Ultrathin freestanding PDA-Doped rGO/MWCNT composite paper for electromagnetic interference shielding applications

The scalable and controllable preparation of carbon nanomaterial-based scaffolds with superior electromagnetic interference (EMI) shielding properties in addition to being ultrathin, robust, lightweight, flexible, and foldable is a challenging task. However, commonly used techniques such as integrating conducting moieties and high-temperature annealing cannot simultaneously meet the demands of high specific shielding effectiveness (SSE), robustness, and flexibility. Here, we adopted a novel PDA reduction technique to integrate various functionalities, including a nitrogen doping source, extended reduction of GO, and a large accessible area to accommodate multiwall carbon nanotubes (MWCNTs). The prepared ultrathin PDA-rGO/CNT composite sheet exhibited a low density (0.26 g/cm3), high flexibility, and superior shielding effectiveness (SE) under a wide range of microwave frequencies (i.e., the X band and Ku band). The total shielding effectiveness (SET) reached 47.6 dB and 48.7 dB in the X band and Ku band, respectively, at a thickness of 82 µm and a high SSE; in particular, the SE/density reached a maximum value of 183.3 and 187.3 dB cm3/g, respectively, which are superior to those of previously reported studies. This comprehensive study revealed the synergistic effect of PDA doping and MWCNTs, resulting in excellent shielding properties. Hence, this superior SSE and flexibility makes ultrathin lightweight PDA-rGO/CNT composite sheets a suitable candidate for replacing metallic counterparts for foldable and wearable electronic components.