Size-Tunable Yolk–Shell Gold–Silver Nanostructures for Photothermal Treatment of Multidrug-Resistant Bacteria

Framelike nanostructures consisting of interconnected, ultrathin ridges have attracted wide attention due to their high atomic utilization efficiency among typical hollow architectures but are yet to be comprehensively studied for photothermal applications. Herein, we report a facile synthesis of AuAg yolk–shell cubic nanoframes (YSCNFs) with tunable edge lengths, followed by the exploration of their photothermal conversion and in vitro bacteria-killing performance, together with our endeavors to understand the mechanism fundamentally. By adopting the rationally screened capping agent docosyltrimethylammonium chloride (DCTAC) throughout the stepwise synthesis, sharp cubic edges could be generated and largely reserved, leaving the 5 nm cubic nanoframes well standing. The increase in the cubic edge length leads to the red shift of the major LSPR absorption peak toward the NIR region, and abundant hot-spots appear at the frame corner and core surface according to finite-difference time-domain (FDTD) simulation. The photothermal conversion efficiency of YSCNFs can reach as high as 65.6% when a very low power density of 0.27 W cm^–2 is used, which displays a powerful ability in combating multidrug-resistant bacteria. The present study offers a systematic investigation of bimetallic yolk–shell nanoframes including size/morphology control, photothermal properties, mechanism studies, and antibacterial applications, which could be of great value for the rational design of high-efficiency photothermal nanomaterials for services to biomedicine.