Colloidal silver nanoparticles: an effective nano-filler material to prevent fungal proliferation in bamboo

Silver nanoparticles (Ag-NPs) have attracted attention as a promising nano-filler material for reinforcement and anti-bacterial effect in polymers and composites. In this work bamboo samples, Dendrocalamus Giganteus Munro, were impregnated using a colloidal solution of homemade Ag-NPs with the goal of improving its resistance to attacks by fungi. X-ray microtomography (mu CT) was performed to investigate the 3D distribution of Ag-NPs within the biological matrix. 3D image reconstruction showed silver clusters distributed within the parenchymatic tissue. Quantitative information of the Ag-NPs agglomerate population was computed. Ag-NPs were characterized by UV-VIS, SERS, ICP-MS, TSEM, DLS and zeta potential analysis. The antimicrobial activity of homemade and commercial citrate-capped silver nanoparticles was evaluated against the Aspergillus niger fungus. Homemade nanoparticles (NP-01), presenting the smallest diameter (14.3 +/- 3.6 nm), and the highest particle concentration (1.25 x 10(11) particles per mL) were able to inhibit 53% of Aspergillus niger growth in a concentration of 2.00 mg L-1. Both engineered biocomposite material and untreated specimens were exposed to air and humidity. After five months the treated samples were free of fungal colonies, while colonization by the fungal hyphae was present on untreated bamboo specimens.