Synergistic effects of hydrothermally decorated Ag nanoparticles over rGO for antibacterial activities

Abstract

Antibacterial activity of the silver decorated reduced graphene oxide (Ag-rGO) nanocomposites have been investigated against E. coli as a model for gram-negative bacteria. The effect of temperature during the hydrothermal treatment of Ag-rGO nanocomposites synthesized by simultaneous reduction of GO and AgNO3 over the antibacterial activity has been studied. The composite samples were further reduced hydrothermally at different temperatures, viz. 100 °C, 150 °C, and 200 °C for 24 h to integrate silver nanoparticles (AgNPs) into rGO. Variations in the hydrothermal treatment temperature allowed alterations in the morphology and particle size of the AgNPs. The AgNPs grown at room temperature are in bunches and smaller sizes, whereas the hydrothermally treated samples have uniformly distributed bigger AgNPs. The particle size of AgNPs on rGO grows from 45 nm at room temperature to 65 nm and 220 nm in the hydrothermally treated samples at 150 °C and 200 °C, respectively. The antibacterial activity of the Ag-rGO composite has been observed to be size dependent. The Ag-rGO composite hydrothermally treated at 150 °C, having a particle size of ∼65 nm, has been observed to have the highest activity; the zone of inhibition is 3.4 ± 2.8 cm. The Ag nanocrystallite’s edges and defects in the rGO sheets together destroy the bacterial cells in a series of stages, ultimately resulting in cell death and high antibacterial activity.