Abstract
In this study, biogenic silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) were synthesized by a green approach using an aqueous extract from Codonopsis pilosula (CP) roots as a reducing and stabilizing agent. The formation of CP-AgNPs and CP-AuNPs was confirmed and optimized by UV-Vis spectroscopy. The CP-AgNPs and CP-AuNPs obtained under optimum conditions of metal ion concentration, reaction temperature, and reaction time were characterized by high-resolution transition electron microscopy (HR-TEM), selected area electron diffraction (SAED) analysis, field-emission scan electron microscopy (FE-SEM), powder X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, dispersive X-ray spectroscopy (EDX), and dynamic light scattering (DLS) method. It has been found that the biosynthesized CP-AgNPs and CP-AuNPs were formed in spherical shape with an average size of 10±2.5 nm and 20±3.2 nm, respectively. The biosynthesized metallic nanoparticles exhibited selective bacterial activity against three bacterial strains including two Gram-positive bacteria of Bacillus subtilis and Staphylococcus aureus and one Gram-negative bacteria of Escherichia coli. Meanwhile, there was no antibacterial activity detected toward Gram-negative Salmonella enteritidis. CP-AgNPs and CP-AuNPs also manifested an excellent catalytic performance in the reduction of 1,4-dinitrobenzene, 2-nitrophenol, 3-nitrophenol, and 4-nitrophenol.
Highlights
In recent years, there has been a growing interest in the synthesis of metal nanoparticles (MNPs) such as silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) due to their useful properties for applications in different areas of medicine, biology, catalysis, and antibacterial [1,2,3,4]
The optimization procedure is extremely necessary to ensure the stability of any preparation process in general, as well as the quality of MNPs obtained under optimum conditions using aqueous extract of plants as reducing and capping agents in particular [31]
The significant synthesis conditions including the concentration of metal ions, reaction temperature, and reaction time were optimized through UV-Vis measurements based on the surface plasmon resonance phenomenon in MNPs [32]
Summary
There has been a growing interest in the synthesis of metal nanoparticles (MNPs) such as silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) due to their useful properties for applications in different areas of medicine, biology, catalysis, and antibacterial [1,2,3,4]. The aqueous extract of CP roots was used as a reducing and stabilizing agent simultaneously for the biosynthesis of AgNPs and AuNPs. The biosynthesized MNPs were studied for antimicrobial activity toward four bacterial strains including two Gram-positive bacteria (B. subtilis and S. aureus) and two Gram-negative bacteria
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