Dos Santos Almeida Aline, Bahamon Dario A, Peres Nuno M R, de Matos Christiano J S
School of Engineering, Mackenzie Presbyterian University, São Paulo 01302-907, Brazil.
MackGraphe-Graphene and Nanomaterials Research Institute, Mackenzie Presbyterian Institute, São Paulo 01302-907, Brazil.
Nanomaterials (Basel). 2022 Jul 26;12(15):2562. doi: 10.3390/nano12152562.
The use of graphene in surface plasmon resonance sensors, covering a metallic (plasmonic) film, has a number of demonstrated advantages, such as protecting the film against corrosion/oxidation and facilitating the introduction of functional groups for selective sensing. Recently, a number of works have claimed that few-layer graphene can also increase the sensitivity of the sensor. However, graphene was treated as an isotropic thin film, with an out-of-plane refractive index that is identical to the in-plane index. Here, we critically examine the role of single and few layers of graphene in the sensitivity enhancement of surface plasmon resonance sensors. Graphene is introduced over the metallic film via three different descriptions: as an atomic-thick two-dimensional sheet, as a thin effective isotropic material (same conductivity in the three coordinate directions), and as an non-isotropic layer (different conductivity in the perpendicular direction to the two-dimensional plane). We find that only the isotropic layer model, which is known to be incorrect for the optical modeling of graphene, provides sizable sensitivity increases, while the other, more accurate, models lead to a negligible contribution to the sensitivity.
在表面等离子体共振传感器中使用覆盖金属（等离子体）薄膜的石墨烯具有许多已被证实的优点，例如保护薄膜免受腐蚀/氧化，并便于引入用于选择性传感的官能团。最近，一些研究声称少层石墨烯也可以提高传感器的灵敏度。然而，石墨烯被视为各向同性薄膜，其面外折射率与面内折射率相同。在这里，我们批判性地研究了单层和少层石墨烯在表面等离子体共振传感器灵敏度增强中的作用。通过三种不同的描述将石墨烯引入金属薄膜上：作为原子厚度的二维薄片，作为薄的有效各向同性材料（在三个坐标方向上具有相同的电导率），以及作为非各向同性层（在垂直于二维平面的方向上具有不同的电导率）。我们发现，只有已知对石墨烯光学建模不正确的各向同性层模型能使灵敏度有显著提高，而其他更准确的模型对灵敏度的贡献可忽略不计。
