SERS detection of anthraquinone dyes: Using solvothermal silver colloid as the substrate

Anthraquinone dyes have been widely used to color textile fibers since antiquity. Identification of the dyes can help us understand the dyeing processes and when and where the textiles were produced. Herein, we present a strategy based on surface-enhanced Raman scattering (SERS) with a novel silver colloid substrate for the detection of anthraquinone dyes. Quasi-spherical silver particles with different sizes were prepared by the solvothermal method and then characterized by transmission electron microscopy (TEM). The silver colloid substrates exhibited high-density hot spots with good reproducibility (RSDs of 3 ∼ 16 %) and high sensitivity. Among them, Ag-C2 (the molar ratio of AgNO₃ to PVP is 0.367, reacted for 2 h) was used to detect anthraquinone dyes in reference silk fibers as well as ancient textile samples due to the highest sensitivity and the low RSD (5.37 %) in this study. More importantly, Ag-C2 can be utilized to distinguish three madder species (Rubia tinctorum, Rubia cordifolia, and Rubia argyi) depending on the SERS intensity of alizarin and purpurin.