Pieczonka N P W, Moula G, Aroca R F
Materials and Surface Science Group, Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada N9B 3P4.
Langmuir. 2009 Oct 6;25(19):11261-4. doi: 10.1021/la902486w.
The coupling of molecular excitations to localized surface plasmon resonances (LSPR) in silver or gold nanostructures is at the center of single-molecule detection (SMD) using surface-enhanced Raman scattering (SERS). The effect is attributed to the enhanced scattering power caused by coupling with the surface plasmons of the metal. The most efficient coupling is attained when the excitation is in resonance with the molecule and the nanostructure, the case of surface-enhanced resonance Raman scattering (SERRS). This incredible effect has the potential to be a powerful optical tool when used in conjunction with vibrationally differentiable chromophores. Here we present a unique study where the targeted system is a phospholipid that is tagged with a xanthene dye (the SERRS probe), a chromophore that dominates the Raman signal when the laser is in resonance with its absorption. The labeled phospholipid was incorporated into a single fatty acid Langmuir monolayer at varying concentrations and transferred onto a silver nanoparticle film to form Langmuir-Blodgett (LB) monolayers. Because the xanthene dye is tagged to a much larger molecule, the chances of dye aggregation (formation of dimers or higher aggregates) is negligible. Single-molecule detection of the dye tag (SERRS probe monomer) is readily achieved and demonstrated through the use of doped LB monolayers, Raman microscopy, spectral mapping, and efficient coupling of the laser line into the dye absorption band and plasmon resonances.
分子激发与银或金纳米结构中的局域表面等离子体共振（LSPR）的耦合是利用表面增强拉曼散射（SERS）进行单分子检测（SMD）的核心。这种效应归因于与金属表面等离子体耦合所导致的散射功率增强。当激发与分子和纳米结构共振时，即表面增强共振拉曼散射（SERRS）的情况，可实现最有效的耦合。当与具有振动分辨能力的发色团结合使用时，这种惊人的效应有可能成为一种强大的光学工具。在此，我们展示了一项独特的研究，其中目标系统是一种用呫吨染料（SERRS探针）标记的磷脂，当激光与其吸收共振时，该发色团主导拉曼信号。将标记的磷脂以不同浓度掺入单个脂肪酸朗缪尔单层中，并转移到银纳米颗粒膜上以形成朗缪尔 - 布洛杰特（LB）单层。由于呫吨染料标记在一个大得多的分子上，染料聚集（形成二聚体或更高聚集体）的可能性可忽略不计。通过使用掺杂的LB单层、拉曼显微镜、光谱映射以及将激光线有效耦合到染料吸收带和等离子体共振中，很容易实现并证明了对染料标签（SERRS探针单体）的单分子检测。
