Reduced graphene oxide/zinc oxide coated wearable electrically conductive cotton textile for high microwave absorption

Abstract

Due to intensive development in smart electronics and energy devices, wearable electromagnetic interference (EMI) shielding materials such as conducting textiles have emerged to protect human as well as sensitive electronics from electromagnetic pollution. In this work, zinc oxide (ZnO) and reduced graphene oxide (rGO) coated wearable cotton fabrics have been prepared for the application of EMI shielding effectiveness in X-band (8.2–12.4 GHz). The uniform coating of ZnO nanoparticles is achieved by the easy and cost effective in-situ sol-gel method, whereas the uniform coating of rGO is achieved by simple spraying of graphene oxide solution followed by thermal reduction. It is observed that the total EMI shielding effectiveness increases with the rGO loading, however, the reflection loss decreases owing to improved conductivity of the cotton fabric. The as-prepared rGO/ZnO coated cotton (ZnO + 7 wt% rGO) achieves highest total EMI shielding effectiveness of ~99.999% (54.7 dB), which is shared by ~17.783% of reflection and ~82.216% of absorption. Such high absorption dominant EMI shielding is attributed to highly dielectric ZnO nanoparticles, highly conductive rGO sheets and the core-shell structure of the coated cotton fabric. It is also concluded that the excessive loading of rGO can block all the pores of the cotton fabric which is not beneficial for high absorption of the electromagnetic waves. The high absorption of ~90% is demonstrated when the ZnO coated cotton is loaded with 3 wt% rGO. In this work, the detailed mechanism of such absorption dominant EMI shielding has been discussed in details.