Nanoporous Ag-Au Bimetallic Triangular Nanoprisms Synthesized by Galvanic Replacement for Plasmonic Applications

Hongmei Qian,G Bharath,Shoaib Anwer,Shahid Iqbal,Lijuan Chen

doi:10.1155/2018/1263942

Abstract

Galvanic replacement is a versatile method of converting simple noble metallic nanoparticles into structurally more complex porous multimetallic nanostructures. In this work, roughened nanoporous Ag-Au bimetallic triangular nanoprisms (TNPs) are synthesized by galvanic replacement between smooth Ag triangular plates and AuCl4− ions. Transmission electron microscope and the elementary mapping measurements show that numerous protrusions and pores are formed on the {111} facets, and Ag and Au atoms are homogeneously distributed on the triangular plates. Due to the additional “hot spots” generated by the surface plasmon coupling of the newly formed protrusions and pores, the roughened nanoporous Ag-Au TNP aggregates demonstrate a higher surface-enhanced Raman scattering enhancement factor (seven times larger) and better reproducibility than that of smooth Ag triangular particle aggregates. These synthesized roughened nanoporous Ag-Au bimetallic TNPs are a promising candidate for the applications in analytical chemistry, biological diagnostics, and photothermal therapy due to their excellent plasmonic performances and good biocompatibility.

Highlights

Noble metal nanostructures supporting the surface plasmons (SPs) have attracted great scientific and technological interest [1,2,3,4]
It is interesting to know that the average particle size of triangular nanoprisms (TNPs) is almost unaffected before (~284 nm) and after (~289 nm) the galvanic displacement, which confirmed that the formations of nanoporous Ag-Au alloyed nanoprisms are based on the galvanic displacement by using the Ag nanoprisms as a frame
The elementary mapping showed that the Ag and Au atoms were homogeneously distributed on the Ag-Au TNPs with the Ag to Au atomic ratio about 1 : 1.8

Summary

Introduction

Noble metal nanostructures supporting the surface plasmons (SPs) have attracted great scientific and technological interest [1,2,3,4]. The SERS measurements demonstrate that the roughened nanoporous Ag-Au bimetallic TNPs can have a superior plasmonic activity and reproducibility to the Ag triangular plates with a smooth surface, which can be due to the additional “hot spots” generated by the surface plasmon coupling of the newly formed protrusions and pores. These nanoporous Ag-Au bimetallic TNPs, simultaneously having excellent plasmonic properties and good biocompatibility, are a promising candidate for the application in the fields of biomedical and chemical analysis and sensing, and so on.

Experimental

Results and Discussion

Conclusion