The synthesizing approach analysis of hollow Ag/Au nanoparticles in replacement reaction between silver nanoparticle and chloroauric acid

Hollow Ag/Au nanoparticles have many potential applications in the biomedical field due to the flexible tunability of the LSPR and larger electric field enhancement factor compared to their solid counterparts. For the fabrication of hollow Ag/Au nanoparticles, the replacement reaction between HAuCl4 and Ag nanoparticles is considered to be effective. However, the reaction mechanism and the formation procedure of the hollow interior is not fully determined. In the present study, we proposed three possible reaction approaches (shell-to-core, regular core-to-shell and off-center core–to-shell) during the preparation. Based on the analysis of absorption cross-section and local electric field distribution calculated using finite element method of the products at each reaction stage, the off-center core-to-shell synthesizing approach is assumed to be the most reasonable and the electric enhancement factor is the largest. The further experimental results also support our assumption. The reveal of the reaction procedure between HAuCl4 and Ag nanoparticles is believed to help improve the morphology modulation of the hollow Ag/Au nanoparticles and their application in the biomedical field.