Green technology for durable finishing of viscose fibers via self-formation of AuNPs

•Finished viscose fibers were achieved by in-situ synthesis of AuNPs using green technique.•AuNPs were directly incorporated into viscose matrix via employing cellulosic functional groups.•Accoridng to LSPR of AuNPs, fibers aquired violet color with excellent fastness.•After 24 h incubation, Au-treated fibers exhibit good antimicrobial action.•The current technique can be easily adapted to the existing textile machinery for fibers finishing.

Sensitivity of dyes' colors to the surrounding environment causes lower durability and stability of color, which reflects the importance of durable finishing treatment. Current technique offered antimicrobial/durable finishing of viscose fibers through direct formation of AuNPs inside fibers macromolecules without using any external agents. By using the reducing properties of cellulose in viscose, Au+3 was reduced to AuNPs and CHO/OH of cellulose subsequently were oxidized to COOH. For comparison, two different media were used; aqueous and alkaline. Increasing the reactivity and accessibility of cellulose macromolecules in alkali leaded to enlargement of the reduction process and more incorporation of AuNPs. Size of AuNPs inside fiber was recorded to be in range of 22-112 nm and 14-100 nm, in case of using aqueous and alkaline medium, respectively. Structure and properties of fibers were not changed by treatment according to XRD and ATR-FTIR data. The treated fibers were acquired durable violet color by the action of LSPR for AuNPs and darker color obtained using higher Au+3 concentration. The treated fibers exhibited good inhibition against different pathogenic microbes including bacteria and fungi. One-pot, quite simple, inexpensive, green and industrial viable are the significant advantages of the current technique for viscose finishing (pigmentation and antimicrobial action).