Synthesis of hex nut shaped Au-Ag nanostructures via a galvanic replacement reaction and their optical properties

Galvanic replacement reactions have been successfully employed to produce hollow bimetallic nanostructures with a range of shapes. This paper presents a systematic study of the galvanic replacement reaction between 122 nm thick hexagonal Ag nanoplates and HAuCl4 in an aqueous medium. We monitored the morphological and spectral changes as a function of the HAuCl4-to-Ag molar ratio. The replacement reaction on the hexagonal Ag nanoplates resulted in the formation of a series of porous Au-Ag nanostructures with a hex nut shape. The size and density of the pores could be controlled by varying the molar ratio of HAuCl4-to-Ag molar ratio. The localized surface plasmon resonance (LSPR) peaks of these nanostructures were readily tuned from 494 nm to 1044 nm as the porosity of the product was increased.