Facile Green Synthesis of Gold Nanoparticles Using <i>Catunaregam Spinosa</i> Extract for Environmental Remediation and Antimicrobial Activity

Abstract Wastewater contains various pollutants that pose significant risks to both human health and the environment. In this work, gold nanoparticles (AuNPs) were synthesized via an eco‐friendly green method and subsequently evaluated for their catalytic performance in reducing 4‐nitrophenol, degrading organic dyes, and inhibiting bacterial growth. Gold nanoparticles (AuNPs) were synthesized using Catunaregam spinosa (CNS) leaf extract, which functioned as both a bioreducing and stabilizing agent. This green approach enabled a rapid, simple, and energy‐efficient synthesis of AuNPs without the need for external chemical reductants or stabilizers. The synthesized C. spinosa ‐mediated gold nanoparticles (CNS‐AuNPs) were comprehensively characterized using various analytical techniques, including FTIR, UV–vis spectroscopy, FESEM, EDX, AFM, photoluminescence (PL) spectroscopy, and TEM. TEM analysis revealed that the CNS‐AuNPs possessed a nearly spherical morphology with an average particle size of 25.48 ± 1.3 nm. Catalytic activity studies demonstrated that the CNS‐AuNPs effectively reduced 4‐nitrophenol to 4‐aminophenol in the presence of NaBH 4 , achieving a high conversion efficiency of 96% and a rate constant of 0.0107 min −1 . Furthermore, the CNS‐AuNPs exhibited photocatalytic activity toward the degradation of amido black 10B (ADB) dye under visible light, resulting in 87.48% degradation within 120 min, following pseudo‐first‐order kinetics with a rate constant of 0.0149 min −1 . In addition, antibacterial assays using the agar well diffusion method revealed that the CNS‐AuNPs displayed strong inhibitory effects against Staphylococcus aureus , Streptococcus mutans , and Klebsiella pneumoniae . The main objective of this study is to develop an eco‐friendly synthesis method for gold nanoparticles (AuNPs) using C. spinosa extract and to evaluate their potential applications in catalytic pollutant degradation and antibacterial activity for effective environmental remediation. Future work will focus on mechanistic studies, toxicity assessment, and assessing the reusability and stability of CNS‐AuNPs. Efforts will also aim to scale up the green synthesis process and expand antimicrobial testing against a broader range of pathogens. Additionally, the application of CNS‐AuNPs in real wastewater and their integration into advanced treatment systems will be explored.