Observation of luminescent gold nanoclusters using one-step syntheses from wool keratin and silk fibroin effect

Highly fluorescent, water-soluble and green Au nanoclusters (AuNCs) have been synthesized by one-step method with wool keratin as reducer and silk fibrion as stabilizer. Understanding of AuNCs syntheses mechanism and luminescent property is essential for the syntheses of biocompatible AuNCs. This report demonstrates the thiol groups’ dependent syntheses with wool keratin (WK) and silk fibroin (SF) solution with different component ratios. Significantly, it was found that the percentage of SF was critical in determining the size of AuNCs. Interestingly, the fibrils of SF, which is made of stick shaped β sheet crystals, contributes to the cage of AuNCs, while the WK dedicates the thiol groups to synthesize WK@AuNCs. Using the transmission electron microscopy, we show that the WK&SF@AuNCs can grow due to the degradation of protein or particle coalescence from the electron beam irradiation. Through the combination of these two processes, the dynamic growth of nanocrystals involves the variation of Au nanocrystals with a bimodal distribution.