Microwave electromagnetic shielding with free-standing composites based on graphene oxide and silver nanowires

With the growing penetration of microwave applications in modern society, exposure to electromagnetic waves (EMWs) may become an important public health problem. In addition, the coexistence of radio-frequency (RF) devices and systems induces Electromagnetic Interference (EMI) leading to electromagnetic perturbations and lifetime reduction. Consequently, shielding materials capable of blocking EMWs are highly required. In this paper, composite materials using graphene oxide (GO) and silver nanowires (AgNWs) were studied as potential EMW shielding materials. Both GO and AgNWs were synthesized and used to obtain GO-AgNWs composites with different mass ratios of GO and AgNWs (from 1:9 to 3:1, respectively). The sheet size of GO was between 150 and 2000 nm and the thicknesses of flakes in the range of 2-5 nm. UV-Vis spectroscopy proved the successful production of AgNWs and the establishing interaction of NWs with GO sheets in the produced composites. The changes in the surface hydrophilicity/hydrophobicity showed that the selected eco-friendly reduction with ascorbic acid as a reducing agent was efficient in inducing the lowering in the hydrophilicity of the GO surface, while in the case of reduced GO (rGO) functionalized with AgNWs, the contact angle was 73.6 degrees which between rGO and GO due to AgNWs hydrophilic character. The average thickness of free-standing films was around 14.8 mu m. We studied the ratio between these nanomaterials to modulate shielding efficiency in a broad microwave frequency of up to 18 GHz. The shielding efficiency of around 6.5 dB was measured for the rGO free-standing film.