Transition metal ions induce pH-dependent coordination bonds, ionic conductivity and in-situ magnetic particles for tailoring microwave absorption of gels

Abstract

Transition metal ions possess specific properties and coordination chemistry, and the products of complexation reactions, such as complexes and free ions, can modulate the dielectric properties and ionic conductivity of gels. Nevertheless, the lack of a relationship between the coordination modes of metal complexes and electromagnetic wave (EMW) loss limits its application in the EMW absorbing field. Herein, we fabricated pH-dependent gel networks by coordinating with transition metal ions (Fe³⁺, Cu²⁺, and Zn²⁺), which successfully regulate dielectric properties, enhance ionic conductivity, and optimize the EMW absorption properties. Moreover, the gels modified by iron ions exhibit the magnetic response to EMW via in-situ synthesized iron oxides, further improving the impedance matching of the materials. The FePT-2 sample exhibits optimal effective absorption bandwidth (EAB) of 5.61 GHz at 1.5 mm, which expands by approximately 63% over PT, achieving broad-range EMW absorption in X and Ku bands. This study actualizes the regulation of coordination modes of the dielectric response and in-situ magnetic particles within gels for the first time and develops a novel design strategy for optimizing the EMW absorption of gels.