Integrated strength and toughness in graphene/calcium alginate films for highly efficient electromagnetic interference shielding

Abstract

Graphene films are considered promising electromagnetic interference (EMI) shielding materials in view of high electrical conductivity, light weight, and flexibility. Nevertheless, pristine graphene films exhibit only modest mechanical performance because of the weak interfaces between graphene nanosheets. We have developed an advanced graphene film that integrates excellent EMI shielding performance with improved mechanical performance, by intercalating calcium alginate (CA) molecules into reduced graphene oxide (rGO) nanosheets. The rGO/CA film exhibits an EMI shielding effectiveness (EMI SE) of 25.7 dB at only 12 μm thickness, and the corresponding specific EMI SE is 2142 dB mm⁻¹, which is far superior to previously reported EMI shielding materials. Importantly, the rGO/CA film achieves an excellent tensile strength of 118.0 MPa and a toughness of 4.6 MJ m⁻³, which is 102% and 130% higher than those of the rGO film. Such significant enhancement is attributed to the synergistic interfacial interactions of hydrogen bonding between CA and rGO nanosheets and ionic bonding between calcium ions and rGO nanosheets. Moreover, the rGO/CA film shows a high EMI shielding reliability (96% EMI SE retention even after 5000 folding cycles). Its features make the rGO/CA film highly attractive for EMI shielding applications, especially in aircraft, aerospace, and next-generation flexible electronics.