Facile Fabrication of Hollow Ag-Au Alloy Nanostructures Directly on Filter Paper and their Enhanced Catalytic and Antibacterial Applications

Abstract Hollow noble metal alloy nanostructures have recently attracted great attention owing to their exceptional potential for various applications. These nanostructures are generally synthesized in solution. However, for several applications, their deposition on the substrate is needed. Herein, we present the novel synthesis of hollow Au-Ag alloy nanostructures directly on the filter paper. The synthesis was carried out in two steps. First, Ag nanostructures were directly grown on the filter paper by reducing the pre-deposited Ag ions with ascorbic acid, yielding Ag nanostructure substrate (AgNS-S). These NPs were subsequently etched with HAuCl4 exploiting the galvanic replacement reaction (GRR), which yielded hollow Au-Ag alloy nanostructure substrate (HANS-S). Owing to the enhanced surface area and the presence of a high concentration of atoms in the low coordination state, these HANS-S showed excellent catalytic and antibacterial properties. In particular, the rate constants of the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), and the degradation of methyl orange (MO) increased by a factor of approximately 3.5 and 3.4, respectively, when employing HANS-S compared to utilizing AgNS-S. Similarly, the filter paper having hollow Au-Ag alloy nanostructures showed markedly superior antibacterial activity. While AgNS-S did not show any zone of inhibition (ZOI) outside the substrate, HANS-S showed notable ZOI for both S. aureus and E. coli, which verifies the antibacterial activity of these nanostructures against both Gram-positive and Gram-negative bacteria.