategy combining SERS with high mass resolution MALDI FTICR MS was developed in virtue of core-shell silver nanoparticles (AgNPs@PDA), which realized the precise identification and semi-quantification of complex dye mixtures, thus significantly improving the accuracy and applicability of traditional SERS method. Four typical dye components (alizarin, purpurin, berberine and indigo) have been identified and semi-quantified in unearthed dyed silks from Tang Dynasty based on the method. More interestingly, multiple dye components with different contents and their ratio could be precisely determined, which might help in further investigating their dyeing techniques. This dual-mode strategy represents a promising tool for providing solid support for cognition, evaluation and restoration of textile objects in museums and conservation centers.