Fine-tunable ε′-negative response derived from low-frequency plasma oscillation in graphene/polyaniline metacomposites

Abstract

Remarkable ε′-negative responses at radio-frequency endow metacomposites with revolutionary applications in electromagnetic (EM) fields. However, uncovering its regulation mechanism and subsequently achieving fine-tunable ε′-negative response remains challenging. Here, we meticulously designed graphene/polyaniline (GR/PANI) metacomposites above percolation, which directly enable tunable negative permittivity at an order of magnitude of −103. By rationally adjusting the three-dimensional GR network, we were able to form collective low-frequency plasma oscillation of free electrons in composites, which intrinsically contributes to the tunable ε′-negative response. Moreover, an ε′-near-zero (ENZ) response was surprisingly observed at ∼920 MHz due to the ineffectiveness of the plasmonic state at high frequencies. In addition, we carried out equivalent circuit analysis to demonstrate the phase relationship and electrical characteristics of these metacomposites. This work could contribute to a new category of polymer-matrix composites and enable exotic properties beyond their natural and bulk counterparts.