Galvanic Replacement Coupled to Seeded Growth as a Route for Shape-Controlled Synthesis of Plasmonic Nanorattles

Abstract

Shape-controlled synthesis of metal nanoparticles (NPs) requires mechanistic understanding toward the development of modern nanoscience and nanotechnology. We demonstrate here an unconventional shape transformation of Au@Ag core-shell NPs (nanorods and nanocubes) into octahedral nanorattles via room-temperature galvanic replacement coupled with seeded growth. The corresponding morphological and chemical transformations were investigated in three dimensions, using state-of-the-art X-ray energy-dispersive spectroscopy (XEDS) tomography. The addition of a reducing agent (ascorbic acid) plays a key role in this unconventional mechanistic path, in which galvanic replacement is found to dominate initially when the shell is made of Ag, while seeded growth suppresses transmetalation when a composition of Au:Ag (∼60:40) is reached in the shell, as revealed by quantitative XEDS tomography. This work not only opens new avenues toward the shape control of hollow NPs beyond the morphology of sacrificial templates, but also expands our understanding of chemical transformations in nanoscale galvanic replacement reactions. The XEDS electron tomography study presented here can be generally applied to investigate a wide range of nanoscale morphological and chemical transformations.

Electron Tomography: A Unique Tool Solving Intricate Hollow Nanostructures

“…[99] Interestingly, instead of forming a hollow nanocage, the gold core remains almost unchanged, constructing a nanorattle morphology. [99] Interestingly, instead of forming a hollow nanocage, the gold core remains almost unchanged, constructing a nanorattle morphology.…”

“…Mater. [99] Copyright 2016, American Chemical Society. Chemical analysis of hollow structure nanomaterials by EDS tomography.…”

A General Approach to the Synthesis of M@Au/Ag (M = Au, Pd, and Pt) Nanorattles with Ultrathin Shells Less Than 2.5 nm Thick

“…We attribute this outcome to the remaining Ag skeleton after the galvanic replacement reaction with HAuCl 4 . [2a] When excess HAuCl 4 was used, the hollow structure would collapse, accompanied by the release of their Au cores (Figure D).…”

Highly Sensitive Magnetic-SERS Dual-Function Silica Nanoprobes for Effective On-Site Organic Chemical Detection

“…One of the important factors that characterize SERS-active NPs is the morphology of the NPs [10]. To obtain different ranges of the absorption spectrum, various shaped nanostructures based on Ag or Au NPs were prepared by conducting galvanic replacement reaction [11,12]. These nanostructures, especially Ag NPs, exhibited specific absorption spectra depending on the concentration of HAuCl 4 .…”