Influence of Polymeric and Natural Stabilizers on the Green Synthesis of Platinum and Palladium Nanoparticles

Platinum and palladium nanoparticles (Pt- and Pd-NPs) were synthesized using a green reduction approach with ascorbic acid (AA) or saponin from Quillaja bark (Qb) as reducing agents and stabilized with conventional polymers (PVP, polyvinylpyrrolidone, PEG, polyethylene glycol) or natural surfactants (CG (coco glucoside), Qb). The influence of stabilizer type on reduction efficiency, particle size, and colloidal homogeneity was investigated. Pt-NPs exhibited consistently high reduction efficiencies (>87%) in all systems, whereas Pd-NPs showed lower efficiencies and greater sensitivity to synthesis conditions. AFM and DLS analyses confirmed the formation of particles within the nanometric range. In AA-based systems, Pt-NPs were generally smaller than Pd-NPs, while the opposite trend was observed in Qb-based systems. Natural surfactants provided effective NP stabilization, low values of polydispersity index (PdI), good size control, and stable nanostructures. The results demonstrated that biosurfactant-based stabilizers, particularly CG and Qb, can successfully replace synthetic polymeric stabilizers in the green synthesis of noble metal NPs, supporting the development of more sustainable and environmentally friendly synthesis approaches.