SERS in PAH-Os and gold nanoparticle self-assembled multilayers
SERS in PAH-Os and gold nanoparticle self-assembled multilayers
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DOI：
10.1063/1.1954707
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发表时间：
2005-07-22
影响因子：
4.4
通讯作者：
Etchegoin, P
中科院分区：
文献类型：
--
作者：
Tognalli, N;Fainstein, A;Etchegoin, P
我们对Os（byp）修饰的聚烯丙基胺（PAH-Os）和金纳米粒子自组装多层膜[PAH-Os+（Au-nanoparticles/PAH-Os）（n），n=1和5]进行了详细的结构和表面增强拉曼散射（Sers）研究。原子力显微镜和可变角度椭圆偏振光谱测量表明，第一纳米粒子层生长均匀，部分覆盖基板没有集群。分析样品的厚度和粗糙度，我们推断，生长过程的进步，此后通过填充纳米粒子的间隙空间之间的先前吸附的纳米粒子。经过五个浸渍步骤，多层膜达到更紧凑的结构。近金纳米粒子的等离子体之间的相互作用提供了一个新的光学吸收约650 nm，此外，允许在该光谱区域比在单等离子体共振（类似于530 nm）更有效的Sers过程。通过分析拉曼共振扫描和拉曼强度显微图，比较了自组装多层膜的电子共振拉曼和Sers放大机制。作为纳米颗粒覆盖率的函数，我们观察到在拉曼强度扫描中的大的变化，其中最大值从电子跃迁转移到等离子体共振，最后转移到耦合等离子体吸收。另一方面，拉曼显微图证明了强度的巨大不均匀性，我们将其与“热点”联系起来。“数值离散偶极子近似计算，包括金纳米粒子之间的相互作用，提供了一个定性模型的耦合等离子体吸收和红移拉曼热点在这些样品。(C)2005年美国物理学会。
We present a detailed structural and surface-enhanced Raman scattering (SERS) study of poly(allylamine) modified with Os(byp)(2)ClPyCHO (PAH-Os) and gold nanoparticles self-assembled multilayers [PAH-Os+(Au-nanoparticles/PAH-Os)(n), n=1 and 5]. Atomic force microscopy and variable-angle spectroscopic ellipsometry measurements indicate that the first nanoparticle layer grows homogenously by partially covering the substrate without clustering. Analyzing the sample thickness and roughness we infer that the growth process advances thereafter by filling with nanoparticles the interstitial spaces between the previously adsorbed nanoparticles. After five immersion steps the multilayers reach a more compact structure. The interaction between plasmons of near-gold nanoparticles provides a new optical absorption around 650 nm which, in addition, allows a more effective SERS process in that spectral region than at the single-plasmon resonance (similar to 530 nm). We compare the electronic resonance Raman and SERS amplification mechanisms in these self-assembled multilayers analyzing Raman resonance scans and Raman intensity micromaps. As a function of nanoparticle coverage we observe large changes in the Raman intensity scans, with maxima that shift from the electronic transitions, to the plasmon resonance, and finally to the coupled-plasmon absorption. The Raman micromaps, on the other hand, evidence huge intensity inhomogeneities which we relate to "hot spots." Numerical discrete dipole approximation calculations including the interaction between gold nanoparticles are presented, providing a qualitative model for the coupled-plasmon absorption and redshifted Raman hot spots in these samples. (C) 2005 American Institute of Physics.