Electroless deposition of silver nanoparticles on cellulose nanofibrils for electromagnetic interference shielding films

High-efficient electromagnetic interference (EMI) shielding films were successfully fabricated by electroless deposition of silver nanoparticles (AgNPs) on polydopamine (PDA) functionalized cellulose nanofibrils (CNFs) as building blocks according to a pressured-extrusion film-forming process. PDA was first functionalized on CNFs by oxidative self-polymerization of dopamine (DA) to synthesize CNFs@PDA, on which AgNPs were electrolessly deposited. The obtained CNFs@PDA@AgNPs composite films served as tightly-connected conductive network, so as to significantly improve the whole electrical conductivity of the EMI shielding films. Utilizing CNFs as green and soft matrix, the fabricated CNFs@PDA@AgNPs EMI films show an outstanding mechanical enduring performance. The CNFs@PDA@AgNPs films with weight ratios of CNFs:AgNO3 = 1:24 exhibited superb electrical conductivity of 1,000,000 S m-1 and remarkable EMI shielding effectiveness of 93.8 dB at 8.2 GHz in X band. This work provides a simple methodology to achieve surface metallization of insulating fibers to supersede traditional metals for highly efficient EMI shielding applications.