Phytochemical assisted synthesis of silver nanoparticles and their catalytic activity in the chemoselective reduction of nitroarenes

This study introduces an easy, eco-friendly and cost-effective method for producing silver nanoparticles (AgNPs) using aqueous extracts from Aloe barbadensis Miller and Aloe ciliaris under ambient conditions. This method does not require additional reducing agents or complexing additives. The resulting AgNPs were characterized using UV–vis, FTIR, and TEM and displayed spherical morphology, narrow size distributions (9.9–10.5 nm), and symmetric surface plasmon resonance bands centered around 410 nm. The resulting systems exhibited high colloidal stability and consistent metallic content, with values close to the nominal 0.5 wt%. Their catalytic activity was first evaluated through the reduction of p -nitrophenol using NaBH₄. All of the synthesized catalysts demonstrated excellent performance under mild conditions in aqueous medium, achieving complete conversion within minutes. Catalytic systems with the highest performance showed k app values above 0.2 min⁻¹ . They kept over 90 % of their initial activity after ten consecutive cycles and showed silver leaching levels below 7 %. Post-reaction TEM analysis revealed an increase in particle size, as well as occasional changes in morphology, consistent with nanoparticle reshaping phenomena. The most active catalysts were further used to synthesize benzocaine through the aqueous-phase reduction of ethyl p -nitrobenzoate (ENB). Conversions above 80 % were achieved under optimized conditions (NaBH₄/ENB=60), and the catalyst retained its activity upon reuse. This is the first report on the synthesis of benzocaine using AgNPs derived from Aloe vera extracts and NaBH₄ as the reducing agent. The results suggest that these sustainable nanocatalysts have potential in environmentally friendly protocols for synthesizing fine chemicals.