Synthesis of octapod Cu–Au bimetallic nanocrystal with concave structure through galvanic replacement reaction

We synthesized octapod Cu–Au bimetallic alloy with a concave structure by employing a replacement reaction between AuPPh₃Cl and Cu nanocubes. Using Cu nanocube as sacrificial templates, we have successfully generated high-active sites on alloy nanocrystals by carefully tuning the replacement reaction and growth. The key is to afford the proper concentration of AuPPh₃Cl-TOP to the reaction solution. When the Au precursor with high concentration is injected into the galvanic replacement reaction, growth dominates the process, hollowed octapod Cu–Au alloy was obtained. In contrast, when the concentration of the Au precursor is low, the replacement reaction can only take place at the nanocrystals, leading to generated Cu–Au nanocages. This work provides an effective strategy for the preparation of hollow bimetallic nanocrystals with high-active sites.