Ferulic acid promoted in-situ generation of AgNPs@silk as functional colorants

Abstract

A rapid, green and simple procedure for the in-situ generation of AgNPs@silk as functional colorant is described herein. Silver (Ag+) ions were first diffused into the silk fabric matrix by soaking into aqueous AgNO3 solution, subsequently, alcoholic solution of ferulic acid, a natural polyphenol, was added as an eco-friendly reductant for the generation of AgNPs@silk. The formation of AgNPs was confirmed by visible color changes and UV–visible absorption spectra. The residual AgNPs solution was characterized via UV–visible spectroscopy, TEM and DLS. The UV–visible spectra and TEM analyses confirmed the formation of more or less spherical well-dispersed AgNPs. The AgNPs@silk was characterized by SEM, EDS, XRD, XPS and FTIR. The Ag content of AgNPs@silk was determined by nitric acid digestion followed by ICP-OES. The color, antibacterial and UV protection characteristics of AgNPs@silk were also evaluated. AgNPs@silk produced a beautiful color pallete ranging from light creamish brown to dark golden brown. The AgNPs treated silk exhibited outstanding antibacterial activity (>99% bacterial reduction) and excellent laundering durability, where it inhibited >94% of E. coli even after 10 washing cycles. Moreover, AgNPs@silk was highly effective blocking of UV radiation in both UVA and UVB regions, and thus offered excellent UV protection.