With the washing times increased, the silver content slightly decreased from 98.65 see more to 81.65 mg/kg while the corresponding whiteness increased. It is surprising that the antibacterial rate is still more than 97.43% for S. aureus and 99.86% for E. coli after 50 washings. Table 3 The WI, silver content, and antibacterial rate of different washing times Silk samples Laundering cycles Silver content (mg/kg) WI Antibacterial activities   S. aureus E. coli   Surviving cells (CFU/ml) % reduction Surviving cells (CFU/ml) % reduction Untreated – - 90.79 2.28 × 106 – 4.37 × 106 – Silver-treated

fabrics – 98.65 86.32 1.16 × 103 99.49 8.74 × 102 99.98 5 95.02 86.43 3.44 × 103 98.49 1.74 × 103 99.96 10 88.85 87.13 1.28 × 103 99.49 6.11 × 103 99.86 20 87.14 87.58 2.53 × 103 SAHA HDAC order 98.89 1.48 × 103 99.96   50 81.65 87.71 5.86 × 103 97.43 6.11 × 103 99.86 The excellent laundering durability of the silver nanoparticle-treated silk fabrics may be caused by the following this website reasons. Firstly, some imino groups of RSD-NH2 form a silver ammonia complex with silver nanoparticles, which easily penetrate into the amorphous zone of silk fibers. Secondly, silk is a protein fiber and amino acid is its basic structural unit, which has a large number of amino and carboxyl groups on the surface. The van der Waals force between molecules, as well as the hydrogen bond, will enhance the bonding between silver particles

and silk fabrics [20]. The surface morphology of the original silk fabric and the silver nanoparticle-treated silk fabrics is compared in Figure  7. The synthesis condition of the silver nanoparticles is the mixture of 50 mg/l AgNO3 and 2 g/l RSD-NH2 solution. The scanning electron microscope images showed that silver nanoparticles

distributed evenly on the surface of the silver nanoparticle-treated fabric. As the silver nanoparticle-treated silk fabric has good washing properties, silver nanoparticles can be found on the surface of the treated fabric even after washing for 50 times. Also, the K/S value indicates the presence of silver on the silk fabric. As shown in Figure  8, the obvious absorption peaks between 400- and 420-nm wavelength appeared in curves, which is consistent Phosphatidylethanolamine N-methyltransferase with the absorption peak of the silver nanoparticle solution [21]. Thus, we can deduce that there are indeed nanosilver particles on the surface of the silver-treated silk fabrics. Figure 7 SEM images of the surface of the silk fabrics. (a) Original silk fabric. (b) Nanosilver-treated silk fabric. (c) Nanosilver-treated silk fabric after washing for 50 times. Figure 8 K/S spectrum of silver nanoparticle-treated silk fabrics. Conclusions A silver nanoparticle solution was prepared in one step by mixing AgNO3 and RSD-NH2 solution under vigorous stirring at room temperature. The multi-amino compound (RSD-NH2), which has abundant amino and imino groups, was synthesized by methacrylate and polyethylene polyamine in methanol.