Dual functional polyherbal silver nanoparticles for efficient dye degradation and Fe³⁺ ion detection

Silver nanoparticle (AgNP) synthesis using plant extracts has gained significant attention due to its eco-friendly approach and functional versatility. In the present study, stable AgNPs were synthesised using a polyherbal system prepared by employing the extracts of Rubia cordifolia (roots), Terminalia arjuna (bark) and Bombax ceiba (thorns). The combination of chemically diverse phytoconstituents enabled efficient reduction, regulated nucleation and effective surface capping, resulting in well-dispersed, predominantly spherical AgNPs with enhanced colloidal stability. UV-visible spectroscopy confirmed nanoparticle formation through a characteristic SPR peak at 422 nm. HR-TEM analysis revealed predominantly spherical, polycrystalline nanoparticles with an average size of approximately 25 nm. Functionally, the polyherbal AgNPs exhibited excellent catalytic activity, achieving rapid degradation of methylene blue (∼96% within 10 min) and demonstrated sensitive and selective colorimetric detection of Fe³⁺ ions (R ² = 0.996, over a concentration range of 0.5-3 ppm) with a low detection limit (0.443 ppm). The current findings together with comparative evaluation of previously reported single, dual and multi-plant systems, indicate enhanced functional integration achieved through the present polyherbal strategy.