Antibacterial hybrid materials fabricated by nanocoating of microfibril bundles of cellulose substance with titania/chitosan/silver-nanoparticle composite films

Uniform ultrathin titania/chitosan composite films were coated on the cellulose microfibril bundles of natural cellulose substance (common commercial filter paper) by a layer-by-layer self-assembly process. Relying on the strong chelating ability of chitosan for metal ions, silver ions were abundantly adsorbed on the titania/chitosan composite film coated cellulose substance and were thereafter in situ reduced to silver nanoparticles (Ag-NPs) under UV irradiation. As such, hybrid cellulose/titania/chitosan/Ag-NP composite materials were obtained, which feature the same hierarchically fibrous structure as the initial cellulose substance. Meanwhile, the hybrid fibres in the composite materials exhibit a cable-like core-shell structure, displaying a cellulose microfibril bundle core as well as a nanometer-thick titania/chitosan/Ag-NP composite film shell with Ag-NPs (4-20 nm in diameter) well distributed. The antibacterial activities of the titania/chitosan/Ag-NP composite film coated cellulose materials were evaluated against both Gram-positive and Gram-negative bacteria, and the materials as such disinfected almost all the inoculated bacteria due to the intrinsic biocidal effect of titania composition, positively charged chitosan component and high loading content of Ag-NPs with small sizes, showing excellent antibacterial activities.