Gold, iron and silver nanoparticles: Synthesis, characterization and applications in antibacterial, cytotoxic and wastewater treatment: A comprehensive review

Advances in nanotechnology have positioned metal nanoparticles, especially gold (Au), iron (Fe) and silver (Ag), at the forefront of innovations in biomedical, environmental and catalytic applications. These qualities have enabled wide-ranging applications in wastewater cleanup, bio sensing, cancer treatment and antibacterial treatment. However, the synthesis method, structural characteristics, surface chemistry and colloidal stability of these nanoparticles significantly impact their performance and safety. This paper covers in detail the mechanics, benefits, drawbacks and environmental effects of both conventional and green synthesis techniques for creating Au, Fe and Ag nanoparticles. To illustrate their significance in determining nanoparticle size, shape, composition and surface functionality, key characterization techniques, including UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), forier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS) and zeta potential, are reviewed. The review also examines these nanoparticles' cytotoxicity to both healthy and malignant cells, as well as their antibacterial mechanisms, including membrane rupture, the production of reactive oxygen species (ROS) and biomolecular interference. Their functions in wastewater treatment are also investigated, with particular attention to catalytic reduction, heavy-metal removal, dye degradation and disinfection procedures. Significant obstacles still exist despite tremendous advancements, such as concerns about the toxicity of nanoparticles, their persistence in the environment, their economic viability and the scalability of green synthesis techniques. This analysis tackles existing gaps and proposes the creation of safer, more sustainable and application-oriented nanomaterials.