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 AgNO3 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 AgNO3. 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 AgNO3. 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-/O2 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.