Naturally Derived Luminescent Material in Engineered Silk and Its Application as a Fluorescent Dye with a Large Stokes Shift and Sensing Capability.

Silkworms have provided valuable byproducts (spanning from high-quality textiles to health supplements) to humans for millennia. Despite their importance in sericultural economy and biotechnology, manifold possibilities inherent in the myriad natural or artificially generated silk varieties have been underestimated. In this paper, we report that the Yeonnokjam silk strain, which shows light-green color, contains quercetin fluorochrome (QueF) in sericin, and QueF can be used as a fluorescence dye with a large Stokes shift and high sensitivity to environmental temperature and pH, thus functioning as an environmental sensing material. A Stokes shift exceeding 180 nm, a quantum efficiency of 1.28%, and a rapid fluorescence decay of 0.67 ns are obtained, which are influenced by solvent polarities. Moreover, QueF can be used as a UV blocker as well, and its low cytotoxicity and biocompatibility further suggest promising prospects for diverse application in cosmetics and medical materials in the future.