Fluffy\nand Ordered Graphene Multilayer Films with Improved Electromagnetic\nInterference Shielding over X‑Band

Abstract

Highly\nordered nitrogen-doped graphene multilayer films with large interlayer\nvoid are successfully fabricated by thermal annealing of the compact\nstacking graphene oxide/copper phthalocyanine (GO/CuPc) multilayer\nfilms. Scanning electron microscopic (SEM), X-ray diffraction (XRD),\nRaman, X-ray photoelectron spectroscopic (XPS), and electrical conductivity\nmeasurements indicate that the breakaway of oxygen functional groups\non/in the GO sheets at high temperature and the in situ pyrolysis\nof CuPc molecules in the interlayer of graphene sheets synergistically\nfacilitate the restoration of GO in graphitization, the effective\nnitrogen doping by replacing carbon atoms in graphene frameworks,\nthe retention of layer-by-layer stacking structure of graphene sheets\nin plane, and the formation of interlayer voids, leading to the enhancement\nin the electrical conductivity (3.64 × 10³ S/m). In\naddition, due to the formation of a Fabry–Pérot resonance\ncavity in the unique layer-by-layer stacking structure with larger\ninterlayer voids, constructive interference of internal reflections\naligned between parallel reflecting planes endows the fluffy graphene\nmultilayer films with excellent electromagnetic interference (EMI)\nshielding effectiveness (exceeds 25 dB in all X-bands). The optimal\nshielding effectiveness is up to 55.2 dB with a smaller thickness\nof 0.47 mm, which makes it possible to become a practical EMI shielding\nmaterial with a distinct competitive advantage.