等离子体生物传感用金纳米颗粒：金属结晶度和纳米尺度粗糙度的作用
Gold Nanoparticles for Plasmonic Biosensing: The Role of Metal Crystallinity and Nanoscale Roughness
摘要：
贵金属纳米粒子由于局部表面等离子体激元的激发而显示出特定的光学性质，这使得它们成为高灵敏度生物纳米传感器的有吸引力的候选者。潜在的物理原理是分析物诱导的纳米颗粒周围介质的介电性质的改变或通过共振增强的等离子体激元场增加光学活性分析物的激发和发射速率。无论哪种方式，除了纳米颗粒的几何形状外，金属的介电性质和纳米级表面粗糙度对传感性能起着重要作用。然而，由于基本原理尚未得到很好的理解，我们的目标是在这里通过分析光刻制造的纳米粒子的光学特性，不同的结晶度和粗糙度参数的一个更好的理解。我们通过热退火改变这些参数，并应用薄金膜作为模型系统来检索介电函数的修改。我们调查，一方面，消光光谱，反映了远场性质的等离子体激元激发，另一方面，表面增强拉曼光谱，作为近场探针。我们的研究结果提供了更好的洞察局部表面等离子体及其在生物纳米传感中的应用。
英文摘要：
Noble metal nanoparticles show specific optical properties due to the excitation of localized surface plasmons that make them attractive candidates for highly sensitive bionanosensors. The underlying physical principle is either an analyte-induced modification of the dielectric properties of the medium surrounding the nanoparticle or an increase of the excitation and emission rates of an optically active analyte by the resonantly enhanced plasmon field. Either way, besides the nanoparticle geometry the dielectric properties of the metal and nanoscale surface roughness play an important role for the sensing performance. As the underlying principles are however not yet well understood, we aim here at an improved understanding by analyzing the optical characteristics of lithographically fabricated nanoparticles with different crystallinity and roughness parameters. We vary these parameters by thermal annealing and apply a thin gold film as a model system to retrieve modifications in the dielectric function. We investigate, on one hand, extinction spectra that reflect the far-field properties of the plasmonic excitation and, on the other hand, surface-enhanced Raman spectra that serve as a near-field probe. Our results provide improved insight into localized surface plasmons and their application in bionanosensing.
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