Syzygium cumini-mediated synthesis of rGO/Ag-Au nanostructures: Efficient catalysts for rapid degradation of organic dyes

Background: The increasing human health risk caused by contamination of water by both natural and synthetic dye pollutants has become a crucial issue and poses an immense urge to find a sustainable approach for the removal of dye contaminants from wastewater. Photocatalysis performed in the presence of nanomaterials holds huge promise as an efficient and environmentally safe oxidation technology for organic dye removal from waste water. Methods: Our preparation methodology utilizes the extract derived from the endocarp of Syzygium cumini (SC) effects for concurrent reduction of GO and metal ions to form rGO/Ag-Au. The prepared rGO/Ag-Au nanostructures effectively breakdown organic dye pollutants like methylene blue (MB) and methyl orange (MO) dyes. Significant findings: A robust interaction between the rGO matrix and the Ag-Au nanoparticles was established by structural characterization, while morphological investigation displayed the nanoscale Ag-Au particles uniformly coated over the rGO sheet surface. The catalytic efficiency of the rGO/Ag-Au nanocomposite toward methylene blue (MB) and methyl orange (MO) chromophores decomposition was assessed with the aid of sodium borohydride (NaBH₄). The decoration of well-spaced Ag-Au nanoparticles over the rGO sheet created firm catalytic active sites in the rGO/Ag-Au composite. With the improved catalytic active surface, the MB/MO dye was completely removed in a very short time of 2.5 to 5 min. The rGO/Ag-Au composite exhibited exceptional catalytic prowess in the disintegration of both dyes, leading to complete degradation. The remarkable efficacy in the dye degradation process can be attributed to the predominance of both electrostatic as well as π-π interactions between the nanocomposite and the dyes. As a result, the current study has developed an easy-to-use and green method for creating rGO/Ag-Au composites, offering a workable way to dispose of hazardous organic dyes in an affordable and efficient way.