Biosynthesized copper nanoparticles from <i>Breonadia salicina</i> leaf extract: Applications in methyl green dye removal and antimicrobial activity

In this study, the extract of Breonadia salicina leaves (BSL)-copper nanoparticles (Cu NPs) were green-synthesized in a single step using Breonadia salicina leaf extract and demonstrated potent antibacterial and antifungal activities, along with high efficiency in removing methyl green dye from water. The green synthesis of BSL-Cu NPs was characterized using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and zeta potential analysis. Phytochemical analysis of Breonadia salicina leaf extract revealed abundant phenols, flavonoids, and other bioactive compounds, which facilitated the stabilization and enhanced antimicrobial activity of the biosynthesized BSL-Cu NPs. The BSL–Cu NPs exhibited significant antibacterial activity against S. epidermidis , S. aureus , S. typhimurium , and E. coli , as well as notable antifungal effects against Candida parapsilosis . Multiple parameters affecting methyl green (MG) dye adsorption were investigated, revealing that the highest removal efficiency reached 96.60% under optimal conditions: an adsorbent dosage of 0.02 g, pH 6.0, contact time of 120 min, initial MG concentration at 450 mg/L, and temperature maintained at 298 K. The adsorption process followed the pseudo-second-order kinetic model, and equilibrium data aligned well with the Langmuir isotherm with an adsorption capacity of 1000.1 mg/g at 45°C. Thermodynamic results showed that the adsorption was both spontaneous and endothermic. The adsorption mechanisms involved electrostatic attraction and hydrogen bonding. In conclusion, BSL-Cu NPs green-synthesized using Breonadia salicina leaf extract showed potent antimicrobial activity and high efficiency in MG dye removal, demonstrating their potential for sustainable environmental and biomedical applications.