Green synthesis of silver nanoparticles from Centella asiatica and its application in photodegradation of methylene blue dye in paper industry effluent

This study explores the green synthesis of silver nanoparticles (AgNPs) using Centella asiatica leaf extract and evaluates their structural, photocatalytic, and antimicrobial properties. FTIR analysis revealed the presence of various functional groups including hydroxyl, carboxyl, alkyl, amine, and aromatic rings, which originated from bioactive compounds such as tyrosine, ascorbic acid, stigmasterol, and kaempferol. These biomolecules served as reducing and capping agents in the synthesis of AgNPs. SEM analysis showed AgNPs with varied morphologies—tubular and cuboidal—ranging from 35 to 100 nm in size. Zeta potential analysis confirmed the colloidal stability of AgNPs with an average particle size of 132.8 nm. Photocatalytic degradation of methylene blue dye demonstrated a 90% reduction under sunlight within 120 minutes, attributed primarily to localized surface plasmon resonance (LSPR)-induced electron transfer on the AgNP surface. Antibacterial assays revealed potent inhibition against Escherichia coli , Salmonella typhimurium , and Bacillus subtilis , with MIC values of 9.5, 6.5, and 6.25 µg/mL, respectively. The AgNPs outperformed ciprofloxacin in both inhibition zone diameter and MIC values. These findings highlight the eco-friendly synthesis of AgNPs using C. asiatica , showcasing their potential as efficient agents for environmental remediation and antimicrobial applications.