Biomimetic synthesis, characterization and antibacterial efficacy of ZnO and Au nanoparticles using echinacea flower extract precursor

Zinc oxide and gold nanoparticles (ZnONPs and AuNPs) are biomimetically synthesized using Echinacea angustifolia flower extract and their structure and biological activities are reported. In this process, the dried flowers extracts reduced the zinc metal from the precursor Zinc nitrate hexahydrate [Zn(NO₃)₂.4H₂O] and stabilized within 6 h. Gold nanoparticles were synthesized in 10 min by the addition of hydrogen tetracholoroaureate (III) hydrate to the Echinacea flower extract. Nanoparticles were characterized through UV–vis, FTIR and SEM. The synthesis of ZnONPs and AuNPs were analyzed through UV–visible spectrophotometry and spectral absorption bands of the flower reaction mixture were observed at 368 and 560 nm, respectively. SEM analysis showed that the zinc oxide and gold nanoparticles prepared were dispersed and the average size ranged from 90–170 and 80–120 nm, respectively. Both nanoparticles have been found to be spherical. Antibacterial activity was investigated against commonly known pathogenic bacterial strains and the results showed that the nanoparticles exhibited significant activities against both gram positive and gram negative bacteria. (paper)