Rosmarinus officinalis leaf extract mediated green synthesis of silver nanoparticles and investigation of its antimicrobial properties

• Silver nanoparticles by reduction of AgNO3 with polyphenols present in rosemary leaf extract.
• Silver nanoparticles has average particle size of 29 nm and stabilized with biomolecules.
• Anti-bacterial and anti-fungal properties of silver nanoparticles investigated.
• MIC and MBC of silver nanoparticles against tested microbes are reported.

Green synthesis of metallic nanoparticles (NPs) has been reported using plant extracts, which has dual properties of stabilizing and emulsifying agents. Development of biologically inspired synthesis of nanoparticles has evolved as an important branch in nanotechnology. In this work, silver nanoparticles (Ag-NPs) were synthesized at room temperature using rosemary (Rosmarinus officinalis Linn.) leaf extract. Formation of green Ag-NPs was confirmed by some thoughtful techniques like as UV-visible, FT-IR, SEM & TEM, and XRD. Polyphenols in R. officinalis leaf extract acts as reducing and stabilizing agents for the formation of size controlled Ag-NPs and after 30 min nucleation started to proceed. Surface plasmon resonance (SPR) confirmed the formation of Ag-NPs with maximum absorbance at λmax of 450 nm. The Fourier transform infrared spectroscopy (FT-IR) spectra of leaf extract shows the presence of phenolic functional groups which reduces silver ion to Ag-NPs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show the spherical morphology of Ag-NPs with the size range of 10–33 nm. X-ray diffraction (XRD) spectra show four prominent peaks of the crystalline metallic Ag-NPs. At last antimicrobial activities of green NPs were examined and results showed that Green synthesized Ag-NPs had effective antibacterial and antifungal activities. By these deals, green synthesis of NPs as an eco-friendly and inexpensive method in large scale for medicinal and industrial application severely recommended.

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