Etching‐Free Epitaxial Growth of Gold on Silver Nanostructures for High Chemical Stability and Plasmonic Activity

Abstract

A robust method for epitaxial deposition of Au onto the surface of Ag nanostructures is demonstrated, which allows effective conversion of Ag nano­structures of various morphologies into Ag@Au counterparts, with the anisotropic ones showing excellent plasmonic properties comparable to the original Ag nanostructures while significantly enhanced stability. Sulfite plays a determining role in the success of this epitaxial deposition as it strongly complexes with gold cations to completely prevent galvanic replacement while it also remains benign to the Ag surface to avoid any ligand‐assisted oxidative etching. By using Ag nanoplates as an example, it is shown that the corresponding Ag@Au nanoplates possess remarkable plasmonic properties that are virtually Ag‐like, in clear contrast to Ag@Au nanospheres that exhibit much lower plasmonic activities than their Ag counterparts. As a result, they display high durability and activities in surface‐enhanced Raman scattering applications. This strategy may represent a general platform for depositing a noble metal on less stable metal nanostructures, thus opening up new opportunities in rational design of functional metal nanomaterials for a broad range of applications.

Self‐Templating Approaches to Hollow Nanostructures

“…The Au/Ag ratio during galvanic replacement is changed from 1:3 to 1:1 by replacing AuCl 4 − with AuCl 2 − , which can also impact the alloying/dealloying processes. More recently, we developed a new Au(I) precursor, Na 3 Au(SO 3 ) 2 , to suppress the galvanic replacement for the epitaxial growth of Au on Ag nanostructures ( Figure a) . The new complex exhibits a decreased reduction potential (0.111 V vs SHE) and remains stable at pH ≈ 12.…”

Ag–Au bimetallic nanocomposites stabilized with organic–inorganic hybrid microgels: synthesis and their regulated optical and catalytic properties

“…14,15 The similarity between the lattice spacings of Ag and Au allows the fabrication of Ag-Au bimetallic nanocrystals with tunable morphology, 16 and the optical performance of Ag-Au NPs can be regulated by adjusting their structure and the relative contents of Ag and Au. 17,18 Compared to the co-reduction approach, the galvanic replacement (GR) reaction strategy had received more attention due to offering facile reaction conditions and allowing the fabrication of bimetallic NPs with tunable structures that can be controlled by adjusting the concentration ratio of metal precursor salts. [19][20][21] The unique porous structure of Ag-Au bimetallic NPs is characterized by an increased number of surface active sites and a large void volume, which not only promotes electron transfer on the nanocatalyst surface, but also accelerates the reaction of the substrate in contact with the catalyst and thus improves catalytic activity.…”

Intracellular Biodegradation of Ag Nanoparticles, Storage in Ferritin, and Protection by a Au Shell for Enhanced Photothermal Therapy

“…The samples were centrifuged three times and redispersed in water.Ag@AuNPs hybrids (Ag@AuNPs). Ag@AuNPs core/shell structures were prepared in three steps, following a well-established seeded growth approach described previously 40. Firstly, 0.2 mL of AgNO3 (0.1 M), 12 mL of trisodium citrate (0.075 M) and 0.48 mL of H2O2 (30 wt%) were diluted up to 200 mL with milliQ degassed water under stirring, to obtain Ag nanoplates solution.…”