Bio-synthesis of graphene oxide-decorated silver nanocomposites using <i>Usnea antarctica</i> and <i>Umbilicaria antarctica</i> from Antarctic Peninsula and evaluation of their antimicrobial activities

In this study, silver@graphene oxide nanocomposites (Ag@GO NCs) derived from extracts of Antarctic lichens Usnea antarctica and Umbilicaria antarctica were synthesized and their antimicrobial activity against to fish pathogen bacteria were evaluated. According to the results of characterization test, spherical Ag NPs were well dispersed on the surface of graphene oxide. While the diameters of Usnea antartica extract-based NCs were observed at an average of 28 nm, the diameters of Umbilica antartica extract-based NCs were found 40 nm. The absorption points of Usnea antartica and Umbilicaria antartica extract-based Ag@GO NCs were detected at 445 nm. The highly stable structures of NCs synthesized with both lichen extracts were exhibited with zeta potential. In addition, functional groups that play a role in the synthesis were revealed by FT-IR analysis and its crystal structure was revealed by XRD analysis. The lichen-based NCs have excellent antimicrobial activity against to Staphylococcus aureus, Aeromonas hydrophila, Pseudomonas aeruginosa, and Yersinia ruckeri strains. As a result, we suggest that Ag@GO NCs were synthesized with both lichen extracts by an effective, inexpensive, and eco-friendly method and are applicable for antimicrobial activity studies.