Eco-Friendly Synthesis of Ag and Au Nanoparticles Using Lactic Acid from Fermentation Waste and Cyclodextrins as Colloidal Stabilizers

In this study, we demonstrate a novel, environmentally friendly approach to synthesizing gold (AuNPs) and silver (AgNPs) nanoparticles (NPs) using industrial lactic acid as a reducing agent and amphiphilic β-cyclodextrins modified with dodecenyl succinic anhydride (β-CDMod) as stabilizing ligands. The synthesized NPs, AuNPs@CDModDS1, AuNPs@CDModDS5, and AgNPs@CDModDS5, exhibit stable surface plasmon resonance band characteristics and remain colloidally stable in water for up to three weeks. Transmission electron microscopy revealed spherical NPs with varying sizes: AuNPs@CDModDS1 (6.7 ± 0.1 nm), AuNPs@CDModDS5 (17 ± 12 nm), and AgNPs@CDModDS5 (9 ± 6 nm). The NPs demonstrated remarkable catalytic efficiency in the reduction of 4-nitrophenol, with AgNPs@CDModDS5 showing the highest catalytic activity (κ = 27 L·s–1·m–2). The pH-sensitive β-CDModDS5 ligand enhanced NP stability, facilitated substrate anchoring, and stabilized reaction intermediates, presenting a versatile and sustainable approach to NP synthesis.