A viable synthesis route of Ag-Cu bimetallic nanoclusters on halloysite nanotubes and the study of the antibacterial properties

Many metal nanoparticles are good antibacterial agents, especially Ag and Cu, which have excellent antibacterial properties. It was reported that the antimicrobial activity of Ag and Cu bimetallic nanoparticles against broadspectrum bacteria was expected to be more effective than that exerted by Ag-only or Cu-only nanoparticles. However, Ag-Cu bimetallic nanoclusters were difficult to synthesize because Cu nanoparticles are unstable in water without any stabilizer. In this study Ag-Cu bimetallic nanoclusters on halloysite nanotubes (HNT) could be successfully prepared using a chemical reduction method, and their antimicrobial effects were demonstrated. HNT is aluminosilicate with a hollow tubular structure. HNT's architecture makes it an interesting nanomaterials that can be used as an important and effective carrier for applications such as drug delivery or catalysis carrier. To load Ag-Cu bimetallic nanoclusters efficiently, HNT was modified by sodium hydroxide (HNT-b). The synthesis process was straightforward, environmentally sustainable, and economically viable to produce stable Ag-Cu bimetallic nanoclusters on the HNT surface. HNT-b/bimetallic nanocomposites with monodispersed spherical morphology of the metal NPs was characterized by TEM, EDS, TG, XRD, and ICP-OES. The results showed the lattice spacings were 0.243 nm and 0.209 nm for Ag NPs, 0.225 nm and 0.211 nm for Cu NPs. The antibacterial properties of Ag-Cu NCs/HNT-b were tested by the inhibition zone test and growth inhibition assay. The results showed that the bimetallic NCs demonstrated synergistic effects and improved antibacterial properties from 30% to 53%. In particular, Ag-Cu NCs/HNT-b exhibited complete bactericidal behavior.