Joseph Shereena, Sarkar Swagato, Joseph Joby
Photonics Research Lab, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India.
ACS Appl Mater Interfaces. 2020 Oct 14;12(41):46519-46529. doi: 10.1021/acsami.0c12525. Epub 2020 Oct 2.
Surface plasmon resonance-based sensors have emerged as commercially fostering portable biodetectors. The scientific community is engaged in extensive research to improve their performance in terms of sensitivity, selectivity, and reproducibility for the recognition of specific biomolecules. Essentially, there is a need for miniaturizing the size of existing sensors with innovative designs without compromising their bioaffinity and sensitivity performance. In this work, we propose and demonstrate a grating-coupled surface plasmon polariton (SPP) sensor on a thin flat gold layer using a hybrid configuration. The proof of concept of the grating architecture has been realized through an innovative fabrication procedure, with experimental verification of its bulk sensitivity. The geometry is identical to the prism-coupling configuration, yet with miniaturization and compactness. Characteristics of the excited modes in the spectral regime of interest are investigated using the finite-difference time-domain simulations. The effective index calculation of the resonance conditions and the accompanying field distribution can identify the excited SPP and metal-assisted guided-mode resonance modes. Detailed probing of the electric field distribution of the desired SPP mode reveals an extended evanescent decay length of 1284 nm, close to the theoretical limit, and an extended propagation length of 270 μm. The experimental demonstration of the reflectance dip with two different analyte media perceived an increased bulk sensitivity of 1133 nm/RIU. Remarkably, this resonant mode exhibits sensing capabilities for a wide range of analyte refractive indexes. We believe that the fabricated configuration with observed high sensitivity and calculated ultradeep evanescent field penetration depth along with extended propagation length can lead to the designing of a hands-on biochip for detecting large biomolecules.
基于表面等离子体共振的传感器已成为商业上促进便携式生物探测器发展的技术。科学界正在进行广泛研究，以提高其在识别特定生物分子方面的灵敏度、选择性和可重复性。从本质上讲，需要在不影响其生物亲和力和灵敏度性能的前提下，通过创新设计来缩小现有传感器的尺寸。在这项工作中，我们提出并展示了一种采用混合配置的薄平面金层上的光栅耦合表面等离子体激元（SPP）传感器。通过创新的制造工艺实现了光栅结构的概念验证，并对其整体灵敏度进行了实验验证。该几何结构与棱镜耦合配置相同，但具有小型化和紧凑性。使用时域有限差分模拟研究了感兴趣光谱范围内激发模式的特性。共振条件的有效折射率计算以及伴随的场分布可以识别激发的SPP和金属辅助导模共振模式。对所需SPP模式的电场分布进行详细探测，发现其倏逝衰减长度延长至1284 nm，接近理论极限，传播长度延长至270μm。在两种不同分析物介质下对反射率下降的实验演示表明整体灵敏度提高了1133 nm/RIU。值得注意的是，这种共振模式对广泛的分析物折射率具有传感能力。我们相信，所制造的配置具有高灵敏度、计算得出的超深倏逝场穿透深度以及延长的传播长度，可用于设计一种用于检测大型生物分子的实用型生物芯片。
