Crosslinked pectin nanofibers with well-dispersed Ag nanoparticles: Preparation and characterization

Nanofibers with well-dispersed Ag nanoparticles (AgNPs) are promising for some applications. Dispersion electrospinning is a straightforward preparation method but is suffered from the negative effects that the further treatments of nanofibers after electrospinning may bring to the dispersed AgNPs. In this study, we report a post reduction method to fabricate nanofibers with well-dispersed AgNPs. Crosslinked nanofibers of a hydrophilic polysaccharide, pectin, are used. When being immersed in the aqueous solution of AgNO₃, the crosslinked pectin nanofibers swell, allowing Ag⁺ ions enter inside. The surrounding crosslinked pectin macromolecules functionalize as in situ reducing reagents to reduce Ag⁺ ions, nucleating the crystallization of AgNPs locally. X-ray diffraction characterizations indicate that the formed AgNPs are face-centered cubic crystalline. Results of optical imaging, UV-vis spectroscopy, scanning electron microscopy (SEM), electron dispersive spectrometry as well as transmission electron microscopy (TEM) indicate that the content and size of AgNPs increase with the increase of AgNO₃ concentration and incubation time. SEM and TEM results show that the dispersion of the AgNPs does not affect the nanofibrous structure and size of the crosslinked pectin nanofibers. TEM results also demonstrate that AgNPs distribute homogeneously along both the length and diameter direction of nanofibers. The composite nanofibers can sustainably release silver for 4 weeks and inhibit the growth of Escherichia coli for 7 days, showing great potential as long-term antibacterial materials. The method may also be used to disperse AgNPs in other hydrophilic nanofibers which need further treatments after electrospinning.