Sulforhodamine adsorbed Langmuir-Blodgett layers on silver island films: Effect of probe distance on the metal-enhanced fluorescence
Sulforhodamine adsorbed Langmuir-Blodgett layers on silver island films: Effect of probe distance on the metal-enhanced fluorescence
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DOI：
10.1021/jp067635q
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发表时间：
2007-05-17
影响因子：
3.7
通讯作者：
Lakowicz, Joseph R.
中科院分区：
文献类型：
--
作者：
Ray, Krishanu;Badugu, Ramachandram;Lakowicz, Joseph R.
金属增强荧光（MEF）已成为生物医学传感的一种重要方法。本文研究了磺酰罗丹明B（SR B）在银岛膜上的单分子膜的距离效应。SRB被静电结合到沉积在玻璃和SIF基底上的十八胺（ODA）的LB层中。SRB和SIF或玻璃表面之间的距离通过沉积不同数量的惰性硬脂酸（SA）间隔层来控制。通过将ODA沉积的基底浸入SRB的水溶液中，将SRB并入带正电荷的LB层中。与SIF表面相距10 nm的染料掺入的ODA层显示出最大的金属增强的荧光强度;与来自玻璃表面的荧光强度相比，强度增加了7倍。相应的增强因子随着探针距SIF表面的距离的增加或减小而减小。此外，SIF表面上的SRB显示出减少的寿命。我们观察到最短的寿命从SRB与5 nm的距离从SIF表面和寿命增加一致的荧光团和SIF表面之间的距离增加。这些观察到的光谱变化、荧光强度的增加和荧光寿命的降低与由于银纳米颗粒和荧光团之间的近场相互作用而产生的预期效应一致。我们还分析了复杂的荧光非均匀衰减金属纳米结构表面使用连续的衰减时间分布。衰减时间分布似乎是敏感的金属和荧光团之间的距离，并代表潜在的异质性的样品。本系统的研究提供了重要的信息，荧光团的距离上的金属增强荧光现象的效果。
Metal-enhanced fluorescence (MEF) has become an important method in biomedical sensing. In this paper, we present the distance-dependent MEF of the sulforhodamine B (SRB) monolayer on silver island films (SIFs). SRB is electrostatically incorporated into the Langmuir-Blodgett (LB) layers of octadecylamine (ODA) deposited on glass and SIFs substrates. The distances between SRB and SIFs or glass surfaces are controlled by depositing a varied number of inert stearic acid (SA) spacer layers. SRB is incorporated into positively charged LB layers of ODA by immersing the ODA deposited substrates into an aqueous solution of SRB. Dye-incorporated ODA layers with 10 nm separation distance from the SIFs surface show maximum metal-enhanced fluorescence intensity; similar to 7-fold increase in intensity as compared to that from the glass surface. The corresponding enhancement factor is reduced with increasing or decreasing the probe distance from the SIFs surface. Additionally, SRB on SIF surfaces show reduced lifetimes. We observed the shortest lifetime from the SRB with 5 nm distance from the SIF surfaces and the lifetime increased consistently with increasing the distances between the fluorophore and the SIFs surface. These observed spectral changes, increase in fluorescence intensity and decreased fluorescence lifetimes, are in accordance with the expected effects due to near-field interactions between the silver nanoparticles and fluorophores. We have also analyzed the complex fluorescence heterogeneous decays on metallic nanostructured surfaces using continuous distributions of decay times. The decay-time distributions appear to be sensitive to the distance between the metal and fluorophore and represent the underlying heterogeneity of the samples. The present systematic study provides significant information on the effect of fluorophore distance on the metal-enhanced fluorescence phenomenon.