Polyelectrolyte layer-by-layer assembly to control the distance between fluorophores and plasmonic nanostructures
Polyelectrolyte layer-by-layer assembly to control the distance between fluorophores and plasmonic nanostructures
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DOI：
10.1021/cm071510w
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发表时间：
2007-11-27
影响因子：
8.6
通讯作者：
Lakowicz, Joseph R.
中科院分区：
文献类型：
--
作者：
Ray, Krisharm;Badugu, Ramachandram;Lakowicz, Joseph R.
在过去的几年里，我们已经证明了金属增强荧光（MEF）和显着的变化，在金属纳米结构和纳米粒子的存在下的荧光团的物理性质。MEF在很大程度上取决于几个因素，例如纳米结构的化学性质、尺寸、形状以及其与询问荧光团的距离。在此，我们阐明了逐层（LbL）组装的潜力，以了解组装在等离子体纳米结构表面[以银岛膜（SIF）的形式]上的硫代罗丹明B（SR B）的MEF的距离依赖性。通过构建不同数量的聚（苯乙烯磺酸盐）（PSS）和聚（烯丙胺盐酸盐）（PAH）的交替层来控制来自SIF表面的荧光团的不同接近度。阴离子激光染料SR 13可以静电附着到带正电的PAH层。利用偏振吸收光谱法测定了SRB探针分子在PSS/PAH层状组装体中的吸附取向。所观察到的探针跃迁偶极矩相对于表面法线的倾斜角为40度。我们的研究结果表明，MEF确实是距离依赖。因此，我们观察到在离金属纳米结构化表面近似9 nm的距离处来自SRB单层的荧光强度的近似6倍的最大增加，其中在约30 nm的分离距离处增强降低到近似1.5倍。一致地，最小寿命比在没有银的载玻片上的最小寿命短约4倍，对于15层PSS/PAH组件，寿命几乎相同。强度-时间衰减与寿命分布模型进行了分析，以支持在纳米范围内的金属-荧光团相互作用的距离效应。本研究提供了更好的理解等离子体纳米结构和荧光团之间的相互作用，更重要的是，它们的距离依赖性的性质，在那里我们使用了一个强大的，简单的，和廉价的替代静电LBL组件作为自下而上的纳米纤维技术来控制从表面的探针距离。
In the past several years we have demonstrated the metal-enhanced fluorescence (MEF) and the significant changes in the photophysical properties of fluorophores in the presence of metallic nanostructures and nanoparticles. MEF is largely dependent on several factors, such as chemical nature, size, shape of the nanostructure, and its distance from the interrogating fluorophore. Herein, we elucidate the potential of layer-by-layer (LbL) assembly to understand the distance dependence nature of MEF from sulforhodamine B (SRB) assembled on the plasmonic nanostructured surfaces [in the form of Silver Islands films (SIFs)]. The varied proximity of fluorophores from the SIF surfaces was controlled by constructing different numbers of alternate layers of poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH). An anionic laser dye SR13 could be electrostatically attached to the positively charged PAH layer. Orientation of the SRB probe molecule adsorbed in PSS/PAH-layered assembly was determined by polarized absorption spectroscopy. The observed tilt angle of the probe transition dipole moment with respect to the surface normal was 40 degrees. Our results show that MEF is indeed distancedependent. Accordingly, we observed a maximum of a similar to 6-fold increase in the fluorescence intensity from a monolayer of the SRB at a distance of similar to 9 nm from the metal-nanostructured surface, with the enhancement decreasing down to similar to 1.5-fold at about a 30 nm separation distance. Consistently, the minimum lifetimes were about 4-fold shorter than those on glass slides without silver, with the lifetimes being about nearly the same for 15 layers of the PSS/PAH assembly. The intensity-time decays were analyzed with a lifetime distribution model to underpin the distance effect on the metal-fluorophore interaction in the nanometric range. The present study provides improved understanding of the interaction between plasmonic nanostructures and fluorophores and, more importantly, their distance dependence nature, where we used a robust, easy, and inexpensive alternate electrostatic LbL assembly as a bottom-up nanofabrication technique to control the probe distance from the surface.