可调形态的Au/Ag双金属纳米间隙阵列提升表面增强拉曼散射效果

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本文主要探讨了一种具有可调形态的Au / Ag双金属纳米间隙阵列在表面增强拉曼散射（Surface Enhanced Raman Scattering, SERS）中的应用。研究人员Yaxin Wang、Xiaoyu Zhao等人通过将金(Au)和银(Ag)沉积在二维聚苯乙烯(PS)模板上，成功地构建出一种弯曲的双金属薄膜，其由纳米帽状的Au / Ag单元组成。这种独特的结构设计使得通过调整双层厚度和PS直径，可以实现"Y"形纳米间隙和"V"形接合点的精确排列。相比于传统的银或单层金，弯曲的Au / Ag双金属薄膜展现出显著的SERS增强效应。这种增强主要归因于两个关键因素：一是相邻Au / Ag纳米帽之间的纳米间隙，它们能够显著增强局部电磁场；二是Ag / Au双金属复合材料，它提供了更多的探针分子驻留可能性。这种设计的优势在于，纳米间隙的形状和大小变化能够精细调控增强效应，从而优化光与分子之间的相互作用，提高Raman信号的灵敏度和选择性。研究中，作者回顾了1970年代以来SERS现象的发现，指出这是一种当分子靠近金属表面时，由于金属对光的散射和吸收增强，导致Raman散射信号显著增大的现象。在当前的研究中，利用Au / Ag双金属结构，科学家们不仅探索了新型纳米尺度增强机制，还可能为开发新型传感器、生物标记物检测以及量子光学等领域提供创新的解决方案。此外，文章可能还涉及了实验方法，如原子层沉积(Atomic Layer Deposition, ALD)或者电子束蒸发(Electron Beam Evaporation)来制备这些复杂的纳米结构，以及如何通过控制模板参数来实现纳米结构的可控生长。同时，文中可能会展示一些实验结果，比如不同几何形态下SERS增强系数的对比分析，以及实际应用中对目标分子识别的性能提升。这篇研究论文深入探讨了Au / Ag双金属纳米间隙阵列在SERS中的新颖应用，强调了结构可调性和增强效果的调控策略，为未来纳米光子学和化学传感技术的发展开辟了新的研究方向。

Au/Ag bimetal nanogap arrays with tunable

morphologies for surface-enhanced Raman

scattering

Yaxin Wang,

Xiaoyu Zhao,

Wenting Gao,

Lei Chen,

San Chen,

Maobin Wei,

Ming Gao,

Cong Wang,

Yongjun Zhang

and Jinghai Yang

When Au and Ag were deposited onto two-dimensional polystyrene (PS) templates, a curved bimetallic ﬁlm

composed of nanocap-shaped Au/Ag units was formed. The “Y”-shaped nanogaps and “V”-shaped

junctions were tailored between the neighbour nanocaps by changing the bilayer thickness and PS

diameters. Compared to the curved Ag, the curved Au monolayer and the ﬂat Au/Ag bilayer on a silicon

wafer, the curved Au/Ag bimetallic ﬁlm exhibited signiﬁcant SERS enhancement, which was mainly

attributed to two important factors, the nanogaps between the adjacent Au/Ag nanocaps and the

composite of the Ag/Au bimetallic ﬁlm. And the nanogaps generated extremely intense local

electromagnetic ﬁelds and the composite provided more possibilities for the residence of probing

molecules.

1. Introduction

Surface-enhanced Raman scattering (SERS) observed in the

1970s is a phenomenon where a Raman signal is strongly

enhanced when molecules are attached to the rough surface of

metal nanostructures.

1,2

In recent years, a tremendous amount

of studies have focused on SERS due to its single-molecule

sensitivity and excellent ngerprint eﬀect for practical applica-

tions in detection and recognition technology elds.

3–7

Currently, the development of patterned substrates with nano-

gap arrays is an important aspect of SERS studies, because

the large electromagnetic (EM) elds can be excited at the

nanogaps, termed as “hot spots”, due to the surface plasmon

resonances (SPR) of the nanostructure, which can signicantly

amplify Raman scattering intensity of the attached mole-

cules.

8–10

A variety of nanostructures with “hot spots” have been

fabricated by diﬀerent approaches including chemical func-

tionalization method,

electron lithography technique

and

salt-induced aggregation.

13,14

In comparison, nanosphere

lithography (NSL) is a simple, economic and robust route for the

fabrication of a uniformly ordered nanostructure array owing to

its good monodispersity, wide size range (nanometer-to-

micrometer) and easy availability.

15–18

In addition to the construction of the substrate with high

density of hot spots, the material composition is another

key factor for SERS enhancement. Generally, SERS-active

substrates have been restricted to some noble metals mate-

rials.

Comparing with other noble metals, Ag and Au nano-

particles have been widely used in SERS studies due to the

higher plasmonic enhancement for Ag and better bio-

compatibility for Au.

20,21

But the toxicity of Ag and weak SERS

active of Au have limited the development of SERS spectroscopy

for the application of the single metallic substrate. To optimize

SERS eﬀect and other optical properties, recently, a number of

studies focus on some composites or bimetal materials system,

including Au@SiO

, Ag/ZnO.

22,23

Au/Ag bimetal system attracts

tremendous attentions from the SERS community because it

exhibits both the dramatic Raman enhancement and good

compatibility.

24–27

The bimetal lms composed of the Ag and Au

are preferable choices for the enhancement of SERS signal and

application in analytical technique.

In this work, we fabricate the SERS-active substrate

composed of Au/Ag metallic nanogap array by NSL. The

morphologies and the properties of the metallic nanogaps are

modied by adjusting the PS diameter and the lm thickness.

The inuences of the diﬀerent morphologies and the compo-

sitions of Au/Ag on Raman eﬀects are investigated.

2. Experimental section

Assemble of PS array

The monodisperse polystyrene colloid particles (PS) were

purchased from Duke Cooperation (10 wt% aqueous solution).

The diluted polystyrene solution was applied onto the modi ed

Key Laboratory of Functional Materials Physics and Chemistry, Jilin Normal

University, Ministry of Education, Siping 136000, PR China. E-mail:

zhangyongjunwyx@126.com; jhyang@jlnu.edu.cn

Key Laboratory of Excited State Physics, Changchun Institute of Optics Fine Mechanics

and Physics, Chinese Academy of Sciences, Changchun, 130033, PR China

Huaibei Normal University, Huaibei, 235000, PR China

Cite this: RSC Adv.,2015,5,7454

Received 21st September 2014

Accepted 22nd December 2014

DOI: 10.1039/c4ra10882e

www.rsc.org/advances

RSC Advances

PAPER

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