Malekian Bita, Xiong Kunli, Emilsson Gustav, Andersson Jenny, Fager Cecilia, Olsson Eva, Larsson-Langhammer Elin M, Dahlin Andreas B
Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden.
Insplorion AB, Sahlgrenska Science Park, Medicinaregatan 8A, 41390 Gothenburg, Sweden.
Sensors (Basel). 2017 Jun 20;17(6):1444. doi: 10.3390/s17061444.
Plasmonic nanostructures are widely used for various sensing applications by monitoring changes in refractive index through optical spectroscopy or as substrates for surface enhanced Raman spectroscopy. However, in most practical situations conventional surface plasmon resonance is preferred for biomolecular interaction analysis because of its high resolution in surface coverage and the simple single-material planar interface. Still, plasmonic nanostructures may find unique sensing applications, for instance when the nanoscale geometry itself is of interest. This calls for new methods to prepare nanoscale particles and cavities with controllable dimensions and curvature. In this work, we present two types of plasmonic nanopores where the solid support underneath a nanohole array has been etched, thereby creating cavities denoted as 'nanowells' or 'nanocaves' depending on the degree of anisotropy (dry or wet etch). The refractometric sensitivity is shown to be enhanced upon removing the solid support because of an increased probing volume and a shift of the asymmetric plasmonic field towards the liquid side of the finite gold film. Furthermore, the structures exhibit different spectral changes upon binding inside the cavities compared to the gold surface, which means that the structures can be used for location-specific detection. Other sensing applications are also suggested.
等离子体纳米结构通过光谱学监测折射率变化或作为表面增强拉曼光谱的基底，被广泛应用于各种传感应用中。然而，在大多数实际情况下，传统的表面等离子体共振因其在表面覆盖方面的高分辨率和简单的单材料平面界面，更适合用于生物分子相互作用分析。尽管如此，等离子体纳米结构可能会有独特的传感应用，例如当纳米级几何形状本身受到关注时。这就需要新的方法来制备具有可控尺寸和曲率的纳米级颗粒和腔体。在这项工作中，我们展示了两种类型的等离子体纳米孔，其中纳米孔阵列下方的固体支撑物已被蚀刻，从而根据各向异性程度（干法或湿法蚀刻）创建了被称为“纳米阱”或“纳米洞穴”的腔体。由于探测体积增加以及不对称等离子体场向有限金膜的液体一侧移动，去除固体支撑物后折射灵敏度会提高。此外，与金表面相比，这些结构在腔体内部结合时会表现出不同的光谱变化，这意味着这些结构可用于特定位置的检测。还提出了其他传感应用。
