Green fabrication of surface-active Fe/Ni/Zn@f-MWCNT nanocomposites for photocatalytic dye degradation and antibacterial applications

Multifunctional Fe/Ni/Zn trimetallic nanocomposites were synthesized via a rapid, microwave-assisted green route using Garcinia gummi-gutta leaf extract. To enhance stability and performance, these nanoparticles were decorated onto carboxyl-functionalized multi-walled carbon nanotubes (Fe/Ni/Zn@f-MWCNTs). Structural and morphological characterization using UV–visible spectroscopy, FT-IR, XRD, TEM, and EDX analysis confirmed the formation of metal oxide-based nanostructures and their successful integration with the MWCNT framework. Optical analysis revealed a significant band gap narrowing from 3.66 eV in unsupported nanoparticles to 2.90 eV in the nanocomposite, facilitating superior visible-light harvesting. The supported system demonstrated markedly accelerated photocatalytic kinetics, achieving 94.66% degradation of methylene blue within 35 min, compared to 84.89% over 55 min for unsupported particles. Furthermore, the Fe/Ni/Zn@f-MWCNTs exhibited potent antibacterial activity against Gram-positive ( S. aureus, Bacillus sp. ) and Gram-negative ( E. coli, P. aeruginosa ) strains, with inhibition zones reaching 20–26 mm. The combined effect of the trimetallic nanocomposite and the conductive MWCNT support, facilitating charge separation and increasing surface area, renders this nanocomposite a high-performance, sustainable material for dual environmental remediation and biomedical applications. This study highlights the potential of plant-mediated microwave synthesis in producing advanced, eco-friendly nanohybrids.