Characterization of Quercus acatissima extract conjugated with gold-nanourchin and its enhanced bacterial growth inhibition

In this study, the antimicrobial potential was confirmed from the plant extract of Quercus acatissima conjugated with gold-nanourchin (Qa-AuNu) against gram-negative and gram-positive bacteria. The plant extract has the ability to inhibit Escherichia coli (9 +/- 0.4 mm) and Bacillus subtilis (8 +/- 0.4 mm), however, the activity was considerably increased when the plant extract was conjugated with AuNu as 16 +/- 0.4 mm and 13.5 +/- 0.5 mm, respectively. Further, the Qa-AuNu was characterized by morphological and structural analyses. The size and shape of the Qa-AuNu were confirmed by FE-SEM, FE-TEM, and AFM as 60 nm in diameter and star-shaped with spike-like structure. EDX analysis clearly displayed the presence of Au elements in the sample. The XRD pattern confirmed the crystalline nature of the Qa-AuNu with three different peaks located at 38.2 degrees, 44.3 degrees, and 65.1 degrees corresponding to the (111), (200), and (220) diffraction planes, respectively. In addition, FTIR results confirmed the functional group in Q. acatissima that is involved in the conjugation of AuNu. This result clearly confirmed that the bonding of AuNu with plant extract via chemical bond enhanced the antibacterial potential as indicated by the large zone of inhibition.