In-situ modification of laser-induced graphene with silver nanoparticles and its electronic conductivity modulation

With the rapid development of high-frequency communication technology, electromagnetic interference (EMI) issue has been increasing. Hence, EMI shielding materials for the 5G frequency band are in high demand. Here, a two-step laser-induced strategy was developed to rapidly prepare silver nanoparticles/porous graphene flexible composite in a solid-phase synthesis process. AgNO₃ solution can be efficiently adsorbed by hydrophilic laser-induced graphene (LIG) obtained by the first laser irradiation with tuned parameters, which provides favorable conditions for the abundant and homogeneous loading of Ag nanoparticles on LIG after in-situ the second laser irradiation. Furthermore, the microstructures, structural properties and electronic conductivity of the prepared Ag/LIG composites with different AgNO₃ additive concentrations are detailedly analyzed. As a result, with a 0.5 mol/L AgNO₃ additive concentration, Ag nanoparticles in the composite film maintain small size while exhibiting the best dispersion, exhibiting a high conductivity of 2788 S/m. In the 18-27 GHz frequency band, the EMI shielding effectiveness increases from 18-26 dB of LIG to 36-40 dB of composite materials. The EMI shielding effectiveness of Ag/LIG-0.5 at the 26 GHz reaches 38 dB with an over 90% shielding effectiveness retention rate after 200 bending cycles.