The structure and plasmonic properties regulation of Au@Ag core-shell nanostructures with Au triangular nanoprisms as the core mediated by halide

In this work, Au@Ag core-shell nanoparticles with different size Au TNPs as the core were synthesized through seed-mediated growth method. Various types of Au TNP@Ag core-shell nanoparticles were easily prepared by varying the amounts of AgNO ₃ using the CTAC as surfactant. We have further investigated their plasmonic properties of various types of Au TNP@Ag core-shell nanoparticles. Au TNP@Ag core-shell nanoparticles have tunable localized surface plasmon resonance properties which can be controlled by volumes of AgNO ₃. The absorption peak of Au TNP@Ag core-shell nanoparticles increased from one to five and the intensity gradually increased with the increase of the volume of AgNO ₃ . Moreover, by changing the core size from 62 nm to 110 nm, the characteristic absorption of Au TNP@Ag core-shell nanoparticles could be shifted from visible to infrared range. Then we analyze the influence of halide ions on the shape formation of Au TNP@Ag core-shell nanoparticles. Au TNP@Ag triangular nanoprism, Au TNP@Ag nanocube and Au TNP@Ag right bipyramid only can be obtained in the in the presence of Cl ^- while not other halide ions (Br ^-, I ^-). The adsorption of Cl ^- and oxidative etching of Cl ^-/O ₂ lead to the formation of single crystal Au TNP@Ag nanocube and Au TNP@Ag right bipyramid with well-defined shaped Au TNP. The present work expanded the field of gold and silver core-shell nanoparticles. More importantly, a large number of new nanomaterials have been obtained and shows promising applications in optics and sensing.