Plant-Mediated Synthesis of Nickel-Doped Cobalt Oxide/Reduced Graphene Oxide Nanocomposites for Combined Antibacterial Activity and EMI Shielding

The growing demand for environmentally conscious approaches in electromagnetic interference (EMI) mitigation has created interest in developing lightweight and multifunctional shielding materials synthesized through greener routes. In this study, nickel-doped cobalt oxide (Ni-<i>d</i>-Co) nanoparticles were synthesized via a plant-mediated method using <i>Aloe barbadensis</i> Miller phytoextract and integrated with reduced graphene oxide (RGO) to form RGO/Ni-<i>d</i>-Co epoxy nanocomposites. Structural, morphological, and spectroscopic analyses confirmed the successful doping of Ni²⁺ into Co₃O₄ and enhanced interfacial interaction with RGO sheets. The nanocomposites exhibited a marked enhancement in EMI shielding effectiveness, achieving ∼16.9 dB at 10 wt % loading. Shielding was primarily absorption-driven, minimizing secondary reflection and aligning with sustainable design goals. In addition, the nanocomposites demonstrated antibacterial activity against <i>Escherichia coli</i>. The combination of eco-friendly synthesis, effective EMI shielding, and antibacterial performance underscores the potential of these nanocomposites as scalable, multifunctional materials for next-generation electronics and biomedical applications.