The morphology regulation and plasmonic spectral properties of Au@AuAg yolk-shell nanorods with controlled interior gap

Jian Zhu; Shuang Zhang; Guo-Jun Weng; Jian-Jun Li; Jun-Wu Zhao

doi:10.1016/j.saa.2020.118343

The morphology regulation and plasmonic spectral properties of Au@AuAg yolk-shell nanorods with controlled interior gap

Spectrochim Acta A Mol Biomol Spectrosc. 2020 Aug 5:236:118343. doi: 10.1016/j.saa.2020.118343. Epub 2020 Apr 6.

Authors

Jian Zhu¹, Shuang Zhang², Guo-Jun Weng², Jian-Jun Li², Jun-Wu Zhao³

Affiliations

¹ The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China. Electronic address: zhujian@xjtu.edu.cn.
² The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China.
³ The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China. Electronic address: nanoptzhao@163.com.

PMID: 32302959
DOI: 10.1016/j.saa.2020.118343

Abstract

Au@AuAg yolk-shell nanorods with tunable and uniform interior gap were synthesized through galvanic replacement reaction, where Au@Ag core-shell nanorods served as sacrificial templates and HAuCl₄ solution served as reductant. The effects of HAuCl₄, Ag shell thickness and aspect ratio (AR) of Au nanorods on the morphology of Au@AuAg yolk-shell nanorods had been investigated systemically. The results clearly indicated that AuAg alloy shell thickness of Au@AuAg yolk-shell nanorods could be increased from 3.6 to 10.0 nm by varying the amount of HAuCl₄. Meanwhile, the shape of AuAg alloy shell could be tuned by changing the shape of Ag coating. With the increasing of Ag coating thickness, the interior gap could be finely tuned in the range from 2.6 to 8.1 nm. The uniformity of interior gap could be improved by increasing the AR of Au nanorods. All these tunable geometries can further affect the plasmonic spectral properties of Au@AuAg yolk-shell nanorods. Because of the appearance of interior gap, the longitudinal localized surface plasmon resonance (LSPR) peak of Au@AuAg yolk-shell nanorods was located between that of bare Au nanorods and Au@Ag core-shell nanorods without interior gap. The increase of outer AuAg shell thickness can weaken the coupling between the inner and outer surface of the AuAg shell and lead to the decrease of AR, so the transverse and longitudinal LSPR bands gather together. The decrease of Ag coating thickness can enhance the coupling between inner Au nanorod and outer AuAg shell, which results in the red shift of the longitudinal LSPR band. This paper provides a method for studying the plasmonic coupling between two metal surfaces with a metal layer or a dielectric layer, which is also a new approach for regulating the plasmonic spectral properties of bimetallic nanoparticles. The controllability of Au@AuAg yolk-shell nanorods in both the interior gap and outer alloy shells makes them have potential applications in biomedicine, catalysis, nanoreactors, and energy storage.

Keywords: Au@AuAg yolk-shell nanorods; Interior gap; Localized surface plasmon resonance; Morphology regulation; Spectral properties.