Green approach for the fabrication of silver-oxidized cellulose nanocomposite with antibacterial properties

Herein we present facile and green two-steps method for the fabrication of silver-carboxylated nanocellulose (Ag-ONCs) nanocomposite. Respecting the Circular Economy principle, the ONCs are prepared starting from the treatment of agriculture bagasse waste with ammonium persulfate--APS. This method permits to obtain ONCs fibers with rod or whisker shapes, with size and length in the range 6-10 nm and 90-150 nm, respectively. Ag-ONCs are then fabricated using a green photochemical approach. The UV irradiation works as radical initiator for the silver reduction, in water solution and at room temperature. The ONCs act as a template and reducing agent for silver nanoparticles formation, due to the specific hydroxyl and carboxyl groups on the cellulose surface. The structural and morphological properties of ONCs and Ag-ONCs nanocomposite are well evaluated by FT-IR, XRD, UV-Vis, AFM, SEM and TEM characterizations. The results showed that well crystalline, quasi-spherical silver nanoparticles of about 4-10 nm dispersed in the ONCs matrix are fabricated. Qualitative antibacterial tests towards gram negative (Escherichia coli and Pseudomonas aeruginosa) and gram positive (Staphylococcus aureus and Bacillus subtilis) bacteria are carried out and the results demonstrated that the Ag-ONCs inhibit the bacteria growth, with 12-14 mm of inhibition zone for both the bacteria groups. Also, quantitative antibacterial tests for E. coli, chosen as representative for its diffusion, are carried out and the bacteria growth rate and the inhibition rate for Ag-ONCs at different concentrations are evaluated. The analysis showed that the MIC (minimum inhibition concentration) for Ag is about 110 µg/mL for E. coli. These results demonstrated that the Ag-ONCs possess suitable and promising antibacterial behavior and could be used for industrial and technological application.