Kang Jiwon, Yoo Young Jin, Ko Joo Hwan, Mahmud Abdullah Al, Song Young Min
School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Gwangju 61005, Republic of Korea.
Anti-Viral Research Center, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Gwangju 61005, Republic of Korea.
Nanomaterials (Basel). 2023 Jan 12;13(2):319. doi: 10.3390/nano13020319.
Over the past few decades, advances in various nanophotonic structures to enhance light-matter interactions have opened numerous opportunities for biosensing applications. Beyond the successful development of label-free nanophotonic biosensors that utilize plasmon resonances in metals and Mie resonances in dielectrics, simpler structures are required to achieve improved sensor performance and multifunctionality, while enabling cost-effective fabrication. Here, we present a simple and effectual approach to colorimetric biosensing utilizing a trilayered Gires-Tournois (GT) resonator, which provides a sensitive slow-light effect in response to low refractive index (RI) substances and thus enables to distinguish low RI bioparticles from the background with spatially distinct color differences. For low RI sensitivity, by impedance matching based on the transmission line model, trilayer configuration enables the derivation of optimal designs to achieve the unity absorption condition in a low RI medium, which is difficult to obtain with the conventional GT configuration. Compared to conventional bilayered GT resonators, the trilayered GT resonator shows significant sensing performance with linear sensitivity in various situations with low RI substances. For extended applications, several proposed designs of trilayered GT resonators are presented in various material combinations by impedance matching using equivalent transmission line models. Further, comparing the color change of different substrates with low RI NPs using finite-difference time-domain (FDTD) simulations, the proposed GT structure shows surpassing colorimetric detection.
在过去几十年中，各种用于增强光与物质相互作用的纳米光子结构取得了进展，为生物传感应用带来了众多机遇。除了成功开发利用金属中的等离子体共振和电介质中的米氏共振的无标记纳米光子生物传感器外，还需要更简单的结构来实现更高的传感器性能和多功能性，同时实现具有成本效益的制造。在此，我们提出了一种利用三层吉雷斯 - 图尔诺（GT）谐振器进行比色生物传感的简单有效方法，该谐振器对低折射率（RI）物质会产生灵敏的慢光效应，从而能够通过空间上明显的颜色差异将低RI生物颗粒与背景区分开来。对于低RI灵敏度，通过基于传输线模型的阻抗匹配，三层结构能够推导出最优设计，以在低RI介质中实现单位吸收条件，而这用传统的GT结构很难实现。与传统的双层GT谐振器相比，三层GT谐振器在存在低RI物质的各种情况下都具有显著的传感性能和线性灵敏度。为了实现更广泛的应用，通过使用等效传输线模型进行阻抗匹配，给出了几种不同材料组合的三层GT谐振器设计方案。此外，使用时域有限差分（FDTD）模拟比较不同低RI NPs底物的颜色变化，所提出的GT结构显示出卓越的比色检测能力。
