AuBr2–-Engaged Galvanic Replacement for Citrate-Capped Au–Ag Alloy Nanostructures and Their Solution-Based Surface-Enhanced Raman Scattering Activity

详细信息    查看全文

• 作者：Tingting Bai ; Yibin Tan ; Jiemeng Zou ; Mengxiao Nie ; Zhirui Guo ; Xiang Lu ; Ning Gu
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：December 24, 2015
• 年：2015
• 卷：119
• 期：51
• 页码：28597-28604
• 全文大小：557K
• ISSN：1932-7455

文摘

This work demonstrates that AuBr₂^– can serve as a suitable Au^I precursor in the galvanic replacement reaction with Ag nanoparticles (NPs), especially for preparing citrate-capped Au–Ag alloy nanostructures. A cost-effective recipe for stable AuBr₂^– solution was presented by the reduction of AuBr₄^– derived from the ion exchange between AuCl₄^– and optimal amount of Br^–. This recipe successfully suppressed the disproportionation of Au⁺ without the aid of concentrated salt solution, ensuring the colloidal stability of the citrate-capped Ag NPs during the replacement reaction. A comparative study was then performed on the structural evolution of citrate-capped Ag NPs during the replacement reaction with AuBr₂^– and AuCl₄^–. Uniform Au–Ag nanoshells were gradually formed when AuBr₂^– was employed, while porous Au–Ag nanoframes are generated by using AuCl₄^–. Moreover, the as-obtained AuBr₂^– solution can also be extended to the synthesis of complex nanostructures, such as Au@Au–Ag nanorattles. Finally, an improved solution-based Raman spectroscopic technique was established to precisely characterize the surface-enhanced Raman scattering (SERS) properties of these Au–Ag alloy nanostructures. It is found that, under the same amount of Au ions, the Au–Ag alloy nanoshells exhibit stronger SERS activity than the porous and fragile Au–Ag nanoframes. This AuBr₂^–-based strategy nicely complements the galvanic replacement reaction and provides a promising opportunity to synthesize chemically stable and surface accessible Au–Ag alloy nanostructures for biomedical applications.