Magnetic and conductive graphene papers toward thin layers of effective electromagnetic shielding

Graphene-based hybrids, specifically free-standing graphene-based hybrid papers, have recently attracted increasing attention in many communities for their great potential applications. As the most commonly used precursors for the preparation of graphene-based hybrids, electrically-insulating graphene oxides (GO) generally must be further chemically reduced or thermally annealed back to reduced GO (RGO) if high electrical conductivity is needed. However, various concerns are generated if the hybrid structures are sensitive to the treatments used to produce RGO. In this work, we develop a highly facile strategy to fabricate free-standing magnetic and conductive graphene-based hybrid papers. Electrically conductive graphene nanosheets (GNs) are used directly to grow Fe₃O₄ magnetic nanoparticles without additional chemical reduction or thermal annealing, thus completely avoiding the concerns in the utilisation of GO. The free-standing Fe₃O₄/GN papers are magnetic, electrically conductive and present sufficient magnetic shielding (>20 dB), making them promising for applications in the conductive magnetically-controlled switches. The shielding results suggest that the Fe₃O₄/GN papers of very small thickness (<0.3 mm) and light weight (∼0.78 g cm^-3) exhibit comparable shielding effectiveness to polymeric graphene-based composites of much larger thickness. Fundamental mechanisms for shielding performance and associated opportunities are discussed.