Nanocellulose from coconut midrib used for antibacterial and electromagnetic interference shielding applications†

Midrib of coconut (Cocos nucifera) is a natural source of cellulose, which is renewable and biodegradable. The use of natural cellulose for practical applications exemplifies a sustainable reuse of agricultural waste. This work presents the preparation of nanocellulose from coconut midrib using optimized pretreatment and acid hydrolysis processes. The resulting nanocellulose was characterized through various analyses to confirm the morphology and composition. Nanocellulose thus synthesized was used for preparing cellulose nanopaper. In order to improve the water resistance of the cellulose nanopaper, we used a simple approach of functionalization by impregnating it with chitosan (CS), followed by in situ polymerization of polypyrrole (PPy) in the matrix. The functionalized cellulose nanopaper shows good electrical conductivity and an electromagnetic interference (EMI) shielding effectiveness of 21.92 dB at 10 GHz, which makes it a potential material for EMI shielding applications. In addition, the functionalized cellulose nanopaper exhibits bacterial reductions of 93.47% and 82.79% towards Staphylococcus aureus and Escherichia coli, respectively. This work provides a facile and efficient method for the synthesis of nanocellulose from coconut midrib and a useful approach to functionalize cellulose nanopaper. Cellulose nanopapers thus prepared were demonstrated to have applications in EMI shielding and antibacterial coating.