One-step method for the fabrication of pure and metal-decorated densified CNT films for effective electromagnetic interference shielding

Light-weight, thin, and robust electromagnetic shielding materials with high electrical conductivity are needed for advanced modern electronics and telecommunication technologies to protect circuits from electromagnetic interference. Carbon nanotubes (CNT) are ideal candidates for electromagnetic shielding materials due to their excellent mechanical strength, high electrical conductivity, and light weight. However, the relatively poor electrical conductivity of CNT films, a result of the many points of contact resistance between neighboring CNTs, is an obstacle towards their utilization as a shielding material. Here, we propose a facile CNT film fabrication method that enhances the conductivity of CNT films by collapsing the separation between neighboring CNTs (i.e., densifying the material) in the CNT network. The dense CNT films resulting from this facile method exhibit high electrical conductivity (∼10⁶ S m^-1), and achieve excellent shielding of 99.999992% (71 dB) at frequencies between 8.2 GHz and 12.4 GHz with a thickness of 14.3 μm. The remarkable absolute shielding effectiveness (3.50 × 10⁵ dB cm^-2 g^-1) is due to the material's low density (i.e., ∼1.0 g/cm³), thinness (i.e., 1.3–14.3 μm), and metal-like conductivity. Also, the produced CNT sheet is an ideal substrate for gold decoration that can dramatically enhance the EMI shielding performance further (EMI SE increased from 43.90 dB in the loose film to 56.67 dB in the dense film, which further increased to 66.12 dB when the dense CNT film was coated with a thin gold layer). The outstanding properties of gold-decorated dense CNT films make them strong candidates to meet the electromagnetic shielding needs of modern cutting-edge, lightweight, and compact electronic devices.