Cocos nucifera Leaf Extract Mediated Green Synthesis of Silver Nanoparticles for Enhanced Antibacterial Activity

Antibiotic resistance is currently a global human health concern and insists on the importance of the production of new, alternative and most effective antibiotics. Nano-sized trace metals such as silver nanoparticles (AgNPs) is a potential material with antibacterial properties and hence the synthesis of this material is of considerable interest to the scientific community mainly for antimicrobial applications. In this work, we have successfully green synthesized the AgNPs using Cocos nucifera leaf aqueous extract as the natural reducing and stabilizing agent, and aqueous silver nitrate (AgNO 3 ) solution as a precursor by a newly developed technique. The material was characterized by ultraviolet–visible (UV–Vis) spectrophotometry, X-ray diffractometry (XRD), Fourier transform infrared (FT-IR) spectroscopy, and transmission electron microscopy (TEM) analyses; and subsequently, evaluated their potential candidacy as antibacterial agents against some common human pathogens by the standard disc diffusion method. The synthesized AgNPs were identified by XRD analysis as a cubic crystal system with an average crystallite size of 14.2 nm. The aqueous colloidal suspension of AgNPs shows a UV–Vis absorption maxima of 380 nm indicating its formation. FT-IR analysis identified the C–N, –OH and N–H as the major and probable functional groups in the leaf extract responsible for the production of stable AgNPs. The results of antibacterial studies of the material showed the considerable zones of inhibition against both Gram-positive ( Staphylococcus aureus and Bacillus subtilis ) and Gram-negative ( Salmonella typhimurium , Escherichia coli , Pseudomonas aeruginosa, and Citrobacter freundii ) bacteria ranging from 10 to 20 mm with less inhibition for the former than the latter. The maximum (20 mm) and minimum (10 mm) inhibition zone was shown by C. freundii and Bacillus subtilis , respectively and P. aeruginosa shows the second-highest zone of inhibition (19 mm). The antibacterial performance of the material implies that the C. nucifera leaf extract mediated green synthesized AgNPs can be regarded as a potential candidate for antimicrobial application appreciably. Graphic Abstract