Copper/Silver Bimetallic Nanoparticles Supported on Aluminosilicate Geomaterials as Antibacterial Agents

This study aims to understand how properties of modified aluminosilicate geomaterials influence the antibacterial performance of nanocomposites when prepared with bimetallic nanoparticles (NPs). Copper/silver (Cu/Ag) bimetallic NPs were synthesized in the presence of imogolite (Imo), montmorillonite (Mtt), or zeolite (Zeo) using a simple one-pot method and characterized for their crystal phases, micro- and nanomorphologies, particle size, elemental composition, and electrophoretic mobility. The antibacterial activity was evaluated through minimum inhibition concentration assays of NPs and nanocomposites for Gram (−) Escherichia coli and Gram (+) Staphylococcus aureus bacteria. Deposition of metallic Cu⁰, Ag⁰, and cuprite NPs was confirmed in Zeo_Cu/Ag and Imo_Cu/Ag nanocomposites, whereas only Cu⁰ and Ag⁰ were identified in Mtt_Cu/Ag. The bimetallic NPs were more uniformly distributed on Zeo and Mtt than Imo. Particle sizes of 28.1 ± 5.0, 9.4 ± 2.3, 10.1 ± 1.7, and 12 ± 1.3 nm were determined for Cu/Ag NPs, Imo_Cu/Ag, Mtt_Cu/Ag, and Zeo_Cu/Ag, respectively. The release rate of Cu and Ag ions from Zeo_Cu/Ag was higher than those of pristine Cu/Ag NPs and the other two nanocomposites. The antimicrobial action of bimetallic NPs and nanocomposites was dose-dependent in relation to the concentration of concerned materials and their stability in the medium. The physicochemical characteristics of Zeo resulted in a homogeneous distribution and low oxidation and agglomeration of Cu/Ag NPs, consequently increasing the antibacterial activity. Results of this study highlight the benefits of using a geomaterial support to achieve high antibacterial activity of bimetallic NPs, which could help reduce the consumption of pure Cu/Ag salts in NP-based antibacterial applications.