Controlled in-situ synthesis of silver nanoparticles in natural cellulose fibers toward highly efficient antimicrobial materials.

In this report, we presented in-situ synthesis of silver nanoparticles in natural cellulose fibers which embody high oxygen (ether and hydroxyl) density and could be considered as aggregated nanoreactors and stabilizers for the nucleation and growth of silver nanoparticles. The morphologies of natural cellulose fibers and silver nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-visible spectroscopy. The content of silver nanoparticles in cellulose fibers was measured by inductive coupled plasma-mass spectrometry (ICP-ms). Experimental results revealed that sodium borohydride (NaBH4) played dual effects in the formation of silver nanoparticles. The mean size (d) and size distribution (sigma) of silver nanoparticles could be adjusted by changing the concentration of NaBH4. Monodisperse silver nanoparticles (d = 2.7 nm, sigma = 0.6 nm) in cellulose fibers were successfully prepared under optimized conditions. When the NaBH4 concentration was very low (0.1 mM), a stable colloidal solution (storage stability > 1 month) of silver nanoparticles was produced, which provides a novel, mild approach to the preparation of stable colloidal solutions of metal nanoparticles. The ability of silver nanoparticle-loaded cellulose fibers to prohibit the propagation of Escherichia coli was estimated by the Minimum Inhibitory Concentration (MIC). Based on the experimental observations, the antibacterial mode of silver nanoparticle-loaded cellulose fibers was discussed in details.