Plasmonic core-shell luminescent nanoparticles: A self-supporting sensing platform

金属纳米粒子内部电磁场的限制是局域表面等离子体共振(LSPR)光学现象的根源。这种限制与局域场强度的大幅增强有关，这反过来又导致放置在金属表面附近的荧光物种的量子产率和辐射率显著增加。此外，人们可以利用LSPR频率对金属纳米颗粒的组成、几何形状、尺寸和介电环境的依赖关系来设计最佳的纳米结构，能够增强从紫外到近红外(NIR)光谱中荧光团的发射强度。*由多层二氧化硅包裹的纳米银核组成的核壳纳米颗粒可以显著减少自猝灭(即相邻荧光团之间的信号损失)，并提高检测灵敏度和光稳定性。通过仔细控制核心和以同心层排列的荧光团之间的间距，这些纳米结构可以用来提高Förster共振能量转移(FRET)效率和定位于这些多层复合NPs上的施主-受主对之间的距离。我们最近展示了将这些纳米探针用作等离子体增强剂，用于微弱荧光分析物、特定基因在痕量水平上的定量检测以及细胞膜附近生理离子的光稳定性成像。*这些多层核壳纳米颗粒具有理想的自支撑传感平台所需的许多特征：它们具有高光学检测灵敏度、出色的化学和光物理稳定性、在水中的高分散性以及易于表面官能化。此外，在生物传感应用或功能细胞成像工作中，它们的机动性是探测扩展样本量内容的一项资产。在这项研究计划中，我们将设计新型的多层核壳荧光纳米结构，最大限度地利用等离子体增强发光和FRET，研究它们的光物理特性，并将它们发展成分子传感纳米结构，用于灵敏地检测痕量基因、生物标志物、毒素、病原体、肿瘤细胞等，以及其他在分析化学、材料科学、等离子体、光子学和生物技术领域的应用。

The confinement of electromagnetic fields within metallic nanoparticles is at the origin of the optical phenomenon known as localized surface plasmon resonance (LSPR). This confinement is associated with large enhancements in local field intensity, which lead in turn to significant increases in the quantum yield and radiative rates of fluorescent species placed close to the metal surface. Furthermore, one can take advantage of the LSPR frequency's dependence on the composition, geometry, size and dielectric environment of metallic nanoparticles to design optimal nanostructures able to enhance the emission intensity of fluorophores across the spectrum from UV to the near infrared (NIR). ***A significant reduction of self-quenching (i.e. signal losses occurring between neighboring fluorophores) and an  enhancement of detection sensitivity and photostability can be obtained with core-shell nanoparticles composed of a nanometer-size silver core coated by multiple layers of silica. By careful control of the spacing between the core and fluorophores arranged in concentric layers, these nanostructures can be used to enhance Förster resonant energy transfer (FRET) efficiency and range between donor-acceptor pairs localized on these multilayer composite NPs. We recently demonstrated the use of these nanoprobes as plasmonic enhancers for weakly fluorescent analytes, for the quantitative detection of specific genes at the trace level and for photostable imaging of physiological ions near cellular membranes.****These multilayer core-shell nanoparticles present many of the features required of an ideal self-supported sensing platform: they offer high optical detection sensitivity, excellent chemical and photophysical stability, high dispersability in water, and facile surface functionalization. Furthermore, their mobility is an asset for probing the contents of extended sample volumes in biosensing applications or for functional cell imaging work. In this research program, we will design novel multilayer core-shell fluorescent nanoarchitectures that maximize plasmonic enhancement of luminescence and FRET, investigate their photophysical characteristics, and develop them into molecular sensing nanostructures for the sensitive detection of trace amounts of genes, biomarkers, toxins, pathogens, tumor cells, etc. and other applications in the fields of analytical chemistry, materials science, plasmonics, photonics and biotechnology.**