Core–Shell Nanomaterials for Microwave Absorption and Electromagnetic Interference Shielding: A Review

Core–shell nanoparticles are a unique class of nanostructured materials, which received significant attention in the last two decades owing to their exciting properties and a wide variety of applications. By judiciously tuning the "core" as well as the "shell", an assortment of "core–shell" nanostructures can be obtained with tailorable properties which can play pivotal roles in designing materials for electromagnetic interference (EMI) shielding and microwave absorption. In recent times when the use of high-end electronics has been on the rise, electromagnetic pollution is inevitable and it affects every walk of life. Among numerous e-pollutions, a recently highlighted domain that has far-reaching consequences is electromagnetic interference. EMI is the disturbance created during an electronic device's operation when it is in the vicinity of an electromagnetic field caused by another electronic or electric device. Since EMI decreases the lifetime and degrades the performance of the electronic instruments and even affects human health, it is crucial to protect sophisticated instruments and components from EM interference. High-performance EMI shields capable of attenuating microwave propagation efficiently have been developed in the past decade. Herein, in this review, we attempted to provide a logical guide to various "core–shell" nanostructures (≤500 nm) that have been synthesized in the past decade for the application in microwave absorption and EMI shielding. The prime focus of this review article is to highlight the fundamental concept of EMI shielding and microwave absorption that have been reported for various systems in the literature along with various synthetic and fabrication strategies in designing suitable broadband EM absorbers/screeners. Finally, we also made an effort to provide a holistic outlook and perspective in which upcoming research will continue to flourish.