Au–Cu Janus Nanostructures as NIR-II Photothermal Antibacterial Agents

Metal nanoparticles have been found to exhibit a broad spectrum of antibacterial activities, yet not all metals possess the captivating plasmonic properties necessary for effective interaction with incident light. In this study, we demonstrate the feasibility of synergistically enhancing the Cu-induced antibacterial activity through the incorporation of plasmonic photothermal therapy by hybridlike anchoring the Cu component on a gold (Au) nanoplate that can effectively absorb near-infrared light. To fabricate the Janus structure, plate-like Au seeds were mixed with copper(ii) nitrate, cetyltrimethylammonium bromide, ascorbic acid, and hexamethylenetetramine, resulting in the formation of Au–Cu Janus nanostructures (JNSs). Notably, the plasmonic absorption of Au was preserved without being hindered by the Cu coating. Photothermal measurements revealed that the temperature rise of Au–Cu JNSs aqueous suspensions could reach up to 28.3 °C in just 10 min when exposed to 1064 nm laser light at a power density of 1 W·cm^–2, with a photothermal conversion efficiency of 42.14%. Additionally, they show broad-spectrum antibacterial properties, making them potential contenders for addressing a wide range of bacterial infections. Our findings demonstrate that the antibacterial performance of metal nanoparticles composed of less plasmon-active components but with exceptional antibacterial properties can be significantly enhanced by coupling them with a plasmon-active nano-antenna through a Janus architecture. The Au–Cu JNSs possess potential application prospects in photothermal therapy, broad-spectrum antibacterial treatments, biomedical imaging, targeted drug delivery, sensitive diagnostics, and the development of advanced materials.