Preparation of monodisperse bimetallic nanorods with gold nanorod core and silver shell and their plasmonic property and SERS efficiency
Preparation of monodisperse bimetallic nanorods with gold nanorod core and silver shell and their plasmonic property and SERS efficiency
复制标题
金纳米棒核银壳单分散双金属纳米棒的制备及其等离子体特性和SERS效率
DOI：
10.1002/jrs.4495
复制
发表时间：
2014-06-01
影响因子：
2.5
通讯作者：
Zha, Liusheng
中科院分区：
文献类型：
--
作者：
Dong, Xu;Zhou, Jianfeng;Zha, Liusheng
本研究以尺寸和形状分布较窄的Au纳米棒为晶种，采用晶种介导法还原AgNO3，合成了具有金(Au)纳米棒核和银(Ag)壳的单分散双金属纳米棒(Au@AgNRs)。随着AgNO_3使用量的增加，其侧面的银壳厚度增加的速度快于其两个尖端的银壳厚度，导致其长径比减小。在Au@AgNRs的消光光谱上观察到四个等离子体激元带，它们分别属于核壳结构双金属纳米棒的纵向偶极等离子体激元模式、横向偶极等离子体激元模式和八极等离子体激元模式。随着银壳层厚度的增加，由于长径比的减小和银等离子体共振贡献的增强，其纵向等离子体激元带显著蓝移，横向等离子体激元带蓝移，两个八极等离子体激元带轻微红移。当作为表面增强拉曼散射(SERS)衬底时，Au@AgNRs具有比Au纳米棒更强的表面增强拉曼散射(SERS)活性，并且由于其良好的单分散性，所获得的拉曼信号具有高度的重复性。由于表面电场的增强和电子配基效应的化学增强，它们的SERS活性随着银层厚度的增加而显着增加。版权所有©2014 John Wiley&Sons，Ltd.
In this study, monodisperse bimetallic nanorods with gold (Au) nanorod core and silver (Ag) shell (Au@AgNRs) were synthesized through seed-mediated growth process by reduction of AgNO3 using Au nanorods with narrow size and shape distribution as seeds. With increasing the used amount of AgNO3, the Ag shell thickness of their lateral facets is raised faster than that of their two tips, leading to a decrease of their aspect ratios. Four plasmon bands are observable on the extinction spectra of Au@AgNRs, which are attributed to the longitudinal dipolar plasmon mode, transverse dipolar plasmon mode, and octupolar plasmon mode of the core-shell structured bimetallic nanorods, respectively. As their Ag shell thickness increases, their longitudinal plasmon band blue-shifts notably with the transverse plasmon band blue-shifting and the two octupolar plasmon bands red-shifting slightly, due to the decrease of their aspect ratios and enhancement of Ag plasmon resonance contribution. When used as surface-enhanced Raman scattering (SERS) substrate for probing minute amounts of 4-mercaptobenzoic acid in aqueous solution, Au@AgNRs have much stronger SERS activity than Au nanorods, and the obtained Raman signals are highly reproducible arising from their excellent monodispersity. Their SERS activity is remarkably increased with their Ag shell thickness thanks to the enhancing surface electric field and the chemical enhancement associated with electronic ligand effect. Copyright © 2014 John Wiley & Sons, Ltd.